A novel mutation inKCNK16causing a gain-of-function in the TALK-1 potassium channel: a new cause of maturity onset diabetes of the young

Abstract

Word count2820 3 ABSTRACT Background Maturity-onset diabetes of the young (MODY) is a heterogeneous group of monogenic disorders of impaired glucose-stimulated insulin secretion (GSIS). Mechanisms include β-cell KATP channel dysfunction (e.g., KCNJ11 (MODY13) or ABCC8 (MODY12) mutations); however, no other β-cell channelopathies have been identified in MODY. MethodsA four-generation family with autosomal dominant non-obese, non-ketotic antibody-negative diabetes, without mutations in known MODY genes, underwent exome sequencing. Whole-cell and single-channel K + currents, Ca 2+ handling, and GSIS were determined in cells expressing either mutated or wild-type (WT) protein. ResultsWe identified a novel non-synonymous genetic mutation in KCNK16 (NM_001135105: c.341T>C, p.Leu114Pro) segregating with MODY. KCNK16 is the most abundant and -cell-restricted K + channel transcript and encodes the two-pore-domain K + channel TALK-1. Whole-cell K + currents in transfected HEK293 cells demonstrated drastic (312-fold increase) gain-of-function with TALK-1 Leu144Pro vs. WT, due to greater single channel activity. Glucose-stimulated cytosolic Ca 2+ influx was inhibited in mouse islets expressing TALK-1 Leu114Pro (area under the curve [AUC] at 20mM glucose: Leu114Pro 60.1 vs. WT 89.1; P=0.030) and less endoplasmic reticulum calcium storage (cyclopiazonic acid-induced release AUC:Leu114Pro 17.5 vs. WT 46.8; P=0.008). TALK-1 Leu114Pro significantly blunted GSIS compared to TALK-1 WT in both mouse (52% decrease, P=0.039) and human (38% decrease, P=0.019) islets.