FIG. 7.

Homozygous embryos die at 2.5 to 3.5 dpc. Morphological alterations and TUNEL staining in control and Fibrillarin mutant embryos. A failure in transition to the blastocyst stage first became apparent at 60 h after mating, with subsequent formation of a disorganized, multicystic structure and finally extensive cellular degeneration at 84 h post coitum. TUNEL staining of Fibrillarin^−/− embryos showed strong staining of most cells (f), suggesting apoptotic cell death. In contrast, wild-type and +/− blastocysts (b and d, respectively) showed very few labeled cells.