title: The contribution of GPR98 and DFNB31 genes to a Spanish Usher syndrome type 2 cohort.
abstract: BACKGROUND
  Usher syndrome type 2 (USH2) is an autosomal recessive disease characterized by moderate to severe hearing loss and retinitis pigmentosa. To date, three disease-causing genes have been identified, USH2A, GPR98, and DFNB31, of which USH2A is clearly the major contributor. The aim of this work was to determine the contribution of GPR98 and DFNB31 genes in a Spanish cohort of USH2A negative patients using exhaustive molecular analysis, including sequencing, dosage, and splicing analysis.
  
  
  METHODS
  Linkage analysis was performed to prioritize the gene to study, followed by sequencing of exons and intron-exon boundaries of the selected gene, GPR98 (90 exons) or DFNB31 (12 exons). Functional splicing analyses and comparative genomic hybridization array to detect large rearrangements were performed when appropriate.
  
  
  RESULTS
  We confirmed that mutations in GPR98 contribute a significant but minor role to Usher syndrome type 2. In a group of patients referred for molecular diagnosis, 43 had been found to be positive for USH2A mutations, the remaining 19 without USH2A alterations were screened, and seven different mutations were identified in the GPR98 gene in seven patients (five in the homozygous state), of which six were novel. All detected mutations result in a truncated protein; deleterious missense mutations were not found. No pathological mutations were identified in the DFNB31 gene.
  
  
  CONCLUSIONS
  In Spain, USH2A and GPR98 are responsible for 95.8% and 5.2% of USH2 mutated cases, respectively. DFNB31 plays a minor role in the Spanish population. There was a group of patients in whom no mutation was found. These findings confirm the importance of including at least GPR98 analysis for comprehensive USH2 molecular diagnosis.
authors: INSERM, U827, Montpellier F-34000, France.
authors: Gema
authors: G
authors: García-García
authors: Thomas
authors: T
authors: Besnard
authors: David
authors: D
authors: Baux
authors: Christel
authors: C
authors: Vaché
authors: Elena
authors: E
authors: Aller
authors: Sue
authors: S
authors: Malcolm
authors: Mireille
authors: M
authors: Claustres
authors: Jose M
authors: JM
authors: Millan
authors: Anne-Françoise
authors: AF
authors: Roux
mesh_terms: D018389:Codon, Nonsense; D015331:Cohort Studies; D016326:Extracellular Matrix Proteins / Q000235:genetics; D016368:Frameshift Mutation; D006239:Haplotypes; D006720:Homozygote; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D017384:Sequence Deletion; D013030:Spain; D052245:Usher Syndromes / Q000145:classification / Q000235:genetics* / Q000503:physiopathology
chemical_list: C417525:ADGRV1 protein, human; D018389:Codon, Nonsense; D016326:Extracellular Matrix Proteins; D008565:Membrane Proteins; D043562:Receptors, G-Protein-Coupled; C112735:USH2A protein, human; C477219:WHRN protein, human