A C. elegans histone methyltransferase promotes spermatocyte gene expression, spermatid production and fertility

Abstract

To better understand the tissue-specific regulation of chromatin state in cell-fate determination and development, we defined the tissue-specific expression of all 36 lysine methyltransferase (KMT) genes by endogenous mRNA detection in C. elegans. We found that most KMTs are expressed in only one or two tissues and that the germline is the tissue with the most general KMT expression. We discovered that the germline-expressed C. elegans ortholog of mammalian PRDM9, SET-1 7, promotes fertility through gene regulation in primary spermatocytes. SET-17 drives transcription of spermatocyte-specific genes from four genomic clusters to promote spermatid production. SET-1 7 is concentrated in stable, chromatin-associated nuclear foci at actively transcribed gene clusters, which we term spermatocyte transcription bodies. Our results identify the spatially restricted function of a PRDM9 ortholog in spermatocyte transcription and we propose that the spatial organization of chromatin factors might be a conserved mechanism in tissue-specific control of transcription.