Xantha Karp (@xanthakarp.bsky.social)

A stress-dependent postembryonic role for the core CPA factor CFIM-1 in germline integrity Post-transcriptional processing of pre-mRNAs generates a diversity of 3’ UTR transcript isoforms that can vary in their function and stability. The differential enrichment of transcript isoforms has been implicated in diseases ranging from cancer to neurodevelopmental disorders. However, the post-embryonic developmental roles of the core ensemble of cleavage and polyadenylation (CPA) factors that mediate these post-transcriptional changes remain poorly characterized. Here, we report a stress- dependent role for the core CPA factor CFIM-1 in germline integrity in Caenorhabditis elegans. Total loss-of-function of cfim-1 elicits a temperature-sensitive sterile phenotype in hermaphrodites. These changes in brood size are accompanied by broad sperm, oocyte and germline morphology defects. Surveying the transcriptome of cfim-1(lf) worms, we uncover changes in transcript isoform abundance for dozens of genes with known functions related to the development and maintenance of these structures, consistent with a model in which post-transcriptional regulation of target genes via cfim- 1 is crucial to the development and maintenance of germline integrity. Our findings collectively define a novel post-embryonic role for a core CPA factor in tissue-specific development. ### Competing Interest Statement The authors have declared no competing interest. Canadian Institutes of Health Research, PJT 155928 https://www.biorxiv.org/content/10.1101/2025.07.01.662614v1