Glycogen Storage Disease Type Ia Screening Using Dried Blood Spots on Filter Paper: Application of COP-PCR for Detection of the c.648G>T G6PC Gene Mutation.

Glycogen storage disease type Ia (GSDIa, OMIM #232200) is an autosomal recessive metabolic disease characterized by impaired glucose homeostasis and has a long-term complication of hepatocellular adenoma/carcinoma. GSDIa is caused by deleterious mutations in the glucose-6-phosphatase gene (G6PC). Recent studies have suggested that early treatment by gene replacement therapy may be a good solution to correct the glucose metabolism and prevent serious late complications. Early treatment of the disease needs an early disease detection system. Thus, we aimed to develop a screening system for GSDIa using dried blood spots (DBS) to detect the c.648G>T mutation in G6PC, which is a frequent mutation in the East Asian population. In this study, a total of 51 DBS samples (50 healthy controls and one patient with c.648G>T) were tested by modified competitive oligonucleotide priming PCR (mCOP-PCR). In control DBS samples, the c.648G allele was amplified at lower Cq (quantification cycle) values (<11), while the c.648T allele was amplified at higher Cq values (>14). In the patient DBS sample, the c.648T allele was amplified at a lower Cq value (<11), and the c.648G allele was amplified at a higher Cq value (>14). Based on these findings, we concluded that our mCOP-PCR system clearly differentiated the wild-type and mutant alleles, and may be applicable for screening for GSDIa with the c.648G>T mutation in G6PC.