Clonal dynamics of the blood stem cell niche

PROJECT SUMMARY
The mechanisms by which the hematopoietic stem and progenitor (HSPC) niche is affected by clonal
hematological disorders such as myelodysplastic syndrome (MDS) remain poorly understood. Furthermore, the
heterogeneity and clonal response of endothelial and stromal cells (the main components of the HSPC niche) in
MDS in vivo remain unexplored. To tackle these aspects, I developed a new zebrafish model of MDS by driving
the protooncogene CMYC overexpression specifically in blood cells. Additionally, I crossed a genetic lineage
tracing zebrafish line called GESTALT to a double transgenic zebrafish line carrying two fluorescent reporters
allowing to purify specifically niche endothelial and stromal cells. This way, I created a new GESTALT line that
permits CRISPR-CAS9 based barcoding during zebrafish embryonic development, purification of adult marrow
niche cells and recovery of niche DNA barcodes by sequencing. Combining these novel tools, I induced MDS in
barcoded zebrafish and read out the clonality and the transcriptome of endothelial and stromal cells. I discovered
that clones of stromal cells selectively expand, and endothelial cells are transcriptionally remodeled in MDS.
Given these data, I hypothesize that MDS remodels the clonality and transcriptional profile of the HSPC
niche and that mechanisms involved in HSPC-niche interactions promote disease progression. Under
the mentorship of Dr. Leonard Zon, I will investigate the mechanisms by which MDS remodels the niche using a
combination of in silico computational approaches, genetic (GESTALT) and color based (Zebrabow) lineage
tracing, confocal microscopy and in vivo mosaic mutagenesis. Once I establish my laboratory, I will build a
multidisciplinary team to deepen my computational analyses and broaden my in vivo genetic and biochemical
perturbations of the clonal mechanisms of niche involvement in MDS. My overarching goal is to identify novel
targetable mechanisms specific to the HSPC niche that would prevent and/or halt MDS progression. This
K99/R00 award will enable me to develop new technical skills, participate in courses that will improve my ability
to manage a laboratory, and attend conferences that will broaden my network and my knowledge of
hematological disease modeling, Zebrabow lineage tracing paired with confocal microscopy and zebrafish
mutagenesis. The scientific advisory committee I have put together includes experts in the fields of
hematopoiesis, lineage tracing, and stem cell biology and, along with Dr. Zon, will give me feedback on my
research and career progress. These proposed research and career development activities will pave the way for
me to become an independent investigator discovering and studying new mechanisms responsible for
hematopoietic disorders progression mediated by the blood stem cell niche.

Grant Number: 5K99DK134760-02
NIH Institute/Center: NIH
Principal Investigator: Chloe Baron