Abstracts Category : Other

Coordination of patterning and morphogenesis during early development in Xenopus laevis

by Exner Cameron Thompson

Over the course of development, cells and tissues of the embryo must take on the correct fates and morphologies to produce a functioning organism. The patterning events and morphogenetic processes that accomplish this task have been the subject of decades of research, the consequence of which has been a detailed comprehension of the molecular mechanisms that regulate each. Equally important is an understanding of the mechanisms that coordinate patterning with morphogenesis, such that they occur with the correct relative spatiotemporal dynamics. My thesis work sought to characterize such co-regulation in the context of two developmental events in a vertebrate model, the African clawed frog <i>Xenopus laevis:</i> induction of bottle cell formation at the onset of gastrulation after germ layer induction, and regulation of the morphogenetic movements of neurulation in relation to neural plate patterning. Chapter 1 of this dissertation provides a general introduction to the patterning and morphogenetic events of early development relevant to my thesis. Chapter 2 presents a discussion of my work to characterize the function of two signaling pathways, namely Nodal signaling and Wnt/Planar Cell Polarity, in the induction of bottle cells. My experiments confirm the requirement for Nodal signaling in bottle cell induction, but do not support a role for the individual transcriptional targets of Nodal signaling tested here or for Wnt/PCP. Chapter 3 summarizes my work to address the function of two transcription factor-encoding genes, <i>sall1</i> and <i> sall4,</i> in neural development, including their roles in anteroposterior neural patterning, neural tube morphogenesis, and neural differentiation. My work shows that both <i>sall1</i> and <i>sall4</i> are required for all three processes, and supports the hypothesis that their key role in this context is to transcriptionally repress stem cell factors of the <i>pou5f3</i> family, allowing progression through neural development. As a whole, this work summarizes my research to characterize molecules that co-regulate early patterning and morphogenetic events in the <i> X. laevis</i> embryo.