title: Disruption of a ciliary B9 protein complex causes Meckel syndrome.
abstract: Nearly every ciliated organism possesses three B9 domain-containing proteins: MKS1, B9D1, and B9D2. Mutations in human MKS1 cause Meckel syndrome (MKS), a severe ciliopathy characterized by occipital encephalocele, liver ductal plate malformations, polydactyly, and kidney cysts. Mouse mutations in either Mks1 or B9d2 compromise ciliogenesis and result in phenotypes similar to those of MKS. Given the importance of these two B9 proteins to ciliogenesis, we examined the role of the third B9 protein, B9d1. Mice lacking B9d1 displayed polydactyly, kidney cysts, ductal plate malformations, and abnormal patterning of the neural tube, concomitant with compromised ciliogenesis, ciliary protein localization, and Hedgehog (Hh) signal transduction. These data prompted us to screen MKS patients for mutations in B9D1 and B9D2. We identified a homozygous c.301A>C (p.Ser101Arg) B9D2 mutation that segregates with MKS, affects an evolutionarily conserved residue, and is absent from controls. Unlike wild-type B9D2 mRNA, the p.Ser101Arg mutation failed to rescue zebrafish phenotypes induced by the suppression of b9d2. With coimmunoprecipitation and mass spectrometric analyses, we found that Mks1, B9d1, and B9d2 interact physically, but that the p.Ser101Arg mutation abrogates the ability of B9d2 to interact with Mks1, further suggesting that the mutation compromises B9d2 function. Our data indicate that B9d1 is required for normal Hh signaling, ciliogenesis, and ciliary protein localization and that B9d1 and B9d2 are essential components of a B9 protein complex, disruption of which causes MKS.
authors.affiliation: Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, 94158, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Dowdle
authors.forename: Jon F
authors.initials: JF
authors.lastname: Robinson
authors.forename: Andreas
authors.initials: A
authors.lastname: Kneist
authors.forename: M Salomé
authors.initials: MS
authors.lastname: Sirerol-Piquer
authors.forename: Suzanna G M
authors.initials: SG
authors.lastname: Frints
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Corbit
authors.forename: Norann A
authors.initials: NA
authors.lastname: Zaghloul
authors.forename: Norran A
authors.initials: NA
authors.lastname: Zaghloul
authors.forename: Gesina
authors.initials: G
authors.lastname: van Lijnschoten
authors.forename: Leon
authors.initials: L
authors.lastname: Mulders
authors.forename: Dideke E
authors.initials: DE
authors.lastname: Verver
authors.forename: Klaus
authors.initials: K
authors.lastname: Zerres
authors.forename: Randall R
authors.initials: RR
authors.lastname: Reed
authors.forename: Tania
authors.initials: T
authors.lastname: Attié-Bitach
authors.forename: Colin A
authors.initials: CA
authors.lastname: Johnson
authors.forename: José Manuel
authors.initials: JM
authors.lastname: García-Verdugo
authors.forename: Nicholas
authors.initials: N
authors.lastname: Katsanis
authors.forename: Carsten
authors.initials: C
authors.lastname: Bergmann
authors.forename: Jeremy F
authors.initials: JF
authors.lastname: Reiter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002925:Ciliary Motility Disorders / Q000235:genetics*; D004252:DNA Mutational Analysis; D004677:Encephalocele / Q000235:genetics*; D008040:Genetic Linkage; D006720:Homozygote; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D054259:Neural Tube / Q000002:abnormalities; D010641:Phenotype; D007690:Polycystic Kidney Diseases / Q000235:genetics*; D017689:Polydactyly / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012174:Retinitis Pigmentosa; D015398:Signal Transduction; D015027:Zebrafish / Q000235:genetics
chemical_list: C509166:MKS1 protein, mouse; D011506:Proteins; D012333:RNA, Messenger