Several subtypes of MODY have been described in women with GDM, including MODY2 (mutation in glucokinase gene), MODY3 (mutation in hepatocyte nuclear factor 1a), and MODY4 (mutation in insulin promoter factor 1) .
Velho, "Long-term follow-up of oral glucose tolerance test-derived glucose tolerance and insulin secretion and insulin sensitivity indexes in subjects with glucokinase mutations (MODY2)," Diabetes Care, vol.
Genetic defects in six genes are known to cause MODY: the hepatocyte nuclear factor-4[alpha]: HNF-4[alpha]/(MODY1); glucokinase: GCK/(MODY2); the hepatocyte nuclear factor-1[alpha]: HNF-1[alpha]/(MODY3); insulin promoter factor-1: IPFl/ (MODY4); hepatocyte nuclear factor-1[beta]: HNF-1[beta]/(MODY5); and transcriptional factor, neurogenic differentiation1: Neuro-D1/(MODY 6) (3-5).
Mutations in the glucokinase gene lead to an impaired sensing of blood glucose by the pancreatic [beta] cell, causing an autosomal dominant form of type 2 diabetes, maturity-onset diabetes of the young type 2 (MODY2).
Moreover, the promoter and the complete coding region for isoform 1 of GCK gene was sequenced in 13 pregnant women with suspect MODY2. In detail, fragments containing the promoter and ten exons were amplified by PCR using specific primers designed based on the reference gene sequence.