Dissecting gene regulation of stem cell quiescence in Ciona - PROJECT SUMMARY
During development, the formation of heterogenous tissues, organs, and cellular networks depends on a careful
balance between cellular proliferation, quiescence, and differentiation. Once cells have fully differentiated, their
ability to proliferate or differentiate are most often lost, and so most adult cells are generally incapable of self-
regeneration or repair. The development of regenerative therapies will require harnessing this latent ability, but
first we need a deeper understanding of the processes that control it. Thus, understanding the genetic
architecture underlying quiescent progenitor behavior is key to developing and applying emerging therapies with
new technologies such as cellular reprogramming or genome editing. The objective of this proposal is to
characterize the regulation and functions of potentially important genes controlling quiescence, differentiation,
and proliferation in marine invertebrate and chordate Ciona robusta. Ciona are among our closest invertebrate
relatives, and so during development we share similar structural and molecular features. However, Ciona
undergo a dramatic conversion from larval to adult forms called metamorphosis, when the larval body plan
degenerates and is replaced by quiescent progenitors which must bypass programmed cell death to reemerge
post-metamorphosis and generate the adult body plan. One such cell population are larval neural progenitors
called Neck cells which are established in a discrete stem cell niche-like compartment. The signaling pathways
and genetic components that direct Neck entry, maintenance, and exit from quiescence remain uncharacterized.
I propose using the Neck cell population as a model to identify unique mechanisms regulating quiescence and
regeneration that can be harnessed for future therapies. The rationale for this proposal is that, by exploiting the
tractability of Ciona, the accessibility of these Neck cells, and their stereotyped cellular behaviors, I can closely
examine regulatory control of Neck cell quiescence, proliferation, and differentiation. I will do so by pursuing two
specific aims. 1) To investigate the control of Neck quiescence and proliferation during the larval stage by the
integration of extracellular cues and intracellular transcriptional control. 2) To investigate a novel mechanism for
transcriptional priming and delay of Neck cell differentiation. I will pursue these aims using an innovative
approach that combines cell lineage-specific, CRISPR/Cas9-based somatic gene knockouts and fluorescence
microscopy. The expected outcomes of the proposed work include identifying previously unrecognized functions
for conserved but poorly studied genes in neurodevelopment and how their spatiotemporal regulation can be
instructive for the precise timing of quiescence. This will establish a foundation for a targeted investigation of
neurodevelopmental processes underlying a wide range of human disorders.
