What about the males? the C. elegans sexually dimorphic nervous system and a CRISPR-based tool to study males in a hermaphroditic species

Abstract

Sexual dimorphism is a device that supports genetic diversity while providing selective pressure against speciation. This phenomenon is at the core of sexually reproducing organisms. Caenorhabditis elegans provides a unique experimental system where males exist in a primarily hermaphroditic species. Early works of John Sulston, Robert Horvitz, and John White provided a complete map of the hermaphrodite nervous system, and recently the male nervous system was added. This addition completely realized the vision of C. elegans pioneer Sydney Brenner: a model organism with an entirely mapped nervous system. With this ‘connectome’ of information available, great strides have been made toward understanding concepts such as how a sex-shared nervous system (in hermaphrodites and males) can give rise to sex-specific functions, how neural plasticity plays a role in developing a dimorphic nervous system, and how a shared nervous system receives and processes external cues in a sexually-dimorphic manner to generate sex-specific behaviors. In C. elegans, the intricacies of male-mating behavior have been crucial for studying the function and circuitry of the male-specific nervous system and used as a model for studying human autosomal dominant polycystic kidney disease (ADPKD). With the emergence of CRISPR, a seemingly limitless tool for generating genomic mutations with pinpoint precision, the C. elegans model system will continue to be a useful instrument for pioneering research in the fields of behavior, reproductive biology, and neurogenetics.

Keywords:

• C. elegans
• cilia
• polycystin
• sexual dimorphism
• male
• nervous system
• behavior

Acknowledgements

The authors thank current Barr lab members Jyothi Shilpa Akella, Kade Power, Inna Nikonorova, and especially Juan Wang for discussions, insights, and helpful feedback on this work; Arantza Barrios for feedback and clarifications on the MCM and PHD neurons; Brittany Klimek for her help with genotyping. We especially thank Helen Ushakov who expertly does our microinjections and Gloria Androwski who keeps our lab running; Barth Grant for early advice regarding CRISPR techniques; and Wormbase for quick responses and for being awesome. We also thank the National BioResource Project (Tokyo Women's Medical College, Tokyo, Japan) and Caenorhabditis Genetics Center (CGC) for strains.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The CGC is supported by the National Institutes of Health – Office of Research Infrastructure Programs [P40 OD010440]. This work was funded by the National Institutes of Health (NIH) awards DK059418 and DK116606 to MMB and NIH Institutional Research and Academic Career Development Award (IRACDA) K12GM093854 to JDW.