RUI: Ret Signaling in Pronephric Duct Morphogenesis

Rider University, Lawrenceville NJ

Investigators

Abstract

0235938 Drawbridge The goal of the PI's undergraduate-based research program is to identify, characterize and elucidate the specific function of cell-surface and guidance molecules involved in pronephric duct (PND) migration in amphibian embryos, with emphasis on the axolotl, a urodele amphibian. PND extension is a morphogenetic event critical to the establishment of the urogenital system in all vertebrates. In the axolotl embryo, PND migration occurs with impressive precision: cells of the PND primordium coalesce from intermediate mesoderm immediately ventral to somites 3-7 and actively migrate caudally as a cohesive stream until they reach and fuse with the cloaca. In mammals, it has been demonstrated that GDNF activation of the transmembrane tyrosine kinase Ret and its ligand-binding partner, GFRa1, is required for proper development of the metanephros - the adult kidney of amniote vertebrates. Asking whether Ret signaling might function in more primitive excretory systems, the PIs lab has recently shown that the activation of Ret is sufficient to explain PND pathfinding in the axolotl. These data have led to the hypothesis that axolotl PND migration occurs via migration of the Ret/GFRa1-expressing PND cells up an endogenous gradient of GDNF. During the course of the project proposed here, this model will be tested by (1) determination of the expression pattern of axolotl GDNF via in situ hybridization and whole mount immunocytochemistry; (2) inactivation of Ret, GFRa1 and GDNF in axolotl embryos to determine whether these proteins are necessary for PND migration. These data will provide a rigorous test of the hypothesis that Ret signaling performs an essential role in PND morphogenesis in anamniote embryos. Intellectual merit: Despite the fact that PND morphogenesis is the central event in establishing the excretory system, little is known about its formation in vertebrates that don't make a metanephros, i.e. fish and amphibians. The PI is one of only a few investigators exploiting fish or amphibian embryos to ask questions about PND morphogenesis; she is the only investigator currently studying this in the axolotl, even though its PND morphogenesis has been better characterized than either Xenopus or zebrafish. In addition, her work provides the first evidence showing that Ret function is required for morphogenesis of anamniote excretory systems. Thus, the PIs work contributes fundamental information about excretory system development and evolution. Broader impacts: The proposed activities will be conducted by the PI and undergraduates at Rider University, some doing independent research projects, some as participants in the PIs Recombinant DNA Techniques course. Rider's student demographic includes 15% underrepresented minorities, 37% first-generation college students and 58% women. Thus, the PIs research program benefits several groups typically underrepresented in science careers. In addition, most of her students performing independent research have the opportunity to present their work at regional or national scientific meetings.