Generation of an induced pluripotent stem cell line (MUSIi014-A) from an affected member of a family with autosomal dominant diabetes carrying p.L475P mutation in ZYG11A gene associated with a cell cycle arrest in beta-cell.

A heterozygous mutation (c.T1424C: p.L475P) in ZYG11A completely segregating with hyperglycemia in a Thai family with familial diabetes of the adulthood has been reported as a cause of cell cycle arrest in 1.1B4 cell line. This mutation is a suggestive cause of failure in adaptive beta-cell expansion which, thereby, contributes to the development of diabetes in the family. Here, an induced pluripotent stem cell (iPSC) line from peripheral blood mononuclear cells (PBMCs) of an affected family member carrying the mutation was generated using Sendai viral reprogramming. The established iPSC line is characterized and confirmed for pluripotency and chromosomal integrity.

Gain of Function of Malate Dehydrogenase 2 and Familial Hyperglycemia.

CONTEXT: Genes causing familial forms of diabetes mellitus are only partially known. OBJECTIVE: We set out to identify the genetic cause of hyperglycemia in multigenerational families with an apparent autosomal dominant form of adult-onset diabetes not due to mutations in known monogenic diabetes genes. METHODS: Existing whole-exome sequencing (WES) data were used to identify exonic variants segregating with diabetes in 60 families from the United States and Italy. Functional studies were carried out in vitro (transduced MIN6-K8 cells) and in vivo (Caenorhabditis elegans) to assess the diabetogenic potential of 2 variants in the malate dehydrogenase 2 (MDH2) gene linked with hyperglycemia in 2 of the families. RESULTS: A very rare mutation (p.Arg52Cys) in MDH2 strongly segregated with hyperglycemia in 1 family from the United States. An infrequent MDH2 missense variant (p.Val160Met) also showed disease cosegregation in a family from Italy, although with reduced penetrance. In silico, both Arg52Cys and Val160Met were shown to affect MDH2 protein structure and function. In transfected HepG2 cells, both variants significantly increased MDH2 enzymatic activity, thereby decreasing the NAD+/NADH ratio-a change known to affect insulin signaling and secretion. Stable expression of human wild-type MDH2 in MIN6-K8 cell lines enhanced glucose- and GLP-1-stimulated insulin secretion. This effect was blunted by the Cys52 or Met160 substitutions. Nematodes carrying equivalent changes at the orthologous positions of the mdh-2 gene showed impaired glucose-stimulated insulin secretion. CONCLUSION: Our findings suggest a central role of MDH2 in human glucose homeostasis and indicate that gain of function variants in this gene may be involved in the etiology of familial forms of diabetes.