The regulation of spermatogenesis and sperm function in nematodes

Abstract

In the nematode C. elegans, both males and self-fertile hermaphrodites produce sperm. As a result, researchers have been able to use a broad range of genetic and genomic techniques to dissect all aspects of sperm development and function. Their results show that the early stages of spermatogenesis are controlled by transcriptional and translational processes, but later stages are dominated by protein kinases and phosphatases. Once spermatids are produced, they participate in many interactions with other cells — signals from the somatic gonad determine when sperm activate and begin to crawl, signals from the female reproductive tissues guide the sperm, and signals from sperm stimulate oocytes to mature and be ovulated. The sperm also show strong competitive interactions with other sperm and oocytes. Some of the molecules that mediate these processes have conserved functions in animal sperm, others are conserved proteins that have been adapted for new roles in nematode sperm, and some are novel proteins that provide insights into evolutionary change. The advent of new techniques should keep this system on the cutting edge of research in cellular and reproductive biology.

Convergent evolution of sperm gigantism and the developmental origins of sperm size variability inCaenorhabditisnematodes

“…Concerning Caenorhabditis nematodes, the genetic control of spermatogenesis is well‐characterized in C. elegans (L'Hernault ; Geldziler et al. ; Ellis and Stanfield ), yet the developmental mechanisms underlying sperm size differences, for example between hermaphrodites and males, are not understood. During C. elegans spermatogenesis, the onset of meiosis involves the formation of primary spermatocytes, characterized by their separation from a syncytial germ cell progenitor pool, during which they increase substantially in cell size (Wolf et al.…”

Co-option of alternate sperm activation programs in the evolution of self-fertile nematodes

“…We used reverse transcription PCR (RT-PCR) to characterise the expression of each gene in C. briggsae. The five members of the C. elegans spe-8 group are expressed in spermatids 16 , where they respond to an unknown signal. In C. briggsae, their expression is also correlated with spermatogenesis-the transcripts are present in larval hermaphrodites, larval males and adult males, but absent from adult hermaphrodites ( Fig.…”

“…Mutations in any of these genes block hermaphrodite self-fertility, but do not prevent male sperm from activating and fertilising oocytes. All five genes are expressed in sperm and three encode transmembrane proteins 16 . Furthermore, SPE-8 is a protein tyrosine kinase whose localisation to the plasma membrane in spermatids requires the other genes 11 .…”

Rogue Sperm Indicate Sexually Antagonistic Coevolution in Nematodes

“…Given the broad range of interactions between sperm, oocytes, and chemical and physical cues inside the female reproductive tract (Figure 3) (reviewed in [36]), nematodes in the genus Caenorhabditis could provide valuable models for investigating postcopulatory sexual selection and sexual conflicts in the laboratory.…”