Microtubule-binding protein required for ciliogenesis. May function in ciliogenesis by mediating the transport of proteins like BBS4 to the cilium, but also through the organization of the centriolar satellites (By similarity). Plays a role in retina morphogenesis and/or homeostasis (PubMed:21680557). Homodimer; disulfide-linked (Probable). Interacts with CEP290. Interacts with PCM1 (By similarity). Interacts with ARMC9, TOGARAM1, CSPP1 and CEP104 (By similarity). Restricted to the centrosomes and the spindle microtubules during mitosis (By similarity). Enriched in the inner segment of the photoreceptor (PubMed:19777273). Widely expressed (PubMed:19777273). Expressed in retina by rod photoreceptors but also detected in outer plexiform and ganglion cell layers (at protein level) (PubMed:21680557, PubMed:19777273). Expressed in the retina from postnatal stages to adulthood. Highest levels are observed at postnatal stage P1 and P4 and expression decreases afterward. Steady levels are observed from P12 to adulthood. Expression increases in the outer segments from P12 to P19 paralleling the differentiation of outer segments. Mice lacking Ccdc66 are viable but display degeneration of the retina. Initial formation of the retina is normal up to postnatal stage P10. Malformation of photoreceptors develops around P13. The degeneration progresses slowly until 3 months after birth, when the outer nuclear layer is reduced to 5-6 rows. From 5 to 7 months, only a thin outer nuclear and photoreceptor layer with severely shrunken outer and inner segments is preserved. It is associated with impaired photoreceptor function with early visual impairment detectable 1 month after birth and progressing slightly until 7 months. Partial nucleotide duplication in position 392 that disrupts the frame.