title: Heterogeneous phenotype in a family with the FERM domain-containing 7 gene R335X mutation.
abstract: OBJECTIVE
  Infantile nystagmus (IN) is characterized by bilateral involuntary, periodic, and predominantly ocular oscillations. In this article, we describe a mutation screen conducted on a 4-generation family in which 4 patients were affected with X-linked IN (XLIN).
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  A 4-generation Chinese Han family including 4 symptomatic members with IN and 200 normal male controls.
  
  
  METHODS
  DNA was extracted from peripheral blood, and the FERM domain-containing 7 gene (FRMD7) was amplified on DNA samples of all the available family members. The mutation screen was conducted by performing direct DNA sequencing.
  
  
  RESULTS
  A nonsense mutation (R335X) in the FRMD7 gene was identified in 4 male patients and an asymptomatic female member.
  
  
  CONCLUSIONS
  Although the R335X mutation in the FRMD7 gene has been previously described, the clinical features, including both disease penetrance and severity, among individuals with FRMD7 mutation in our family vary greatly. One female member with the heterozygous R335X mutation had no clinical manifestation of the disease. This incomplete penetrance suggests that random X-chromosome inactivation may play a role in the pathogenesis of IN, and that loss of functional FRMD7 may account for the development of this disorder. Our findings may be helpful in the genetic counseling of patients with nystagmus.
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China; Department of Medical Information, Xiangya School of Medicine, Central South University, Changsha, China; Department of Neurology, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Yi
authors: Y
authors: Guo
authors: Department of Neurology, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Zhi
authors: Z
authors: Song
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Hongbo
authors: H
authors: Xu
authors: Department of Ophthalmology, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Junhui
authors: J
authors: Yi
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China; Department of Neurology, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Wen
authors: W
authors: Zheng
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Hong
authors: H
authors: Xiang
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Xiong
authors: X
authors: Deng
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Hongwei
authors: H
authors: Lv
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Kai
authors: K
authors: Gao
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China.
authors: Yong
authors: Y
authors: Qi
authors: Center for Experimental Medicine, Third Xiangya Hospital, Central South University, Changsha, China; Department of Neurology, Third Xiangya Hospital, Central South University, Changsha, China. Electronic address: hdeng008@yahoo.com.
authors: Hao
authors: H
authors: Deng
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018389:Codon, Nonsense; D003598:Cytoskeletal Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D020417:Nystagmus, Congenital / Q000235:genetics*; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D018389:Codon, Nonsense; D003598:Cytoskeletal Proteins; C516168:FRMD7 protein, human; D008565:Membrane Proteins