Fig. 1.
Reduced fertility in SvEv-Ramp2+/− females and high incidence of postnatal lethality SvEv-Ramp2+/− litters. A, Average number of pups per litter after implantation to weaning (SvEv-Ramp2+/+ intercrosses R2 value = 0.74; SvEv-Ramp2+/− intercrosses R2 value = 0.97). A total of 140 litters were scored for SvEv-Ramp2+/− intercrosses at birth and weaning, and 55 litters were scored for SvEv-Ramp2+/+ intercrosses. Unless otherwise mentioned, three to 17 litters per gestational time point were scored. The black arrows indicate the gestational age at which Ramp2−/− embryos die from lymphatic vascular defects and at which postnatal pup loss is observed in SvEv-Ramp2+/− intercrosses. B, Representative litters from wild-type SvEv and SvEv-Ramp2+/− intercrosses at E9.5 of pregnancy, showing a high incidence of fetal growth restriction that is independent of fetuses' genotype in SvEv-Ramp2+/− intercrosses. Arrows point to severely growth-restricted embryos. Embryos were imaged at the same magnification and later grouped digitally based on their genotype. C, Crown to rump length (millimeters) of E9.5 embryos from SvEv-Ramp2+/+ intercrosses and SvEv-Ramp2+/− intercrosses; *, P < 0.05. Number in the column represents number of embryos measured. D, Pie charts demonstrating that postnatal death observed from 140 SvEv-Ramp2+/− intercross litters was independent of pup genotype (left) and pup gender (right). Note that the white slice of the lower left pie chart represents a single Ramp2−/− mouse that we discovered alive after birth. Consistent with the knockout phenotype, this animal was severely hydropic. E, Reciprocal crosses of SvEv-Ramp2+/− mice. An average of two to three litters were scored for each time point. Loss of pups throughout pregnancy was observed only when the female was SvEv-Ramp2+/−.