# The chromatin remodeler LET-418/Mi-2 regulates the intracellular pathogen response in the C. elegans intestine

## TL;DR

This study shows that the chromatin remodeler LET-418 in C. elegans helps regulate the immune response to intracellular pathogens in the intestine.

## Contribution

The study identifies LET-418 and MEP-1 target genes in the C. elegans intestine and reveals their role in modulating the intracellular pathogen response.

## Key findings

- LET-418 and MEP-1 share over half of their target genes in the C. elegans intestine.
- LET-418 represses innate immune responses, including the intracellular pathogen response.
- let-418 mutants show reduced levels of the pathogen Nematocida parisii, indicating increased immune response.

## Abstract

Chromatin remodeling provides essential transcriptional regulation for all biological processes. In Caenorhabditis elegans, the chromatin remodeler LET-418, a homolog of the human Mi-2β protein, plays a critical role in regulating development, organogenesis, tissue maintenance, stress resistance and lifespan. LET-418 is part of several chromatin remodeling complexes and contributes significantly to the balance between growth and defense mechanisms, yet its target genes remain unclear. Using DNA methylation profiling, we identified genomic binding sites and associated target genes of LET-418 and its MEC-complex-specific interactor MEP-1 in the intestine. Consistent with their presence in the same complex, the two proteins shared more than half of their target genes. Functional analysis revealed that LET-418 and MEP-1 target genes are highly active in the intestine and are involved in repressing innate immune responses, including the intracellular pathogen response (IPR). Consistently, in let-418 mutants, IPR-induced genes, such as pals-5 or pals-2 are strongly upregulated, in a manner dependent on ZIP-1, a major transcription factor for IPR. Additionally, we found pathogen levels of the natural intracellular intestinal pathogen Nematocida parisii significantly reduced in let-418 mutants, supporting the observation of increased IPR in this mutant. Altogether, these findings reveal a crucial role for LET-418 as a modulator of the IPR, aligning with its role in maintaining the balance between development and defense.

The online version contains supplementary material available at 10.1186/s12864-025-12153-0.