Glycogen storage disease type Ia: molecular diagnosis of 51 Japanese patients and characterization of splicing mutations by analysis of ectopically transcribed mRNA from lymphoblastoid cells.
Glycogen storage disease type Ia (GSD-Ia) is an autosomal recessive disorder of glycogen metabolism caused by a deficiency of glucose-6-phosphatase (G6Pase) that is expressed in the liver, kidney, and intestinal mucosa. Clinical manifestations include short stature, hepatomegaly, hypoglycemia, hyperuricemia, and lactic acidemia. To elucidate a spectrum of the G6Pase gene mutations and their frequencies, we analyzed mutations in 51 unrelated Japanese patients with GSD-Ia. The most prevalent mutation was g727t, accounting for 88 of 102 mutant alleles examined, followed by R170X mutation, which accounted for 6 mutant alleles, and R83H mutation which was observed in 3 mutant alleles. In addition, 3 different, novel mutations, IVS1-1g<a, Gly122-to-Asp (G122D) and His179-to-Pro (H179P), were identified. We were able to detect "ectopically" transcribed G6Pase-mRNA in Epstein-Barr virus-transformed lymphoblastoid cells and observed aberrant mRNA splicing associated with the g727t and IVS1-1g<a mutations. To our knowledge, this is the first report that ectopic expression can be utilized for the characterization of GSD-Ia mutations. Our findings suggest that a screening for the g727t, R170X, and R83H mutations by simple DNA-based diagnostic methods can detect 95% of the G6Pase mutant alleles in Japanese patients with GSD-Ia, and remaining mutations can be identified and characterized by the direct sequencing of genomic DNA and/or the analysis of ectopically expressed mRNA. The noninvasive molecular diagnosis for GSD-Ia may ultimately replace the conventional means of enzymatic diagnosis that requires liver biopsy.
Akanuma
J
J
Department of Medical Genetics, Tohoku University School of Medicine, Sendai, Japan.
Nishigaki
T
T
Fujii
K
K
Matsubara
Y
Y
Inui
K
K
Takahashi
K
K
Kure
S
S
Suzuki
Y
Y
Ohura
T
T
Miyabayashi
S
S
Ogawa
E
E
Iinuma
K
K
Okada
S
S
Narisawa
K
K
D000483:Alleles; D017398:Alternative Splicing; D002461:Cell Line, Transformed; D005091:Exons; D005260:Female; D005838:Genotype; D005952:Glucose-6-Phosphatase / Q000235:genetics*; D005953:Glycogen Storage Disease Type I / Q000235:genetics*; D006801:Humans; D007564:Japan; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D009154:Mutation; D010375:Pedigree; D017354:Point Mutation; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D012333:RNA, Messenger; D005952:Glucose-6-Phosphatase