DRC9 (dynein regulatory complex subunit 9) is a structural component of the nexin-dynein regulatory complex (N-DRC) that maintains axoneme integrity and regulates microtubule sliding in motile cilia and flagella. As a component of the N-DRC, DRC9 functions to preserve the alignment of the distal axoneme and control microtubule dynamics essential for ciliary and flagellar movement. DRC9 binds calmodulin at low cellular calcium concentrations, thereby modulating calcium and calmodulin-dependent protein kinase IV (CAMK4) signaling cascades. This calcium-sensing capability positions DRC9 at the intersection of structural axoneme organization and calcium-dependent regulatory pathways. DRC9 is particularly critical for male fertility, where it is required for proper sperm flagellum assembly, axoneme organization, and flagellar motility. Mutations or deficiencies in DRC9 would be expected to impair sperm tail formation and function, leading to male infertility through compromised sperm motility. The gene's role in both structural maintenance of the axoneme and calcium-responsive signaling regulation highlights its importance in coordinating ciliary/flagellar function with cellular calcium homeostasis.