UC San Diego

Heart disease has been the leading cause of death in the U.S. over the past century despite its decreasing rate over the last 50 years. Understanding the function of new genes and pathways in a simple model system may provide novel insights and lead to new therapeutic targets for heart disease in humans. In mammalian systems, calcineurin-NFAT signaling has been implicated in the regulation of the cardiac hypertrophic response. However, how this gene interacts with other molecular pathways in the heart is unknown. In order to better understand this signaling process, the singular function of calmodulin (CaM), calcineurin (Pp2B-14D), and Nuclear Factor of Activated T-Cells (NFAT), in the heart was investigated, using the animal model system Drosophila melanogaster. Loss-of-function and gain-of-function studies were conducted in a tissue-specific manner using the GAL4/UAS system by means of RNAi and overexpression lines, respectively. The flies were dissected to expose the beating heart tube; hearts were filmed and analyzed using Semi-Automated Optical Heartbeat Analysis (SOHA) and key cardiac performance indicators were measured. Slightly significant differences between NFAT gene knockdown and respective controls using two RNAi lines were observed, yet there were no obvious changes observed in cardiac size. However, this may be due to insufficient KD or due to compensation by changes in expression of other genes. Overall, cardiac size was reduced in Pp2B-14D KD and increased in Pp2B-14D OE. Finally, CaM KD resulted in significant contractile defects when compared to their respective controls.