# Regulation of MORC-1 is key to the CSR-1–mediated germline gene licensing mechanism in C. elegans

## TL;DR

A study in C. elegans shows that MORC-1 overexpression disrupts gene regulation normally controlled by CSR-1, affecting germline development and fertility.

## Contribution

The study identifies MORC-1 as a downstream regulator of CSR-1 in germline gene licensing and chromatin regulation.

## Key findings

- Loss of CSR-1 leads to MORC-1 overexpression and chromatin defects in C. elegans germline.
- MORC-1 overexpression represses CSR-1 licensed genes and reduces fertility in wild-type worms.
- Removing MORC-1 rescues chromatin defects and partially restores gene expression in csr-1 mutants.

## Abstract

The Argonaute CSR-1 is essential for germline development in C. elegans. Loss of CSR-1 leads to the down-regulation of thousands of germline-expressed genes, supporting a model in which CSR-1 “licenses” gene expression via a poorly understood mechanism. In contrast, a small subset of genes is up-regulated in csr-1 mutants, including morc-1, which encodes a conserved GHKL-type ATPase. We show that morc-1 is overexpressed in csr-1 mutants and accumulates over CSR-1 licensed targets, coinciding with aberrant gain of H3K9me3, reduced H3K36me3, and transcriptional repression. Notably, loss of morc-1 fully rescues these chromatin defects and partially restores gene expression and fertility in csr-1 mutants. Conversely, ectopic overexpression of MORC-1 in the wild-type germ line is sufficient to repress CSR-1 licensed targets and severely compromise fertility. These findings support a model in which CSR-1 prevents MORC-1 overexpression and consequent misregulation of CSR-1 licensed genes.

MORC-1 acts downstream of CSR-1 to regulate germline chromatin states and is a key component of the gene licensing mechanism.