Identification of an M(r) 60,000 polypeptide unique to the meiotic spindle of the mouse oocyte

The mouse oocyte expresses an M(r) 60,000 (p60) polypeptide that is associated with the first and second meiotic spindles. Immunoreactive p60 was not detectable in the meiotic spindles of male germ cells or in mitotic spindles. P60 was identified with a polyclonal antibody whose predominant activity is directed against ankyrin. However, immunoadsorption experiments demonstrated that p60 is not an ankyrin isoform and represents a secondary activity of the polyclonal antibody. Circumstantial evidence suggest that p60 may be a microtubule-associated protein. Since the most obvious difference between the female meiotic spindle and other spindles is the long half-life of the former, we hypothesize that p60 may function in the maintenance of the long-lived female meiotic apparatus.