Affects microtubule function during spermatogenesis.
Chromosome movement during meiosis usually appears normal in homozygous males, but failure of cytokinesis after meiosis I or II is frequent, with two or four nuclei found associated with a single, abnormally large mitochondrial derivative in the developing spermatids. Smaller mitochondrial derivatives than normal are also seen. Nuclear shaping during spermatogenesis occurs normally, but nuclear alignment is defective. Spermatid cysts often contain fewer axonemes than normal, and the axonemes generally lack one or both central pair microtubules. The axonemes are shorter than normal. Broken axonemes or axoneme fragments are common. Some spermatid cyst elongation takes place. Chromosome segregation during meiosis is sometimes abnormal in βTub85D7/βTub85Dn males. βTub85D7/βTub85Dn males are sterile.
Although relatively well organised near the basal body, the axonemes in the spermatids of homozygous males are abnormally short, appear to fray apart as the distance from the basal body exceeds more than a few μm and lack one or both central pair microtubules. Occasional failure of cytokinesis after meiosis I or II is seen. Nuclear shaping is normal.