# Genetic regulation of active and reserve intestinal stem cell states

> **NIH NIH R01** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2020 · $74,002

## Abstract

ABSTRACT: Complete physiologic renewal of intestinal epithelium occurs about every week and is
driven by actively proliferating ISCs (aISCs) located in the epithelial-crypt base. A rare subset cells in
the crypt, still not completely defined but that are collectively known as `reserve' ISCs (rISCs), are
`quiescent' or slowly dividing, and can convert into aISCs when certain health conditions or radio- or
chemotherapeutic exposures damage and deplete the native aISC pool. The rISC to aISC conversion
process is traditionally studied in mice where irradiation (IR) is used to deplete aISCs and induce rISCs.
Here, rISCs are defined by their resistance to IR-induced death, and then by their `plastic' ability to
generate actively dividing ISC progeny, which replenish the aISC pool and drive subsequent epithelial
regeneration. The mechanisms conferring rISC radio-resistance and plasticity are unknown. In prior
work we demonstrated that the transcription factor Sox9 is required for the generation and function of
rISCs in mice. Lineage tracing with a Sox9CreERT2 driver showed that after IR, all regenerating epithelium
is derived from cells that expressing Sox9, and epithelium-specific genetic ablation of Sox9 profoundly
impeded epithelial regeneration and cell survival post-IR. These findings indicate that Sox9-dependent
mechanisms govern rISC function. Growing evidence in the stem cell and radiation fields suggest that
slowing the cell-cycle rate in dividing cells can enhance radioresistance after IR-exposure, and can
modulate cell fate commitment versus self-renewal decisions. We have found that elevated Sox9 levels
are associated with slowly dividing cells in the crypt, and that Sox9-overexpression in rapidly dividing
aISCs can slow or halt their proliferation. We hypothesize that Sox9-expression levels modulate
cell-cycle progression to determine and diversify rISC (Sox9HI) and aISC (Sox9LO) functions in
the intestinal crypt. If supported by the results of our experiments, this study will uncover the
underlying pathways governing rISC radioresistance and plasticity, and could provide a unifying
mechanism describing whether and how rISC properties exist among a broad range of cell types in the
crypt. Aim 1: Assess the effects of increasing Sox9 levels on cell-cycle progression in ISCs. Aim 2:
Determine if Sox9-mediated G1-elongation confers radio-resistance. Aim 3: Determine if Sox9-
mediated G1-elongation confers a `secretory precursor' rISC phenotype.

## Key facts

- **NIH application ID:** 10026771
- **Project number:** 3R01DK115806-02S1
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** SCOTT T MAGNESS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $74,002
- **Award type:** 3
- **Project period:** 2019-09-19 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10026771

## Citation

> US National Institutes of Health, RePORTER application 10026771, Genetic regulation of active and reserve intestinal stem cell states (3R01DK115806-02S1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10026771. Licensed CC0.

---

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