Clathrin is essential for meiotic spindle function in porcine oocytes (SUPPLEMENTAL MOVIES)

Abstract

Mammalian oocytes acquire competence for fertilization during meiotic maturation, a process that includes completion of the first meiotic division and formation of the second metaphase spindle. Clathrin is a large protein complex that has originally been defined for its role in intracellular membrane traffic, but was recently shown to have a second independent function, involving the stabilization of kinetochore fibers in mitotic spindles of dividing somatic cells. To study whether clathrin also functions at meiotic spindles in oocytes we microinjected green fluorescent protein-tagged C-terminal and N-terminal clathrin protein constructs into isolated porcine oocytes prior to in vitro maturation. In oocytes, both constructs associated with meiotic spindles similar to endogenous clathrin, but induced misalignment and clumping of chromosomes, formation of satellite spindles, and failure of polar body extrusion. These results demonstrate a crucial role for clathrin in the function of the first and second meiotic spindle in maturing oocytes.