Isolation of embryos
Heterozygous male and female mice were intercrossed in order to obtain Ptdsr-deficient progeny. Females were daily monitored for vaginal plugs, and noon of the day of plug detection was defined as E0.5. Embryos at indicated time points were dissected in sterile PBS, washed in ice-cold PBS and transferred to cold fixative. Extra-embryonic membranes were kept and used for genotyping. Ptdsr -/- embryos and their wild-type littermates were used for experiments.