ClpP Ensures Mitochondrial Integrity and Spermatocyte Meiotic Progression in Mice.

Abstract

Background: Caseinolytic peptidase P (ClpP) plays a key role in maintaining cellular homeostasis for mitochondrial quality control. However, the specific function of ClpP during meiosis and its subcellular localization in spermatocytes remain poorly understood.

Objective: To investigate the function of ClpP in spermatocyte meiosis.

Materials and methods: ClpP expression was examined in mouse spermatocytes, and tamoxifen was utilized to achieve spatiotemporal-specific deletion of Clpp mediated by Ddx4-Cre^ERT2 in spermatocytes. We analyzed the meiotic progression of Clpp conditional KO (Clpp^cKO) using spermatocyte chromosome spreading, combined with immunofluorescence and transmission electron microscopy, to determine the morphology and number of spermatocyte mitochondria in Clpp^cKO mice.

Results: A progressive increase in ClpP expression levels was evident from the leptotene stage to the pachytene stage in mouse spermatocytes, and a decrease in ClpP expression was observed from the diplotene stage to the metaphase I (MI) stage. Compared with wild-type male mice, adult Clpp^cKO male mice had reduced testis size and no mature spermatozoa in their epididymides. A large proportion of pachytene and diplotene spermatocytes, as well as round or elongated spermatids, were eliminated from the seminiferous tubules of the Clpp^cKO mice. The mitochondria of Clpp^cKO spermatocytes appeared as "giant mitochondria." However, Clpp^cKO spermatocytes exhibited normal meiotic synapsis and impaired recombination, with reduced RAD51 foci and abnormal MLH1 localization.

Conclusions: ClpP is critical for spermatocyte survival and mitochondrial integrity during meiosis. As a consequence of its deficiency, meiotic progression and spermatogenesis are disrupted, highlighting its essential role in the meiosis of spermatocytes.