Fig. 1.

MYH10 is required for cytokinesis during male meiosis. (a) Developmental timeline of mouse spermatogenesis. Arrows mark the onset of expression of the Ddx4-Cre and Hspa2-Cre transgenes. Meiotic germ cells, including primary spermatocytes, secondary spermatocytes, and round spermatids are represented schematically, and intercellular bridges, resulting from incomplete cytokinesis, are shown. (b) Absence of MYH10 protein in Myh10^fl/− Ddx4-Cre testes. Western blot analysis was performed on testicular or ovarian protein extracts from 2 month-old adult mice. The genotype of each sample, determined by analysis of tail DNA, is indicated above each lane. MYH11, the smooth muscle myosin II heavy chain, and ACTB served as loading controls (Deng et al., 1993). (c) Testicular seminiferous tubule from a 2-month-old wild type mouse contains a full spectrum of germ cells. (d) Tubules from 2-month-old Myh10^fl/− Ddx4-Cre mice exhibit spermiogenic arrest. Germ cells with four nuclei (Inset, enlarged view of boxed area), two small nuclei, or two large nuclei are marked. (e) Epididymal tubules from 2-month-old wild type mice are filled with sperm. (f) Epididymal tubules from 2-month-old Myh10^fl/− Ddx4-Cre mice lack sperm but contain round multi-nucleated cells. Sections (c–f) are stained with H&E. Abbreviations: Pa, pachytene spermatocytes; RS, round spermatids; ES, elongated spermatids. Scale bar, 50 µm.