Year 5

Heart disease is a major cause of morbidity and mortality in our society. Congestive heart failure and cardiac arrhythmias are the most common mechanism by which heart disease leads to sudden cardiac death. Genetic studies in the general population have determined that susceptibility to cardiac arrhythmia and congestive heart failure is due to mutations in certain genes that guide cardiac development. Specifically, mutations in certain molecules called transcription factors are the leading mechanisms by which genetic defects lead to congenital heart defects and cardiac arrhythmias. Our laboratory studies the mechanism by which transcription factors and signaling molecules guide cardiac development and lead to selective formation of different cardiac cells. Our laboratory has pioneered work that has lead to the discovery of mutations that lead to cardiac arrhythmia and heart failure. In the past year, we have made steady progress in characterization of some of the key factors that guide cardiac cell development. To this end, we have identified a molecule called R-spondin-3 (Rspo3) that is critical for cardiac cell growth and probably survival. We have determined that Rspo3 functions to keep cardiac cell proliferating and loss of Rspo3 leads to thin cardiac muscle and heart failure. The mutation of Rspo3 in mouse leads to not only heart failure, but also leads to arrhythmias and valvlular heart disease. Therefore, Rspo3 functions in multiple aspect cardiac development and plays an essential role in proliferation of resident cardiac stem cells. Since, Rspo3 is known to function in a specific cardiac pathway called Wnt pathway, our hypothesis is that Rspo3 is a needed growth factor that is guiding cardiac stem cells towards growth and proliferation. We have submitted a manuscript about our work with Rspo3.
Our laboratory has also identified a molecule called OSR1 which plays a critical role in cardiac septation and development of conduction system. Mice that lack Osr1 have defects in atrial septation and show evidence of cardiac arrhythmias. We are in the process of submitting a manuscript that describes our results with OSR1. In summary, the generous funding by CIRM has helped us identify important new molecules with novel mechanisms critical in cardiac development.