The A-tubule links stabilize the A-tubules and restrict sliding. (A) Diagram summarizing the differences between CU428 and FAP256A/B-KO cilia. (B) Diagram of WT cilia with the A-tubule and membrane links drawn in black in straight and bending cilia. (C) Diagram of FAP256A/B-KO mutant cilia without the A-tubule links showing bent A-tubules and sliding A-tubules and CP microtubules during bending.