Fertility is compromised after oocyte-specific deletion of Katanin A-subunit, Katna1, but not Katnal1

Katanins are microtubule severing enzymes that play roles in shaping diverse microtubule-based structures during all cell cycle stages. To address the role of katanin A-subunits in mammalian oocytes, we have used the Zp3-CreLox approach to specifically delete katanin A1 (Katna1) and katanin A-like 1 (Katnal1) from the start of oocyte growth in mice. Here, we show that Katnal1 is not required for normal female fertility, but that deletion of Katna1 causes a 50% decrease in fertility. Further investigation in Katna1-/- oocytes revealed no effect on MI spindle morphology but a significant effect on the morphology of MII spindles. This was accompanied by a decreased rate of fertilisation. Resultant Katna1+/- heterozygous embryos that reached the 2-cell stage developed at normal rates to the blastocyst stage. Diploid homozygous parthenotes derived from Katna1-/- oocytes revealed a reduced rate of blastocyst formation, decreased cell number and increased nuclear size. The ability of the paternal allele to rescue preimplantation development suggests the origin of the decrease in the fertility of conditional Katna1-/- mice lies in abnormalities arising in the egg to embryo transition prior to embryonic genome activation.