Model for Asl function in centriole organization and length control. (A and B) Not all long centrioles are alike. Centrioles in asl mutant mGSCs (A) are organized in a manner distinct from the giant centrioles normally found in SCs (B). This indicates that these two structures, although of similar scale, arise via distinct mechanisms. (C and D) Expanded roles for Asterless at the centriole. In the male germline, Asl plays a critical role in regulating centrosome duplication via Plk4, and controlling centriole length upstream of, and likely directly through, Cep97. (D) In developing STs, Asl is required for normal nuclear attachment and axoneme formation.