# Identifying necessary chromatin states and targets for hemogenic specification and reprogramming

> **NIH NIH F31** · UNIVERSITY OF PENNSYLVANIA · 2020 · $45,520

## Abstract

Project Summary
Many patients with hematological disorders rely on hematopoietic stem cell (HSC) transplants for treatment.
However, for numerous patients, this option is dramatically impacted by the lack of optimally matched donors.
Generation of HSCs ex vivo would greatly improve treatment for these patients. Understanding how HSCs form
in vivo is crucial for the efficient derivation of HSCs ex vivo. During development, HSCs originate from a subset
of endothelium, known as hemogenic endothelium. HSCs form through a process known as endothelial-to-
hematopoietic transition (EHT). The complete genetic and molecular mechanism underlying EHT is still not fully
understood, but it is known that RUNX1 is absolutely necessary for EHT. Ectopic expression of RUNX1 in
embryonic non-hemogenic endothelium at E8.5 is able to induce EHT and blood cell formation. However, four
days later in mouse development, RUNX1 is not as effective at reprogramming fetal endothelium to undergo
EHT. Efficient hemogenic specification of fetal endothelium requires twice as much RUNX1, and proceeds via a
different route than that of embryonic ECs. We hypothesize that the differential hemogenic competency observed
between fetal and embryonic endothelium is due, at least in part, to changes in chromatin organization that
prevent RUNX1 from binding key target genes. In order to understand how RUNX1 can efficiently specify
embryonic endothelium as hemogenic, we will identify direct targets of RUNX1 and determine if these targets
are marked by repressive heterochromatin in fetal endothelium. Additionally, we will determine if there are
underlying baseline differences in chromatin structure between fetal and embryonic endothelium by profiling the
genes in lamina associated domains (LADs) and using stochastic optical reconstruction microscopy (STORM)
to determine global chromatin and nucleosome organization. Additionally, we will use DNA fluorescent in situ
hybridization (FISH) to determine if important RUNX1 targets are localized to the nuclear periphery in fetal
endothelium, which is what is preventing these genes from getting activated. These experiments will provide
insight on the precise chromatin landscape and gene expression necessary for efficient hemogenic specification
from endothelium. These studies will provide potential avenues for ex vivo generation of HSCs for therapeutic
uses.

## Key facts

- **NIH application ID:** 9907211
- **Project number:** 1F31HL150952-01
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Elizabeth Howell
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $45,520
- **Award type:** 1
- **Project period:** 2020-06-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9907211

## Citation

> US National Institutes of Health, RePORTER application 9907211, Identifying necessary chromatin states and targets for hemogenic specification and reprogramming (1F31HL150952-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9907211. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*