Figure 4.

Sox2^βgeo null blastocysts show defective ICM development in culture. (A–H) Phase contrast microscopy of embryos from Sox2^βgeo intercrosses, with wild-type (+/+; A) and Sox2^βgeo null (−/−; E) blastocysts and different blastocyst outgrowths grown in culture for 3 d (B–D,F–H). Wild-type and mutant blastocysts look similar, but the ICM of null blastocysts fails to outgrow. (I) RT–PCR marker analysis of Sox2^βgeo null blastocyst outgrowths. Morulae from Sox2^βgeo heterozygous intercrosses were cultured for 5 d. BSC loading control refers to Bluescript RNA that was not added to an RNA preparation, but added directly to the subsequent RT reaction. No DNA refers to the negative control used during the PCR reaction. (J–Q) Pl1 RNA in situ hybridization on Sox2^βgeo null ICM outgrowths. Isolated ICMs (J–M) were grown in culture for 4 d and analyzed for Pl1 expression (N–Q). Mutant (P,Q) but not wild-type (N) or Sox2^βgeo heterozygous (O) ICM outgrowths express PL1. Bars: A,E, 35 μm; B–D,F–H, 100 μm; J–Q, 27 μm.