Fig. 3. Brdt mutant epididymal sperm are abnormal. (A) Morphology of epididymis from controls and homozygous mutants showing that very few sperm are present in the epididymis of the Brdt^BD1/BD1 mutant mice. (B) Light microscopy showing epididymal sperm of wild-type and Brdt^BD1/BD1 mutant mice. The photomicrographs show the variations of the abnormalities in the mutants, which occur throughout the sperm, including in the sperm head, mid-piece (M) and tail. (C) Electron microscopy of sperm reveals variation in the extent of nuclear condensation, as reflected by regions of reduced electron density and also by a failure of the acrosome to form normally. Residual cytoplasm, which should have been discarded as the residual body, is seen and it contains aberrant mitochondria. Magnifications in C: WT, x13,000; mutant, upper right, x8,300; lower left, x10,000; lower right, x8,300. A, acrosome; N, nucleus; M, midpiece. Scale bar: 5 µm.