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. Specifically or prominently expressed in mouse blastocysts compared to 4-cell stage embryos. Mice display impaired cilia formation associated with renal cystic dysplasia, as well as ductal plate malformation of the liver and polydactyly. Additional phenotypes, occurring at varying frequencies, include randomized heart looping, holoprosencephaly, microphthalmia, cleft palate, ventricular septal defect and thinning of the myocardial wall. Depending on their genetic background, mutant mice die between 14.5 dpc and P1. Belongs to the B9D family.