B9 domain-containing protein 2 (B9D2)

B9 domain-containing protein 2 (B9D2) is a highly conserved ciliary protein found exclusively in ciliated organisms[1][4][5]. It localizes primarily to the transition zone at the base of cilia, where it forms a critical heterotrimeric complex with MKS1 and B9D1[1][3][4][5]. This complex serves as a selective diffusion barrier for ciliary membrane proteins, facilitating compartmentalization of signaling pathways such as Hedgehog signaling and playing a decisive role in ciliogenesis and ciliary membrane organization[1][3][4][5]. Loss of B9D2 disrupts the formation and maintenance of both motile and primary cilia, resulting in severe multi-organ developmental defects associated with ciliopathies including Meckel-Gruber syndrome and Joubert syndrome[1][2]. Beyond its ciliary functions, B9D2 is crucial for the maturation and maintenance of epithelial tight junctions and cell polarity, impacting tissue architecture during development (notably in the liver)[2]. There are no known therapeutic drugs or direct modulators targeting B9D2.

Other names

MKSR2MKS10JBTS34ICIS-1MKS1-related protein 2involved in cilia stability-1B9 protein domain 2B9D2