# Solving cell-type specific differences of the Wnt-directed gene regulatory network in Hydra vulgaris.

> **NIH NIH F31** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2023 · $40,288

## Abstract

A fundamental question of developmental biology is to understand how a limited number of signaling pathways
direct the specification of many cell types. One such signaling pathway is the canonical Wnt signaling pathway,
which is highly conserved across animals, plays a role in a myriad of developmental processes, and its
dysregulation is common in disease. To direct different developmental outcomes, Wnt signaling must activate
different gene regulatory networks (GRNs) in different contexts. To reveal general principles of how Wnt ligands
can activate unique GRNs, I will use Hydra vulgaris to discover how two distinct cell types uniquely respond to
the Wnt signaling pathway. Hydra offer several advantages for studying Wnt directed-GRNs: 1) Hydra is a
relatively simple organism and we have molecularly and spatially defined all cell types and 2) the adult Hydra is
in a constant state of development such that all developmental pathways, including the Wnt-directed pathways,
are continuously active. Wnt signaling is high at Hydra’s oral end (i.e., the head) and directs the differentiation
of multiple distinct oral cell fates. The principal effect of canonical Wnt signaling is the stabilization of the beta-
catenin (Bcat) protein, which together with its binding partner TCF activates transcription of target genes. To
activate target gene expression in specific developmental contexts, Bcat/TCF must work in a combinatorial
fashion with other TFs. However, it is largely unknown what TFs are facilitating the activation of Wnt targets and
whether these interactions are conserved across species and during disease. Based on my preliminary data,
I hypothesize that ectodermal Homeobox TFs and endodermal bHLH TFs work in a combinatorial manner
with Bcat/TCF to direct cell-type specific GRN modules in Hydra. Towards testing this hypothesis, I will use
ChIP-seq to identify the cell-type specific direct targets of Bcat/TCF in the two oral epithelial cell types of Hydra
(ectoderm and endoderm) (Aim 1). I will then use our Hydra single cell Atlas to determine the expression pattern
of the direct targets. To determine if direct targets are co-regulated by Homeobox or bHLH TFs, I will knockdown
these TFs in the epithelial cells to test if they are required for specification. I will then identify the Wnt target
genes that also require these TFs for proper expression by conducting RNA-seq on the knockdown Hydra (Aim
2). Finally, I will perform unbiased approaches to identify additional co-regulating TFs for functional testing (Aim
3), which will also provide alternative hypotheses if needed. Upon completion of this project, I will have generated
a comprehensive list of the primary targets of Bcat/TCF in Hydra and potentially have discovered a role for
Homeobox and bHLH TFs in differentially regulating these primary targets. ChIP experiments conducted in mice,
have shown that Bcat can bind specific Homeobox TFs to control target gene expression in different
developmental c...

## Key facts

- **NIH application ID:** 10751675
- **Project number:** 1F31GM149176-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Hannah Morris Little
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $40,288
- **Award type:** 1
- **Project period:** 2023-07-03 → 2025-07-02

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10751675

## Citation

> US National Institutes of Health, RePORTER application 10751675, Solving cell-type specific differences of the Wnt-directed gene regulatory network in Hydra vulgaris. (1F31GM149176-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10751675. Licensed CC0.

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