ABCMdb

ABCC6 p.Arg518*

ClinVar:	c.1552C>T , p.Arg518* D , Pathogenic
LOVD-ABCC6:	p.Arg518Gln D p.Arg518* D

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[hide] Pseudoxanthoma elasticum: Point mutations in the A... Hum Mutat. 2001;18(1):85. Meloni I, Rubegni P, De Aloe G, Bruttini M, Pianigiani E, Cusano R, Seri M, Mondillo S, Federico A, Bardelli AM, Andreassi L, Fimiani M, Renieri A
Pseudoxanthoma elasticum: Point mutations in the ABCC6 gene and a large deletion including also ABCC1 and MYH11.
Hum Mutat. 2001;18(1):85., [PMID:11439001]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a mendelian disorder characterized by calcification of elastic fibers in skin, arteries, and retina. It results in dermal lesions, arterial insufficiency and retinal hemorrhages, leading to macular degeneration. PXE is transmitted either as an autosomal dominant or recessive trait and several sporadic cases have been observed. Mutations in the ABCC6 gene have been identified very recently in patients. Here, we report on a large Italian family affected by pseudoxanthoma elasticum for which linkage analysis had pointed to a region encompassing markers D16S3069-D16S405-D16S3103; hemizygosity of marker D16S405 allowed us to detect a submicroscopic deletion of at least 900 kb involving ABCC6, ABCC1, and MYH11. Mutation analysis on the other allele of the family, as well as on two additional sporadic cases, revealed nonsense (Y227X, R518X, R1164X) and frame-shift (c.960delC) mutations in ABCC6 (MRP6) further confirming the role of this multi-drug resistance gene in the etiology of pseudoxanthoma elasticum. Furthermore, clinical re-examination of members of the family harboring the deletion led to the detection of additional features, potentially caused by the deletion of the MYH11 gene. In the course of the analysis five nonpathogenic variants were found in ABCC6: 1233T>C, 1245G>A, 1838 T>G (V614A), 1890C>G, and 3506+83C>A. Hum Mutat 18:85, 2001.

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6 Mutation analysis on the other allele of the family, as well as on two additional sporadic cases, revealed nonsense (Y227X, R518X, R1164X) and frame-shift (c.960delC) mutations in ABCC6 (MRP6) further confirming the role of this multi-drug resistance gene in the etiology of pseudoxanthoma elasticum. Login to comment
57 Two of them (R518X and R1164X) are C to T transitions in a CpG dinucleotide causing a substitution of arginine (CGA) with a stop codon (TGA); they were identified in exon 12 and exon 24 in the two sporadic cases in the heterozygous state (patients 11 and 12). Login to comment
95 Mutations and variants in ABCC6 nt change Mutations 681 C ->G 960delC 1552 C ->T 3490 C ->T Non pathogenic variants 1233 T ->C 1245 G ->A 1838 T->G 1890 C->G c.3506+83 C ->A protein change Y227X frame-shift from I320 R518X R1164X N411N N415N V614A T630T _ exon 7 11 exon 8 family exon 12 11 exon 24 12 exon 10 11 exon 10 11 exon 14 11, 12 exon patient 11 11 12 exon 14 exon 24 11 11, 12 11, 12 Re-evaluation of the phenotype in the family with the large deletion did not reveal significant additional manifestations, suggesting that heterozygous ABCC1 and MYH11 deletion does not give rise to an obvious phenotype. 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
32 2 2 1 15 France F 50 R391G 1171A4G 9 1 0 0 A999_S1403del EX23_29del 23-29 16 France M 42 R1138Q 3413G4A 24 1 0 0 R1138Q 3413G4A 24 17 France F 35 R518X/? 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
81 In order to identify a possible founder origin of recurrent disease-associated alleles, a limited haplotype analysis was performed in 11 unrelated families carrying the same mutation (p.Q378X, p.R518X, p.R1141X) in homozygous state (data not shown). Login to comment
83 The analysis of the two families with the p.R518X mutation revealed common haplotypes, suggesting a possible consanguinity. Login to comment
86 The same comparison, in the case of p.R518X mutation, revealed different alleles, between Italian and French patients, identical-by state. 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] Pseudoxanthoma elasticum is a recessive disease ch... J Invest Dermatol. 2006 Apr;126(4):782-6. Ringpfeil F, McGuigan K, Fuchsel L, Kozic H, Larralde M, Lebwohl M, Uitto J
Pseudoxanthoma elasticum is a recessive disease characterized by compound heterozygosity.
J Invest Dermatol. 2006 Apr;126(4):782-6., [PMID:16410789]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is caused by mutations in the ABCC6 gene. Historically, PXE has been suggested to be inherited either in an autosomal dominant or autosomal recessive manner. To determine the exact mode of inheritance of PXE and to address the question of phenotypic expression in mutation carriers, we identified seven pedigrees with affected individuals in two different generations and sequenced the entire coding region of ABCC6 in affected individuals, presumed carriers with a limited phenotype and unaffected family members. Two allelic mutations were identified in each individual with unambiguous diagnosis of PXE, as well as in those with only minimal clinical signs suggestive of PXE but with positive skin biopsy. Missense mutations were frequently detected in the latter cases. In conclusion, PXE is inherited in an autosomal recessive manner and presence of disease in two generations is due to pseudodominance.

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31 R1164Q/R518X R1164Q/R1164Q R1164Q/- -/- Family 5 Del23-29/R391G Del23-29/Del23-29 Family 3 R1141X/del23-29 R1141X/del23-29 Del23-29/- R1141X/T811M Family 1 Figure 1. Login to comment
49 In Family 5, the proband was compound heterozygote for R1164Q/R518X, the missense mutation being inherited from the clinically unaffected father while the nonsense mutation was either a de novo mutation or reflected germline mosaicism in the clinically unaffected mother whose peripheral blood DNA did not carry this mutation. 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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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] Gene expression profiling of ABC transporters in d... Lab Invest. 2008 Dec;88(12):1303-15. Epub 2008 Oct 20. Hendig D, Langmann T, Kocken S, Zarbock R, Szliska C, Schmitz G, Kleesiek K, Gotting C
Gene expression profiling of ABC transporters in dermal fibroblasts of pseudoxanthoma elasticum patients identifies new candidates involved in PXE pathogenesis.
Lab Invest. 2008 Dec;88(12):1303-15. Epub 2008 Oct 20., [PMID:18936737]

Abstract [show]
Mutations in the ABCC6 gene, encoding the multidrug resistance-associated protein 6 (MRP6), cause pseudoxanthoma elasticum (PXE). This heritable disorder leads to pathological alterations in connective tissues. The implication of MRP6 deficiency in PXE is still unknown. Moreover, nothing is known about a possible compensatory expression of other ATP binding-cassette (ABC) transporter proteins in MRP6-deficient cells. We investigated the gene expression profile of 47 ABC transporters in human dermal fibroblasts of healthy controls (n=2) and PXE patients (n=4) by TaqMan low-density array. The analysis revealed the expression of 37 ABC transporter genes in dermal fibroblasts. ABCC6 gene expression was not quantifiable in fibroblasts derived from PXE patients. Seven genes (ABCA6, ABCA9, ABCA10, ABCB5, ABCC2, ABCC9 and ABCD2) were induced, whereas the gene expression of one gene (ABCA3) was decreased, comparing controls and PXE patients (with at least twofold changes). We reanalyzed the gene expression of selected ABC transporters in a larger set of dermal fibroblasts from controls and PXE patients (n=6, each). Reanalysis showed high interindividual variability between samples, but confirmed the results obtained in the array analysis. The gene expression of ABC transporter genes, as well as lineage markers of PXE, was further examined after inhibition of ABCC6 gene expression by using specific small-interfering RNA. These experiments corroborated the observed gene expression alterations, most notably in the ABCA subclass (up to fourfold, P<0.05). We therefore conclude that MRP6-deficient dermal fibroblasts exhibit a distinct gene expression profile of ABCA transporters, potentially to compensate for MRP6 deficiency. Moreover, our results point to a function for ABCC6/MRP6 in sterol transport, as sterols are preferential regulators of ABCA transporter activity and expression. Further studies are now required to uncover the role of ABCA transporters in PXE.

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62 Table 1 Main characteristics of dermal fibroblasts derived from PXE patients and healthy controls used in the present study Sample ID Gender Agea Biopsy source ABCC6 genotypeb Statusc Age at disease onseta Number of involved organs PXE patients P60F Female 58 Axilla c.37-1G4A (SSM) c.37-1G4A (SSM) hm 56 3 P229F Female 50 NA c.1171A4G (p.R391G) c.1208C4A (p.A413N) c.2252T4A (p.M751K) cht NA NA P265F Female 62 Cervix c.1132C4T (p.Q378X) c.3421C4T (p.R1141X) cht 16 3 P3M Male 57 Cervix c.3421C4T (p.R1141X) c.3883-6G4A (SSM) cht 46 5 P128M Male 51 Cervix c.3769_3770insC (p.L1259fsX1277) c.3769_3770insC (p.L1259fsX1277) hm 48 3 P308M Male 42 NA c.3421C4T (p.R1141X) c.-90ins14 (c)ht NA NA P341M Male 41 NA c.1552C4T (p.R518X) ND ht NA NA Healthy controls F37A Female 37 Abdomen - - - wt - - F42A Female 42 Abdomen - - - wt - - F52C Female 52 Cheek - - - wt - - M2FS Male 2 Foreskin - - - wt - - M45D Male 45 Face - - - wt - - M56D Male 56 Face - - - wt - - hm, homozygote; cht, compound heterozygote; ht, heterozygote; wt, wild type; SSM, splice site mutation; NA, not applicable; ND, nondetected. 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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82 Summary of ABCC6/MRP6 mutations identified in German PXE patients Change in Number of Allelic frequency Exona nucleotideb Amino acid Statusc families in blood donorsd Referenceg i-1e c.37-1G>Af altered splicing hm 1 0 / 200 This study 2 c.113G>C p.W38S ht 1 0 / 200 This study i-3 c.346-6G>A altered splicing ht 2 Nd A, B 7 c.754C>T p.L252F ht 1 0 / 200 This study 9 c.1132C>T p.Q378X ht 4 Nd B, C 9 c.1171A>G p.R391G ht 1 Nd B, D 10 c.1244T>C p.V415A ht 1 0 / 200 This study 12 c.1460G>A p.R487Q ht 1 0 / 200 This study 12 c.1491C>A p.N497K ht 1 0 / 200 This study 12 c.1552C>T p.R518X ht 1 Nd B, E i-12 c.1574_1575insG p.L525fsX73 ht 1 0 / 200 This study 16 c.1995delG p.A667fsX20 ht 3 Nd A, F, G 18 c.2252T>A p.M751K ht 3 Nd F, G 18 c.2278C>T p.R760W ht 2 Nd B, F, G Change in Number of Allelic frequency Exona nucleotideb Amino acid Statusc families in blood donorsd Referenceg 18 c.2294G>A p.R765Q ht 2 Nd A, F, G, H 19 c.2552T>C p.L851P ht 1 Nd F i-21 c.2787+1G>T altered splicing ht 7 Nd B, C, F, I, J 22 c.2835_2850del16 p.P946fsX17 ht 1 Nd F 22 c.2855T>G p.F952C ht 1 Nd F 23 c.3145T>G p.S1049A ht 1 0 / 200 This study 23 c.3188T>G p.L1063R ht 1 0 / 200 This study 24 c.3340C>T p.R1114C ht 1 Nd B, K, G, L 24 c.3341G>A p.R1114H ht 1 Nd G, H, L, M 24 c.3389C>T p.T1130M ht 1 Nd B, D, G, H, K, L, M, N 24 c.3413G>A p.R1138Q ht 1 Nd A, B, D, J, K, L, N 24 c.3412C>T p.R1138W ht 1 Nd N 24 c.3421C>T p.R1141X hm, ht 26 Nd B, G, J, K, L, M, N, O, P, Q, R, S i-24 c.3505_3506+2delA GGT altered splicing ht 1 0 / 200 This study i-24 c.3507-3C>T altered splicing ht 2 Nd B 26 c.3715T>C p.Y1239H ht 1 Nd L 26 c.3723G>C p.W1241C ht 1 Nd A, L i-26 c.3736-1G>A altered splicing ht 1 Nd B, L, N 27 c.3775delT p.W1259fsX13 ht 1 Nd B, J, L, O i-27 c.3883-6G>A altered splicing ht 1 Nd B 28 c.3902C>T p.T1301I ht 1 Nd A, G, L 28 c.3932G>A p.G1311E ht 1 Nd L 28 c.3940C>T p.R1314W ht 1 Nd A, G, L 28 c.3941G>A p.R1314Q ht 1 Nd A, B, G, L 29 c.4182delG p.N1394fsX8 ht 2 Nd G, H, L 30 c.4209C>A p.S1403R ht 1 Nd F 31 c.4434delA p.R1479fsX25 hm 1 Nd F 23-29 Ex23_Ex29del p.A999_S1403del ht 5 Nd A, B, D, E, G, H, O, R a The exon that contains the ABCC6 sequence variation. Login to comment
89 Genotypes and phenotypes of the PXE patients analyzed in this study Phenotype Genotypeb No.a Sex, Age Age on diagnosis Organ involvement Mutations 1 M 36 11 E, S, G p.R1141X p.R1141X 2 F 44 39 E, S, G, A p.R1141X Ex23_Ex29del 3 F 41 7 E, S p.R1141X p.R1141X 4 F 46 19 E, S, A p.R1141X p.R1141X 5 F 59 55 E, S, A c.37-1G>A c.37-1G>A 6c F 63 16 E, S, H, V, A Ex23_Ex29del c.4182delG 7 F 24 15 E, S c.4434delA c.4434delA 8 M 60 23 E, S p.Q378X p.R1141X 9 F 79 65 E, S, A c.2787+1G>T p.R1141X 10 F 55 35 E, S, G, H, V, A p.Q378X c.2787+1G>T 11 F 47 14 S c.1995delG c.2787+1G>T 12c F 36 24 E, S c.2787+1G>T c.4182delG 13 F 56 8 E, S p.R1141X c.3507-3C>T 14 M 72 55 E, S, H, V p.R1141X 15 F 69 51 E, S c.1995delG p.R765Q 16 F 19 11 S p.R760W p.R1141X 17c F 59 50 E, S, H, V, A p.R1141X p.G1311E 18c M 54 32 E, S p.R1141X p.Y1239H 19-1 M 63 53 E, H p.L252F p.V415A p.R765Q 19-2 F 58 48 E, S p.L252F p.V415A p.R765Q 20 M 54 44 E, S, V, A c.3775delT c.346-6G>A 21 M 52 43 E, S, A p.R1141X c.3883-6G>A 22-1 M 47 36 E, S, G, H, V p.R518X 22-2 M 45 34 E, S, H p.R518X 23 F 35 22 E, S, A p.W38S 24 F 40 30 E c.346-6G>A 25-1 M 58 46 E, S, A p.R1141X c.3883-6G>A 25-2 M 19 10 S p.R1141X c.3883-6G>A 26-1 F 46 18 E, S, V p.R487Q c.3883-6G>A 27c F 62 30 E, S, A p.Q378X p.R1114H 28 F 59 49 E, A p.R1314Q c.3507-3C>T 29c F 30 10 E, S c.1995delG p.R1114C 30 M 67 52 E p.L1063R p.R1141X 31 F 50 46 E, S, V p.M751K p.R1141X 32 F 27 24 S Ex23_Ex29del 33c F 34 19 E, S Ex23_Ex29del p.T1130M 34 F 33 19 E, S c.2787+1G>T p.W1241C 35 M 47 15 E, S, G, H, V, A Ex23_Ex29del 36 M 72 63 E, S p.S1049A c.3736-1G>A p.S1403R 37 F 34 16 E, S c.2787+1G>T 38 F 42 8 E, S, V p.R1141X p.R1314W 39 F 37 20 E, S p.N497K 40 F 54 33 E, S, V, A p.M751K p.R1141X 41 M 53 49 E, S, G, H, V p.R1141X 42-1 F 52 38 E, S p.R391G p.R1141X 42-2 F 43 28 E, S p.R391G p.R1141X 43 F 64 58 S, A 44-1 F 51 27 E, S, A p.R1141X 44-2 F 18 9 E, S 44-3 F 54 26 E, S, V, A p.R1141X 45-1 F 64 49 E, S, G, V p.R1138Q 45-2 F 62 48 E, S, A p.R1138Q 46 M 56 25 E, S, V p.R1141X p.T1301I 47 F 34 23 E, S p.R760W c.2787+1G>T 48 M 47 24 E, S, V, A c.2835_2850del16 p.F952C p.R1141X 49 F 28 11 E, S, G, V p.M751K p.R1141X 50 F 39 25 E, S, V p.L851P p.R1141X c.3505_3506+2 delAGGT 51 F 61 16 E, S, H, A p.Q378X p.R1141X 52-1 F 40 20 E, S p.R1138W p.R1141X 52-2 F 43 23 E, S p.R1138W p.R1141X 53 M 68 66 E, H, V, G, A c.1574_1575insG p.R1141X F = female, M = male, wt = wild-type, hm = homozygote, ht = heterozygote, cht = compound heterozygote, nd = not determined, MSM = microsatellite marker, E = eyes, S = skin, G = gastrointestinum, H = heart, V = vascular tissue and A = arterial hypertension. Login to comment
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] Pseudoxanthoma elasticum: clinical phenotypes, mol... Exp Dermatol. 2009 Jan;18(1):1-11. Epub 2008 Oct 22. Li Q, Jiang Q, Pfendner E, Varadi A, Uitto J
Pseudoxanthoma elasticum: clinical phenotypes, molecular genetics and putative pathomechanisms.
Exp Dermatol. 2009 Jan;18(1):1-11. Epub 2008 Oct 22., [PMID:19054062]

Abstract [show]
Pseudoxanthoma elasticum (PXE), a prototype of heritable multisystem disorders, is characterised by pathologic mineralisation of connective tissues, with primary clinical manifestations in the skin, eyes and the cardiovascular system. The causative gene was initially identified as ABCC6 which encodes an ABC transporter protein (ABCC6) expressed primarily in the liver and the kidneys. The critical role of ABCC6 in ectopic mineralisation has been confirmed by the development of Abcc6(-/-) knock-out mice which recapitulate the features of connective tissue mineralisation characteristic of PXE. Over 300 distinct loss-of-function mutations representative of over 1000 mutant alleles in ABCC6 have been identified by streamlined mutation detection strategies in this autosomal recessive disease. More recently, missense mutations in the GGCX gene, either in compound heterozygous state or digenic with a recurrent ABCC6 nonsense mutation (p.R1141X), have been identified in patients with PXE-like cutaneous findings and vitamin K-dependent coagulation factor deficiency. GGCX encodes a carboxylase which catalyses gamma-glutamyl carboxylation of coagulation factors as well as of matrix gla protein (MGP) which in fully carboxylated form serves as a systemic inhibitor of pathologic mineralisation. Collectively, these observations suggest the hypothesis that a consequence of loss-of-function mutations in the ABCC6 gene is the reduced vitamin K-dependent gamma-glutamyl carboxylation of MGP, with subsequent connective tissue mineralisation. Further progress in understanding the detailed pathomechanisms of PXE should provide novel strategies to counteract, and perhaps cure, this complex heritable disorder at the genome-environment interface.

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68 Identification of additional recurrent nonsense mutations (p.Q378X in exon 9, p.R518X in exon 12 and p.R1164X in exon 24) as well as clustering of the missense mutations to exons 24 and 28 corresponding to the NBFs that are critical for the ATP binding and hydrolysis have allowed the development of streamlined mutation detection strategies to facilitate identification of mutations in the ABCC6 gene with the overall detection rate of up to 99% (for review see reference 26). Login to comment

[hide] Added value of infrared, red-free and autofluoresc... Br J Ophthalmol. 2010 Apr;94(4):479-86. Epub 2009 Sep 1. De Zaeytijd J, Vanakker OM, Coucke PJ, De Paepe A, De Laey JJ, Leroy BP
Added value of infrared, red-free and autofluorescence fundus imaging in pseudoxanthoma elasticum.
Br J Ophthalmol. 2010 Apr;94(4):479-86. Epub 2009 Sep 1., [PMID:19726431]

Abstract [show]
PURPOSE: Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder caused by mutations in the ABCC6 gene and primarily affects the oculocutaneous and cardiovascular systems. However, the phenotype, including the ophthalmological manifestations, varies in severity. The present study aims to evaluate the added value of novel funduscopic imaging techniques, such as near-infrared reflectance, red-free and autofluorescence imaging in PXE. METHODS: In 22 molecularly proven PXE patients and 25 obligate carriers, PXE retinopathy was evaluated using funduscopy, white light, red-free, infrared and autofluorescence imaging. RESULTS: At least one characteristic of PXE retinopathy was evident on funduscopy of all eyes. Angioid streaks could be subdivided in those with (brick red) or without (feathered) adjacent RPE alterations. Infrared imaging showed the brick-red-coloured streaks as well-demarcated dark fissures, even when these passed unnoticed on funduscopy. Feathered types were detected as triangular areas of hypoautofluorescence. The peau d'orange was much more visible and much more widespread on infrared imaging, with extension from the posterior pole towards the whole midperiphery. Comets and comet tails were best seen with red-free imaging. CONCLUSIONS: Infrared, red-free and autofluorescence imaging are more sensitive than white light funduscopy and imaging in visualising early retinal signs of PXE. In addition, this specialised imaging allows a better appreciation of the extent of lesions. Hence, such imaging increases the chances of making a correct diagnosis early, and aids in the accurate evaluation of evolution of disease in the ophthalmic follow-up of PXE patients.

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78 In 55% of fundi (24/44), the Table 1 Ophthalmological characteristics of patients Case Age, sex Eye BCVA AS Pd`O C(T) ODD NV PDT Anti-VEGF ABCC6 mutations 1 61, F OD 2/10 + + + À + + À p.R1459C/e OS 9/10 + + + À + + À 2 43, F OD 12/10 + + + À À À À p.R1141X/p.R1141X OS 12/10 + + + À À À À 3 35, M OD 11/10 + + + À À À À p.E125K/p.L1025P OS 1/300 + + + À + + + 4 21, M OD 10/10 + + + À À À À p.R1141X/p.R1141X OS 10/10 + + + + À À À 5 11, M OD 10/10 À + + À À À À c.3506+2T/C/e 3506+2T/COS 10/10 À + + À À À À 6 55, F OD 1/20 + + + À + À À p.R1141X/p.R1141X OS 1.5/10 + + + À + À À 7 40, M OD 4/10 + + + À + + À p.R265G/p.R1141X OS 1/10 + + + À + + À 8 22, F OD 10/10 + + + À À À À p.R1141X/p.R1141X OS 10/10 + + + À À À À 9 29, F OD 10/10 + + + À À À À p.G1263R/c.4182delGG OS 10/10 + + + À À À À 10 20, M OD 10/10 + + + + À À À c.3507-3C/A/p.T944I OS 10/10 + + + + À À À 11 37, F OD 10/10 + + + + À À À p.Q154R/e OS 9/10 + + + + À À À 12 66, F OD 1/20 + À À À + À À p.R1141X/p.R1141X OS 1/10 + À À À + À À 13 68, F OD 10/10 + À À À À À À p.R760Q/p.R1141X OS 10/10 + À À À À À À 14 68, M OD 2/10 + À + À + À À p.A1303P/p.L946I OS CF + À + À + À À 15 58, F OD 7/10 + + + À + À + p.R1141X/c.4103delC OS CF + + + À + + À 16 62,M OD 1/20 + + + À + À + p.R1141X/p.Q1237X OS CF + + + À + À À 17 47, F OD 10/10 + À À À À À À c.3506+2T/C/e OS 10/10 + À À À À À À 18 54, F OD 10/10 + + + À + À + p.R1141X/p.A1303P OS 10/10 + + + À À À À 19 30, F OD 10/10 + + + À À À À p.S398R/c.3364delT OS 10/10 + + + À À À À 20 39, F OD 12/10 + + + À À À À p.R1141X/e OS 10/10 + + + À À À À 21 30, F OD 10/10 + + + À À À À p.G666R/c.1868-5T/G OS 10/10 + + + + À À À 22 34, M OD 12/10 + + + À À À À c.3364delT/p.R518X OS 12/10 + + + À À À À anti-VEGF, anti-vascular endothelial growth factor antibodies; AS, angioid streaks; BCVA, best-corrected visual acuity (Snellen); CF, counting fingers; C(T), Comet (tails); F, female; M, male; MD, macular degeneration; NV, neovascularisation; ODD, optic disc drusen; Pd`O, Peau d`Orange; PDT, photodynamic therapy. Login to comment

[hide] Premature termination codon read-through in the AB... J Invest Dermatol. 2013 Dec;133(12):2672-7. doi: 10.1038/jid.2013.234. Epub 2013 May 23. Zhou Y, Jiang Q, Takahagi S, Shao C, Uitto J
Premature termination codon read-through in the ABCC6 gene: potential treatment for pseudoxanthoma elasticum.
J Invest Dermatol. 2013 Dec;133(12):2672-7. doi: 10.1038/jid.2013.234. Epub 2013 May 23., [PMID:23702584]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder manifesting with ectopic connective tissue mineralization, caused by mutations in the ABCC6 gene, with ~35% of all mutations being premature termination mutations. In this study, we investigated the therapeutic potential of the nonsense codon read-through-inducing drug, PTC124, in treating PXE. The ability of this drug to facilitate read-through of nonsense mutations was examined in HEK293 cells transfected with human ABCC6 expression constructs harboring seven different PXE-associated nonsense mutations, and was evaluated by immunofluorescence and In-Cell ELISA. Our data demonstrated that PTC124 did not exhibit cytotoxicity in concentrations up to 20 mug ml(-1), and the facilitated read-through varied not only with dose but also with sequence context. Considering the redundancy of the genetic code, it was postulated that in case of the most common recurrent nonsense mutation, p.R1141X, the read-through may result in substitution of the arginine 1,141 by glycine, tryptophan, or cysteine. Their potential pathogenicity was tested in a recently developed zebrafish messenger RNA (mRNA) rescue assay, and demonstrated that all three mRNA transcripts were able to rescue abcc6a morpholino-induced phenotype of zebrafish. Thus, our results suggest that read-through of nonsense mutations in ABCC6 by PTC124 may have potential for pharmacologic treatment of PXE.

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38 Different pseudoxanthoma elasticum (PXE)- associated nonsense mutations tested for PTC124 read-through Mutation Nucleotide sequence1 Location (exon) Mutation frequency (%)2 p.R1141X TGA-A 24 54 p.R1164X TGA-C 24 10 p.R518X TGA-G 12 1.2 p.R1398X TGA-G 29 1.2 p.Q378X TAG-A 9 o1 p.Q1143X TAG-G 24 o1 p.R1275X TGA-C 27 o1 1 The sequence depicts the stop codon (bold) followed by the nucleotide shown. Login to comment