Component of the tectonic-like complex, a complex localized at the transition zone of primary cilia and acting as a barrier that prevents diffusion of transmembrane proteins between the cilia and plasma membranes. Required for ciliogenesis and sonic hedgehog/SHH signaling. Part of the tectonic-like complex (also named B9 complex). Localizes at the transition zone, a region between the basal body and the ciliary axoneme. Embryos show randomized left-right axes, holoprosencephaly, microphthalmia and a variably expressive curved body axis. Cc2d2a null embryos also have cilia defects, which are exemplified by the absence of Arl13b staining in neural tube and surrounding mesenchyme.