KINESIN-RELATED PROTEINS IN THE MAMMALIAN TESTES - CANDIDATE MOTORS FOR MEIOSIS AND MORPHOGENESIS

The kinesin superfamily of molecular motors comprises proteins that pa rticipate in a wide variety of motile events within the cell. Members of this family share a highly homologous head domain responsible for f orce generation attached to a divergent tail domain thought to couple the motor domain to its target cargo. Many kinesin-related proteins (K RPs) participate in spindle morphogenesis and chromosome movement in c ell division. Genetic analysis of mitotic KRPs in yeast and Drosophila , as well as biochemical experiments in other species, have suggested models for the function of KRPs in cell division, including both mitos is and meiosis. Although many mitotic KRPs have been identified, the r elationship between mitotic motors and meiotic function is not clearly understood. We have used sequence similarity between mitotic KRPs to identify candidates for meiotic and/or mitotic motors in a vertebrate. We have identified a group of kinesin-related proteins from rat teste s (termed here testes KRP1 through KRP6) that includes new members of the bimC and KIF2 subfamilies as well as proteins that may define new kinesin subfamilies. Five of the six testes KRPs identified are expres sed primarily in testes. Three of these are expressed in a region of t he seminiferous epithelia (SE) rich in meiotically active cells. Furth er characterization of one of these KRPs, KRP2, showed it to be a prom ising candidate for a motor in meiosis: it is localized to a meiotical ly active region of the SE and is homologous to motor proteins associa ted with the mitotic apparatus. Testes-specific genes provide the nece ssary probes to investigate whether the motor proteins that function i n mammalian meiosis overlap with those of mitosis and whether motor pr oteins exist with functions unique to meiosis. Our search for meiotic motors in a vertebrate testes has successfully identified proteins wit h properties consistent with those of meiotic motors in addition to un covering proteins that may function in other unique motile events of t he SE.