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Br J Ophthalmol. 2008 Jan;92(1):135-41. Epub 2007 Oct 25.

Skewed X inactivation in an X linked nystagmus family resulted from a novel, p.R229G, missense mutation in the FRMD7 gene.

Author information

1
Department of Neurology, Gaziosmanpa┼ča University, Medical Faculty, Tokat, Turkey.

Abstract

AIMS:

This study aimed to identify the underlying genetic defect of a large Turkish X linked nystagmus (NYS) family.

METHODS:

Both Xp11 and Xq26 loci were tested by linkage analysis. The 12 exons and intron-exon junctions of the FRMD7 gene were screened by direct sequencing. X chromosome inactivation analysis was performed by enzymatic predigestion of DNA with a methylation-sensitive enzyme, followed by PCR of the polymorphic CAG repeat of the androgen receptor gene.

RESULTS:

The family contained 162 individuals, among whom 28 had NYS. Linkage analysis confirmed the Xq26 locus. A novel missense c.686C>G mutation, which causes the substitution of a conserved arginine at amino acid position 229 by glycine (p.R229G) in exon 8 of the FRMD7 gene, was observed. This change was not documented in 120 control individuals. The clinical findings in a female who was homozygous for the mutation were not different from those of affected heterozygous females. Skewed X inactivation was remarkable in the affected females of the family.

CONCLUSIONS:

A novel p.R229G mutation in the FRMD7 gene causes the NYS phenotype, and skewed X inactivation influences the manifestation of the disease in X linked NYS females.

PMID:
17962394
DOI:
10.1136/bjo.2007.128157
[Indexed for MEDLINE]

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