Fabry disease: Characterization of α-galactosidase A double mutations and the D313Y plasma enzyme pseudodeficiency allele
Fabry disease, an X‐linked inborn error of glycosphingolipid catabolism, results from mutations in the gene encoding the lysosomal exoglycohydrolase, α‐galactosidase A (α‐Gal A; GLA). In two unrelated classically affected males, two α‐Gal A missense mutations were identified: R112C + D313Y (c.334C&g...
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Published in | Human mutation Vol. 22; no. 6; pp. 486 - 492 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Hoboken
Wiley Subscription Services, Inc., A Wiley Company
01.12.2003
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Subjects | |
Online Access | Get full text |
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Summary: | Fabry disease, an X‐linked inborn error of glycosphingolipid catabolism, results from mutations in the gene encoding the lysosomal exoglycohydrolase, α‐galactosidase A (α‐Gal A; GLA). In two unrelated classically affected males, two α‐Gal A missense mutations were identified: R112C + D313Y (c.334C>T + c.937G>T) and C172G + D313Y (c.514T>G + c.937G>T). The D313Y lesion was previously identified in classically affected males as the single mutation [Eng et al., 1993] or in cis with another missense mutation, D313Y + G411D (c.937G>T + c.1232G>A) [Guffon et al., 1998]. To determine whether the D313Y mutation was a deleterious mutation or a coding region sequence variant, the frequency of D313Y in normal X‐chromosomes, as well as its enzymatic activity and subcellular localization in COS‐7 cells was determined. D313Y occurred in 0.45% of 883 normal X‐chromosomes, while the R112C, C172G, and G411D missense mutations were not detected in over 500 normal X‐chromosomes. Expression of D313Y in COS‐7 cells resulted in& tilde;60% of wild‐type enzymatic activity and showed lysosomal localization, while R112C, C172G, G411D, and the double‐mutated constructs had markedly reduced or no detectable activity and were all retained in the endoplasmic reticulum. The expressed D313Y enzyme was stable at lysosomal pH (pH 4.6), while at neutral pH (pH 7.4), it had decreased activity. A molecular homology model of human α‐Gal A, based on the X‐ray crystal structure of chicken α‐galactosidase B (α‐Gal B; α‐N‐acetylgalactosaminidase) was generated [Garman et al., 2002], which provided evidence that D313Y did not markedly disrupt the α‐Gal A enzyme structure. Thus, D313Y is a rare exonic variant with about 60% of wild‐type activity in vitro and reduced activity at neutral pH, resulting in low plasma α‐Gal A activity. Hum Mutat 22:486–492, 2003. © 2003 Wiley‐Liss, Inc. |
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Bibliography: | Communicated by William Sly ArticleID:HUMU10275 National Institutes of Health - No. R37 DK34045, 5 P30 HD28822 istex:BBE1A4FE11823A315BBC6E55DE8546A78F6B8866 National Center of Research Resources, National Institutes of Health - No. 5 MO1 RR00071 ark:/67375/WNG-KDMHNM9P-T Genzyme Corporation ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1059-7794 1098-1004 |
DOI: | 10.1002/humu.10275 |