Deficiency of spermatogenesis and reduced expression of spermatogenesis-related genes in prefoldin 5-mutant mice

• Mice harboring MM-1α/prefoldin 5 mutation exhibit male infertility in addition to neurodegeneration.
• Differentiation from the round spermatids to elongated spermatids was compromised.
• Defect of at least MM-1α transcriptional activity compromises differentiation of spermatids.

MM-1α is a c-Myc-binding protein and acts as a transcriptional co-repressor in the nucleus. MM-1α is also PDF5, a subunit of prefoldin that is chaperon comprised of six subunits and prevents misfolding of newly synthesized nascent polypeptides. Prefoldin also plays a role in quality control against protein aggregation. It has been reported that mice harboring the missense mutation L110R of MM-1α/PFD5 exhibit neurodegeneration in the cerebellum and also male infertility, but the phenotype of infertility has not been fully characterized. In this study, we first analyzed morphology of the testis and epididymis of L110R of MM-1α mice. During differentiation of spermatogenesis, spermatogonia, spermatocytes and round spermatids were formed, but formation of elongated spermatids was compromised in L110R MM-1α mice. Furthermore, reduced number/concentration of sperm in the epididymis was observed. MM-1α was strongly expressed in the round spermatids and sperms with round spermatids, suggesting that MM-1α affects the differentiation and maturation of germ cells. Changes in expression levels of spermatogenesis-related genes in mice testes were then examined. The fatty-acid-binding protein (fabp4) gene was up-regulated and three genes, including sperm-associated glutamate (E)-rich protein 4d (speer-4d), phospholipase A2-Group 3 (pla2g3) and phospholipase A2-Group 10 (pla2g10), were down-regulated in L110R MM-1α mice. L110R MM-1α and wild-type MM-1α bound to regions of up-regulated and down-regulated genes, respectively. Since these gene products are known to play a role in maturation and motility of sperm, a defect of at least MM-1α transcriptional activity is thought to induce expressional changes of these genes, resulting in male infertility.