# Elucidating the Role of Notch/HES Signaling in Alveolar Epithelial Type II to Type I Cell Differentiation

> **NIH NIH F31** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2024 · $42,094

## Abstract

PROJECT SUMMARY
The alveolar epithelium plays a critical role in maintaining normal lung function and is comprised of type 1 and
type 2 alveolar epithelial cells (AEC1s and AEC2s, respectively). AEC1s provide broad coverage of the
alveolar surface and serve as the interface for gas exchange. AEC2s produce pulmonary surfactant to regulate
alveolar surface tension and, importantly, also function as progenitor cells that can differentiate into AEC1s
after lung injury. Defects in AEC1 regeneration underlie severe pulmonary diseases such as idiopathic
pulmonary fibrosis (IPF), a progressive scarring disease of the lungs that results in gradual deterioration of
lung function leading to respiratory failure and death within 3-5 years. The lack of curative therapies stems
from disease pathogenesis remaining poorly understood. Our laboratory recently demonstrated that the
specific defect in epithelial regeneration that drives the pathogenesis of fibrosis is impaired AEC2 to AEC1
differentiation. However, there remains a critical gap in knowledge of the cellular instructions that promote
AEC1 differentiation after alveolar damage, although it is known that downregulation of the transcription factors
ETV5 and CTNNB1 promote differentiation. To identify signaling pathways that may regulate AEC2 to AEC1
differentiation, we performed scRNA-Seq on lineage-labeled AEC2s during regeneration after alveolar injury
and observed that the Notch2 receptor and canonical Notch target gene, Hes1, were highly upregulated in
AEC2s differentiating into AEC1s. scRNA-Seq datasets from normal human lungs similarly revealed high
expression of NOTCH2 and HES4 (a paralog of HES1 not found in mice) in AEC1s. These preliminary findings
led us to speculate that activation of the canonical Notch signaling pathway is required for AEC2 to AEC1
differentiation. This proposal will test our central hypothesis that NOTCH2 activation promotes AEC2 to
AEC1 differentiation via HES-mediated repression of ETV5 and CTNNB1 expression via the following two
aims: (1) Test the hypothesis that Notch2 signaling is required for AEC2 to AEC1 differentiation after alveolar
injury and (2) Test the hypothesis that HES4 promotes human AEC2 to AEC1 differentiation by repressing
ETV5 and CTNNB1 expression. We will utilize conditional knockout mouse models in addition to primary
human and human iPSC-derived organoid systems to explore the dynamics of Notch/HES signaling in AECs.
The results of these studies will advance our current understanding of how Notch/HES regulates differentiation
in AECs and, in doing so, establish a foundation for investigating how the Notch pathway can be leveraged to
promote restoration of normal alveolar structure and function after lung injury. By defining key pathways
involved in alveolar regeneration, this proposal may inform the development of targeted therapies for IPF and
other pulmonary diseases characterized by ineffectual restoration of AEC1s.

## Key facts

- **NIH application ID:** 10994560
- **Project number:** 1F31HL175884-01
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Jessica Liang
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $42,094
- **Award type:** 1
- **Project period:** 2024-09-24 → 2028-09-23

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10994560

## Citation

> US National Institutes of Health, RePORTER application 10994560, Elucidating the Role of Notch/HES Signaling in Alveolar Epithelial Type II to Type I Cell Differentiation (1F31HL175884-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10994560. Licensed CC0.

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