title: Genotype-phenotype correlation in two frequent mutations and mutation update in type III glycogen storage disease.
abstract: Deficiency of glycogen debranching enzyme (AGL) activity causes glycogen storage disease type III (GSD-III). Generalized loss of AGL activity results in GSD-IIIa, and muscle-specific retention of AGL activity results in GSD-IIIb. To date, no common mutation has been described among GSD-III patients, except for three alleles; two linked specifically with GSD-IIIb, and the third found only in North African Jews with GSD-IIIa. Here we report two frequent mutations, each of which was found in the homozygous state in multiple patients, and each of which was associated with a subset of clinical phenotype in those patients with that mutation. A novel point mutation of a single T deletion at cDNA position 3964 (3964delT) was first detected in an African American patient, who has a severe phenotype and early onset of clinical symptoms. The second mutation was an A to G transition at position -12 upstream of the 3' splice site of intron 32 (IVS32-12A > G). This lesion, previously implicated as a IIIb mutation in a Japanese patient, was identified in a confirmed GSD-IIIa Caucasian patient presenting with mild clinical symptoms. These two mutations together account for more than 12% of the molecular defects in the GSD-III patients tested. Our molecular and clinical data suggest a genotype-phenotype correlation for each of these mutations. Furthermore, this current study, coupled with our previous reports, describes the molecular tools necessary for the development of a DNA-based diagnostic test for GSD-III.
authors.affiliation: Division of Medical Genetics, Duke University Medical Center, Durham, North Carolina, 27710, USA.
authors.forename: W L
authors.initials: WL
authors.lastname: Shaiu
authors.forename: P S
authors.initials: PS
authors.lastname: Kishnani
authors.forename: J
authors.initials: J
authors.lastname: Shen
authors.forename: H M
authors.initials: HM
authors.lastname: Liu
authors.forename: Y T
authors.initials: YT
authors.lastname: Chen
mesh_terms: D000328:Adult; D017668:Age of Onset; D001483:Base Sequence; D044383:Black People / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D005838:Genotype; D006004:Glycogen Debranching Enzyme System / Q000235:genetics*; D006010:Glycogen Storage Disease Type III / Q000175:diagnosis / Q000201:enzymology* / Q000453:epidemiology / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D008297:Male; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics*; D018807:Polymorphism, Single-Stranded Conformational; D012326:RNA Splicing / Q000235:genetics; D044465:White People / Q000235:genetics; D001741:Black or African American
chemical_list: D006004:Glycogen Debranching Enzyme System