Genetic approaches, preferentially in model systems that both allow accurate measurement of heart function as well as efficient genetic screening, are necessary for substantial progress in identifying the genetic basis of heart failure. In proposal, we will test the hypothesis that the powerful mutagen, N-ethyl-N- nitrosourea (ENU), mutagenesis in mice, and gene-deletion screens in Drosophila, will lead to the discovery of novel disease-causing and disease-modifying genes for human heart failure. In order to test these hypotheses, we have performed a recessive mutagenesis screen in adult mice at 8 and 16 weeks of age using non-invasive echocardiography to screen for abnormalities in cardiac function and have already identified a heritable region on chromosome 1 that maps to a cardiomyopathic phenotype. To complement the mouse studies we propose to use the fly to identify novel cardiomyopathic genes. Drosophila genetics provides more than 19,000 molecularly-defined P-elements inserted throughout the Drosophila genome that facilitate the generation of high-density genomic coverage. We have developed an innovative approach to phenotype cardiac function in adult awake Drosophila and have identified a P-element mutation in the short gastrulation (sog) gene that results in dilated cardiomyopathy. Based on our preliminary findings, we propose that mouse and Drosophila genetics can identify novel genes and mechanisms that are responsible for human dilated cardiomyopathies. Accordingly, we propose the following specific aims:
Aim 1 : To identify novel genes causing cardiomyopathy using an ENU phenotype-driven recessive screen in adult mice. We propose to map the disease causing gene located on chromosome 1 in the ENU family with abnormal cardiac function.
Aim 2 : To investigate the biochemical and genetic mechanisms through which mutations in the dpp/BMP signaling pathway lead to dilated cardiomyopathy in adult Drosophila. Genetic complementation experiments will be performed in Drosophila to prove that sog deficiency causes cardiomyopathy.
Aim 3 : To test whether decreased antagonism of the BMP pathway in mice, will result in a cardiomyopathic phenotype under conditions of pressure overload. TAG experiments will be performed in knock out mice deficient in the endogenous mammalian BMP antagonists chordin and noggin.
Aim 4 : To identify novel genes causing cardiomyopathy by performing a genome-wide screen of deletion mutants in Drosophila. Flies heterozygous for PiggyBac derived deletion mutants from the Exelixis collection will be screened for cardiomyopathy using optical coherence tomography followed by fine mapping of the disease-causing gene(s). Thus, these four integrated aims will harness the power of mouse and Drosophila genetics to identify and evaluate novel candidate genes for their role in cardiomyopathy.
