# Dissecting the roles of Polycomb repressive complex 2 accessory subunits during early developmental transitions

> **NIH NIH F31** · UNIVERSITY OF PENNSYLVANIA · 2020 · $45,520

## Abstract

Project Summary
The objective of this proposal is to determine the distinct molecular roles and temporal requirements of the two
subtypes of the Polycomb Repressive Complex 2 (PRC2), PRC2.1 and PRC2.2, during differentiation. PRC2 is
an essential chromatin modifier that trimethylates lysine 27 on histone H3 (H3K27me3), which leads to the
formation of facultative heterochromatin, a structure that is refractory to transcription and prevents ectopic
gene activation. The epigenetic function of PRC2 is essential for embryogenesis, and defects in this complex
cause Weaver Syndrome, a congenital multi-system developmental disorder. Despite its ubiquitous expression
during development, PRC2 is capable of targeting distinct sets of genes for silencing in different cell lineages,
resulting in cell-type specific gene repression. However, the mechanisms regulating the targeting of PRC2 are
poorly understood. PRC2 interacts with a variety of accessory subunits, resulting in the formation of two
biochemically distinct subcomplexes—PRC2.1 and PRC2.2. Genetic knockouts of subunits comprising PRC2.1
and PRC2.2 in mice result in embryonic lethality at different times and with different phenotypes,
demonstrating that the two PRC2 subcomplexes have non-overlapping essential functions in development.
Unlike PRC2, the accessory subunits comprising PRC2.1 and PRC2.2 exhibit dynamic expression patterns
during development, suggesting they may regulate distinct developmental stages. However, the molecular
roles that PRC2.1 and PRC2.2 may play at different stages of development, as well as whether they target
different genomic regions for silencing, remain unknown. I will investigate these questions using auxin-
inducible degradation (AID) to acutely degrade subunits specific to PRC2.1 and PRC2.2 during the
differentiation of mouse embryonic stem cells (mESCs). Because of its rapid kinetics, this approach will allow
me to define the immediate molecular consequences of removing the selected subunit, avoiding confounding
secondary and compensatory effects that have plagued previous genetic approaches. In Aim 1 I will combine
AID with nascent RNA sequencing to determine the functions of PRC2.1 and PRC2.2 in regulating the
transcriptional state of pluripotent mESCs. In Aim 2 I will use AID to selectively degrade PRC2.1 and PRC2.2
subunits at different times during the differentiation of mESCs to epiblast-like cells (EpiLCs) and neuronal
progenitors (NPCs). I will measure resulting changes in gene expression, chromatin structure, and cell
morphology to determine the functions of and temporal requirements for each PRC2 subcomplex at different
developmental stages. Collectively, these Aims will shed mechanistic light on the distinct molecular roles of
PRC2.1 and PRC2.2 in regulating pluripotency and differentiation.

## Key facts

- **NIH application ID:** 9991071
- **Project number:** 1F31HD102121-01
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Ana Petracovici
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $45,520
- **Award type:** 1
- **Project period:** 2020-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9991071

## Citation

> US National Institutes of Health, RePORTER application 9991071, Dissecting the roles of Polycomb repressive complex 2 accessory subunits during early developmental transitions (1F31HD102121-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9991071. Licensed CC0.

---

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