Deciphering early cell fate decisions from the multipotent neural plate border.

The early developing embryo is a complex dynamic environment. During development, individual cells within the embryo must respond appropriately to a multitude of 'signals' to yield distinct cell types, e.g., neurons, muscle cells and bone to form our body's organs and structures e.g., brain, heart, and skeleton. Currently, how immature embryonic cells 'decide' their fate is not fully understood.

Precise control of such developmental processes is encoded in the genome in the form of multifactorial gene regulatory networks. However, how cells interpret external signals to activate internal cell-type specific gene regulatory networks is not clear.

This problem is exemplified in the neural plate border (NPB). The NPB is a discrete, transient region of the early developing embryo. Cells within the NPB region are multipotent, meaning they give rise to a number of different cell types and tissues.

Specifically, NPB cells generate neural crest and sensory placode cells. Neural crest cells in turn contribute to a wide range of derivatives in the vertebrate body, including elements of the peripheral nervous system, parts of the heart, pigment cells and the craniofacial skeleton. While placode cells form the cranial sensory structures, nose, ears, and lens.

Defects in the development of the neural crest and sensory placodes are associated with one-third of all congenital birth defects including cleft palate and other facial abnormalities. As well as a number of syndromes including DiGeorge, which presents in defects in the thymus and thyroid glands together with heart problems, and Hirschsprung syndrome which manifests in the intestinal nervous system resulting in defects in gastrointestinal tract movements.

Furthermore, a number of cancers are known to arise from neural crest derived structures such as melanoma, neuroblastoma, and glioma.

It is not known how the NPB is endowed with such unique multipotency and, when and how individual NPB cells are directed towards different lineages (i.e., neural crest or placodes). Tackling these questions has proved challenging due to the sparsity and transitory nature of NPB cells. However, with the advent of next-generation single-cell technologies and genome engineering tools it is now possible to address these questions.

I plan to combine next-generation single-cell 'Multiomics' with innovative developmental biology techniques I have adapted, to resolve the complexities of cell fate decisions from the NPB. In particular, I will determine the combinatorial action of signalling molecules, transcription factors, and regulatory elements comprising the complex gene regulatory networks that direct NPB cells towards specific fates.

I will conduct my research using the chicken embryo which is an excellent model for developmental biology owing to its accessibility, affordability, and similarity to human embryo development. I will extract NPB cells from chicken embryos using genetic tools I have previously developed. I will then perform single-cell 'Multiomics' experiments with isolated NPB cells to generate gene expression and regulatory data, from the same cells.

I will integrate and functionally validate these datasets to reconstruct gene regulatory networks underlying NPB cell fate decisions.

Unravelling the intricate mechanisms driving cell fate decisions will help us to understand the underlying cause(s) of disease as well as identifying potential targets for therapeutic intervention. Also, due to their unique multipotency, there is broad interest in using NPB cells in stem cell-based treatments. Identifying the molecular mechanisms and interactions underlying NPB development will facilitate development of efficient, targeted, protocols for this purpose.