ABCMdb

ABCC6 p.Arg391Gly

LOVD-ABCC6:	p.Arg391Gly D
Predicted by SNAP2:	A: D (91%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), G: D (66%), H: D (85%), I: D (95%), K: D (75%), L: D (95%), M: D (95%), N: D (91%), P: D (95%), Q: D (85%), S: D (91%), T: D (91%), 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] 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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24 Among these, five are missense mutations (R391G, A766D, D1238H, L1335P, E1400K), one is a nonsense mutation (W1223X), one is a small in-frame deletion of 33 bp (1088-1120del), and two are predicted to impair splicing (V74del, IVS25-3C4A). Login to comment
25 All new mutations but three (R391G identified in family 15, D1238H identified in family 11, and E1400K identified in families 1 and 3) fulfil the criteria described for defining nucleotide sequence variants as disease-causing (Cotton and Scriver, 1998). 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
42 Therefore, R391G was assumed to be disease-causing. Login to comment
51 All the five novel missense mutations are located within intracellular domains of the molecule, three in the nucleotide binding domains (A766D in NBD1, L1335P and E1400K in NBD2) and two in a cytoplasmic loop (R391G, D1238H). 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

[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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158 However, there were also single mutations (p.G129E, p.L248F, p.S317R, p.L355R, p.T364R, p.N370D, and p.R391G) that did cosegregate with the disease haplotype in families in which they were observed, and were absent in 200 control chromosomes. Login to comment
160 In the second round we were again able to identify the mutations p.S317R, p.L355R, p.T364R, p.N370D, and p.R391G by nested sequencing of the long-range PCR products for exons 8 and 9, and to demonstrate their cosegregation with the disease haplotype. 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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30 In addition, a previously unpublished nonsense mutation W1324X was F568S/R1141X W1324X/R1141X Family 4 R1138W/R1138W R1138W/R1138W -/R1138W R1138W/- R1138W/- R1138W/- Family 6 R391G/R1138W R391G/R1138W Family 7 Family 2 Del23-29/W218C R391G/W218C Del23-29/W218C Del23-29/R391G W218C/- Del23-29/- Del23-29/- ? Login to comment
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
42 In Family 2, the three children were compound heterozygotes with two different combinations (del23-29/W218C and R391G/W218C). Login to comment
43 The mother with minimal clinical signs but with a positive skin biopsy was compound heterozygous for two of these mutations (del23-29/R391G) and manifested with asymptomatic angioid streaks and hypertension. Login to comment
45 In Family 3, the clinically affected son was homozygous for the del23-29 mutation, whereas the mother manifesting with vision loss, intermittent claudication, stroke, and hypertension was a compound heterozygote for del23-29/R391G mutations. Login to comment
51 Segregation of the mutant alleles in Families 6 and 7 suggested that the homozygosity for the R1138W mutation (Family 6) and compound heterozygosity for the R391G/R1138W mutations (Family 7) in affected individuals in two subsequent generations were due to consanguinity, a conclusion supported by examination of the family pedigrees (see Figure 1) and by haplotype analysis (data not shown). Login to comment
71 It is of interest that in Family 2, the eldest son and the daughter had a clearcut clinical diagnosis of PXE, yet the second son, upon examination by a dermatologist and an ophthalmologist, showed no clinical evidence of PXE at the age of 37 years even though he was compound heterozygous for R391G/W218C mutations. Login to comment

[hide] Serum factors from pseudoxanthoma elasticum patien... J Invest Dermatol. 2006 Jul;126(7):1497-505. Epub 2006 Mar 16. Le Saux O, Bunda S, VanWart CM, Douet V, Got L, Martin L, Hinek A
Serum factors from pseudoxanthoma elasticum patients alter elastic fiber formation in vitro.
J Invest Dermatol. 2006 Jul;126(7):1497-505. Epub 2006 Mar 16., [PMID:16543900]

Abstract [show]
Pseudoxanthoma elasticum (PXE) is a heritable disorder mainly characterized by calcified elastic fibers in cutaneous, ocular, and vascular tissues. PXE is caused by mutations in ABCC6, a gene encoding an ABC transporter predominantly expressed in liver and kidneys. The functional relationship between ABCC6 and elastic fiber calcification is unknown. We speculated that ABCC6 deficiency in PXE patients induces a persistent imbalance in circulating metabolite(s), which may impair the synthetic abilities of normal elastoblasts or specifically alter elastic fiber assembly. Therefore, we compared the deposition of elastic fiber proteins in cultures of fibroblasts derived from PXE and unaffected individuals. PXE fibroblasts cultured with normal human serum expressed and deposited increased amounts of proteins, but structurally normal elastic fibers. Interestingly, normal and PXE fibroblasts as well as normal smooth muscle cells deposited abnormal aggregates of elastic fibers when maintained in the presence of serum from PXE patients. The expression of tropoelastin and other elastic fiber-associated genes was not significantly modulated by the presence of PXE serum. These results indicated that certain metabolites present in PXE sera interfered with the normal assembly of elastic fibers in vitro and suggested that PXE is a primary metabolic disorder with secondary connective tissue manifestations.

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178 Serum samples Control #1 (M) Normal wt/wt 45 Control #2 (M) Normal wt/wt 34 Control #3 (pool)1 Normal wt/wt Av. 68 Control #4 (pool)1 Normal wt/wt Av. 18 PXE 1 (F) PXE R391G/del23-29 50 PXE 2 (F) PXE IVS21+1 G4T/4104delC 51 PXE 3 (F) PXE IVS13-29 T4A/R1141X 41 PXE 4 (M) PXE ?/? Login to comment

[hide] Histological skin changes in heterozygote carriers... J Eur Acad Dermatol Venereol. 2007 Mar;21(3):368-73. Martin L, Chassaing N, Delaite D, Esteve E, Maitre F, Le Bert M
Histological skin changes in heterozygote carriers of mutations in ABCC6, the gene causing pseudoxanthoma elasticum.
J Eur Acad Dermatol Venereol. 2007 Mar;21(3):368-73., [PMID:17309461]

Abstract [show]
BACKGROUND: Pseudoxanthoma elasticum (PXE) is related to mutations in the ABCC6 gene and characterized pathologically by dystrophic and mineralized elastic fibres. Heterozygote carriers of ABCC6 mutations may have a limited PXE phenotype. OBJECTIVE: To compare histological changes in the skin of genotyped siblings from two PXE pedigrees. METHODS: Mutation analysis of ABCC6 was performed. Skin biopsy samples were stained (orcein) and immunolabelled for elastin, and for vitronectin and bone sialoprotein, which are partially responsible for the mineralization within the elastorrhexic fibres. Results In all individuals mutation analysis of ABCC6 allowed definition of the genotype status, i.e. PXE (n = 2), heterozygote (n = 7) or wild type (n = 2). The study identified three histological phenotypes related to the ABCC6 genotype in siblings from both families. Heterozygote carriers had changes in dermal elastic fibre organization, morphology and labelling midway between those seen in PXE skin and normal skin. CONCLUSION: Even though the number of individuals studied here is small and precludes any hasty generalization, having a single mutation in the ABCC6 gene seems enough to modify dermal elastic fibres. The relevance of performing a skin biopsy to identify heterozygote carriers in the family of a PXE patient remains to be determined.

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44 The intensity of staining was qualified in each section as 'absent`, 'weak`, 'moderate` or 'heavy` in keratinocytes, papillary fibroblasts, reticular fibroblasts, pre-elastic fibres, mature elastic fibres, and elastorrhexic fibres. Results Mutation detection In family 1, the index patient had a missense mutation (replacement of arginine by glycine at codon 391, R391G) and the large deletion EX23_29del. Login to comment
46 EX23-29del, R391G and L1335P are already known as disease-causing mutations.22,23 IVS24-3 C→T has not previously been described. 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] 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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112 Allele 1 Allele 2 Probe/DNA similarity Long range+breakpoint determination aCGH Remark 3 p.Arg391Gly c.1171A4G 24-27 del. Identical c.3307À1006_3882+1582del Yes *, Min. (16157574À16164330) Max. (16157202À16164346) 4 p.Arg1221Cys c.3661C4T Exon 30 del. Identical c.4209À?_4403+?del - *, True positive 7 p.Arg518Stop c.1552C4T Exon 2 del. 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

[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] Mutations in the ABCC6 gene as a cause of generali... J Invest Dermatol. 2014 Mar;134(3):658-65. doi: 10.1038/jid.2013.370. Epub 2013 Sep 5. Li Q, Brodsky JL, Conlin LK, Pawel B, Glatz AC, Gafni RI, Schurgers L, Uitto J, Hakonarson H, Deardorff MA, Levine MA
Mutations in the ABCC6 gene as a cause of generalized arterial calcification of infancy: genotypic overlap with pseudoxanthoma elasticum.
J Invest Dermatol. 2014 Mar;134(3):658-65. doi: 10.1038/jid.2013.370. Epub 2013 Sep 5., [PMID:24008425]

Abstract [show]
Generalized arterial calcification of infancy (GACI) is an autosomal recessive disorder characterized by congenital calcification of large- and medium-sized arteries, associated with early myocardial infarction, heart failure, and stroke, and premature death. Most cases of GACI are caused by mutations in the ENPP1 gene. We first studied two siblings with GACI from a non-consanguineous family without mutations in the ENPP1 gene. To search for disease-causing mutations, we identified genomic regions shared between the two affected siblings but not their unaffected parents or brother. The ABCC6 gene, which is mutated in pseudoxanthoma elasticum (PXE), resided within a small region of homozygosity shared by the affected siblings. Sequence analysis of ABCC6 revealed that the two affected siblings were homozygous for the missense mutation p.R1314W. Subsequently, ABCC6 mutations were identified in five additional GACI families with normal ENPP1 sequences. Genetic mutations in ABCC6 in patients with PXE are associated with ectopic tissue mineralization in the skin and arterial blood vessels. Thus, our findings provide additional evidence that the ABCC6 gene product inhibits calcification under physiologic conditions and confirm a second locus for GACI. In addition, our study emphasizes the potential utility of shared homozygosity mapping to identify genetic causes of inherited disorders.

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36 Family D 1 2 1 Family E c.3692insTT +/- 1 2 1 2 3 Family F I II g.del23-29 +/- p.R760W +/- 1 2 1 2 3 4 1 2 1 2 1 2 1 Family A Family B Family C I II p.R1314W +/- p.R1314W +/- c.2787+1G>T c.3736-1G>A +/- p.R391G +/- p.R391G +/- p.R1141X +/- c.346-6G>A +/- +/+ 1 2 3 4 p.R1141X +/+ +/- c.346-6G>A +/- 1 2 -/- -/- +/- +/+ +/+ +/+ +/- +/+ Figure 1. Login to comment
46 Only one ABCC6 mutation has been identified for the proband of Family C (patient 4; p.R391G) and the proband of Family E (patient 6; c.3692insTT). Login to comment
47 The p.R391G mutation resides in the fourth intracellular loop corresponding to the second transmembrane domain of ABCC6 protein, whereas the c.3692insTT mutation causes a frameshift and predicts truncation of the protein as a result of a premature termination codon 125bp downstream of the mutation and likely leads to nonsense-mediated mRNA decay (Table 2). Login to comment
77 Molecular and biochemical features of GACI patients Patient Family Age Mutation 1 Mutation 2 Mutation type Plasma [FGF23], RUml 1 1 1 A 3 Yrs p.R1314W p.R1314W MS/MS 59 2 A 6 Yrs p.R1314W p.R1314W MS/MS 97 3 B 1 Mo c.2787&#fe; 1G4T c.3736-1G4A SS/SS NT2 4 C 5 Yrs p.R391G ND MS/ND 83 5 D 1 Mo p.R1141* c.346-6G4A NS/SS3 NT 6 E 1 Mo c.3692 insTT ND FS/ND 374 7 F 1 Mo p.R760W del23-29 MS/del 1,430 Abbreviations: FS, frame shift; GACI, generalized arterial calcification of infancy; Mo, month; MS, missense; ND, not detected; NS, nonsense; NT, not tested; SS, splice site; Yrs, years. Login to comment