Abstract 570: A Functional Mutation in WNT16a Up-regulates Pancreatic Expression of TCF7L2 Variants Through Wnt Signaling Pathway
Type 2 (non-insulin-dependent) diabetes mellitus (T2DM) is associated with a marked increase in the risk of coronary heart disease. The discovery of TCF7L2 as a global T2DM gene has triggered investigations to explore the clinical utility of its variants for guiding the development of new diagnostic and therapeutic strategies. However, interpreting the resulting associations into function still remains unclear. Canonical Wnt signaling regulates β-catenin and its binding with TCF7L2, which in turn is critical for the production of glucagon like protein-1 (GLP-1). This study examines the role of a novel frame-shift insertion discovered in a conserved region of WNT16a, and it is proposed that this mutation affects T2DM susceptibility in conjunction with gene variants in TCF7L2. Our results predicted that the insertion would convert the upstream open reading frame in the Wnt16a mRNA to an alternative, in-frame translation initiation site, resulting in the prevention of nonsense-mediated decay that would normally occur in the wild-type message, leading to a consequent stabilization of the mutated WNT16a message. To examine the role of Wnt16a in the Wnt signaling pathway, DNA and serum samples from 2,034 individuals (48% with T2DM) from the Sikh Diabetes Study were used in this investigation, of which 32% were WNT16a insertion carriers. There was a 3.2 fold increase in Wnt16a mRNA levels in pancreatic tissues from the insertion carriers and a significant increase (70%, p<0.0001) in luciferase activity in the constructs carrying the insertion. The expression of TCF7L2 mRNA in pancreas was also elevated (~23-fold) among the insertion carriers (p=0.003). Our results suggest synergistic effects of WNT16a insertion mutants and the at-risk ‘T ‘allele of TCF7L2 (rs7903146) for compounding the risk of T2DM, perhaps by impacting genes related to β-cell function in the Wnt/β-catenin/TCF7L2 signaling pathway.
- © 2013 by American Heart Association, Inc.