The formation of the embryonic nervous system is a crucial early event in vertebrate development. The process by which the nervous system forms is complex, beginning with the induction of the neural epithelium to form the neural plate, to the subsequent curling and fusion of the neural folds into the neural tube. Key to the process of neurulation are the coordinated cell shape changes and cell movements that occur in the neural plate and neural folds. Amongst the molecules thought to be involved in regulating these cell-cell interactions are members of the cadherin family of cell adhesion molecules. Recently, a new family of cadherin-like genes, the protocadherins, has been isolated, but whose functions during development are generally unknown. At least some protocadherins can function as cell adhesion molecules, and many are expressed in the early nervous system. Thus an important question is whether protocadherins function to mediate cell adhesion during vertebrate neurulation.
This study proposes an in depth analysis of one such protocadherin, NF-protocadherin (NFPC), isolated from Xenopus. NFPC exhibits a striking expression pattern in the early embryonic nervous system, where it is initially restricted to the tips of the neural folds. Furthermore, the cellular protein TAF1, previously shown to interact with NFPC, is also expressed in the neural folds and neural plate, albeit in a broader domain than NFPC. This suggests a role for NFPC and TAF1 in mediating the adhesive events that lead to the formation and/or closing of the neural tube. Accordingly, to dissect the roles of NFPC and TAF1 in neurulation, we propose to disrupt NFPC and TAF1 expression in early embryos, using an antisense morpholino approach, and assess the consequences to neural tube formation. Furthermore, as it is not known how protocadherins function as cell adhesion molecules, and whether they may have additional roles in cell signaling, the mechanism by which NFPC acts will be investigated by isolating and analyzing other cytoplasmic factors with which it interacts.
The results from these studies will provide broader insights into the molecular mechanisms by which the vertebrate nervous system forms, as well as an understanding of how protocadherins contribute to this process. These studies will also lead to elucidation of the intracellular proteins that interact with protocadherins, providing valuable information into how the adhesion between neighboring cells is translated into cellular differentiation and tissue histogenesis. These studies will impact the education and training of students at Montana State University, as both undergraduate and graduate students will be integrally involved in the described projects. Furthermore, many of the techniques utilized in this proposal, such as the injection of RNA and antisense morpholinos into frog embryos, and the analysis of their effect on development, are currently being adapted for use by undergraduates in the Vertebrate Embryology Lab at Montana State University. This in turn will help to train future scientists in the processes, methods and technologies of modern cell and developmental biology.
