In Caenorhabditis elegans, gap junctions couple cells of the somatic gonad with the germline to support germ cell proliferation and gametogenesis. A strong loss-of-function mutation (T239I) affects the second extracellular loop (EL2) of the somatic INX-8 hemichannel subunit. These mutant hemichannels form non-functional gap junctions with germline-expressed innexins. We conducted a genetic screen for suppressor mutations that restore germ cell proliferation in the T239I mutant background and isolated seven intragenic mutations, located in diverse domains of INX-8 but not the EL domains. These second-site mutations compensate for the original channel defect to varying degrees, from nearly complete wild-type rescue, to partial rescue of germline proliferation. One suppressor mutation (E350K) supports the innexin cryo-EM structural model that the channel pore opening is surrounded by a cytoplasmic dome. Two suppressor mutations (S9L and I36N) may form leaky channels that support germline proliferation but cause the demise of somatic sheath cells. Phenotypic analyses of three of the suppressors reveal an equivalency in the rescue of germline proliferation and comparable delays in gametogenesis but a graded rescue of fertility. The mutations described here may be useful for elucidating the biochemical pathways that produce the active biomolecules transiting through soma–germline gap junctions.
Bibliographical noteFunding Information:
Funding: This research was funded by the National Institutes of Health grant GM57173 to D.G.
Acknowledgments: The authors would like to thank our colleagues Gabriela Huelgas-Morales, Caroline Spike, and Tatsuya Tsukamoto for helpful discussions regarding experiments. Some strains were provided by the Caenorhabditis Genetics Center, which is funded by grant P40OD010440 from the NIH Office of Research Infrastructure Programs.
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Copyright 2020 Elsevier B.V., All rights reserved.
- Gap junctions
- Soma–germline interactions
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural