The developmental origin of adult pluripotent stem cells

Project Summary: Although many highly regenerative animals harbor adult pluripotent stem cells, the
molecular and cellular mechanisms by which these cells form during development remains unknown in any
species. Major gaps in our understanding of adult pluripotent stem cell formation include the identity of the
molecules that govern the specification and, or maintenance of these cellular populations. Studying
regenerative species can reveal mechanisms for how adult pluripotent stem cells are maintained through
development, nature’s solution for making a faithful and easily programmable population of stem cells. Many
research organisms have been developed into model systems to interrogate cellular contributions and
molecular players in regeneration, yet it has been challenging to access embryogenesis in most of these
species. This has created a gap in knowledge in understanding the developmental origins of adult pluripotent
stem cells and in turn, has left many outstanding questions, specifically: how are adult pluripotent stem cells
(aPSCs) formed in highly regenerative species. The long-term goal of this project is to determine how the
identity of adult pluripotent stem cell population is established during development and how it is retained in
adult animals. The overall objective of this proposal is to identify mechanisms for aPSC formation during
embryonic development in Hofstenia and to determine the accompaning stem cell-specific chromatin state.
Preliminary data indicate one pair of cells in the embryo gives rise to cells that resemble aPSCs in distribution,
behavior, and gene expression. The rationale for this proposed work is through leveraging the developmental
lineage of aPSCs in Hofstenia we identify the essential genetic components of sustained pluripotency. Our
central hypothesis is that specific gene regulatory networks form aPSCs either by the specification or
maintenance of open chromatin. This hypothesis will be tested by pursuing three specific aims: I will (1) identify
the complete molecular trajectory of adult pluripotent stem cell (aPSC) formation to understand the progression
of stem cell properties and reveal putative regulators of stem cell formation, (2) define the chromatin landscape
associated with of aPSCs during development to uncover genomic states that enable pluripotency, and (3)
functionally assess transcription factors involved in specifying and, or, maintaining stem cells. Our approach is
innovative because it is one of the first to mechanistically interrogate the developmental origin of an adult
pluripotent stem cell population, and further because it uses an integrative strategy that combines genomic and
cell biological approaches. The proposed research is significant because it will advance our understanding of
the regulation of stem cell identity in development and may open new avenues of research for understanding
stem cell biology. During the fellowship award period I will learn a multitude of approaches in Hofstenia,
expanding my experimental toolkit to address mechanistic questions about stem cells all within training
environment of Harvard University which has the experts in all the disciplines which my work will span.

Grant Number: 1F32GM153139-01A1
NIH Institute/Center: NIH
Principal Investigator: Paul Bump