Molecular analysis of the AGL gene: identification of 25 novel mutations and evidence of genetic heterogeneity in patients with Glycogen Storage Disease Type III.
OBJECTIVE
Glycogen Storage Disease Type III (limit dextrinosis; Cori or Forbes disease) is an autosomal recessive disorder of glycogen metabolism caused by deficient activity of glycogen debranching enzyme in liver and muscle (Glycogen Storage Disease Type IIIa) or liver only (Glycogen Storage Disease Type IIIb). These two clinically distinct phenotypes are caused by mutations in the same gene (amylo-1,6-glucosidase or AGL). Although most patients with Glycogen Storage Disease Type III have private mutations, common mutations have been identified in some populations, and two specific mutations in exon 3, c.18_19delGA (p.Gln6HisfsX20) and c.16C>T (p.Gln6X), are associated with the Glycogen Storage Disease Type IIIb phenotype.


METHODS
To further examine the heterogeneity found in Glycogen Storage Disease Type III patients, we have sequenced the AGL gene in 34 patients with a clinically and/or biochemically confirmed diagnosis of Glycogen Storage Disease Type III.


RESULTS
We have identified 38 different mutations (25 novel and 13 previously reported) and have compiled a list of all mutations previously reported in the literature.


CONCLUSIONS
We conclude that Glycogen Storage Disease Type III is a highly heterogeneous disorder usually requiring full gene sequencing to identify both pathogenic mutations. The finding of at least one of the two exon 3 mutations in all of the Glycogen Storage Disease Type IIIb patients tested allows for diagnosis of this subtype without the need for a muscle biopsy.
Goldstein
Jennifer L
JL
Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710, USA.
Austin
Stephanie L
SL
Boyette
Keri
K
Kanaly
Angela
A
Veerapandiyan
Aravind
A
Rehder
Catherine
C
Kishnani
Priya S
PS
Bali
Deeksha S
DS
D000595:Amino Acid Sequence; D005091:Exons / Q000235:genetics; D018740:Genetic Heterogeneity; D006004:Glycogen Debranching Enzyme System / Q000235:genetics*; D006010:Glycogen Storage Disease Type III / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009206:Myocardium / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
D006004:Glycogen Debranching Enzyme System; C030563:amylo-1,6-glucosidase