The Protease Degrading Sperm Histones Post-Fertilization in Sea Urchin Eggs Is a Nuclear Cathepsin L That Is Further Required for Embryo Development
2012
Proteolysis of sperm histones in the sea urchin
male pronucleusis the consequence of the activation at fertilization of a maternal
cysteine protease. We previously showed that this protein is required for male
chromatin remodellingand for cell-cycle progression in the newly formed embryos. This enzyme is present in the nucleus of unfertilized eggs and is rapidly recruited to the
male pronucleusafter insemination. Interestingly, this
cysteine-proteaseremains co-localized with chromatin during S phase of the first cell cycle, migrates to the mitotic spindle in M-phase and is re-located to the nuclei of daughter cells after
cytokinesis. Here we identified the protease encoding cDNA and found a high sequence identity to
cathepsinproteases of various organisms. A phylogenetical analysis clearly demonstrates that this sperm histone protease (SpHp) belongs to the
cathepsin Lsub-type. After an initial phase of ubiquitous expression throughout cleavage stages, SpHp gene transcripts become restricted to endomesodermic territories during the
blastulastage. The transcripts are localized in the
invaginating
endodermduring
gastrulationand a gut specific pattern continues through the prism and early
pluteusstages. In addition, a concomitant expression of SpHp transcripts is detected in cells of the skeletogenic lineage and in accordance a pharmacological disruption of SpHp activity prevents growth of skeletal rods. These results further document the role of this nuclear
cathepsin Lduring development.
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