Article

Remapping of the RP15 locus for X-linked cone-rod degeneration to Xp11.4-p21.1, and identification of a de novo insertion in the RPGR exon ORF15.

Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA.
The American Journal of Human Genetics (impact factor: 10.6). 11/2000; 67(4):1000-3. DOI:10.1086/303091 pp.1000-3
Source: PubMed

ABSTRACT X-linked forms of retinitis pigmentosa (XLRP) are among the most severe, because of their early onset, often leading to significant vision loss before the 4th decade. Previously, the RP15 locus was assigned to Xp22, by linkage analysis of a single pedigree with "X-linked dominant cone-rod degeneration." After clinical reevaluation of a female in this pedigree identified her as affected, we remapped the disease to a 19.5-cM interval (DXS1219-DXS993) at Xp11.4-p21.1. This new interval overlapped both RP3 (RPGR) and COD1. Sequencing of the previously published exons of RPGR revealed no mutations, but a de novo insertion was detected in the new RPGR exon, ORF15. The identification of an RPGR mutation in a family with a severe form of cone and rod degeneration suggests that RPGR mutations may encompass a broader phenotypic spectrum than has previously been recognized in "typical" retinitis pigmentosa.

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    Article: Identification of novel mutations in X-linked retinitis pigmentosa families and implications for diagnostic testing.
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    ABSTRACT: The goal of this study was to identify mutations in X-chromosomal genes associated with retinitis pigmentosa (RP) in patients from Germany, The Netherlands, Denmark, and Switzerland. In addition to all coding exons of RP2, exons 1 through 15, 9a, ORF15, 15a and 15b of RPGR were screened for mutations. PCR products were amplified from genomic DNA extracted from blood samples and analyzed by direct sequencing. In one family with apparently dominant inheritance of RP, linkage analysis identified an interval on the X chromosome containing RPGR, and mutation screening revealed a pathogenic variant in this gene. Patients of this family were examined clinically and by X-inactivation studies. This study included 141 RP families with possible X-chromosomal inheritance. In total, we identified 46 families with pathogenic sequence alterations in RPGR and RP2, of which 17 mutations have not been described previously. Two of the novel mutations represent the most 3'-terminal pathogenic sequence variants in RPGR and RP2 reported to date. In exon ORF15 of RPGR, we found eight novel and 14 known mutations. All lead to a disruption of open reading frame. Of the families with suggested X-chromosomal inheritance, 35% showed mutations in ORF15. In addition, we found five novel mutations in other exons of RPGR and four in RP2. Deletions in ORF15 of RPGR were identified in three families in which female carriers showed variable manifestation of the phenotype. Furthermore, an ORF15 mutation was found in an RP patient who additionally carries a 6.4 kbp deletion downstream of the coding region of exon ORF15. We did not identify mutations in 39 sporadic male cases from Switzerland. RPGR mutations were confirmed to be the most frequent cause of RP in families with an X-chromosomal inheritance pattern. We propose a screening strategy to provide molecular diagnostics in these families.
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    Article: Clinical course of cone dystrophy caused by mutations in the RPGR gene.
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    ABSTRACT: Mutations in the RPGR gene predominantly cause rod photoreceptor disorders with a large variability in clinical course. In this report, we describe two families with mutations in this gene and cone involvement. We investigated an X-linked cone dystrophy family (1) with 25 affected males, 25 female carriers, and 21 non-carriers, as well as a small family (2) with one affected and one unaffected male. The RPGR gene was analyzed by direct sequencing. All medical records were evaluated, and all available data on visual acuity, color vision testing, ophthalmoscopy, fundus photography, fundus autofluorescence, Goldmann perimetry, SD-OCT, dark adaptation, and full-field electroretinography (ERG) were registered. Cumulative risks of visual loss were studied with Kaplan-Meier product-limit survival analysis. Both families had a frameshift mutation in ORF15 of the RPGR gene; family 1 had p.Ser1107ValfsX4, and family 2 had p.His1100GlnfsX10. Mean follow up was 13 years (SD 10). Virtually all affected males showed reduced photopic and normal scotopic responses on ERG. Fifty percent of the patients had a visual acuity of <0.5 at age 35 years (SE 2.2), and 75% of the patients was legally blind at age 60 years (SE 2.3). Female carriers showed no signs of ocular involvement. This report describes the clinical course and visual prognosis in two families with cone dystrophy due to RPGR mutations in the 3' terminal region of ORF15. Remarkable features were the consistent, late-onset phenotype, the severe visual outcome, and the non-expression in female carriers. Expression of RPGR mutations in this particular region appears to be relatively homogeneous and predisposed to cones.
    Albrecht von Graæes Archiv für Ophthalmologie 08/2011; 249(10):1527-35. · 2.17 Impact Factor
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    Investigative Ophthalmology &amp Visual Science 08/2006; 47(7):3052-64. · 3.60 Impact Factor

Keywords

4th decade
 
broader phenotypic spectrum
 
clinical reevaluation
 
de novo insertion
 
linkage analysis
 
mutations
 
new interval overlapped
 
new RPGR exon
 
retinitis pigmentosa
 
rod degeneration
 
RP15 locus
 
RPGR
 
RPGR mutation
 
RPGR mutations
 
Sequencing
 
severe form
 
significant vision loss
 
X-linked dominant cone-rod degeneration
 
X-linked forms