# The epigenetic factor Zrf1 regulates intestinal stem cell proliferation during midgut regeneration

## TL;DR

The study identifies Zrf1 as a key epigenetic regulator of intestinal stem cell proliferation in fruit flies, offering insights into tissue regeneration and disease.

## Contribution

Zrf1 is newly identified as an epigenetic regulator integrating multiple signaling pathways to control stem cell proliferation.

## Key findings

- Zrf1 regulates intestinal stem cell proliferation during midgut regeneration in Drosophila.
- Zrf1 interacts with RISC components but functions in epigenetic regulation rather than canonical RNAi.
- Zrf1 modulates chromatin-based gene silencing through interactions with Polycomb group proteins.

## Abstract

Stem cells are essential for tissue maintenance and regeneration, balancing self-renewal and differentiation to support homeostasis and repair. Through an RNAi screen in the Drosophila midgut, we identified the epigenetic factor Zrf1 as a critical regulator of intestinal stem cell (ISC) proliferation. Functional analyses reveal that Zrf1 integrates inputs from multiple signaling pathways and interacts with components of the RNA-induced silencing complex (RISC). Our findings suggest that Zrf1 is potentially a key chromatin regulator necessary for maintaining stem cell proliferation, enhancing our understanding of the molecular controls underlying stem cell function and chromatin-associated defects.

Tissue homeostasis, such as the constant renewal of the intestinal epithelium, relies on the precise regulation of adult stem cells. Understanding the molecular cues that govern stem cell proliferation is critical for regenerative medicine and for deciphering pathologies like cancer. Using the Drosophila midgut as a model, we identified the epigenetic factor Zrf1 as a key regulator of intestinal stem cell (ISC) proliferation. Functional analyses reveal that Zrf1 integrates inputs from multiple conserved signaling pathways, including EGFR, Notch, and Yorkie, to control the regenerative response. Mechanistically, Zrf1 physically associates with components of the RNA-induced silencing complex (RISC). However, its function is not in canonical RNAi, but in epigenetic regulation. Zrf1 modulates chromatin-based gene silencing, in part through genetic interactions with Polycomb group proteins, thereby influencing gene expression programs essential for proliferation. Our research uncovers a novel regulatory axis that links mitogenic signaling to the epigenetic state of stem cells, providing a deeper understanding of tissue regeneration and potentially new therapeutic targets for diseases characterized by deregulated stem cell activity.