Figure 1: Expression patterns of Sbno1 during mouse preimplantation development and phenotypes of Sbno1 knockout embryos (Sbno1^Δ/Δ).

(a) Expression levels of Sbno1 transcripts during the preimplantation period were analyzed by semi-quantitative RT-PCR. β-Actin was used as an internal control. (b) Immunohistochemistry showed that Sbno1 (green) is clearly localized in the nuclei from the two-cell to blastocyst stages. β-Catenin staining (red) demarcates the cell membrane, and DAPI staining (blue) identifies the nuclei. (c,d) At E3.5, control Sbno1^Δ/+ embryos develop to blastocysts with an inner cell mass (ICM), trophectoderm (TE) and blastocoel (BC), whereas development of Sbno1^Δ/Δ embryos was halted with a morula-like morphology. (e,f) In Sbno1^Δ/Δ embryos, Sbno1 protein (green) was absent from the two-cell stage. (g,h) When two-cell stage embryos were cultured in vitro, Sbno1^Δ/Δ embryos developed normally to the compacted morula stage, but failed to form blastocysts and collapsed. (i–m) TUNEL (green in i,j) and phospho-histone H3 staining (pHH3, red in k,l) revealed increased cell death and decreased proliferation in Sbno1^Δ/Δ embryos, respectively. Uncropped image of gel is shown in Supplementary Fig. 9.