Abstract
Purpose: :
To identify the genetic defect in a Turkish family with autosomal recessive retinitis pigmentosa, nanophthalmos and optic disc drusen.
Methods: :
Ophthalmological examinations consisted of measurement of the best-corrected visual acuity and the refractive error, electroretinography, optical coherence tomography, B-mode ultrasonography and fundus photography. The involvement of the MFRP gene in this family was studied by direct DNA sequencing of the coding exons of MFRP and by linkage analysis with microsatellite markers. After exclusion of MFRP, genome-wide homozygosity mapping was performed with 250K SNP microarrays. Mutation analysis of the CRB1 gene was performed by direct sequencing.
Results: :
Clinical evaluation of both affected individuals of the family revealed a decreased axial length (18-19 mm), retinal dystrophy, macular edema and hyperopia >+8.0. Sequencing of MFRP did not reveal any pathogenic changes and CA-marker analysis showed that the region does not segregate within the disease in this family. Genome-wide homozygosity mapping using SNP microarrays revealed a 28-Mb homozygous region encompassing the CRB1 gene, and direct sequencing disclosed a novel homozygous missense mutation (c.2498G>A, p.Gly833Asp) in CRB1.
Conclusions: :
Previous studies associated mutations in the MFRP gene with the syndrome of nanophthalmos-retinitis pigmentosa-foveoschisis-optic disk drusen. In this study we demonstrate that a similar disease complex can be caused by mutations in the CRB1 gene.
Keywords: retinitis • mutations • drusen