Microtubule-dependent meiotic nuclear movement and the interaction between KASH5 and dynein. (A) Immunoprecipitates (IP) from mouse testis using a KASH5 antibody or control (Cont.) IgG were analyzed by immunoblot using the indicated antibodies. Total soluble extract (0.05%) was loaded as input. GAPDH, glyceraldehyde 3-phosphate dehydrogenase. (B) Time-lapse images of a mitotic cell or pachytene spermatocytes treated with or without nocodazole (Noc) were collected for 5 min at 30-s intervals (Video 1–3). Note that TRF1 signals distribute randomly in the nucleus of mitotic cells, whereas TRF1 signals localize near the NE of pachytene spermatocytes. Bar, 5 µm. (C) A model for mechanical bridging of the NE by SUN1 and KASH5 proteins during mammalian meiotic prophase. SUN1 and KASH5 locate at the INM and ONM, respectively, of the NE and interact across the lumen between the membranes. KASH5 associates with the dynein–dynactin complexes, whereas SUN1 may associate with telomeres on the opposite outsides of the NE, thus transferring the driving force generated by cytoplasmic microtubules to telomeres in the nucleus.