Abstract 939: Galpha-i Signaling in Neural Crest Cells is Required for Normal Migration of Cardiac Neural Crest Cells, Cardiac Development, and Survival

Abstract

G protein coupled receptors (GPCRs) have long been known to play crucial roles in transducing environmental signals to the adult cardiovascular system. In recent years, the roles of G protein-mediated signaling pathways in orchestrating the interactions of different tissues during cardiovascular development have become increasingly evident. To analyze the role of G protein signaling pathways in vivo we have generated mice where the function of the heterotrimeric G alpha subunit Gai can be ablated in a cell type specific manner utilizing the Cre-loxP system. We have mated these mice to two different neural crest-specific Cre lines in order to probe the effects of loss of Gai mediated signaling on the ability of neural crest cells (NCC) to contribute to the developing outflow tract and aortic arch arteries. METHODS: We have generated mice that express the Gai-inhibiting pertussis toxin S1 subunit (PTX) from the ROSA26 locus in a Cre recombination dependent manner (ROSA-PTX mice). These were mated to mice expressing either the Wnt1 Cre or P0 Cre transgene. Wnt1Cre is active in both premigratory and migratory NCC, whereas P0Cre is active only in migratory NCC and their derivatives. RESULTS: P0Cre-ROSA-PTX mice were normal at birth and demonstrated no structural heart defects. In contrast, Wnt1Cre-ROSA-PTX mice were present in normal numbers at late gestation but died perinatally due in part to cardiac outflow tract defects. Excision reporter and in situ hybridization studies suggest this is secondary to a delay/blockage of cardiac NCC migration into the developing outflow tract. NCC migration into the pharyngeal arches was unaffected in these mice and no craniofacial, thymic, or aortic arch abnormalities were observed. CONCLUSIONS: These results indicate that Gai-mediated signaling is required in premigratory or early migratory cardiac NCC for normal development of the outflow tract. In contrast, endothelin A receptor knockout mice (currently the only GPCR knock out with a neural crest phenotype) are thought to exhibit defects of postmigratory NCC function. RNA profiling of NCC for GPCRs involved in this Gai-dependent pathway has revealed several potential candidate receptors, including orphan receptors. Further analysis of these receptors is underway.