Null retinoschisin-protein expression from an RS1 c354del1-ins18 mutation causing progressive and severe XLRS in a cross-sectional family study

Camasamudram Vijayasarathy, Lucia Ziccardi, Yong Zeng, Nizar Smaoui, Rafael C. Caruso, Paul A. Sieving

Research output: Contribution to journalArticle

Abstract

PURPOSE. To explore the retinoschisin (RS1) protein biochemical phenotype from an RS1 exon-5 deletion/insertion frameshift mutation in a family with X-linked retinoschisis (XLRS) and describe the clinical and electrophysiological features. METHODS. Six XLRS males underwent ophthalmic examination and electroretinogram (ERG) recording. The RS1 gene was sequenced. Mutant RS1-RNA and protein expression were assessed by transfecting COS-7 cells with minigene constructs. RESULTS. All six males carried the RS1 c354del1-ins18 mutation in which an 18-bp insertion replaced nucleotide 354, duplicating the adjacent upstream intron 4-to-exon 5 junction and creating a premature termination codon downstream. Analysis indicated normal pre-mRNA splicing producing mRNA transcripts. Truncated RS1 protein was expressed transiently but was degraded rapidly by a proteasomal pathway rather than by nonsense-mediated mRNA decay. Two boys, 1.5 and 5 years of age, had foveal cysts and minimal peripheral schisis, and retained near-normal scotopic b-wave amplitude and normal ERG waveforms. The 5-year-old's ERG was diminished when repeated 3 years later. Four older XLRS relatives 32 to 45 years old had substantial b-wave loss and strongly electronegative ERGs; three had overt macular atrophy. Cross-sectional family analysis showed the b-/a-wave amplitude ratio as inversely related to age in the six males. CONCLUSIONS. The c354del1-ins18 mutation caused an RS1-null biochemical phenotype and a progressive clinical phenotype in a 5-year-old boy, whereas the older XLRS relatives had macular atrophy and marked ERG changes. The phenotypic heterogeneity with age by cross-sectional study of this family mutation argues that XLRS disease is not stationary and raises questions regarding factors involved in progression.

Original languageEnglish
Pages (from-to)5375-5383
Number of pages9
JournalInvestigative Ophthalmology and Visual Science
Volume50
Issue number11
DOIs
Publication statusPublished - Nov 2009

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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