Fig. 3.

Tssk6-null sperm cannot fuse with eggs. Eggs devoid of zona pellucida were loaded with the DNA stain Hoechst 33342 prior to IVF as described in the Materials and Methods. Fusion was assessed by transference of fluorescent Hoechst 33342 from the egg to the fused sperm and observed under DIC and epifluorescence microscopy at 20 and 120 minutes. (A) WT sperm fused to the eggs were stained with Hoechst 33342 after 20 minutes of incubation (WT). Tssk6-null sperm were not stained after 120 minutes incubation, indicating that fusion did not occur (KO). Note that the unfertilized eggs that did not undergo fusion maintain their chromatin aligned at metaphase II as seen in the positive staining (KO). (B) Quantification of the experiments was performed as in Fig. 2. The data represent a combination of four independent experiments and are presented as a percentage of the total eggs used.