title: Molecular characteristics of four Japanese cases with KCNV2 retinopathy: report of novel disease-causing variants.
abstract: OBJECTIVE
  To describe the molecular characteristics of four Japanese patients with cone dystrophy with supernormal rod responses (CDSRR).
  
  
  METHODS
  Four individuals with a clinical and electrophysiological diagnosis of CDSRR were ascertained. The pathognomonic findings of the full-field electroretinograms (ERGs) included a decrease in the rod responses, a square-shaped a-wave, an excessive increase in the b-wave in the bright flash responses, and decreased cone-derived responses. Mutational screening of the coding regions and flanking intronic sequences of the potassium channel, subfamily V, member 2 (KCNV2) gene was performed with bidirectional sequencing. The segregation of each allele was confirmed by screening other family members. Subsequent in silico analyses of the mutational consequences for protein function were performed.
  
  
  RESULTS
  There were two siblings from one family and one case in each of the two families. One family had a consanguineous marriage. Mutational screening revealed compound heterozygosity for the two alleles, p.C177R and p.G461R, in three patients, and homozygosity for complex alleles, p.R27H and p.R206P, in one patient from the consanguineous family. There were three putative novel variants, p.R27H, p.C177R, and p.R206P. The four variants in the families with KCNV2 were highly conserved in other species. In silico analyses predicted that all of the missense variants would alter protein function.
  
  
  CONCLUSIONS
  Biallelic disease-causing variants were identified in four Japanese patients with CDSRR suggesting that the pathognomonic electrophysiological features are helpful in making a molecular diagnosis of KCNV2. Three novel variants were identified, and we conclude that there may be a distinct spectrum of KCNV2 alleles in the Japanese population.
authors.affiliation: National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Fujinami
authors.forename: Kazushige
authors.initials: K
authors.lastname: Tsunoda
authors.forename: Natsuko
authors.initials: N
authors.lastname: Nakamura
authors.forename: Yu
authors.initials: Y
authors.lastname: Kato
authors.forename: Toru
authors.initials: T
authors.lastname: Noda
authors.forename: Kei
authors.initials: K
authors.lastname: Shinoda
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tomita
authors.forename: Tetsuhisa
authors.initials: T
authors.lastname: Hatase
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Usui
authors.forename: Masakazu
authors.initials: M
authors.lastname: Akahori
authors.forename: Takeshi
authors.initials: T
authors.lastname: Itabashi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwata
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsubota
authors.forename: Yozo
authors.initials: Y
authors.lastname: Miyake
mesh_terms: D000293:Adolescent; D000595:Amino Acid Sequence; D044466:Asian People / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D003710:Demography; D004596:Electroretinography; D005190:Family; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007564:Japan; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry / Q000235:genetics*; D012164:Retinal Diseases / Q000235:genetics* / Q000503:physiopathology; D016415:Sequence Alignment; D055815:Young Adult
chemical_list: C489610:KCNV2 protein, human; D024642:Potassium Channels, Voltage-Gated