# The Role of Hippo-Yap1 Signaling in Germ-layer Specification

> **NIH NIH R01** · TEMPLE UNIV OF THE COMMONWEALTH · 2022 · $409,033

## Abstract

ABSTRACT
Understanding
diagnose,
on
signaling well-known for its essential activities promoting cell proliferation during
development. suggest important roles of YAP as a cell-fate determinant in
early embryogenesis. Accordingly, our ongoing studies using human Embryonic Stem Cells (hESCs) 2D-
models of gastrulation reveals that YAP is essential for the correct specification of the three germ-layers. The
YAP KO-derived human 2D-gastruloids display expanded mesoderm and endoderm layers (ME) and reduced
ectoderm layer, compared to WT. NODAL signaling homeostasis is essential for normal gastrulation; active
NODAL cues are needed for ME differentiation. However, efficient NODAL inhibition is needed for the
acquisition of an ectodermal potential. Our data suggest that the gastrulation phenotype in YAP KO cells is
associated with an overly active NODAL signaling. The NODAL gene codifies for the ligand that activates the
intracellular Smad2.3 signaling. Interestingly, our transcriptomic and epigenomic analysis suggest that YAP is
needed to repress the well-characterized Proximal Epiblast Enhancer (PEE) of the NODAL gene during the
exit of pluripotency toward an ectodermal fate. Our data further suggest that YAP restricts the chromatin
development the human embryo will lead to discovery therapeutic tools to
treat and prevent birth defects. The overarching goal of this proposal is to advance our knowledge
the signaling and epigenetic mechanisms that regulate the process of human gastrulation. The Hippo-
effector YAP1 (YAP) is
However, increasing evidences
the of the of
accessibility of the NODAL locus, essential for gene repression. These
general
specification”.
findings form the premise of our
hypothesis: “Epigenetic regulation NODAL signaling by YAP is crucial for correct germ-layer
We will address this idea in the following Aims. In Aim1
of
, we will analyze the role of YAP in
human 3D-gastruloids. We hypothesize that the ability of human epiblast cells to undergo three-dimensional
gastrulation, and organization in an anteroposterior axis is regulated by YAP. To test this idea, we will apply a
state-of-art synthetic human embryology model to study gastrulation in 3D. We also hypothesize that YAP-
repression of the PEE of the NODAL gene is essential to balance pluripotency and ectoderm differentiation.
To address this idea, we will investigate enhancer function and chromatin structure by combining cutting-edge
CRISPR and genome-sequencing approaches (Aim2). Findings from Aim 1 and 2 will inform about human-
specific regulatory roles of YAP that occur during axial organization. Finally, we will utilize a conditional YAP
KO mouse to investigate the role of YAP in the differentiating epiblast, in vivo (Aim3). Our findings will inform
on new mechanisms that regulate the activity of NODAL signaling and help to decipher the role of YAP during
gastrulation.

## Key facts

- **NIH application ID:** 10521817
- **Project number:** 1R01HD106969-01A1
- **Recipient organization:** TEMPLE UNIV OF THE COMMONWEALTH
- **Principal Investigator:** Concepcion Estaras
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $409,033
- **Award type:** 1
- **Project period:** 2022-09-01 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10521817

## Citation

> US National Institutes of Health, RePORTER application 10521817, The Role of Hippo-Yap1 Signaling in Germ-layer Specification (1R01HD106969-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10521817. Licensed CC0.

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