Project Details
Description
Crosstalk of Splicing and Signaling during HSPC Fate Choices
Project Abstract
Myelodysplastic syndrome (MDS) is a spectrum of disorders arising from hematopoietic stem and progenitor
cell (HSPC) dysfunction resulting in ineffective hematopoiesis and cytopenias. Spliceosomal components are
mutated in greater than 60% of all MDS cases, yet it remains a puzzle how dysfunction in general splicing
factors can mediate the specific outcomes observed in MDS. The slow progress comes, in part, due to our
poor understanding of splicing regulation of HSPC fate choices. Indeed, as RNA splicing is mostly studied in
yeast and cell culture, tissue-specific regulation of splicing in vivo is largely unexplored. Here, using HSPC
development as a paradigm, we seek to illuminate how the molecular regulation of RNA splicing impacts
HSPC fate choices. By understanding this fundamental process, we strive to identify potentially novel ways to
target splicing factor-defective HSPCs in MDS. We recently reported a severe HSPC formation defect in
zebrafish loss-of-function mutants for the spliceosomal component, splicing factor 3b, subunit 1 (sf3b1), which
is the most commonly mutated splicing factor in MDS. We uncovered that Sf3b1 regulates stat3 (signal
transducer and activator of transcription 3) pre-mRNA splicing and demonstrated that mis-splicing of stat3
results in diminished pathway activation. We determined that overexpression of an active form of Stat3 can
suppress the HSPC defects in sf3b1 mutants, demonstrating that Sf3b1 regulation of STAT3 signaling is
important for HSPC formation. In preliminary studies, we determined that STAT3 inhibition serves as a
conserved synthetic lethality with SF3B1 heterozygosity in both zebrafish and human MDS HSPCs. Based on
these findings, we performed a chemical modifier screen in sf3b1 mutant zebrafish and identified other Sf3b1-
regulated signaling pathways critical for HSPCs. These studies establish zebrafish as an excellent model for
discovery of HSPC splicing regulation and novel MDS vulnerabilities. Here, we will test the hypothesis that the
splicing factor Sf3b1 is a key director of the choice of splice isoforms for signaling pathway components
essential for HSPC formation. We will use zebrafish genetic and screening capabilities coupled with studies in
human MDS cells to explore the role of specific splice isoforms on HSPC fate decisions, determine the function
of cis-regulatory sequences on Sf3b1-regulated splicing choices in vivo, and identify novel vulnerabilities for
SF3B1-mutated HSPCs. Accomplishing these aims will inform our basic understanding of the poorly
understood role of splicing in HSPC fate decisions and lead to the identification of novel approaches for
selective targeting of SF3B1-mutated MDS HSPCs.
Status | Active |
---|---|
Effective start/end date | 9/1/20 → 6/30/24 |
Funding
- National Institute of Diabetes and Digestive and Kidney Diseases: $415,030.00
- National Institute of Diabetes and Digestive and Kidney Diseases: $405,904.00
- National Institute of Diabetes and Digestive and Kidney Diseases: $413,367.00
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