ClpP Ensures Mitochondrial Integrity and Spermatocyte Meiotic Progression in Mice

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.

To investigate the function of ClpP in spermatocyte meiosis.

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.

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.

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.