title: Functional modelling of a novel mutation in BBS5.
abstract: BACKGROUND
  Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy disorder with 18 known causative genes (BBS1-18). The primary clinical features are renal abnormalities, rod-cone dystrophy, post-axial polydactyly, learning difficulties, obesity and male hypogonadism.
  
  
  RESULTS
  We describe the clinical phenotype in three Saudi siblings in whom we have identified a novel mutation in exon 12 of BBS5 (c.966dupT; p.Ala323CysfsX57). This single nucleotide duplication creates a frame shift results in a predicted elongated peptide. Translation blocking Morpholino oligonucleotides were used to create zebrafish bbs5 morphants. Morphants displayed retinal layering defects, abnormal cardiac looping and dilated, cystic pronephric ducts with reduced cilia expression. Morphants also displayed significantly reduced dextran clearance via the pronephros compared to wildtype embryos, suggesting reduced renal function in morphants. The eye, kidney and heart defects reported in morphant zebrafish resemble the human phenotype of BBS5 mutations. The pathogenicity of the novel BBS5 mutation was determined. Mutant mRNA was unable to rescue pleiotropic phenotypes of bbs5 morphant zebrafish and in cell culture we demonstrate a mislocalisation of mutant BBS5 protein which fails to localise discretely with the basal body.
  
  
  CONCLUSIONS
  We conclude that this novel BBS5 mutation has a deleterious function that accounts for the multisystem ciliopathy phenotype seen in affected human patients.
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Al-Hamed
authors.forename: Charles
authors.initials: C
authors.lastname: van Lennep
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Hynes
authors.forename: Paul
authors.initials: P
authors.lastname: Chrystal
authors.forename: Lorraine
authors.initials: L
authors.lastname: Eley
authors.forename: Fatimah
authors.initials: F
authors.lastname: Al-Fadhly
authors.forename: Riham
authors.initials: R
authors.lastname: El Sayed
authors.forename: Roslyn J
authors.initials: RJ
authors.lastname: Simms
authors.forename: Brian
authors.initials: B
authors.lastname: Meyer
authors.affiliation: International Centre for Life, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle NE1 3BZ, UK. john.sayer@ncl.ac.uk.
authors.forename: John A
authors.initials: JA
authors.lastname: Sayer