ABCMdb

ABCC6 p.Arg518Gln

ClinVar:	c.1552C>T , p.Arg518* D , Pathogenic
LOVD-ABCC6:	p.Arg518Gln D p.Arg518* D
Predicted by SNAP2:	A: D (95%), C: D (95%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (95%), K: D (95%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (59%), S: D (95%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, S: D, T: D, V: D, W: D, Y: D,

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[hide] Molecular genetics of pseudoxanthoma elasticum: a ... Trends Mol Med. 2001 Jan;7(1):13-7. Uitto J, Pulkkinen L, Ringpfeil F
Molecular genetics of pseudoxanthoma elasticum: a metabolic disorder at the environment-genome interface?
Trends Mol Med. 2001 Jan;7(1):13-7., [PMID:11427982]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a relatively rare heritable disorder affecting the skin, eyes and cardiovascular system, with considerable morbidity and mortality. The disease affects the elastic fibers of affected organs, which become progressively calcified. Thus, PXE has been considered as a prototypic heritable connective tissue disorder affecting the elastic fiber system. Recently, PXE has been linked to mutations in the MRP6/ABCC6 gene, a member of the ABC transporter family, expressed primarily in the liver and the kidneys. This information, together with clinical observations suggesting environmental, hormonal and/or dietary modulation of the disease, raises the intriguing possibility that PXE is a primary metabolic disorder at the environment-genome interface.

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75 Thisraisesthequestionoftherelationshipbetweenthe MRP6mutationsandthemanifestationsinPXE affectingtheelasticfibersinvariousorgans.Itmaywell Opinion CR1339C G1345R TRENDS in Molecular Medicine 10 kb NBF2NBF1 0.5 kb Extracellular Intracellular GS 5' 3' R1138Q R1164X R1141X R1138W 2787+1G T A455P R518Q R1114P R1314W (a) (b) (c) EcoRI SmaI SmaI SmaI SacI SacI SmaI N GS 2542delG 1944del22 4220insAGAA 3775delT 3736-1G A Fig. 3. Login to comment

[hide] A spectrum of ABCC6 mutations is responsible for p... Am J Hum Genet. 2001 Oct;69(4):749-64. Epub 2001 Aug 31. Le Saux O, Beck K, Sachsinger C, Silvestri C, Treiber C, Goring HH, Johnson EW, De Paepe A, Pope FM, Pasquali-Ronchetti I, Bercovitch L, Marais AS, Viljoen DL, Terry SF, Boyd CD
A spectrum of ABCC6 mutations is responsible for pseudoxanthoma elasticum.
Am J Hum Genet. 2001 Oct;69(4):749-64. Epub 2001 Aug 31., [PMID:11536079]

Abstract [show]
To better understand the pathogenetics of pseudoxanthoma elasticum (PXE), we performed a mutational analysis of ATP-binding cassette subfamily C member 6 (ABCC6) in 122 unrelated patients with PXE, the largest cohort of patients yet studied. Thirty-six mutations were characterized, and, among these, 28 were novel variants (for a total of 43 PXE mutations known to date). Twenty-one alleles were missense variants, six were small insertions or deletions, five were nonsense, two were alleles likely to result in aberrant mRNA splicing, and two were large deletions involving ABCC6. Although most mutations appeared to be unique variants, two disease-causing alleles occurred frequently in apparently unrelated individuals. R1141X was found in our patient cohort at a frequency of 18.8% and was preponderant in European patients. ABCC6del23-29 occurred at a frequency of 12.9% and was prevalent in patients from the United States. These results suggested that R1141X and ABCC6del23-29 might have been derived regionally from founder alleles. Putative disease-causing mutations were identified in approximately 64% of the 244 chromosomes studied, and 85.2% of the 122 patients were found to have at least one disease-causing allele. Our results suggest that a fraction of the undetected mutant alleles could be either genomic rearrangements or mutations occurring in noncoding regions of the ABCC6 gene. The distribution pattern of ABCC6 mutations revealed a cluster of disease-causing variants within exons encoding a large C-terminal cytoplasmic loop and in the C-terminal nucleotide-binding domain (NBD2). We discuss the potential structural and functional significance of this mutation pattern within the context of the complex relationship between the PXE phenotype and the function of ABCC6.

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85 PXE Mutations The most-prevalent mutations detected in the ABCC6 gene were missense substitutions (21 [58.3%] mutations, Table 1 ABCC6 Mutations in a Cohort of Patients with PXE CHANGE IN STATUS a ORIGIN(S)b EXON(S)c REFERENCE(S)Amino Acid Nucleotide … 179-195del ht Belgium 2 Present study … 938-939insT ch, ht SA, UK 8 Present study N411K 1233TrG ht US 10 Present study A455P 1363GrC Nd Nd 11 Uitto et al. (2001) R518Q 1553GrA ch, ht Belgium 12 Present study, Uitto et al. (2001) F568S 1703TrC ch US 13 Present study … ABCC6del15 hm SA 15 Present study … 1944del22 ht Holland 16 Bergen et al. (2000) … 1995delG ht Germany 16 Present study L673P 2018TrC ch SA 16 Present study R765Q 2294GrA ht Germany 18 Present study Y768X 2304CrA ch, ht SA 18 Present study … 2322delC ht US 18 Present study … 2542delG Nd Nd 19 Uitto et al. (2001) … IVS21ϩ1GrT ch US, Germany i-21 Present study, Uitto et al. (2001) R1030X 3088CrT ht SA, UK 23 Present study R1114P 3341GrC hm UK 24 Present study S1121W 3362CrG ch Germany 24 Present study R1138W 3412CrT hm Nd 24 Ringpfeil et al. (2000) R1138P 3413GrC ch Germany 24 Present study R1138Q 3413GrA ch UK, US 24 Present study, Ringpfeil et al. (2000) R1141X 3421CrT All All 24 Present study and othersd R1164X 3490CrT ch Germany, UK 24 Ringpfeil et al. (2001) G1203D 3608GrA ch Germany 25 Present study … IVS26-1GrA ch Belgium i-26 Present study, Ringpfeil et al. (2000, 2001) Q1237X 3709CrT ch Belgium 26 Present study … 3775delT ht, hm SA, US, Holland 27 Present study, Bergen et al. (2000) V1298F 3892GrT ht US 28 Present study T1301I 3902CrT ch Belgium 28 Present study G1302R 3904GrA hm US 28 Present study A1303P 3907GrC ch Belgium 28 Present study R1314W 3940CrT hm US 28 Present study R1314Q 3941GrA ch Germany 28 Present study G1321S 3961GrA ht US 28 Present study R1339C 4015CrT All SA, US 28 Present study, Struk et al. (2000) Q1347H 4041GrC hm US 28 Present study D1361N 4081GrA ch Germany 29 Present study … 4104delC ch Belgium 29 Present study R1398X 4192CrT ch Belgium 29 Present study … ABCC6del23-29 ch US 23-29 Present study, Ringpfeil et al. (2001) … 4220insAGAA ht Holland 30 Bergen et al. (2000) I1424T 4271TrC ht US 30 Present study … ABCC6del ht Holland all Bergen et al. (2000) a Nd p not determined; hm p homozygote; ht p heterozygote; ch p compound heterozygote. Login to comment

[hide] Evidence for a founder effect for pseudoxanthoma e... Hum Genet. 2002 Oct;111(4-5):331-8. Epub 2002 Sep 7. Le Saux O, Beck K, Sachsinger C, Treiber C, Goring HH, Curry K, Johnson EW, Bercovitch L, Marais AS, Terry SF, Viljoen DL, Boyd CD
Evidence for a founder effect for pseudoxanthoma elasticum in the Afrikaner population of South Africa.
Hum Genet. 2002 Oct;111(4-5):331-8. Epub 2002 Sep 7., [PMID:12384774]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a heritable elastic tissue disorder recently shown to be attributable to mutations in the ABCC6 ( MRP6) gene. Whereas PXE has been identified in all ethnic groups studied to date, the prevalence of this disease in various populations is uncertain, although often assumed to be similar. A notable exception however is the prevalence of PXE among South African Afrikaners. A previous report has suggested that a founder effect may explain the higher prevalence of PXE in Afrikaners, a European-derived population that first settled in South Africa in the 17th century. To investigate this hypothesis, we performed haplotype and mutational analysis of DNA from 24 South African families of Afrikaner, British and Indian descent. Among the 17 Afrikaner families studied, three common haplotypes and six different disease-causing variants were identified. Three of these mutant alleles were missense variants, two were nonsense mutations and one was a single base-pair insertion. The most common variant accounted for 53% of the PXE alleles, whereas other mutant alleles appeared at lower frequencies ranging from 3% to 12%. Haplotype analysis of the Afrikaner families showed that the three most frequent mutations were identical-by-descent, indicating a founder origin of PXE in this population.

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59 The remaining R1141X mutations, characterized in Family 224 (Afrikaner) and Family 212 (British ancestry) were found in different haplotypes indicating that 333 Table 1 ABCC6 mutations identified in a cohort of South African PXE patients of Afrikaner and other ancestries (nt nucleotide, aa amino acid, ni not identified, UK United Kingdom, Black black South Africans) Family Allele 1 Allele 2 Ancestry nt change aa change Exon Haplotype nt change aa change Exon Haplotype 201 4015C→T R1339C 28 I 4015C→T R1339C 28 I Afrikaner 203 4015C→T R1339C 28 I 3413G→A R1138Q 24 III Afrikaner 205 3413G→A R1138Q 24 III 2304C→A Y768X 18 II Afrikaner 206 4015C→T R1339C 28 I 3421C→T R1141X 24 Other Afrikaner 208 4015C→T R1339C 28 I 4015C→T R1339C 28 I Afrikaner 209 4015C→T R1339C 28 I 2018T→C L673P 16 Other Afrikaner 211 4015C→T R1339C 28 I 3413G→A R1138Q 24 III Afrikaner 222 4015C→T R1339C 28 I 4015C→T R1339C 28 I Afrikaner 223 4015C→T R1339C 28 I 2304C→A Y768X 18 II Afrikaner 225 4015C→T R1339C 28 I 4015C→T R1339C 28 I Afrikaner 226 4015C→T R1339C 28 I 2304C→A Y768X 18 II Afrikaner 228 4015C→T R1339C 28 I 2304C→A Y768X 18 II Afrikaner 229 4015C→T R1339C 28 I 4015C→T R1339C 28 I Afrikaner 213 939insT Frameshift 8 Other ni ni ni Other Afrikaner 214 4015C→T R1339C 28 I ni ni ni Other Afrikaner 224 3421C→T R1141X 24 Other ni ni ni Other Afrikaner 204 ni ni Other ni ni ni Other Afrikaner 212 3421C→T R1141X 24 Other 939insT Frameshift 8 Other UK 215 3775delT Frameshift 27 Other 4104delC Frameshift 29 Other UK 217 ABCC6del15 Frameshift 15 Other ABCC6del15 Frameshift 15 Other Indian 207 3088C→T R1030X 23 Other ni ni ni Other UK 216 3421C→T R1141X 24 Other ni ni ni Other UK 219 1553G→A R518Q 12 Other ni ni ni Other UK 221 ni ni Other ni ni ni Other Black Table 2 Frequencies of mutant ABCC6 alleles found in a cohort of PXE patients of Afrikaner and other ancestries (? Login to comment
60 unidentified alleles, MDR mutation detection rate) Mutation Overall Afrikaner ancestries Others ancestries Allele Allele Allele Allele Allele Allele count frequency (%) count frequency (%) count frequency (%) R1339C 18 37.5 18 52.9 0 0 Y768X 4 8.3 4 11.8 0 0 R1141X 4 8.3 2 5.9 2 14.3 R1138Q 3 6.3 3 8.8 0 0 939insT 2 4.2 1 2.9 1 7.1 ABCC6del15 2 4.2 0 0.0 2 14.3 L673P 1 2.1 1 2.9 0 0.0 R1030X 1 2.1 0 0.0 1 7.1 R518Q 1 2.1 0 0.0 1 7.1 3775delT 1 2.1 0 0.0 1 7.1 4104delC 1 2.1 0 0.0 1 7.1 ? Login to comment

[hide] ABCC6/MRP6 mutations: further insight into the mol... Eur J Hum Genet. 2003 Mar;11(3):215-24. Hu X, Plomp A, Wijnholds J, Ten Brink J, van Soest S, van den Born LI, Leys A, Peek R, de Jong PT, Bergen AA
ABCC6/MRP6 mutations: further insight into the molecular pathology of pseudoxanthoma elasticum.
Eur J Hum Genet. 2003 Mar;11(3):215-24., [PMID:12673275]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a hereditary disease characterized by progressive dystrophic mineralization of the elastic fibres. PXE patients frequently present with skin lesions and visual acuity loss. Recently, we and others showed that PXE is caused by mutations in the ABCC6/MRP6 gene. However, the molecular pathology of PXE is complicated by yet unknown factors causing the variable clinical expression of the disease. In addition, the presence of ABCC6/MRP6 pseudogenes and multiple ABCC6/MRP6-associated deletions complicate interpretation of molecular genetic studies. In this study, we present the mutation spectrum of ABCC6/MRP6 in 59 PXE patients from the Netherlands. We detected 17 different mutations in 65 alleles. The majority of mutations occurred in the NBF1 (nucleotide binding fold) domain, in the eighth cytoplasmatic loop between the 15th and 16th transmembrane regions, and in NBF2 of the predicted ABCC6/MRP6 protein. The R1141X mutation was by far the most common mutation identified in 19 (32.2%) patients. The second most frequent mutation, an intragenic deletion from exon 23 to exon 29 in ABCC6/MRP6, was detected in 11 (18.6%) of the patients. Our data include 11 novel ABCC6/MRP6 mutations, as well as additional segregation data relevant to the molecular pathology of PXE in a limited number of patients and families. The consequences of our data for the molecular pathology of PXE are discussed.

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38 Table 2 Summary of ABCC6/MRP6 mutations associated with PXE known today: our data combined with those of the literature Mutation Protein alteration Nucleotide substitution Location Reference Nonsense Q378X 1132C > T Exon 9 19,20 R518X 1552C > T Exon 2 41 Q749X 2247C > T Exon 17 This study Y768X 2304C > A Exon 18 22 R1030X 3088C > T Exon 23 22 R1141X 3421C > T Exon 24 12,20,22,38,39, this study R1164X 3490C > T Exon 24 12,41 Q1237X 3709C > T Exon 26 22 R1398X 4192C >T Exon 29 22 T364R Missense N411K 1091C > G Exon 9 20 A455P 1233T > G Exon 10 22 R518Q 1363G > C Exon 11 38 F568S 1553G > A Exon 12 22,38 L673P 1703T > C Exon 13 22 R765Q 2018T > C Exon 16 22 R1114P 2294G > A Exon 18 22, this study R1114H 3341G > C Exon 24 22 S1121W 3341G > A Exon 24 This study T1130M 3362C > G Exon 24 22 R1138W 3390C > T Exon 24 This study R1138Q 3412C > T Exon 24 12 R1138P 3413G > A Exon 24 12,22 G1203D 3413G > C Exon 24 22 R1221C 3608G > A Exon 25 22 V1298F 3663C > T Exon 26 This study T1301I 3892G > T Exon 28 22 G1302R 3902C > T Exon 28 22 A1303P 3904G > A Exon 28 22, this study R1314W 3907G > C Exon 28 22, this study R1314Q 3940C > T Exon 28 22 G1321S 3941G > A Exon 28 22 R1339C 3961G > A Exon 28 22 Q1347H 4015C > T Exon 28 22,39 G1354R 4041G > C Exon 28 22 D1361N 4060G > C Exon 29 20,38 K1394N 4081G > A Exon 29 22 I1424T 4182G > T Exon 29 This study R1459C 4271T > C Exon 30 22 4377C > T Exon 30 This study Frameshift IVS17-12delT T Intron 17 This study IVS21+1G>T Intron 21 22,38 IVS26-1G>A Intron 26 12,21,22 179del 9 Exon 2 20 179-195del Exon 2 22 960del C Exon 8 41 1944del22 Exon 16 This study 1995delG Exon 16 22 2322delC Exon 18 22 2542delG Exon 19 41 3775delT Exon 27 This study 4104delC Exon 29 22 4182delG Exon 29 This study 938-939insT Exon 8 22 4220insAGAA Exon 30 This study Large deletion Exons 23-29 21, This study Exon 15 22 ABCC1, ABCC6 41, this study Mutation types The mutation types found in this study are summarized in Table 1. Login to comment

[hide] Pseudoxanthoma elasticum: a clinical, histopatholo... Surv Ophthalmol. 2003 Jul-Aug;48(4):424-38. Hu X, Plomp AS, van Soest S, Wijnholds J, de Jong PT, Bergen AA
Pseudoxanthoma elasticum: a clinical, histopathological, and molecular update.
Surv Ophthalmol. 2003 Jul-Aug;48(4):424-38., [PMID:12850230]

Abstract [show]
Pseudoxanthoma elasticum is an autosomally inherited disorder that is associated with the accumulation of mineralized and fragmented elastic fibers in the skin, Bruch's membrane in the retina, and vessel walls. The ophthalmic and dermatologic expression of pseudoxanthoma elasticum and its vascular complications are heterogeneous, with considerable variation in phenotype, progression, and mode of inheritance. Using linkage analysis and mutation detection techniques, mutations in the ABCC6 gene were recently implicated in the etiology of pseudoxanthoma elasticum. ABCC6 encodes the sixth member of the ATP-binding cassette transporter and multidrug resistance protein family (MRP6). In humans, this transmembrane protein is highly expressed in the liver and kidney. Lower expression was found in tissues affected by pseudoxanthoma elasticum, including skin, retina, and vessel walls. So far, the substrates transported by the ABCC6 protein and its physiological role in the etiology of pseudoxanthoma elasticum are not known. A functional transport study of rat MRP6 suggests that small peptides such as the endothelin receptor antagonist BQ123 are transported by MRP6. Similar molecules transported by ABCC6 in humans may be essential for extracellular matrix deposition or turnover of connective tissue at specific sites in the body. One of these sites is Bruch's membrane. This review is an update on etiology of pseudoxanthoma elasticum, including its clinical and genetic features, pathogenesis, and biomolecular basis.

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193 TABLE 3 Summary of ABCC6 Mutations in PXE Patients Mutation Protein Alteration Nucleotide Substitution Location Reference Nonsense Q378X 1132C Ͼ T Exon 9 16,107 R518X 1552C Ͼ T Exon 12 88 Y768X 2304C Ͼ A Exon 18 67 R1030X 3088C Ͼ T Exon 23 67 R1141X 3421C Ͼ T Exon 24 12,45,67,107,111,112,133 R1164X 3490C Ͼ T Exon 24 88,112 Q1237X 3709C Ͼ T Exon 26 67 R1398X 4192C Ͼ T Exon 29 67 Missense T364R 1091C Ͼ G Exon 9 107 N411K 1233T Ͼ G Exon 10 67 A455P 1363G Ͼ C Exon 11 142 R518Q 1553G Ͼ A Exon 12 67,142 F568S 1703T Ͼ C Exon 13 67 L673P 2018T Ͼ C Exon 16 67 R765Q 2294G Ͼ A Exon 18 67 R1114P 3341G Ͼ C Exon 24 67 S1121W 3362C Ͼ G Exon 24 67 R1138W 3412C Ͼ T Exon 24 111 R1138Q 3413G Ͼ A Exon 24 67,111 R1138P 3413G Ͼ C Exon 24 67 G1203D 3608G Ͼ A Exon 25 67 V1298F 3892G Ͼ T Exon 28 67 T13011 3902C Ͼ T Exon 28 67 G1302R 3904G Ͼ A Exon 28 67 A1303P 3907G Ͼ C Exon 28 67 R1314W 3940C Ͼ T Exon 28 67 R1314Q 3941G Ͼ A Exon 28 67 G1321S 3961G Ͼ A Exon 28 67 R1339C 4015C Ͼ T Exon 28 67,133 Q1347H 4041G Ͼ C Exon 28 67 G1354R 4060G Ͼ C Exon 29 107,142 D1361N 4081G Ͼ A Exon 29 67 11424T 4271T Ͼ C Exon 30 67 Frameshift Splicing IVS21 ϩ 1G ϾT Intron 21 67,142 IVS26-1G ϾA Intron 26 67,111,112 Deletion 179del9 Exon 2 107 179-195del Exon 2 67 960delC Exon 8 88 1944del22 Exon 16 12 1995delG Exon 16 67 2322delC Exon 18 67 2542delG Exon 19 67 3775delT Exon 27 12,67 4101delC Exon 29 67 Insertion 938-939insT Exon 8 67 4220insAGAA Exon 30 12 Intragenic deletion Exon 23-29 67,112 Exon 15 67 Intergenic deletion ABCC6 12,88 LOCAL RETINAL TRANSPORT FUNCTION OF ABCC6 ABCC6 Expression in the Retina Bergen et al detected ABCC6 expression in various tissues in man.12 Low expression levels of ABCC6 were observed in the retina as well as other tissues usually affected by PXE, including skin and vessel wall. Login to comment

[hide] Novel ABCC6 mutations in pseudoxanthoma elasticum. J Invest Dermatol. 2004 Mar;122(3):608-13. Chassaing N, Martin L, Mazereeuw J, Barrie L, Nizard S, Bonafe JL, Calvas P, Hovnanian A
Novel ABCC6 mutations in pseudoxanthoma elasticum.
J Invest Dermatol. 2004 Mar;122(3):608-13., [PMID:15086542]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a heritable connective tissue disorder caused by mutations in an ABC (ATP-Binding Cassette) transporter gene (ABCC6), which manifests with cutaneous, ophthalmologic, and cardiovascular findings. We studied a cohort of 19 families with PXE, and identified 16 different mutations, nine of which were novel variants. The mutation detection rate was about 77%. We found that arginine codon 518 was, with the previously described R1141X and EX23_29del, a recurrently mutated amino acid (11.5% of the mutations detected for each variant R518Q and R518X). No clear delineation of genotype/phenotype correlation was identified, and marked intra-familial variability of the disease was seen in one family. One family with pseudodominant inheritance displayed three distinct ABCC6 mutations, providing further evidence for the probable exclusive recessive transmission of PXE. These data contribute to the expanding database of ABCC6 mutations, to the description of phenotypic variability, and inheritance in PXE, and should be helpful for genetic counselling.

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3 We found that arginine codon 518 was, with the previously described R1141X and EX23_29del, a recurrently mutated amino acid (11.5% of the mutations detected for each variant R518Q and R518X). Login to comment
29 2 0 0 6 France M 15 R1141X 3421C4T 24 2 0 1 R1141X 3421C4T 24 7 Morocco F 26 R518Q 1553G4A 12 1 1 1 R518Q 1553G4A 12 8 Turkey F 21 A766D 2297C4A 18 1 0 0 A766D 2297C4A 18 9 France F 41 R518Q 1553G4A 12 1 0 0 T1130M 3389C4T 24 10 France F 30 R518X 1552C4T 12 1 0 0 R518X 1552C4T 12 11-1 Algeria F 75 NA 1 0 0 T1130M 3389C4T 24 11-2 M 39 D1238H 3712G4C 26 1 0 0 11-3 F 36 Q363_R373del 1088-1120del 9 2 0 0 D1238H 3712G4C 26 12 France M 58 ?/? Login to comment
47 In our cohort, we found that arginine codon 518 is a new recurrent mutated amino acid, corresponding to 23% of the mutations detected in the family studied (11.5% for R518X and 11.5% for R518Q). Login to comment

[hide] Pseudoxanthoma elasticum-a connective tissue disea... J Invest Dermatol. 2004 Mar;122(3):ix-x. Uitto J
Pseudoxanthoma elasticum-a connective tissue disease or a metabolic disorder at the genome/environment interface?
J Invest Dermatol. 2004 Mar;122(3):ix-x., [PMID:15086584]

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29 In particular, these investigators found that arginine at position 518 was a recurrently mutated amino acid (either R518Q or R518X), and the remaining novel genetic lesions consisted of missense mutations, a nonsense mutation, a small in-frame deletion, and two potential splicing mutations. Login to comment

[hide] ABCC6 mutations in Italian families affected by ps... Hum Mutat. 2004 Nov;24(5):438-9. Gheduzzi D, Guidetti R, Anzivino C, Tarugi P, Di Leo E, Quaglino D, Ronchetti IP
ABCC6 mutations in Italian families affected by pseudoxanthoma elasticum (PXE).
Hum Mutat. 2004 Nov;24(5):438-9., [PMID:15459974]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a genetic disorder, characterized by cutaneous, ocular and cardiovascular clinical symptoms, caused by mutations in a gene (ABCC6) that encodes for MRP6 (Multidrug Resistance associated Protein 6), an ATP-binding cassette membrane transporter. The ABCC6 gene was sequenced in 38 unrelated PXE Italian families. The mutation detection rate was 82.9%. Mutant alleles occurred in homozygous, compound heterozygous and heterozygous forms, however the great majority of patients were compound heterozygotes. Twenty-three different mutations were identified, among which 11 were new. Fourteen were missense (61%); five were nonsense (22%); two were frameshift (8.5%) and two were putative splice site mutations (8.5%). The great majority of mutations were located from exon 24 to 30, exon 24 being the most affected. Among the others, exons 9 and 12 were particularly involved. Almost all mutations were located in the intracellular site of MRP6. A positive correlation was observed between patient's age and severity of the disorder, especially for eye alterations. The relevant heterogeneity in clinical manifestations between patients with identical ABCC6 mutations, even within the same family, seems to indicate that, apart from PXE causative mutations, other genes and/or metabolic pathways might influence the clinical expression of the disorder.

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64 PXE-causative Mutations Recognized (on one and both alleles) in Italian Patients Family/ Proband Affected subjects Age / gender Clinical score Tot Mutations* Allele 1 Allele 2 Mutation type 001 32 F S2,E2 4 p.R518Q p.T1130MI-3097 002 36 M S3,E2,V2,C2 9 p.R518Q p.T1130M I-3013 001 46 F S1,E3 4 p.R1339C None found I-3094 001 57 F S2,E2 4 p.C440G p.P1346S I-3103 001 57 M E2 2 p.V810M p.R1114C I-3076 001 57 F S2,E4,V3 9 p.R1339C p.R1339C I-3016 001 69 F S3,E2,V2 7 p.N411K p.R1138Q missense I-3082 001 23 M S1,E2 3 p.R518Q p.R1141X I-3074 001 27 F S2,E2 4 p.T364R p.R518X I-3015 001 27 F S2,E3 5 p.Q378X p.R600G I-3062 001 45 M S2,E4,V2 8 p.R1141X p.E1400K 001 50 F S1 1 p.R1275X p.E1400K 002 60 F S3,E3 6 p.R1275X p.E1400K I-3067 003 66 F S2,E2 4 p.R1275X p.E1400K 001 61 F S3,E2 4 p.R518Q p.R1141XI-3027 002 63 F S3,E4,V3 10 p.R518Q p.R1141X missense + nonsense 001 23 F S3,E2 5 p.R1141X p.R1141XI-3056** 002 32 M S2,E2 4 p.R1141X p.R1141X 001 27 F S1,E2 3 p.R1141X p.R1141XI-3057** 002 31 M S3,E2 5 p.R1141X p.R1141X 001 28 M S1,E2 3 p.R1141X None foundI-3045 002 32 F S3,E2,V1 6 p.R1141X None found I-3107 001 29 M S2,E1 3 p.R1030X p.R1141X I-3073 001 31 F S3,E2 5 p.R1141X p.R1141X I-3111 001 32 F S1,E2 3 p.R1141X p.R1141X I-3090 001 34 F S2,E1 3 p.R1141X p.R1141X I-3001 001 37 F S3,E2,V2 7 p.R1030X None found 001 40 F S2,E2 4 p.R1141X p.R1141XI-3007** 002 48 F S1,E2 3 p.R1141X p.R1141X I-3114 001 40 M S2,E2,V3,C1,G2 10 p.R518X p.R518X I-3054 001 44 F S2,E3 5 p.R518X p.R518X 001 47 F S3,E4,C2,G1 10 p.R1141X p.R1141XI-3055** 002 50 F S3,E3 6 p.R1141X p.R1141X 001 50 F S3,E4,V3,C2 12 p.R518X p.R1030X 002 52 F S3,E4,V3 10 p.R518X p.R1030X I-3017 003 55 F S3,E2 5 p.R518X p.R1030X I-3100 001 52 M S3,E3 6 p.Q378X p.Q378X I-3051 001 53 F S3,E4,V2 9 p.R1141X p.R1141X I-3034 001 53 M S3,E4,V3 10 p.R1141X p.R1141X I-3093 001 57 F S3,E3,V2,C3 11 p.R518X None found I-3087 001 57 F S3,E4,V2,C2 11 p.Q378X p.Q378X I-3040 001 60 F S3,E4,V2 9 p.R1141X None found I-3033 001 62 F S3,E4 7 p.R1141X p.R1141X nonsense I-3026 001 36 F S3,E2,G1 6 p.R518X c.2248-2_2248- 1del I-3024 001 40 F S1,E2,V3 6 p.R518X p.L1182PfsX96 I-3072 001 41 F S2,E2,C2 6 p.M1127T c.3736-1G>A I-3002 001 50 F S3,E2 5 p.A820P c.3736-1G>A others Family/ Proband Affected subjects Age / gender Clinical score Tot Mutations* Allele 1 Allele 2 Mutation type 002 57 F S2,E4 6 p.A820P c.3736-1G>A I-3008 001 53 F S2,E2,C1 5 p.M1440CfsX24 p.M1440CfsX24 Patients are identified by an international code: I = Italian, 3001 = family number (European patients are numerated from 3000), 001 = subject number. Login to comment
72 ABCC6/MRP6 Mutations Found in Italian PXE Patients Number of families INTRON EXON cDNA* PROTEIN* References 1 9 c.1091C>G p.T364R Pulkkinen et al., 2001 3 9 c.1132C>T p.Q378X Pulkkinen et al., 2001; Cai et al., 2001 1 10 c.1318T>G p.C440G Present study 1 10 c.1233T>G p.N411K Le Saux et al., 2001 7 12 c.1552C>T p.R518X Meloni et al., 2001; Chassaing et al., 2004 3 12 c.1553G>A p.R518Q Le Saux et al., 2001; Chassaing et al., 2004 1 14 c.1798C>T p.R600G Present study 1 17 c.2248-2_2248- 1del - Present study 1 19 c.2428G>A p.V810M Present study 1 19 c.2458G>C p.A820P Present study 3 23 c.3088C>T p.R1030X Le Saux et al., 2001 1 24 c.3340C>T p.R1114C Present study 1 24 c.3380C>T p.M1127T Present study 1 24 c.3389C>T p.T1130M Chassaing et al., 2004; Gotting et al., 2004 1 24 c.3413G>A p.R1138Q Le Saux et al., 2000; Ringpfeil et al., 2000; Le Saux et al., 2001 13 24 c.3421C>T p.R1141X Bergen et al., 2000; Germain et al., 2000; Ringpfeil et al., 2000; Le Saux et al., 2001; Pulkkinen et al., 2001; Uitto et al., 2001; Hu et al., 2003 ; Gotting et al., 2004 1 25 c.3544_3544dupC p.L1182PfsX96 Present study 2 26 c.3736-1G>A - Ringpfeil et al., 2000; Le Saux et al., 2001 1 27 c.3823C>T p.R1275X Present study 2 28 c.4015C>T p.R1339C Le Saux et al., 2001 1 28 c.4036C>T p.P1346S Present study 2 29 c.4198G>A p.E1400K Chassaing et al., 2004 1 30 c.4318_4318delA p.M1440CfsX24 Present study The number of families in which a specific mutation was found (in heterozygous and in homozygous state) is reported. Login to comment
80 In exon 12, mutation c.1552C>T (p.R518X) was homozygous in two families and heterozygous in other 5 families, and mutation c.1553G>A (p.R518Q) was heterozygous in 3 unrelated families. Login to comment
118 Some were recurrent mutations (p.Q378X, p.R518X, p.R518Q, p.R1141X), however the majority of mutations were sporadic variants. Login to comment

[hide] Pseudoxanthoma elasticum: a clinical, pathophysiol... J Med Genet. 2005 Dec;42(12):881-92. Epub 2005 May 13. Chassaing N, Martin L, Calvas P, Le Bert M, Hovnanian A
Pseudoxanthoma elasticum: a clinical, pathophysiological and genetic update including 11 novel ABCC6 mutations.
J Med Genet. 2005 Dec;42(12):881-92. Epub 2005 May 13., [PMID:15894595]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is an inherited systemic disease of connective tissue primarily affecting the skin, retina, and cardiovascular system. It is characterised pathologically by elastic fibre mineralisation and fragmentation (so called "elastorrhexia"), and clinically by high heterogeneity in age of onset and the extent and severity of organ system involvement. PXE was recently associated with mutations in the ABCC6 (ATP binding cassette subtype C number 6) gene. At least one ABCC6 mutation is found in about 80% of patients. These mutations are identifiable in most of the 31 ABCC6 exons and consist of missense, nonsense, frameshift mutations, or large deletions. No correlation between the nature or location of the mutations and phenotype severity has yet been established. Recent findings support exclusive recessive inheritance. The proposed prevalence of PXE is 1/25,000, but this is probably an underestimate. ABCC6 encodes the protein ABCC6 (also known as MRP6), a member of the large ATP dependent transmembrane transporter family that is expressed predominantly in the liver and kidneys, and only to a lesser extent in tissues affected by PXE. The physiological substrates of ABCC6 remain to be determined, but the current hypothesis is that PXE should be considered to be a metabolic disease with undetermined circulating molecules interacting with the synthesis, turnover, or maintenance of elastic fibres.

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378 Interestingly, among the 49 different missense mutations in ABCC6 (42 previously published and seven new ones in the present study), the majority (43) replace critical amino acids in intracellular domains (seven and 19 mutations are located in I1424T R1459C 4220insAGAA 4318delA G1354R D1361N K1394N E1400K R1298X 410delC 418delG 3775delT R1275X R1221C D1238H W1223X Q1237X IVS26-1G→A R1114C R1114H R1114P S1121W M1127T T1130M R1138P R1138Q R1138W R1141X R1164X R765Q A766D Y768X A781V 2322delC IVS19-2delAG T364R R391G Q378X Q363_R373del 938_939insT 960delC IVS8+2delTG G199X Y227X 179_195del 179_187del G226R V74del Q749X IVS17-12delTT IVS14-5T→G IVS13-29T→A R600G V1298F G1299S T1301I G1302R A1303P S1307P R1314Q R1314W G1321S L1335P R1339C P1346S Q1347H R1030X F1048del R807Q V810M A820P 254delG L673P 1944_1966del 1995delG R518Q R518X K502M A455P G992R IVS21+1G→T G1203DF568SN411K C440G IVS25-3C→A 3544dupC Ex23_29del 30 Ex15del ABCC6del 252015105 Figure 10 Position of the mutations in the ABCC6 gene. Login to comment
379 Table 2 ABCC6 mutations Nucleotide variation Protein alteration Location (gene ) Location (protein) Reference Missense 676 GRA G226R Exon 7 CL 3 This study 1091 CRG T364R Exon 9 TS 7 63, 78 1171 ARG R391G Exon 9 CL 4 88 1233 TRG N411K Exon 10 CL 4 63, 90 1318 TRG C440G Exon 10 TS 8 63 1363 GRC A455P Exon 11 TS 9 86 1505 ART K502M Exon 12 CL 5 This study 1553 GRA R518Q Exon 12 CL 5 63, 86, 88, 90 1703 TRC F568S Exon 13 ECL 5 90 1798 CRT R600G Exon 14 CL 6 63 2018 TRC L673P Exon 16 NBF 1 90 2294 GRA R765Q Exon 18 NBF 1 87, 90 2297 CRA A766D Exon 18 NBF 1 88 2342 CRT A781V Exon 18 NBF 1 This study 2420 GRA R807Q Exon 19 NBF 1 This study 2428 GRA V810M Exon 19 NBF1 63 2458 GRC A820P Exon 19 NBF1 63 2965 GRC G992R Exon 22 ECL 6 This study 3340 CRT R1114C Exon 24 CL 8 63 3341 GRA R1114H Exon 24 CL 8 87 3341 GRC R1114P Exon 24 CL 8 90 3362 CRG S1121W Exon 24 CL 8 90 3380 CRT M1127T Exon 24 CL 8 63 3389 CRT T1130M Exon 24 CL 8 63, 87, 88 3412 CRT R1138W Exon 24 CL 8 17 3413 GRC R1138P Exon 24 CL 8 90 3413 GRA R1138Q Exon 24 CL 8 17, 63, 88, 90 3608 GRA G1203D Exon 25 TS17 90 3663 CRT R1221C Exon 26 COOH 87 3712 GRC D1238H Exon 26 COOH 88 3892 GRT V1298F Exon 28 NBF 2 90 3895 GRA G1299S Exon 28 NBF 2 This study 3902 CRT T1301I Exon 28 NBF 2 90 3904 GRA G1302R Exon 28 NBF 2 87, 90 3907 GRC A1303P Exon 28 NBF 2 87, 90 3919 TRC S1307P Exon 28 NBF 2 This study 3940 CRT R1314W Exon 28 NBF 2 90 3941 GRA R1314Q Exon 28 NBF 2 90 3961 GRA G1321S Exon 28 NBF 2 90 4004 TRC L1335P Exon 28 NBF 2 88 4015 CRT R1339C Exon 28 NBF 2 18, 63, 90 4036 CRT P1346S Exon 28 NBF 2 63 4041 GRC Q1347H Exon 28 NBF 2 90 4060 GRC G1354R Exon 29 NBF 2 78, 86 4081 GRA D1361N Exon 29 NBF 2 90 4182 GRT K1394N Exon 29 NBF 2 87 4198 GRA E1400K Exon 29 NBF 2 63, 88 4271 TRC I1424T Exon 30 NBF 2 90 4377 CRT R1459C Exon 30 NBF 2 87 Nonsense 595 CRT G199X Exon 5 89 681 CRG Y227X Exon 7 84 1132 CRT Q378X Exon 9 63, 78, 83 1552 CRT R518X Exon 12 63, 84, 88 2245 CRT Q749X Exon 17 87 2304 CRA Y768X Exon 18 90 3088 CRT R1030X Exon 23 63, 90 3421 CRT R1141X Exon 24 15, 17, 18, 63, 78, 85, 87, 88, 90 3490 CRT R1164X Exon 24 84, 85, 88 3668 GRA W1223X Exon 26 88 3709 CRT Q1237X Exon 26 90 3823 CRT R1275X Exon 27 63 4192 CRT R1398X Exon 29 90 Splicing alteration IVS8+2delTG Intron 8 This study IVS13-29 TRA Intron 13 This study IVS14-5 TRG Intron 14 This study IVS17-12delTT Intron 17 87 IVS18-2delAG Intron 17 63 IVS21+1 GRT Intron 21 86, 90 IVS25-3 CRA Intron 25 88 IVS26-1 GRA Intron 26 17, 63, 90 Insertion 938_939insT Frameshift Exon 8 90 3544dupC Frameshift Exon 25 63 4220insAGAA Frameshift Exon 30 15, 87 Small deletion 179_187del Frameshift Exon 2 78 179_195del Frameshift Exon 2 90 Pseudoxanthoma elasticum www.jmedgenet.com NBF1 and NBF2, respectively), four are located in transmembrane domains, and only two mutations have been identified in extracellular domains. Login to comment
385 A common founder effect was identified for mutation R1141X in French and Italian populations.63 88 We found that arginine codon 518 was a recurrently mutated amino acid in a cohort of 19 French families with PXE (11.5% of the detected mutations for each variant R518Q and R518X).88 These two mutations represent 19% of the mutations detected in the Italian population.63 In Japanese patients, neither R1141X nor Ex23_29del mutations were identified, whereas mutations 2542delG and Q378X account for 53% and 25%, respectively.93 In South African families of Afrikaaners, mutation R1339C represents more than half the mutations detected,28 with a common haplotype indicating a founder effect.27 28 These mutations are rarely identified in American or European populations.90 The detection rate in different studies varies from 0.55 to 0.83.63 87 88 90 Lack of mutation detection in some patients could reflect exonic deletions (for example, deletion of exon 15), splice site mutations distant from the coding sequence, mutations in the gene regulatory sequences, or investigation of patients with acquired PXE-like syndrome not related to ABCC6 mutations, such as seen in b thalassaemia and sickling syndromes (see below).94 95 Locus heterogeneity of PXE is unlikely, but cannot currently be ruled out. Login to comment

[hide] Molecular genetics of pseudoxanthoma elasticum: ty... Hum Mutat. 2005 Sep;26(3):235-48. Miksch S, Lumsden A, Guenther UP, Foernzler D, Christen-Zach S, Daugherty C, Ramesar RK, Lebwohl M, Hohl D, Neldner KH, Lindpaintner K, Richards RI, Struk B
Molecular genetics of pseudoxanthoma elasticum: type and frequency of mutations in ABCC6.
Hum Mutat. 2005 Sep;26(3):235-48., [PMID:16086317]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a systemic heritable disorder that affects the elastic tissue in the skin, eye, and cardiovascular system. Mutations in the ABCC6 gene cause PXE. We performed a mutation screen in ABCC6 using haplotype analysis in conjunction with direct sequencing to achieve a mutation detection rate of 97%. This screen consisted of 170 PXE chromosomes in 81 families, and detected 59 distinct mutations (32 missense, eight nonsense, and six likely splice-site point mutations; one small insertion; and seven small and five large deletions). Forty-three of these mutations are novel variants, which increases the total number of PXE mutations to 121. While most mutations are rare, three nonsense mutations, a splice donor site mutation, and the large deletion comprising exons 23-29 (c.2996_4208del) were identified as relatively frequent PXE mutations at 26%, 5%, 3.5%, 3%, and 11%, respectively. Chromosomal haplotyping with two proximal and two distal polymorphic markers flanking ABCC6 demonstrated that most chromosomes that carry these relatively frequent PXE mutations have related haplotypes specific for these mutations, which suggests that these chromosomes originate from single founder mutations. The types of mutations found support loss-of-function as the molecular mechanism for the PXE phenotype. In 76 of the 81 families, the affected individuals were either homozygous for the same mutation or compound heterozygous for two mutations. In the remaining five families with one uncovered mutation, affected showed allelic compound heterozygosity for the cosegregating PXE haplotype. This demonstrates pseudo-dominance as the relevant inheritance mechanism, since disease transmission to the next generation always requires one mutant allelic variant from each parent. In contrast to other previous clinical and molecular claims, our results show evidence only for recessive PXE. This has profound consequences for the genetic counseling of families with PXE.

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146 Further mutations with founder alleles among the family chromosomes analyzed are the c.4016G4A (p.R1339Q) mutation, the c.1553G4A (p.R518Q) mutation, and the c.27871 1G4T splice donor site mutation (Supplementary Table S2). Login to comment
261 The four chromosomes that carry the p.R518Q mutation share a related haplotype, which suggests a founder mutation that originates in our cohort from Switzerland. Login to comment

[hide] Mutation detection in the ABCC6 gene and genotype-... J Med Genet. 2007 Oct;44(10):621-8. Epub 2007 Jul 6. Pfendner EG, Vanakker OM, Terry SF, Vourthis S, McAndrew PE, McClain MR, Fratta S, Marais AS, Hariri S, Coucke PJ, Ramsay M, Viljoen D, Terry PF, De Paepe A, Uitto J, Bercovitch LG
Mutation detection in the ABCC6 gene and genotype-phenotype analysis in a large international case series affected by pseudoxanthoma elasticum.
J Med Genet. 2007 Oct;44(10):621-8. Epub 2007 Jul 6., [PMID:17617515]

Abstract [show]
BACKGROUND: Pseudoxanthoma elasticum (PXE), an autosomal recessive disorder with considerable phenotypic variability, mainly affects the eyes, skin and cardiovascular system, characterised by dystrophic mineralization of connective tissues. It is caused by mutations in the ABCC6 (ATP binding cassette family C member 6) gene, which encodes MRP6 (multidrug resistance-associated protein 6). OBJECTIVE: To investigate the mutation spectrum of ABCC6 and possible genotype-phenotype correlations. METHODS: Mutation data were collected on an international case series of 270 patients with PXE (239 probands, 31 affected family members). A denaturing high-performance liquid chromatography-based assay was developed to screen for mutations in all 31 exons, eliminating pseudogene coamplification. In 134 patients with a known phenotype and both mutations identified, genotype-phenotype correlations were assessed. RESULTS: In total, 316 mutant alleles in ABCC6, including 39 novel mutations, were identified in 239 probands. Mutations were found to cluster in exons 24 and 28, corresponding to the second nucleotide-binding fold and the last intracellular domain of the protein. Together with the recurrent R1141X and del23-29 mutations, these mutations accounted for 71.5% of the total individual mutations identified. Genotype-phenotype analysis failed to reveal a significant correlation between the types of mutations identified or their predicted effect on the expression of the protein and the age of onset and severity of the disease. CONCLUSIONS: This study emphasises the principal role of ABCC6 mutations in the pathogenesis of PXE, but the reasons for phenotypic variability remain to be explored.

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254 Collectively, the mutations in exons 24 and 28, including the common mutations R1141X and del 23-29, accounted for 71.5% of all the 316 mutations identified in this study (table 2), and the 11 most prevalent mutations (R1141X, del23-29, R1339C, R1164X, 2787+1GRT, G1302R, R1138Q, R1138W, Q378X, R1314W, R518Q) accounted for 70% (223 of 316) of the mutant alleles identified (table 2). Login to comment
262 Genotype-phenotype correlations The comparison of subjects whose mutations would probably have resulted in no functional protein with those whose mutations would probably have resulted in some functional Table 2 Distinct mutations identified in the international case series of 271 patients with PXE Nucleotide change*À Predicted consequenceÀ Frequency (alleles) Exon-intron location Domain affected` Mutant alleles (%) References1 c.105delA p.S37fsX80 2 2 0.6 28 c.177-185del9 p.R60_Y62del 1 2 0.3 9, 28 c.179del12ins3 p. R60_W64del L60_R61ins 1 2 0.3 c.220-1gRc SJ 1 IVS 2 0.3 c.724gRt p.E242X 1 7 0.3 c.938insT FS 1 8 0.3 25 c.998+2delT SJ 1 IVS 8 0.3 2, 21 c.998+2del2 SJ 1 IVS 8 0.3 18 c.951cRg p.S317R 2 9 TM6 0.6 28 c.1087cRt p.Q363X 1 9 0.3 c.1091gRa p.T364R 1 9 TM7 0.3 9, 19, 21, 28 c.1132cRt p.Q378X 4 9 1.2 9, 17-19, 28, 37 c.1144cRt p.R382W 2 9 IC4 0.6 c.1171aRg p.R391G 3 9 IC4 0.9 9, 18, 28, 37 c.1176gRc p.K392N 1 9 IC4 0.3 c.1388tRa p.L463H 1 11 TM9 0.3 c.1484tRa p.L495H 1 12 IC5 0.3 28 c.1552cRt p.R518X 2 12 0.6 18, 19, 27, 28, 37 c.1553gRa p.R518Q 4 12 IC5 1.2 18, 19, 24, 28, 31 c.1603tRc p.S535P 1 12 TM10 0.3 c.1703tRc p.F568S 1 13 TM11 0.3 24 c.1798cRt p.R600C 1 14 TM11 0.3 c.1857insC FS 1 14 0.3 c.1987gRt p.G663C 1 16 NBF1 0.3 c.1999delG FS 1 16 0.3 c.2070+5GRA SJ 2 IVS 16 0.6 c.2093aRc p.Q698P 2 17 NBF1 0.6 c.2097gRt p.E699D 1 17 NBF1 0.3 c.2177tRc p.L726P 1 17 NBF1 0.3 c.2237ins10 FS 2 17 0.6 c.2252tRa p.M751K 1 18 NBF1 0.3 20, 37 c.2263gRa p.G755R 2 18 NBF1 0.6 c.2278cRt p.R760W 3 18 NBF1 0.9 20, 28, 32, 37 c.2294gRa p.R765Q 2 18 NBF1 0.6 20-22, 25, 28, 32, 37 c.2329gRa p.D777N 1 18 NBF1 0.3 c.2359gRt p.V787I 1 18 NBF1 0.3 c.2432cRt p.T811M 1 19 IC6 0.3 6 c.2643gRt p.R881S 1 20 IC6 0.3 c.2787+1GRT SJ 9 IVS 21 2.8 17, 20, 24, 28, 31, 37 c.2814cRg p.Y938X 1 22 0.3 c.2820insC FS 1 22 0.3 c.2831cRt p.T944I 1 22 TM12 0.3 c.2848gRa p.A950T 1 22 TM12 0.3 c.2974gRc p.G992R 1 22 TM13 0.3 2, 42 c.3340cRt p.R1114C 2 24 IC8 0.6 19, 28, 32, 37, 41 c.3389cRt p.T1130M 3 24 IC8 0.9 18, 19, 21, 22, 28, 30, 32, 37, 41 c.3398gRc p.G1133A 1 24 IC8 0.3 c.3412gRa p.R1138W 7 24 IC8 2.2 28, 30, 37 c.3413cRt p.R1138Q 7 24 IC8 2.2 18, 19, 24, 25, 28, 30, 32, 37, 41 c.3415gRa p.A1139T 2 24 IC8 0.6 c.3415gRa & c.2070+5GRA* p.A1139T & SJ 1 24, IVS 16 IC8 0.3 c.3415gRa & c.4335delG* p.A1139T & FS 1 24, 30 IC8 0.3 c.3421cRt p.R1141X 92 24 29.3 5, 9, 15,18, 19, 21, 22, 24, 28, 30-32, 33, 37, 41 c.3427cRt p.Q1143X 1 24 0.3 c.3490cRt p.R1164X 15 24 4.7 18, 27, 28, 31, 33 c.3491gRa p.R1164Q 1 24 IC8 0.3 28 c.3661cRt p.R1221C 1 26 IC9 0.3 21, 22, 28, 29 c.3662gRa p.R1221H 2 26 IC9 0.6 40 c.3676cRa p.L1226I 1 26 IC9 0.3 c.3722gRa p.W1241X 2 26 0.6 c.3774insC FS 2 27 0.6 c.3775delT p.G1259fsX1272 3 27 0.9 15, 25, 28, 41 c.3880-3882del p.K1294del 1 27 0.3 c.3883-5GRA SJ 1 IVS 27 0.3 c.3892gRt p.V1298F 1 28 NBF2 0.3 25 c.3904gRa p.G1302R 7 28 NBF2 2.2 21, 22, 25, 28 c.3907gRc p.A1303P 1 28 NBF2 0.3 21, 22, 25, 28 c.3912delG FS 1 28 0.3 28 c.3940cRt p.R1314W 4 28 NBF2 1.2 24, 25, 32, 36 c.3941gRa p.R1314Q 1 28 NBF2 0.3 25, 28, 32, 36, 41 c.4004tRa p.L1335Q 1 28 NBF2 0.3 c.4015cRt p.R1339C 16 28 NBF2 5.0 19, 25, 28, 33 c.4016gRa p.R1339H 2 28 NBF2 0.6 c.4025tRc p.I1342T 1 28 NBF2 0.3 protein did not yield significant differences. Login to comment

[hide] Novel clinico-molecular insights in pseudoxanthoma... Hum Mutat. 2008 Jan;29(1):205. Vanakker OM, Leroy BP, Coucke P, Bercovitch LG, Uitto J, Viljoen D, Terry SF, Van Acker P, Matthys D, Loeys B, De Paepe A
Novel clinico-molecular insights in pseudoxanthoma elasticum provide an efficient molecular screening method and a comprehensive diagnostic flowchart.
Hum Mutat. 2008 Jan;29(1):205., [PMID:18157818]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a heritable connective tissue disorder characterized by ocular, cutaneous and cardiovascular manifestations. It is caused by mutations in the ABCC6 gene (chr. 16p13.1), encoding a transmembrane transporter protein, the substrate and biological function of which are currently unknown. A comprehensive clinical and molecular study of 38 Belgian PXE probands and 21 relatives (4 affected and 17 carriers) was performed. An extensive clinical evaluation protocol was implemented with serial fundus, skin and cardiovascular evaluation. We report on 14 novel mutations in the ABCC6 gene. We observed extensive variability in severity of both cutaneous and ocular lesions. The type of skin lesion however usually remained identical throughout the evolution of the disorder, while ophthalmological progression was mainly due to functional decline. Peripheral artery disease (53%) and stroke (15%) were significantly more prevalent than in the general population (10-30% and 0.3-0.5% respectively). Interestingly, we also observed a relatively high incidence of subclinical peripheral artery disease (41%) in our carrier population. We highlight the significance of peripheral artery disease and stroke in PXE patients as well as the subclinical manifestations in carriers. Through follow-up data we gained insight into the natural history of PXE. We propose a cost- and time-efficient two-step method of ABCC6 analysis which can be used in different populations. Additionally, we created a diagnostic flowchart and attempted to define the role of molecular analysis of ABCC6 in the work-up of a PXE patient.

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83 Genotype and Phenotype of 42 Belgian PXE Patients Patient S e x Age/Clinical score at initial presentation Age/Clinical score at most recent follow-up Mutations* Allele 1 Allele 2 01-001 F 52 - S0, E2 65 - S0, E3, HT p.R1141X c.3421C>T p.R760Q c.2279G>A 02-001 M 18 - S1, E2, VR-I 18 - S1, E2, VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 03-001 F 59 - S1, E4 75 - S1, E4, HT, IC, VR-I p.R1141X c.3421C>T p.N793L c.2379C>G 04-001 F 36 - S3, E2 36 - S3, E2 p.N466Y c.1396A>T p.R1339H c.4016G>A 05-001 F 26 - S1, E4 43 - S3, E4, VR-I p.R1141X c.3421C>T p.T364M c.1091C>T 06-001 F 36 - S2, E4 44 - S2, E4, P p.A1303P c.3907G>C None found - 07-001 M 48 - S1, E2, HT 58 - S1, E4, HT p.R1141X c.3421C>T p.R1141X c.3421C>T 08-001 F 26 - S1, E0 44 - S2, E2 p.R1141X c.3421C>T p.R760Q c.2279G>A 09-001 M 49 - S0, E3, P, GIB 65 - S2, E4, P, HT, VR-I, GIB p.A1303P c.3907G>C None found - 10-001 F 46 - S1, E2 63 - S3, E4, HT, AP,VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 11-001 M 25 - S1, E2, GIB 37 - S1, E3, GIB p.R1141X c.3421C>T None found - 12-001 F 52 - S1, E4, CI, HT, VR-I 52 - S1, E4, IC, HT, VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 12-002 F 40 - S1, E2, HT, MVP, VR-I 40 - S1, E2, HT, MVP, VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 13-001 F 65 - S0, E2 80 - S0, E2, P, VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 13-002 F 57 - S3, E4 73 - S3, E4, HT, CI, VR-I p.R1141X c.3421C>T p.R1141X c.3421C>T 14-001 F 23 - S1, E2 27 - S1, E2 p.S398R c.1194C>G - c.3364delT 15-001 F 27 - S1, E2 27 - S1, E2 p.R1138W c.3412C>T p.R1221H c.3662G>A 16-001 M 51 - S2, E2 54 - S2, E2 p.R1141X c.3421C>T p.R1141X c.3421C>T 17-001 M 42 - S1, E3, IC 58 - S1, E3, IC Del23-29 - p.R518Q c.1553G>A 18-001 M 63 - S1, E4 63 - S1, E4 p.E1400K c.4198G>A None found - 19-001 F 34 - S2, E2 50 - S2, E2 p.A1303P c.3907G>C p.R1398X c.4192C>T 20-001 F 52 - S2, E2, HT, IC, GIB 68 - S2, E4, HT, IC, GIB p.R1141X c.3421C>T None found - 21-001 M 20 - S1, E2 26 - S1, E2 p.R1141X c.3421C>T p.R1141X c.3421C>T 22-001 M 53 - S2, E2, IC, AP 69 - S2, E2, HT, IC, AP p.M751K c.2252T>A p.R1164Q c.3491G>A 23-001 F 20 - S1, E2 27 - S1, E2, P, VR-I p.G666V c.1996G>T - c.1868-5T>G 24-001 M 54 - S1, E2 57 - S1, E2 p.T500P c.1498A>C p.E521D c.1563G>C 25-001 F 50 - S1, E3, HT, MI 57 - S2, E3, HT, MI p.R1141X c.3421C>T p.R1141X c.3421C>T 26-001 M 52 - S2, E4, HT 68 - S2, E4, HT, CI p.M751K c.2252T>A Del23-29 - 27-001 F 61 - S3, E4 68 - S3, E4, P, CI, AP p.R1141X c.3421C>T - c.4104delC Allele 2 28-001 F 31 - S1, E2 32 - S1, E2 - c.1674DelC p.R765W c.2293C>T Patient S e x Age/Clinical score at initial presentation Age/Clinical score at most recent follow-up Mutations* Allele 1 Allele 2 29-001 M 30 - S1, E3 32 - S1, E3 p.E125K c.373G>A p.L1025P c.3074T>C 30-001 M 65 - S0, E2, HT, CI, MI 66 - S0, E2, HT, CI, MI p.G1405S c.4213G>A None found - 31-001 F 38 - S1, E4 39 - S1, E4 p.R1141X c.3421C>T Del23-29 - 32-001 M 22 - S1, E2 36 - S1, E2 p.R1141X c.3421C>T p.R518Q c.1553G>A 33-001 F 45 - S2, E3, P 61 - S2, E3, P, VR-II p.R1141X c.3421C>T p.R1141X c.3421C>T 34-001 F 65 - S1, E4, HT 81 - S1, E4, HT, AP p.R1141X c.3421C>T p.T1301I c.3902C>T 35-001 F 62 - S2, E2 78 - S2, E2, HT - c.175_179del p.G1354R c.4060G>C 35-002 F 58 - S2, E2 74 - S2, E4 - c.175_179del p.G1354R c.4060G>C 35-003 M 67 - S2, E2 79 - S2, E3, HT, VR-I - c.175_179del p.G1354R c.4060G>C 36-001 M 53 - S1, E4 59 - S1, E4, HT, AP p.R1114H c.3341G>A p.Q1237X c.3709C>T 37-001 M 18 - S3, E2 18 - S3, E2 p.Q981H c.2943G>T - c.3507-3C>A 38-001 F 27 - S1, E2 27 - S1, E2 p.G1263R c.3787G>A - c.4182delG Table 1 represents the sex of all patients (M = male; F= female) and the age (in years - italics), respectively at initial presentation and last follow-up. Login to comment

[hide] Spectrum of genetic variation at the ABCC6 locus i... J Dermatol Sci. 2009 Jun;54(3):198-204. Epub 2009 Mar 31. Ramsay M, Greenberg T, Lombard Z, Labrum R, Lubbe S, Aron S, Marais AS, Terry S, Bercovitch L, Viljoen D
Spectrum of genetic variation at the ABCC6 locus in South Africans: Pseudoxanthoma elasticum patients and healthy individuals.
J Dermatol Sci. 2009 Jun;54(3):198-204. Epub 2009 Mar 31., [PMID:19339160]

Abstract [show]
BACKGROUND: Pseudoxanthoma elasticum (PXE) is an autosomal recessive metabolic disorder with ectopic mineralization in the skin, eyes and cardiovascular system. PXE is caused by mutations in ABCC6. OBJECTIVE: To examine 54 unrelated South African PXE patients for ABCC6 PXE causing mutations. METHODS: Patients were screened for mutations in ABCC6 using two strategies. The first involved a comprehensive screening of all the ABCC6 exons and flanking regions by dHPLC or sequencing whereas the second involved screening patients only for the common PXE mutations. The ABCC6 gene was screened in ten white and ten black healthy unrelated South Africans in order to examine the level of common non-PXE associated variation. RESULTS: The Afrikaner founder mutation, R1339C, was present in 0.41 of white ABCC6 PXE alleles, confirming the founder effect and its presence in both Afrikaans- (34/63 PXE alleles) and English-speakers (4/28). Eleven mutations were detected in the white patients (of European origin), including two nonsense mutations, 6 missense mutations, two frameshift mutations and a large deletion mutation. The five "Coloured" patients (of mixed Khoisan, Malay, European and African origin) included three compound heterozygotes with R1339C as one of the mutations. The three black patients (sub-Saharan African origin) were all apparent homozygotes for the R1314W mutation. Blacks showed a trend towards a higher degree of neurtral variation (18 variants) when compared to whites (12 variants). CONCLUSION: Delineation of the ABCC6 mutation profile in South African PXE patients will be used as a guide for molecular genetic testing in a clinical setting and for genetic counselling.

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80 Exons 12, 18 and 24 were PCR amplified and sequenced to detect the R518Q, Y768X, R1141X and R1138Q mutations and the common del23-29 mutation was detected as previously described [16]. Login to comment
121 of alleles with mutation Frequency R1339C c.4015C>T 28 NBF2 18 0.375 21 0.447 0.411 (39) [30-32] R1138Q c.3413G>A 24 CL8 5 0.104 1 0.021 0.063 (6) [3,7,32] Y768X c.2304C>A 18 NBF1 5 0.104 3 0.064 0.084 (8) [31] R1141X c.3421C>T 24 CL8 4 0.083 5 0.106 0.095 (9) [3,6,13] R518Q c.1553G>A 12 CL5 2 0.042 1 0.021 0.032 (3) [31-33] Deletion ABCC6del23-29 23-29 - 1 0.021 2 0.043 0.032 (3) [6,16,31,32] L1335P c.4004T>C 28 NBF2 2 0.042 - - Other = 0.063 (6) [3] G1302R c.3904G>A 28 NBF2 1 0.021 - - [31] L726P c.2177T>C 17 NBF1 1 0.021 - - This Study Frameshift c.3775delT 27 CL9 1 0.021 - - [6] Frameshift c.4104delC 29 NBF2 1 0.021 - - [31] Unknown - - - 7 0.146 14 0.298 0.221 (21) - Total 48 47 Mutation detection rate 0.855 0.702 0.717 a ''Coloured``, black and Indian patients are excluded from the table because of the small sample size. Login to comment
137 One was a compound heterozygote for R518Q and an unknown mutation. Login to comment
145 Mutation Afrikaans-speakersa English-speakersa No. Frequency No. Frequency R1339C 34 0.54 4 0.14 R1138Q 5 0.08 1 0.04 Y768X 5 0.08 3 0.11 R1141X 5 0.08 4 0.14 R518Q 1 0.02 2 0.07 del23-29 0 - 3 0.11 Other 0 - 4 0.14 Unknown 13 0.21 7 0.25 Total no. alleles 63 28 a Only 2 families were bilingual Afrikaans/English speaking and not included in this table. Login to comment
195 It detects 79.2% of the PXE mutations in white South African patients including: R1339C, R1138Q, Y768X, R1141X, R518Q, del23-29, L1335P and G1302R (calculated according to detection Strategy 1, Table 1). Login to comment

[hide] Novel deletions causing pseudoxanthoma elasticum u... J Hum Genet. 2010 Feb;55(2):112-7. Epub 2010 Jan 15. Costrop LM, Vanakker OO, Van Laer L, Le Saux O, Martin L, Chassaing N, Guerra D, Pasquali-Ronchetti I, Coucke PJ, De Paepe A
Novel deletions causing pseudoxanthoma elasticum underscore the genomic instability of the ABCC6 region.
J Hum Genet. 2010 Feb;55(2):112-7. Epub 2010 Jan 15., [PMID:20075945]

Abstract [show]
Mutations in ABCC6 cause pseudoxanthoma elasticum (PXE), a heritable disease that affects elastic fibers. Thus far, >200 mutations have been characterized by various PCR-based techniques (primarily direct sequencing), identifying up to 90% of PXE-causing alleles. This study wanted to assess the importance of deletions and insertions in the ABCC6 genomic region, which is known to have a high recombinational potential. To detect ABCC6 deletions/insertions, which can be missed by direct sequencing, multiplex ligation-dependent probe amplification (MLPA) was applied in PXE patients with an incomplete genotype. MLPA was performed in 35 PXE patients with at least one unidentified mutant allele after exonic sequencing and exclusion of the recurrent exon 23-29 deletion. Six multi-exon deletions and four single-exon deletions were detected. Using MLPA in addition to sequencing, we expanded the ABCC6 mutation spectrum with 9 novel deletions and characterized 25% of unidentified disease alleles. Our results further illustrate the instability of the ABCC6 genomic region and stress the importance of screening for deletions in the molecular diagnosis of PXE.

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116 )del Yes *, Min. (14956252À16213237) Max. (14852061À16807177) 28 p.Arg518Gln c.1553G4A Exon 24 del. Login to comment

[hide] [Pseudoxanthoma elasticum]. Ophthalmologe. 2006 Jun;103(6):537-51; quiz 552-3. Ladewig MS, Gotting C, Szliska C, Issa PC, Helb HM, Bedenicki I, Scholl HP, Holz FG
[Pseudoxanthoma elasticum].
Ophthalmologe. 2006 Jun;103(6):537-51; quiz 552-3., [PMID:16763870]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is an inherited disorder that is associated with accumulation of mineralized and fragmented elastic fibers in the skin, vessel walls, and Bruch's membrane. Clinically, patients exhibit characteristic lesions of the skin (soft, ivory-colored papules in a reticular pattern that predominantly affect the neck), the posterior segment of the eye (peau d'orange, angioid streaks, choroidal neovascularizations), and the cardiovascular system (peripheral arterial occlusive disease, coronary occlusion, gastrointestinal bleeding). There is no causal therapy. Recent studies suggest that PXE is inherited almost exclusively as an autosomal recessive trait. Its prevalence has been estimated to be 1:25,000-100,000. The ABCC6 gene on chromosome 16p13.1 is associated with the disease. Mutations within the ABCC6 gene cause reduced or absent transmembraneous transport that leads to accumulation of substrate and calcification of elastic fibers. Although based on clinical features the diagnosis appears readily possible, variability in phenotypic expressions and the low prevalence may be responsible that the disease is underdiagnosed. This review covers current knowledge of PXE and presents therapeutic approaches.

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272 Internetadressen PXE-Selbsthilfegruppe Deutschland : http://www.pxe-groenblad.de PXE International: http://www.pxe.org Tabelle 5 PXE verursachende Mutationen imabcc6-Gen Klassifikation Lokalisation Gen Protein Missense Exon 9 Exon 9 Exon 10 Exon 10 Exon 11 Exon 12 Exon 13 Exon 14 Exon 16 Exon 18 Exon 18 Exon 18 Exon 18 Exon 19 Exon 19 Exon 19 Exon 22 Exon 24 Exon 24 Exon 24 Exon 24 Exon 24 Exon 24 Exon 24 Exon 24 Exon 24 Exon 25 Exon 26 Exon 26 Exon 26 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 28 Exon 29 Exon 29 Exon 29 Exon 29 Exon 29 Exon 30 Exon 30 Exon 30 c.1091CaG c.1171AaG c.1233TaG c.1318TaG c.1363GaC c.1553GaA c.1703TaC c.1798CaT c.2018TaC c.2252TaA c.2278CaT c.2294GaA c.2297CaA c.2428GaA c.2458GaC c.2552TaC c.2855TaG c.3340CaT c.3341GaA c.3341GaC c.3362CaG c.3380CaT c.3389CaT c.3412CaT c.3413GaA c.3413GaC c.3608GaA c.3661CaT c.3712GaC c.3715TaC c.3892GaT c.3902CaT c.3904GaA c.3907GaC c.3932GaA c.3940CaT c.3941GaA c.3961GaA c.3976GaA c.4004TaC c.4015CaT c.4036CaT c.4041GaC c.4060GaC c.4069CaT c.4081GaA c.4182GaT c.4198GaA c.4209CaA c.4271TaC c.4377CaT p.T364R p.R391G p.N411K p.C440G p.A455P p.R518Q p.F568S p.R600G p.L673P p.M751K p.R760W p.R765Q p.A766D p.V810M p.A820P p.L851P p.F952C p.R1114C p.R1114H p.R1114P p.S1121W p.M1127T p.T1130M p.R1138W p.R1138Q p.R1138P p.G1203D p.R1221C p.D1238H p.Y1239H p.V1298F p.T1301I p.G1302R p.A1303P p.G1311E p.R1314W p.R1314Q p.G1321S p.D1326N p.L1335P p.R1339C p.P1346S p.Q1347H p.G1354R p.R1357W p.D1361N p.K1394N p.E1400K p.S1403R p.I1424T p.R1459C Klassifikation Lokalisation Gen Protein Nonsense Exon 9 Exon 12 Exon 17 Exon 18 Exon 23 Exon 24 Exon 24 Exon 26 Exon 26 Exon 27 Exon 29 c.1132CaT c.1552CaT c.2247CaT c.2304CaA c.3088CaT c.3421CaT c.3490CaT c.3668GaA c.3709CaT c.3823CaT c.4192CaT p.Q378X p.R518X p.Q749X p.Y768X p.R1030X p.R1141X p.R1164X p.W1223X p.Q1237X p.R1275X p.R1398X Spleißstellen Intron 21 Intron 25 Intron 26 c.2787+1GaT c.3634-3CaA c.3736-1GaA Insertion Exon 8 Exon 25 Exon 30 c.938-939insT c.3544dupC c.4220insAGAA Deletion Exon 2 Exon 2 Exon 3 Exon 8 Exon 9 Exon 16 Exon 16 Exon 18 Exon 19 Exon 22 Exon 27 Exon 29 Exon 29 Exon 30 Exon 31 c.179del9 c.179-195del c.220-222del c.960delC c.1088-1120del c.1944del22 c.1995delG c.2322delC c.2542delG c.2835-2850del16 c.3775delT c.4101delC c.4182delG c.4318delA c.4434delA Intragenische Deletion Exon 15 Exon 18 Exon 23-29 delEx15 delEx18 delEx23-29 Intergenische Deletion ABCC6 delABCC6 Fazit für die Praxis Eine spezifische Behandlung der Grunderkrankung ist nicht bekannt. Login to comment

[hide] Mutational analysis of the ABCC6 gene and the prox... Hum Mutat. 2006 Aug;27(8):831. Schulz V, Hendig D, Henjakovic M, Szliska C, Kleesiek K, Gotting C
Mutational analysis of the ABCC6 gene and the proximal ABCC6 gene promoter in German patients with pseudoxanthoma elasticum (PXE).
Hum Mutat. 2006 Aug;27(8):831., [PMID:16835894]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a genetic disorder characterized by calcification of elastic fibers in dermal, ocular, and cardiovascular tissues. Recently, ABCC6 mutations were identified as causing PXE. In this follow-up study we report the investigation of 61 German PXE patients from 53 families, hitherto the largest cohort of German PXE patients screened for the complete ABCC6 gene. In addition, we characterized the proximal ABCC6 promoter of PXE patients according to mutation. In this study we identified 32 disease-causing ABCC6 variants, which had been described previously by us and others, and 10 novel mutations (eight missense mutations and two splice site alterations). The mutation detection rate among index patients was 87.7%. Frequent alterations were the PXE-mutations p.R1141X, Ex23,_Ex29del, and c.2787+1G > T. In the ABCC6 promoter we found the polymorphisms c.-127C > T, c.-132C > T, and c.-219A > C. The difference in the c.-219A > C frequencies between PXE patients and controls were determined as statistically significant. Interestingly, c.-219A > C is located in a transcriptional activator sequence of the ABCC6 promoter and occurred in a binding site for a transcriptional repressor, predominantly found in genes that participate in lipid metabolism. Obtaining these genetic data signifies our contribution to elucidating the pathogenetics of PXE.

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125 The disease-causing mutations p.R518Q and p.R518X that were frequently found in French, Italian and Swiss PXE patients (Chassaing et al., 2004; Gheduzzi et al., 2004; Miksch et al., 2005), rarely occurred in our PXE cohort and were not found in PXE families of Dutch origin (Hu et al., 2004). Login to comment

[hide] Parameters of oxidative stress are present in the ... Biochim Biophys Acta. 2008 Jul-Aug;1782(7-8):474-81. Epub 2008 May 10. Garcia-Fernandez MI, Gheduzzi D, Boraldi F, Paolinelli CD, Sanchez P, Valdivielso P, Morilla MJ, Quaglino D, Guerra D, Casolari S, Bercovitch L, Pasquali-Ronchetti I
Parameters of oxidative stress are present in the circulation of PXE patients.
Biochim Biophys Acta. 2008 Jul-Aug;1782(7-8):474-81. Epub 2008 May 10., [PMID:18513494]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is an inherited disorder characterized by calcification of elastic fibres leading to dermatological and vascular alterations associated to premature aged features and to life threatening clinical manifestations. The severity of the disease is independent from the type of mutation in the ABCC6 gene, and it has been suggested that local and/or systemic factors may contribute to the occurrence of clinical phenotype. The redox balance in the circulation of 27 PXE patients and of 50 healthy subjects of comparable age was evaluated by measuring the advanced oxidation protein products (AOPP), the lipid peroxidation derivatives (LOOH), the circulating total antioxidant status (TAS), the thiol content and the extracellular superoxide dismutase activity (EC-SOD). Patients were diagnosed by clinical, ultrastructural and molecular findings. Compared to control subjects, PXE patients exhibited significantly lower antioxidant potential, namely circulating TAS and free thiol groups, and higher levels of parameters of oxidative damage, as LOOH and of AOPP, and of circulating EC-SOD activity. Interestingly, the ratio between oxidant and antioxidant parameters was significantly altered in PXE patients and related to various score indices. This study demonstrates, for the first time, that several parameters of oxidative stress are modified in the blood of PXE patients and that the redox balance is significantly altered compared to control subjects of comparable age. Therefore, in PXE patients the circulating impaired redox balance may contribute to the occurrence of several clinical manifestations in PXE patients, and/or to the severity of disease, thus opening new perspectives for their management.

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74 Table 1 Clinical data of patients Patients' gender/age Clinical scores Mutations Allele 1 Allele 2 M/10 S2E2 c.3413GNA (p.R1138Q) c.3413GNA (p.R1138Q) F/16 S1 c.1171ANG (p.R391G) c.1552CNT (p.R518X) F/18 S3E2V2 c.1484TNA (p.L495H) c.1484TNA (p.L495H) F/21 S2E2 c.2420GNA (p.R807Q) ND F/21 S2E2 c.184TNC (p.Y62H) c.2996_4208del (p.A999_S1403del) F/24 S2E2 c.1799GNA (p.R600H) c.2420GNA (p.R807Q) F/27 S3E2 c.184TNC (p.Y62H) c.2996_4208del (p.A999_S1403del) F/30 S2E2G1 c.2996_4208del (p.A999_S1403del) c.4198GNA (p.E1400K) F/30 S2E3 c.2996_4208del (p.A999_S1403del) c.4198GNA (p.E1400K) M/30 S2E1 c.3421CNT (p.R1141X) c.3735GNA F/32 S2 c.3421CNT (p.R1141X) c.3735GNA F/33 S3E2 c.1987GNA (p.G663S) ND F/33 S3E3 c.1609_1609delG (p.V537fsX26) c.1763_1769del ins56 F/36 S3E2V3 c.3421CNT (p.R1141X) ND F/36 S3E3V2G1 c.3421CNT (p.R1141X) c.3421CNT (p.R1141X) M/39 S1E2V2 c.1552CNT (p.R518X) c.2996_4208del (p.A999_S1403del) M/42 S1E3V2G1 c.1552CNT (p.R518X) c.2996_4208del (p.A999_S1403del) F/43 S3E3 c.1552CNT (p.R518X) c.1552CNT (p.R518X) F/44 S3E2 c.3341GNA (p.R1114H) c.3542GNA (p.G1181D) F/45 S3E3V2C1G1 c.3421CNT (p.R1141X) c.3421CNT (p.R1141X) F/48 S2E2V2 c.1553GNA (p.R518Q) ND M/51 S1E3 c.3662GNA (p.R1221H) ND F/52 S3E3V2 c.3088CNT (p.R1030X) c.3088CNT (p.R1030X) M/54 S1E2G1 c.1799GNA (p.R600H) c.3941GNA (p.R1314Q) F/56 S3E3V2 c.3662GNA (p.R1221H) ND F/60 S2E3V2C1G1 c.951CNA (p.S317R) c.3421CNT (p.R1141X) F/62 S2E3 c.1552CNT (p.R518X) c.3421CNT (p.R1141X) Scores describe the severity of clinical manifestations. Login to comment

[hide] Efficiency of exome sequencing for the molecular d... J Invest Dermatol. 2015 Apr;135(4):992-8. doi: 10.1038/jid.2014.421. Epub 2014 Sep 29. Hosen MJ, Van Nieuwerburgh F, Steyaert W, Deforce D, Martin L, Leftheriotis G, De Paepe A, Coucke PJ, Vanakker OM
Efficiency of exome sequencing for the molecular diagnosis of pseudoxanthoma elasticum.
J Invest Dermatol. 2015 Apr;135(4):992-8. doi: 10.1038/jid.2014.421. Epub 2014 Sep 29., [PMID:25264593]

Abstract [show]
The molecular etiology of pseudoxanthoma elasticum (PXE), an autosomal recessive connective tissue disorder, has become increasingly complex as not only mutations in ATP-binding cassette family C member 6 (ABCC6) but also ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) and gamma-glutamyl carboxylase (GGCX) can cause resembling phenotypes. Identification of modifier genes, such as vascular endothelial growth factor A, has further contributed to the molecular heterogeneity of PXE. In such heterogeneous diseases, next-generation sequencing (NGS) allows to perform mutation screening of several genes in a single reaction. We explored whole-exome sequencing (WES) as an efficient diagnostic tool to identify the causal mutations in ABCC6, GGCX, ENPP1, and vitamin K epoxide reductase complex, subunit 1 (VKORC1) in 16 PXE patients. WES identified a causal ABCC6 mutation in 30 out of 32 alleles and one GGCX mutation, whereas no causal mutations in ENPP1 or VKORC1 were detected. Exomes with insufficient reads (20 depth) for the four genes and patients with single mutations were further evaluated by Sanger sequencing (SS), but no additional mutations were found. The potential of WES compared with targeted NGS is the ease to examine target genes and the opportunity to search for novel genes when targeted analysis is negative. Together with low cost, rapid and less laborious workflow, we conclude that WES complemented with SS can provide a tiered approach to molecular diagnostics of PXE.

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No. Sentence Comment
81 To rule out a whole exon deletion on one allele for the p.(R518Q) mutation in ABCC6, MLPA was also performed for patients P1 (with 3 ABCC6 mutation), which revealed no additional deletion. Login to comment
89 List of mutations found by WES and SS Gene Nucleotide change Protein change Patient ID Hom/Het WES SS Known/PUR Reference ABCC6 c.C118T p.(P40S) P10 Het O O PUR ABCC6 c.998 &#fe; 2 998 &#fe; 3del TG P8 Het O O PUR ABCC6 c.T1484A p.(L495H) P7 Het O O Known Miksch et al., 2005 ABCC6 c.G1553A p.(R518Q) P11 Hom O O Known Uitto et al., 2001 ABCC6 c.G1553A p.(R518Q) P12, P13, P14 Het O O Known Uitto et al., 2001 ABCC6 c.G2263A p.(G755R) P11 Het O O Known Pfendner et al., 2007 ABCC6 c.G2294A p.(R765Q) P3 Het O O Known Le Saux et al., 2001 ABCC6 del2860_2865 P12, P13,14 Het O O PUR ABCC6 c.T2911C p.(W971R) P11 Het O O PUR ABCC6 Ex23_24del P2 Hom O O Known Ringpfeil et al., 2001 ABCC6 c.T3032C p.(L1011P) P9 Hom O O PUR ABCC6 c.C3190T p.(A1064T) P7 Het O O Known Miksch et al., 2005 ABCC6 c.G3413A p.(R1138Q) P11 Het O O Known Le Saux O, 2011 ABCC6 c.C3421T p.(R1141X) P4 Hom O O Known Bergen et al., 2000 ABCC6 c.C3421T p.(R1141X) P52 , P8, P162 Het O O Known Bergen et al., 2000 ABCC6 c.C3490T p.(R1164X) P6, P15 Hom O O Known Struk et al., 2000 ABCC6 c.G4198A p.(E1400K) P10 Het O O Known Chassaing et al., 2004 ABCC6 c.C4216A p.(Q1406K) P3 Het O O PUR GGCX c.C1321T p.(R441C) P7 Het O O PUR Het, heterozygous; Hom, homozygous; PUR, previously unreported; SS, Sanger sequencing; WES, whole-exome sequencing. Login to comment