Xenopus laevis lack the critical sperm factor PLCζ
Rachel E Bainbridge1, Joel C Rosenbaum1, Paushaly Sau1
1Department of Biological Sciences, University of Pittsburgh, Pittsburgh PA 15260.
Biorxiv : the Preprint Server for Biology
|February 13, 2023
Summary
Fertilization in Xenopus laevis involves calcium release, but lacks the PLCζ enzyme. Researchers found no PLCZ1 gene in Xenopus, suggesting its loss and an alternative mechanism for egg activation.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Molecular Genetics
Background:
- Fertilization in vertebrates like Xenopus laevis, mammals, and birds involves a cytosolic calcium increase.
- Sperm-borne Phospholipase C zeta (PLCζ) is believed to trigger this calcium release from the endoplasmic reticulum (ER) in mammals and birds.
- Xenopus laevis sperm extracts can activate mouse eggs, suggesting a shared sperm factor, yet Xenopus lacks an annotated PLCZ1 gene.
Approach:
- Investigated the presence of PLCZ1 orthologs in amphibian sperm, including Xenopus.
- Conducted RNA sequencing on Xenopus laevis testes to identify potential PLCZ1 genes.
- Analyzed existing genomic and transcriptomic datasets for PLCZ1 orthologs in Xenopus.
Key Points:
- PLCZ1 orthologs were identified in 11 amphibian species, with 5 newly characterized.
- No PLCZ1 orthologs were found in Xenopus laevis or Xenopus tropicalis.
- RNA sequencing and dataset analysis failed to detect PLCZ1 in Xenopus sperm.
Conclusions:
- The PLCZ1 gene appears to have been lost in the Xenopus lineage.
- This raises questions about the mechanism of sperm-induced calcium release and egg activation in Xenopus.
- Alternative pathways may mediate fertilization-related calcium signaling in these amphibians.
