Investigating the pathogenicity of the recessive p.A251T variant in monogenic diabetes using iPSC-derived beta-like cells.

Monogenic diabetes, formerly called Maturity-Onset Diabetes of the Young (MODY), involves single-gene mutations, typically with dominant inheritance, and has been associated with variants in 14 genes. Among these, mutations are the most common, and their diagnosis allows the use of alternative therapies, including sulfonylureas. In an earlier study, we described a variant displaying recessive transmission, p.A251T (Misra, S et al, , 2020). Initial functional studies revealed only a modest impact on protein function. We extend these earlier studies to demonstrate that beta-like cells derived from pluripotent stem cells from variant carriers show impaired differentiation into insulin-positive cells, whereas differentiation into alpha cells is significantly enhanced. Additionally, mutant cells showed impaired glucose-stimulated insulin secretion but partially preserved responsiveness to treatment with sulfonylureas. Our study provides proof of principle for the utility of using patient-derived stem cells as a platform to assess the pathogenicity of variants, and to explore potential treatment strategies.