HORMAD1 Is Essential for Male and Female Meiosis Figure 12. Hormad1–/– oocyte derived embryos arrest at blastocyst stage. Embryos derived from wild-type matings (M+/+-F+/+) and matings involving Hormad12/2 oocytes fertilized by wild-type males (M+/+-F2/2), were collected at E0.5, E1.5, E2.5 and E3.5 for the analysis of the early embryonic development. (A-C) No significant differences were noted between wild-type and Hormad12/2 at E 0.5, with normal appearing one cell embryos and polar bodies visible in both. (D-F) At E1.5, there is an excess of 1 cell embryos in Hormad12/2 fertilized oocytes, indicating a lag in embryo development at this stage. (G-I) At E2.5 there is a significantly less number of eight cell embryos formed in Hormad12/2 fertilized oocytes as opposed to the wild-type. A large proportion of 8-cell embryos appear disorganized and apoptotic. (J-L) Blastocysts form at E3.5 in wild-type but very few normal blastocysts are visible in Hormad12/2 embryos. The count only includes morphologically normal blastocysts (L). Error bars represent standard error of the mean. Student’s t test was used to calculate P values (*:P,0.5, **:P,0.001). (M) Embryos derived from Hormad12/2 fertilized oocytes can not implant, as visualized by Sky Blue dye injected into the tail vein of pregnant females at E6.5 gestational age. doi:10.1371/journal.pgen.1001190.g012 PLoS Genetics | www.plosgenetics.org 13 November 2010 | Volume 6 | Issue 11 | e1001190