The MKS1 (559 aas; 0 TMSs)-B9D2 (175 aas, possibly 1 N-terminal TMS)-B9D1 (204 aas, possibly 1 N-terminal TMS) diffusion barrier (transition zone (TZ)) complex. These proteins are components 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. The complex is involved in centrosome migration to the apical cell surface during early ciliogenesis (Tammachote et al. 2009). It is required for ciliary structure and function, including a role in regulating length and appropriate number through modulating centrosome duplication. It may also be required for cell branching morphology. The Meckel Syndrome Protein, Meckelin, may be part of the complex (see TC#9.B.77.1.1). MKS1 interacts with Meckelin (TMEM67; MKS3; Dawe et al. 2007).