title: B9D1 is revealed as a novel Meckel syndrome (MKS) gene by targeted exon-enriched next-generation sequencing and deletion analysis.
abstract: Meckel syndrome (MKS) is an embryonic lethal, autosomal recessive disorder characterized by polycystic kidney disease, central nervous system defects, polydactyly and liver fibrosis. This disorder is thought to be associated with defects in primary cilia; therefore, it is classed as a ciliopathy. To date, six genes have been commonly associated with MKS (MKS1, TMEM67, TMEM216, CEP290, CC2D2A and RPGRIP1L). However, mutation screening of these genes revealed two mutated alleles in only just over half of our MKS cohort (46 families), suggesting an even greater level of genetic heterogeneity. To explore the full genetic complexity of MKS, we performed exon-enriched next-generation sequencing of 31 ciliopathy genes in 12 MKS pedigrees using RainDance microdroplet-PCR enrichment and IlluminaGAIIx next-generation sequencing. In family M456, we detected a splice-donor site change in a novel MKS gene, B9D1. The B9D1 protein is structurally similar to MKS1 and has been shown to be of importance for ciliogenesis in Caenorhabditis elegans. Reverse transcriptase-PCR analysis of fetal RNA revealed, hemizygously, a single smaller mRNA product with a frameshifting exclusion of B9D1 exon 4. ArrayCGH showed that the second mutation was a 1.713 Mb de novo deletion completely deleting the B9D1 allele. Immunofluorescence analysis highlighted a significantly lower level of ciliated patient cells compared to controls, confirming a role for B9D1 in ciliogenesis. The fetus inherited an additional likely pathogenic novel missense change to a second MKS gene, CEP290; p.R2210C, suggesting oligogenic inheritance in this disorder.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street SW,Rochester, MN 55905, USA
authors.forename: Katharina
authors.initials: K
authors.lastname: Hopp
authors.forename: Christina M
authors.initials: CM
authors.lastname: Heyer
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Hommerding
authors.forename: Susan A
authors.initials: SA
authors.lastname: Henke
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Sundsbak
authors.forename: Shail
authors.initials: S
authors.lastname: Patel
authors.forename: Priyanka
authors.initials: P
authors.lastname: Patel
authors.forename: Mark B
authors.initials: MB
authors.lastname: Consugar
authors.forename: Peter G
authors.initials: PG
authors.lastname: Czarnecki
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Gliem
authors.forename: Vicente E
authors.initials: VE
authors.lastname: Torres
authors.forename: Sandro
authors.initials: S
authors.lastname: Rossetti
authors.forename: Peter C
authors.initials: PC
authors.lastname: Harris
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002923:Cilia / Q000235:genetics / Q000473:pathology; D002925:Ciliary Motility Disorders / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D003598:Cytoskeletal Proteins; D004677:Encephalocele / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005091:Exons / Q000235:genetics*; D005260:Female; D005333:Fetus; D005347:Fibroblasts / Q000378:metabolism; D023061:Gene Order; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics; D010375:Pedigree; D010641:Phenotype; D007690:Polycystic Kidney Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D011506:Proteins / Q000235:genetics*; D012174:Retinitis Pigmentosa; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics*
chemical_list: C000592877:B9D1 protein, human; D003598:Cytoskeletal Proteins; D011506:Proteins