Insertional mutation of the murine kisimo locus caused a defect in spermatogenesis

Spermatogenesis is a developmental process that occurs in several phases an d is regulated by a large number of gene products. An insertional transgeni c mouse mutant (termed kisimo mouse) has been isolated that results in abno rmal germ-cell development, showing: abnormal elongated spermatids in the l umina of seminiferous tubules. We cloned the disrupted locus of kisimo and identified a novel testis-specific gene, THEG, which is specifically expres sed in spermatids and was disrupted in the transgenic mouse. The yeast two- hybrid screening method revealed that THEG protein strongly interacts with chaperonin containing t-complex polypeptide-le, suggesting that THEG protei n functions as a regulatory factor in protein assembly. Our findings indica te that the kisimo locus is essential for the maintenance of spermiogenesis and that a gene expression disorder may be involved in male infertility.