The MODY-associated L114P mutation increases islet glucagon secretion and limits insulin secretion resulting in transient neonatal diabetes and glucose dyshomeostasis in adults.

The gain-of-function mutation in the TALK-1 K channel (p.L114P) is associated with maturity-onset diabetes of the young (MODY). TALK-1 is a key regulator of β-cell electrical activity and glucose-stimulated insulin secretion. The gene encoding TALK-1 is the most abundant and β-cell-restricted K channel transcript. To investigate the impact of L114P on glucose homeostasis and confirm its association with MODY, a mouse model containing the L114P mutation was generated. Heterozygous and homozygous L114P mice exhibit increased neonatal lethality in the C57BL/6J and the CD-1 (ICR) genetic background, respectively. Lethality is likely a result of severe hyperglycemia observed in the homozygous L114P neonates due to lack of glucose-stimulated insulin secretion and can be reduced with insulin treatment. L114P increased whole-cell β-cell K currents resulting in blunted glucose-stimulated Ca entry and loss of glucose-induced Ca oscillations. Thus, adult L114P mice have reduced glucose-stimulated insulin secretion and plasma insulin levels, which significantly impairs glucose homeostasis. Taken together, this study shows that the MODY-associated L114P mutation disrupts glucose homeostasis in adult mice resembling a MODY phenotype and causes neonatal lethality by inhibiting islet insulin secretion during development. These data suggest that TALK-1 is an islet-restricted target for the treatment for diabetes.