Using Embryos to Understand the Chromatin State of Mesoderm Induction

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DESCRIPTION (provided by applicant): Birth defects, including those of the neural tube, eye and limb, are caused by improper cellular specification during embryogenesis. One of the primary embryological events necessary for the formation of these specialized tissues is the induction of mesoderm. Our aim is to identify the genomic and biochemical processes that drive the formation of mesoderm with the long-term goal of being able to generate more complex tissue types. While the signaling pathways that mediate mesoderm induction and many other embryological processes are well understood, how downstream transcription factors interface and communicate with chromatin is still a mystery. This juxtaposition is central for normal cellular specification, and is emerging as a critical element of cellular reprogramming. Therefore, inroads into this problem are important for understanding errors during development and will enable the establishment of better protocols for regenerative medicine. With the advent of genomic sequencing technologies, we can now ask fundamental questions about how signaling pathways interface with chromatin, whether they are permissive or active players in generating open chromatin structures and how these signals are communicated between neighboring cells. In this grant, we use Xenopus laevis and Xenopus tropicalis to address the involvement of the chromatin state and its interface with the Nodal signaling factor, smad2/3, during in vivo mesoderm induction. The wealth of embryological resources present in these species, the deep knowledge of their fate maps, combined with newly available genomic tools, presents a prime opportunity to revisit mechanisms underlying classic cell fate and inductive interactions using emerging modern technologies. The central hypothesis of this grant is that the interplay between chromatin state and smad2/3 underlie mesoderm induction and patterning.