Figure: In the germline, the full polq-1 mRNA is produced. In neurons, the transcription of the ceh-10 gene induces the concomitant production of a short polq-1 mRNA.

In the genome, genes sometimes overlap. In this interdisciplinary study, the Bertrand team, in collaboration with the Villoutreix team at MMG, analyzed the consequences of a striking genomic configuration where a gene is nested in an intron of a host gene in the opposite direction. They first studied the example in C. elegans of the neuronal specification gene ceh-10 nested in the DNA repair gene polq-1. Using CRISPR genome engineering and single molecule FISH, they observed that transcription of the nested gene in neurons induces expression of a short version of its host gene. They then extended the analysis to the hundreds of protein coding genes in nested configuration present in the genome. By analyzing single-cell RNA-seq data covering C. elegans embryogenesis, they observed that coexpression between nested and host genes is common and that nested genes tend to induce expression of their hosts.

This study illustrates how the presence of a nested gene can influence expression of its host. 

Soulavie F., Couillault C., Melki M., Buyannemekh K., Barrière A., Villoutreix P. and Bertrand V. (2025). Induction of host genes by nested genes during C. elegans development. iScience 28, 113021.