University of Texas Medical Branch, USA
Title: Reactivation of fetal splicing programs in diabetic hearts
Muge N. Kuyumcu-Martinez received her Ph.D. at Baylor College of Medicine where she also pursued her post-doctoral training. She was promoted to an Instructor position at Baylor College of Medicine. In 2010, she was recruited as a tenure track Assistant Professor to the University of Texas Medical Branch. Since then, she has received the prestigious March of Dimes Basil O'Connor Starter Scholar Award. Her senior author publication has made the cover of the Journal of Biological Chemistry. Her research interests are to understand the signals that regulate alternative splicing decisions in the heart and how splicing dysregulation contributes to diabetic heart disease.
Introduction: Diabetic cardiomyopathy can lead to heart failure and death among diabetics independent of effects from hypertension and coronary heart disease. Chronic activation of Protein Kinase C (PKC) signaling promotes diabetic cardiomyopathy by mechanisms that are not well understood. PKC has been implicated in alternative splicing (AS) regulation in the heart.
Aim: Our goal is to determine whether prolonged PKC activity induces alternative splicing abnormalities in diabetic hearts.
Methods: We performed RNA sequencing followed by computational analysis using MISO algorithm to distinguish AS patterns in diabetic versus normal mouse hearts. We used two Type 1 diabetes mouse models (non-obese diabetic and Streptozotocin induced) as well as Type 2 human heart tissues to validate alternative splicing changes by quantitative RT-PCR. Using PKC inhibitors or PKC alpha/beta specific shRNAs, we identified which AS changes in diabetic hearts are controlled by PKC. Splicing changes that are altered in diabetic hearts were targets of a splicing regulator called CELF1. Therefore, we mutated PKC phosphorylation sites on CELF1 to determine the effect of phosphorylation on CELF1 regulated genes that are mis-spliced in diabetes.
Results: We found genome wide alternative splicing changes in diabetic hearts and identified a set of 22 AS events that reverse to a fetal splicing pattern in adult diabetic hearts. GO analysis indicates that the genes that undergo a developmental AS switch in diabetic hearts have important functions in embryonic development and RNA metabolism. Importantly, PKC isozymes alpha and beta control alternative splicing of these genes in fetal hearts via phosphorylation of splicing regulator CELF1. A mutant of CELF1 that is non-phosphorylatable by PKC can no longer regulate splicing events altered in diabetic hearts.
Conclusion: PKC contributes to diabetic cardiomyopathy by activating embryonic splicing programs in adult hearts.