InterPro domain: IPR006802

This family includes the radial spoke head proteins RSP4 and RSP6 from Chlamydomonas reinhardtii, and several eukaryotic homologues, including mammalian RSHL1, the protein product of a familial ciliary dyskinesia candidate gene [ 1 ]. The radial spoke head proteins are important in maintaining normal movement in motile, "9+2"-structure cilia and flagella. Mutations of the human RSPH9 and RSPH4A genes have been linked to primary ciliary dyskinesia, a genetically heterogeneous inherited disorder arising from dysmotility of motile cilia and sperm [ 2 ]. RSPH6A has also been shown to be required for sperm flagellum formation and male fertility in mice [ 3 ].

1. A mammalian radial spokehead-like gene, RSHL1, at the myotonic dystrophy-1 locus. Biochem. Biophys. Res. Commun. 281, 835-41
2. Mutations in radial spoke head protein genes RSPH9 and RSPH4A cause primary ciliary dyskinesia with central-microtubular-pair abnormalities. Am. J. Hum. Genet. 84, 197-209
3. RSPH6A is required for sperm flagellum formation and male fertility in mice. J. Cell. Sci. 131