Cadherin interactions in ectodermal derivative fate specification

项目总结/文摘

Project Summary/Abstract The ectoderm begins as an epithelial sheet of progenitor cells, and progressively the fate of its cells become limited to neural tissue, non-neural ectoderm (NNE), which becomes epidermis and placodal cells, and neural crest (NC) cells. Any failure in the specification or differentiation of these tissues can lead to defects such as neural tube closure failure, craniofacial abnormality, integu- ment dysfunction or sensory placode disorders. The early ectodermal progenitors are tightly ad- herent in nature, and yet through morphogenetic movements, they segregate into multiple tissues, the neural plate rolls up and separates from the NNE, the NC cells undergo an epithelial to mes- enchymal transition (EMT) separating from the neural tube and migrating to various sites in the developing embryo. Aberrant neural and NC development can lead to a host of common devel- opmental disorders such as spina bifida, aganglionosis of the intestinal tract, albinism and cleft palate. The mechanisms that drive the formation of these tissues, and the process of EMT and migration, are tightly controlled to ensure proper development. From previous studies, we and others have identified that misregulation of adhesion molecules, specifically N-cadherin (Ncad) and E-cadherin (Ecad), leads to abnormal development of the CNS and NC cells. Although these proteins have been well studied in vitro in cancer cells, there is a lack of consensus about the specific functions cadherin proteins have in regulating the development of ectodermal derivatives during early vertebrate development in vivo. Here, we propose to ascertain the role that Ncad and Ecad play to regulate the segregation and development of the neural tube, NNE and neural crest cells, and to clarify which proteins they interact with in these processes. With Aim 1, we will use gain and loss of function studies in avian embryos to test our hypothesis that heterophilic Ecad- Ncad interactions are required for ectoderm to differentiate into neural, NNE and NC cells, further identifying how they interact with each other and other cadherin proteins during NC EMT. Next, we will use an underutilized amphibian model organism, Ambystoma mexicanum (axolotl), to compare the expression and function of the cadherin proteins during early development and alle- viate current discrepancies in the field. This research proposal uses classic embryological meth- ods as well as two vertebrate model organisms, which will allow for analysis of functional conser- vation across vertebrate species. Completion of the proposed studies will provide substantial in- sights into the mechanisms that drive early fate specification, and the development program of ectodermal derivatives in vertebrate embryos.