# The role of Vsx2 super-enhancer in bipolar cell development

> **NIH NIH F31** · ST. JUDE CHILDREN'S RESEARCH HOSPITAL GRADUATE SCHOOL OF BIOMEDICAL SCIENCES, LLC · 2020 · $36,720

## Abstract

Project Summary/Abstract
Vsx2 is a paired-type homeodomain protein that is expressed in all retinal progenitor cells and in mature
bipolar neurons and Müller glia. Mutations in the Vsx2 gene cause microphthalmia in humans and mice
because it is required to regulate retinal progenitor cell proliferation. Due to this early developmental
phenotype, it has been difficult to elucidate the role of Vsx2 in bipolar and Müller glial cell differentiation. To
address this barrier in the field, we characterized the regulatory regions upstream of the Vsx2 gene. We
identified a core regulatory circuit super-enhancer (CRC-SE) upstream of Vsx2 that is specific to bipolar
neurons. Within the CRC-SE is a consensus binding site for Vsx2. When we deleted the Vsx2 CRC-SE in
mice, there is a complete loss of bipolar cells with no effect on retinal progenitor cells or Müller glia. This is the
first bipolar-less animal model and the first developmental-stage and cell-type-specific SE to be identified.
The purpose of this study is to understand how the developmental-stage and cell-type-specific CRC-SE
regulates Vsx2 expression for bipolar cell fate specification. First, I will dissect the CRC-SE and determine the
genomic regions that are driving bipolar cell development. Four evolutionarily conserved regions within the
CRC-SE including the Vsx2 consensus site will be knocked out in mice using CRISPR/Cas9. I will assess
whether these regions are necessary for bipolar cell development through immunohistochemistry and RNA
sequencing. Upon identification of a critical conserved region, I will assess its individual ability to drive bipolar
cell development in a rescue experiment. Chromatin interactions involving the Vsx2 promoter during the birth
of bipolar cells will be elucidated through chromosome conformation capture-on-chip (4C). Lastly, I will
elucidate factors required for bipolar cell specification in the developing retina by examining the fate of retinal
progenitor cells in the CRC-SE knockout mouse that would have normally differentiated into bipolar cells. We
have extended our analysis beyond Vsx2 and found dozens of other cell and developmental-stage specific
CRC-SEs in the developing retina. This suggests that our strategy may be broadly applied in the developing
central nervous system to elucidate the cellular roles of key transcription factors in development and
differentiation.

## Key facts

- **NIH application ID:** 9992188
- **Project number:** 1F31EY031577-01
- **Recipient organization:** ST. JUDE CHILDREN'S RESEARCH HOSPITAL GRADUATE SCHOOL OF BIOMEDICAL SCIENCES, LLC
- **Principal Investigator:** Victoria Honnell
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $36,720
- **Award type:** 1
- **Project period:** 2020-07-01 → 2021-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9992188

## Citation

> US National Institutes of Health, RePORTER application 9992188, The role of Vsx2 super-enhancer in bipolar cell development (1F31EY031577-01). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/9992188. Licensed CC0.

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