# Role of the ETV6 transcription factor in hematopoietic stem cell function

> **NIH NIH F31** · ST. JUDE CHILDREN'S RESEARCH HOSPITAL GRADUATE SCHOOL OF BIOMEDICAL SCIENCES, LLC · 2020 · $41,520

## Abstract

PROJECT SUMMARY
Hematopoietic stem and progenitor cells (HSPCs) are at the root of the hematopoietic system and must give rise
to all blood cells while also being prepared to respond immediately to insults. Accordingly, a thorough
understanding of HSPC biology is essential when developing new and more effective treatments for diseases of
the blood and immune system. E26 transforming-specific variant 6 (ETV6) is a transcription factor that is highly
expressed in HSPCs and critical for their regulation, with conditional knock-out of this transcription factor in mice
leading to a complete loss of this population. However, little is known about the gene networks and direct target
genes that are regulated by ETV6 within HSPCs and the cellular processes that they govern. In 2015, Dr. Nichols
and others identified pathogenic germline ETV6 variants in families with autosomal dominant thrombocytopenia
and predisposition to hematologic malignancies (a syndrome now known as Thrombocytopenia 5). To better
understand how these variants impact hematopoiesis, the Nichols laboratory has developed a novel mouse
strain harboring a heterozygous Etv6R355X variant that is equivalent to a recurrent ETV6R359X variant identified in
individuals with Thrombocytopenia 5. Studies of Etv6R355X/+ mice reveal that they are viable and can establish
HSPC populations. However, when compared to Etv6+/+ littermates, Etv6R355X/+ mice have significantly fewer
HSPCs, a phenotype that progressively worsens with age. Furthermore, when HSPCs from Etv6R355X/+ mice are
challenged with competitive transplantation, they show significantly reduced engraftment potential compared to
Etv6+/+ HSPCs. Based on these findings, I hypothesize that the Thrombocytopenia 5-associated variant ETV6
R355X protein impairs hematopoiesis by altering the expression of key downstream target genes needed for
HSPC maintenance. To address this hypothesis, I will complete the following Specific Aims. In Aim 1, I will
quantify and functionally characterize Etv6+/+ and Etv6R355X/+ HSPCs in the fetal liver and in the bone marrow
throughout the lifetime of the animal and after induction of a hematopoietic stress. Next, in Aim 2, I will perform
single-cell RNA-sequencing (RNA-seq) on HSPCs from Etv6+/+ and Etv6R355X/+ mice to identify genes that are
differentially expressed within specific HSPC sub-populations. Additionally, I will perform CUTandRUN using
Etv6+/+ and Etv6R355X/+ HSPCs. This new technique allows for mapping of protein-DNA interactions using
antibody-targeted controlled cleavage of DNA by micrococcal nucleases to identify putative direct target genes
(in this case of ETV6). Together, these studies will identify gene networks and target genes in HSPCs that are
dysregulated by the Etv6R355X variant which I will validate by qRT-PCR. I will then perform in vitro and in vivo
functional assays guided by known functions of identified target genes of interest and phenotypes observed in
our mouse model to define th...

## Key facts

- **NIH application ID:** 10068851
- **Project number:** 1F31HL154645-01
- **Recipient organization:** ST. JUDE CHILDREN'S RESEARCH HOSPITAL GRADUATE SCHOOL OF BIOMEDICAL SCIENCES, LLC
- **Principal Investigator:** Mackenzie Bloom
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $41,520
- **Award type:** 1
- **Project period:** 2021-01-01 → 2023-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10068851

## Citation

> US National Institutes of Health, RePORTER application 10068851, Role of the ETV6 transcription factor in hematopoietic stem cell function (1F31HL154645-01). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10068851. Licensed CC0.

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