A catalytically competent sperm PLCzeta variant causes fertilization failure through protein insufficiency

Saleh, Alaaeldin, Huang, Zizhen, Islam, Zeyaul, Swann, Karl ORCID: https://orcid.org/0000-0002-4355-1449 and Nomikos, Michail 2026. A catalytically competent sperm PLCzeta variant causes fertilization failure through protein insufficiency. Journal of In Vitro Fertilization and Embryo Transfer 10.1007/s10815-026-04023-9

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Abstract

Purpose The PLCζ p.Arg385Gln (R385Q) variant was recently identified in infertile patients with recurrent fertilization failure and markedly reduced sperm PLCζ levels. However, whether this variant causes infertility through loss of catalytic function or protein insufficiency remains unknown. Methods The structural and functional consequences of the R385Q variant were investigated using structural modelling, protein stability prediction, recombinant PLCζ enzymatic assays, and mouse oocyte microinjection followed by Ca2+ oscillation analysis. Results Structural modelling predicted that the R385Q substitution destabilizes the catalytic domain without disrupting the active site. Consistent with this prediction, recombinant PLCζR385Q exhibited phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolytic activity comparable to wild-type PLCζ. Likewise, microinjection of PLCζR385Q cRNA into mouse oocytes induced Ca2+ oscillations with frequencies and patterns indistinguishable from those elicited by wild-type PLCζ, demonstrating preserved catalytic and oocyte activation activity. Conclusion These findings indicate that the R385Q variant is catalytically competent and does not cause infertility through loss of enzymatic function. Instead, together with our previous demonstration of markedly reduced PLCζ protein levels in patient sperm, the results support a protein insufficiency mechanism in which fertilization failure arises when PLCζ levels fall below the threshold required for physiological oocyte activation. This study expands the spectrum of pathogenic mechanisms underlying PLCζ-associated male infertility.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Biosciences
ISSN:	0740-7769
Date of First Compliant Deposit:	15 September 2026
Date of Acceptance:	27 August 2026
Last Modified:	15 Sep 2026 09:00
URI:	https://orca.cardiff.ac.uk/id/eprint/189594

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