SPE-44 implements sperm cell fate

The sperm/oocyte decision in the hermaphrodite germline of caenorhabditis elegans provides a powerful model for the characterization of stem cell fate specification and differentiation. the germline sex determination program that governs gamete fate has been well studied,but direct mediators of cell-type-specific transcription are largely unknown. we report the identification of spe-44 as a critical regulator of sperm gene expression. deletion of spe-44 causes sperm-specific defects in cytokinesis,cell cycle progression,and organelle assembly resulting in sterility. expression of spe-44 correlates precisely with spermatogenesis and is regulated by the germline sex determination pathway. spe-44 is required for the appropriate expression of several hundred sperm-enriched genes. the spe-44 protein is restricted to the sperm-producing germline,where it localizes to the autosomes (which contain sperm genes) but is excluded from the transcriptionally silent x chromosome (which does not). the orthologous gene in other caenorhabditis species is similarly expressed in a sex-biased manner,and the protein likewise exhibits autosome-specific localization in developing sperm,strongly suggestive of an evolutionarily conserved role in sperm gene expression. our analysis represents the first identification of a transcriptional regulator whose primary function is the control of gamete-type-specific transcription in this system.