Multiple kinesin-like transcripts in Xenopus oocytes.

Recent evidence shows that kinesin-like proteins (Klps) form a very large multigene family. A recent study using the polymerase chain reaction (PCR) identified six new candidate Klps in Drosophila, making the total number of members of this family in Drosophila at least 11 (Stewart et al., 1991, Proc. Natl. Acad. Sci. USA 88, 4424-4427). The functional basis of this diversity is not clear. Different Klps could have cell type-specific functions, or they could perform different functions within the same cell type, or a mixture of both. To investigate the degree to which different Klps are expressed in the same cell, we chose the Xenopus oocyte. During oocyte differentiation, and in the egg, different types of microtubule-based motility occur; all are important to the normal development of the embryo after fertilization. Using PCR we identified and partially sequenced four novel Klp mRNAs from the Xenopus oocyte (denoted XKlps 1-4). Multialign sequence comparison suggests that one of them, XKlp3, may be the Xenopus counterpart of Drosophila Klp4. Similarly Xenopus Eg5 is closely related to Drosophila Klp2. Northern blot analysis reveals that the Xenopus XKlps have different patterns of expression during embryogenesis. These data show that at least four Klps can exist in the same cell and that they can be differentially regulated during early development, and suggest their differential function in oogenesis and early development.