Involved in ciliogenesis (PubMed:28625504). It is required for appropriate acetylation and polyglutamylation of ciliary microtubules, and regulation of cilium length (By similarity). Acts as a positive regulator of hedgehog (Hh) signaling (By similarity). Localized to the proximal region in cilia. Stimulation of Hh signaling leads to redistribution of ARMC9 toward the ciliary tip within 6 hours, follow by a gradual return to its original proximal location (By similarity). Localizes to the daughter centriole of the primary cilium in RPE1 cells (By similarity). Expressed in multiple CNS regions, including the cerebellum, all periventricular regions, and all layers of the retina. Embryos with CRISPR-induced armc9 null mutations show curved body shape, retinal dystrophy, coloboma, reduced cilia number in ventricles, and shortened cilia in photoreceptor outer segments.