Fabry disease: identification of novel alpha-galactosidase A mutations and molecular carrier detection by use of fluorescent chemical cleavage of mismatches.
Fabry disease (FD) (angiokeratoma corporis diffusum) is an X-linked inborn error of glycosphingolipid metabolism caused by defects in the lysosomal alpha-galactosidase A gene (GLA). The enzymatic defect leads to the systemic accumulation of neutral glycosphingolipids with terminal alpha-galactosyl moieties. Clinically, affected hemizygous males have angiokeratoma, severe acroparesthesia, renal failure, and vasculopathy of the heart and brain. While demonstration of alpha-galactosidase deficiency in leukocytes is diagnostic in affected males, enzymatic detection of female carriers is often inconclusive, due to random X-chromosomal inactivation, underlining the need of molecular investigations for accurate genetic counseling. By use of chemical cleavage of mismatches adapted to fluorescence-based detection systems, we have characterized the mutations underlying alpha-Gal A deficiency in 16 individuals from six unrelated families with FD. The mutational spectrum included five missense mutations (C202W, C223G, N224D, R301Q, and Q327K) and one splice-site mutation [IVS3 G(-1) --> C]. Studies at the mRNA level showed that the latter led to altered pre-mRNA splicing with consequent alteration of the mRNA translational reading frame and generation of a premature termination codon of translation. By use of this strategy, carrier status was accurately assessed in all seven at-risk females tested, whereas enzymatic dosages failed to diagnose or exclude heterozygosity.
Germain
D P
DP
CHU Cochin Port-Royal, Université René Descartes, Paris, France. dominique.germain@brs.ap-hop-paris.fr
Poenaru
L
L
D000328:Adult; D000595:Amino Acid Sequence; D020137:Base Pair Mismatch / Q000235:genetics*; D001483:Base Sequence; D018388:Codon, Terminator / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004303:Dosage Compensation, Genetic; D005091:Exons / Q000235:genetics; D000795:Fabry Disease / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D005456:Fluorescent Dyes; D006580:Genetic Carrier Screening / Q000379:methods*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense / Q000235:genetics; D010375:Pedigree; D012326:RNA Splicing / Q000235:genetics; D012680:Sensitivity and Specificity; D000519:alpha-Galactosidase / Q000097:blood / Q000737:chemistry / Q000235:genetics*
D018388:Codon, Terminator; D005456:Fluorescent Dyes; D004247:DNA; D000519:alpha-Galactosidase