Mutational spectrum and identification of five novel mutations in G6PC1 gene from a cohort of Glycogen Storage Disease Type 1a.

BACKGROUND

Glycogen storage disease type-1a is an inherited, autosomal recessive disorder caused by mutations in G6PC1 gene leading to deficiency of glucose-6-phosphatase-α specifically in the liver/kidney/intestine.

PATIENTS AND METHODS

DNA of six unrelated Indian GSD-1a patients were screened for mutations in the entire coding region of G6PC1 gene followed by direct DNA sequencing and functional was tested using glucose-6-phosphatase assay.

RESULTS

Mutational screening of GSD-1a patients identified five novel mutations, viz., 1) p.V99Cfs3, 2) p.G125R, 3) IVS1-2A > T, 4) IVS3 + 39G > A and 5) IVS3 + 42G > A along with three previously reported mutations p.G118D, p.R149Q and p.A331V. Interestingly, each of the p.V99Cfs3, IVS1-2A > T and p.G118D mutations are identified in two unrelated GSD-1a cases. Further allelic distribution of p.V99Cfs3 and p.A331V mutations were confirmed by RFLP analysis, consistent with autosomal recessive inheritance. Functional characterization revealed that glucose-6-phosphatase activity was completely abrogated with the mutant proteins p.G125R, p.R149Q, p.G118D, p.A331V and p.V99Cfs3 than wild-type. However, no significant changes were observed in the expression of mutant constructs at transcription and translation level.

CONCLUSION

Five novel mutations, p.V99Cfs*3, p.G125R, IVS1-2A > T, IVS3 + 39G > A and IVS3 + 42G > A are reported first time to cause GSD-1a among Indian ethnicity and are not yet reported elsewhere, suggesting separate ethnic founder effects for some mutations among Indian ethnicity.