Asl is required for proper function of sperm basal bodies. (A–C) Sas-6 (green) on BBs (Ana1::tdTomato, red) in early/intermediate (left) or late (right) STs. Axonemes, Ac-tub (gray); DNA, DAPI (blue). (A) wt (asl/TM6) STs. In early/intermediate STs (left), basal bodies are docked at the nucleus and form axonemes. The nuclei of late STs are elongated and clustered. (B) Remnant centrioles in asl mutant STs with “elongated” region of Sas-6 (n = 16). ST at all stages were examined. Bracket, distal extension of Ana1 beyond Sas-6. (left) The only remnant centriole (early/intermediate ST) with elongated Sas-6 exhibiting normal nuclear attachment and axoneme nucleation. (right) Representative remnant ST centriole not attached to a nucleus or forming an axoneme. The nuclei of late stage asl STs are fragmented and dispersed (yellow arrowheads). (C) Remnant centrioles in asl mutants with a “normal” distribution of Sas-6 (restricted to the very proximal end; n = 101). (left) Representative remnant centriole in an early/intermediate ST exhibiting normal nuclear attachment and axoneme formation. (middle) Representative remnant centriole in an early/intermediate ST with a disrupted, flared axoneme (arrow). (right) Representative remnant centrioles in late STs not attached to nuclei or nucleating axonemes. Yellow arrowhead indicates nucleus that has not undergone reshaping. Additional examples are shown in Fig. S5. Bars: 5 µm; (insets) 1 µm. Defective, no axoneme or no nuclear attachment or both.