NS is not required for nucleolar integrity or to maintain pluripotency. (A) Representative images of E3.5 NS+/+ or NS+/− and NS−/− mutant embryos stained with DAPI (blue), antifibrillarin (green), and anti-NS (red) antibodies. Fibrillarin nucleolar localization is not perturbed in NS-deficient blastocysts. (B) Representative images of E3.5 NS+/+ or NS+/− and NS−/− mutant embryos stained with DAPI (blue), anti-Oct3/4 (green), and anti-NS (red) antibodies. NS-deficient blastocysts maintain expression of Oct4, the marker of pluripotent stem cells. Magnification, ×200.