title: A novel nonsense mutation in BBS4 gene identified in a Chinese family with Bardet-Biedl syndrome.
abstract: BACKGROUND
  Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disease, and information about BBS in Chinese populations is very limited. The purpose of the present study was to determine the genetic cause of BBS in a Chinese Han family.
  
  
  METHODS
  Clinical data were recorded for the 4-year-old female proband and the available family members. The proband was screened for mutation by Sanger sequencing for a total of 142 exons of the 12 BBS-causing genes (BBS1-BBS12). The variants detected in the proband were further confirmed in the other family members.
  
  
  RESULTS
  We identified a novel homozygous nonsense mutation (c.70A>T, p.K24X) in the BBS4 gene exon 2 in the proband. Such mutant allele was predicted to cause a premature truncation in the N-terminal of the BBS4 protein, and probably induced the nonsense-mediated decay of BBS4 messenger RNAs. The proband's parents and brother were heterozygous for the nonsense mutant allele. It was absent in 50 Chinese control subjects. An additional rare heterozygous missense single nucleotide polymorphism (SNP) named rs200718870 in BBS10 gene was also detected in the proband, her father and her brother. Some manifestations of the proband including atypical retinitis pigmentosa, choroidal sclerosis, high myopia, and early onset of obesity might be associated with this mutation in BBS4 gene. The proband's father also reported surgical removal of an extra finger during childhood.
  
  
  CONCLUSIONS
  The present study described a novel nonsense mutation in BBS4 gene in a Chinese family. This homozygous mutation was predicted to completely abolish the synthesis of the BBS4 protein. We also detected a rare heterozygous missense SNP in BBS10 gene in the family, but did not find sufficient evidence to support the triallelic inheritance.
authors.affiliation: Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China.
authors.forename: Yongpeng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China.
authors.forename: Liyun
authors.initials: L
authors.lastname: Jia
authors.affiliation: Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China; Beijing Institute of Ophthalmology, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Peng
mesh_terms: D020788:Bardet-Biedl Syndrome / Q000235:genetics*; D002675:Child, Preschool; D018389:Codon, Nonsense / Q000235:genetics*; D005260:Female; D006801:Humans; D008869:Microtubule-Associated Proteins; D011506:Proteins / Q000235:genetics*
chemical_list: C429655:BBS4 protein, human; D018389:Codon, Nonsense; D008869:Microtubule-Associated Proteins; D011506:Proteins