Shakes, D. C. | bioRxiv Science

bioRxiv2021

SPE-51, a sperm secreted protein with an Immunoglobulin-like domain, is required for sperm-egg fusion in C. elegans

Despite the importance of fertilization, the molecular basis of sperm-egg interaction is not well understood. In a forward genetics screen for fertility mutants in Caenorhabditis elegans we identified spe-51. Mutant worms make sperm that are unable to fertilize the oocyte but otherwise normal by all available measurements. The spe-51 gene encodes a secreted protein that includes an immunoglobulin (Ig)-like domain and a hydrophobic sequence of amino acids. The SPE-51 protein acts cell-autonomously and localizes to the surface of the spermatozoa. This is the first example of a secreted protein required for the interactions between the sperm and egg with genetic validation for a specific function in fertilization. Our analyses of these genes begin to build a paradigm for sperm-secreted or reproductive tract-secreted proteins that coat the sperm surface and influence their survival, motility, and/or the ability to fertilize the egg.

developmental biology↗

bioRxiv2020

The conserved molting/circadian rhythm regulator NHR-23/NR1F1 serves as an essential co-regulator of C. elegans spermatogenesis

In sexually reproducing metazoans, spermatogenesis is the process by which uncommitted germ cells give rise to haploid sperm. Work in model systems has revealed mechanisms controlling commitment to the sperm fate, but how this fate is subsequently executed remains less clear. While studying the well-established role of the conserved nuclear hormone receptor transcription factor, NHR-23/NR1F1, in regulation of C. elegans molting, we discovered NHR-23/NR1F1 is also constitutively expressed in developing 1{degrees} spermatocytes and is a critical regulator of spermatogenesis. In this novel role, NHR-23/NR1F1 functions downstream of the canonical sex determination pathway. Degron-mediated depletion of NHR-23/NR1F1 within hermaphrodite or male germlines causes sterility due to an absence of functional sperm as depleted animals produce arrested primary spermatocytes rather than haploid sperm. These spermatocytes arrest in prometaphase I and fail to either progress to anaphase or attempt spermatid-residual body partitioning. They make sperm-specific membranous organelles (MOs) but fail to assemble their major sperm protein into fibrous bodies. NHR-23/NR1F1 appears to function independently of the known SPE-44 gene regulatory network, revealing the existence of an NHR-23/NR1F1-mediated module that regulates the spermatogenesis program. Summary StatementA well-characterized regulator of C. elegans molting also unexpectedly controls the spermatogenesis program; our work provides insights into the gene regulatory networks controlling spermatogenesis.

developmental biology↗