A novel compound heterozygous mutation in the cellular retinaldehyde-binding protein gene (RLBP1) in a patient with retinitis punctata albescens.

PurposeTo describe a patient with retinitis punctata albescens (RPA) associated with compound heterozygosity for two novel mutations in the RLBP1 encoding cellular retinaldehyde-binding protein (CRALBP).DesignObservational case report.MethodsThe proband underwent a complete ophthalmic examination and leukocyte genomic DNA samples were obtained from him and his parents. The RLBP1 exons were analyzed by direct sequencing of PCR-amplified fragments.ResultsThe patient had a clinical phenotype suggestive of slowly progressive RPA, characterized by numerous yellow-white dots in the fundus. The RLBP1 sequence analysis revealed a novel compound heterozygotic mutation of Gly145Asp and Ile200Thr transmitted from the mother and father, respectively. Analysis of 100 control chromosomes showed no individuals with these sequence alterations.ConclusionsOnly eight RLBP1 mutations have been reported to date, and here we describe two novel mutations. These additional mutations will aid ongoing functional studies and add to our understanding of the molecular pathology pertaining to RLBP1-associated retinopathies

A novel RPGR exon ORF15 mutation in a family with X-linked retinitis pigmentosa and Coats'-like exudative vasculopathy.

PurposeTo describe the ophthalmic and genetic findings in a family with X-linked retinitis pigmentosa (RP) and Coats'-like exudative vasculopathy.DesignObservational case series.MethodsFamily members underwent comprehensive ophthalmologic examination. Leukocyte genomic DNA samples were obtained and screened for RPGR (RP3) mutations by direct polymerase chain reaction sequencing.ResultsThe proband had RP with bilateral Coats'-like vasculopathy and was treated with fluorescein-potentiated argon laser therapy. The findings in two other affected male patients and three obligate carrier female patients were within the clinical spectrum of a typical X-linked-recessive RP. A novel nonsense RPGR exon ORF15 mutation (912G>T) was found to segregate with RP in this family.ConclusionsThis report expands the clinical heterogeneity spectrum caused by RPGR mutations and our knowledge concerning the molecular pathologic condition that pertains to Coats'-like RP. Consistent with the literature, Coats' response was not observed in all family members who were affected by RP, which suggests the involvement of other genetic and/or environmental factors

A presumed missense mutation of RPGR causes abnormal RNA splicing with exon skipping.

PurposeA patient with retinitis pigmentosa demonstrated a novel RPGR mutation (213G>A, last base of exon 2) predicted to cause a missense change (G52R) in the final protein. This study was performed to determine whether this mutation altered the effectiveness of the adjacent splice site.DesignObservational case report.MethodsTotal RNA was extracted from leukocytes of the proband and his carrier mother. Reverse transcription-polymerase chain reaction (RT-PCR) was performed by using the primers flanking exon 2 of RPGR transcript, followed by gel purification and direct sequencing.ResultsSequencing revealed skipping of exon 2 in the mutated transcript, leading to in-frame deletion of 42 amino acids affecting the critical RCC1-like domain.ConclusionsThe last base of exons is conserved as "G" in 80% of splicing consensus sequences, yet when changed, can completely disrupt constitutive splicing as in this patient. Our data confirm that the evaluation of the effects of some DNA sequence alterations at the RNA level might have important implications for appropriate genotype-phenotype correlations

Detection and Assignment of Mutations and Minihaplotypes in Human DNA Using Peptide Mass Signature Genotyping (PMSG): Application to the Human RDS/Peripherin Gene

Peptide mass-signature genotyping (PMSG) is a scanning genotyping method that identifies mutations and polymorphisms by translating the sequence of interest in more than one reading frame and measuring the masses of the resulting peptides by mass spectrometry. PMSG was applied to the RDS/peripherin gene of 16 individuals from a family exhibiting autosomal dominant macular degeneration. The method revealed an A→T transversion in the 5′ splice site of intron 2 that is the likely cause of the disease. It also revealed four different minihaplotypes in exon 3 that represent particular combinations of SNPs at four different locations. This study demonstrates the utility of PMSG for identifying and characterizing point mutations and local minihaplotypes that are not readily analyzed by other approaches

Histopathologic study of X-linked cone-rod dystrophy (CORDX1) caused by a mutation in the RPGR exon ORF15.

PurposeTo evaluate the donor retina of a patient with X-linked cone-rod dystrophy caused by an RPGR exon ORF15 mutation.DesignHistopathologic study of the retina.MethodsThe eye of a 69-year-old man was fixed at 1.6 hours postmortem and processed for histopathology and immunocytochemistry.ResultsGrossly, the macula was atrophic with a bull's-eye appearance. The remaining retina showed postmortem edema but no intraretinal pigment. Microscopically, the macular retinal pigment epithelium was absent focally and had pigmentary changes elsewhere. Cones and rods were absent from the perifovea and reduced with shortened outer segments elsewhere in the macula. In the remainder of the retina, cones but not rods were reduced and all photoreceptor outer segments were shortened.ConclusionsThe abnormalities in both cone and rod photoreceptors confirm the importance of RPGR in both cell types but leaves unresolved how various exon ORF15 mutations lead to different clinical phenotypes

Histopathologic study of X-linked cone-rod dystrophy (CORDX1) caused by a mutation in the RPGR exon ORF15.

PurposeTo evaluate the donor retina of a patient with X-linked cone-rod dystrophy caused by an RPGR exon ORF15 mutation.DesignHistopathologic study of the retina.MethodsThe eye of a 69-year-old man was fixed at 1.6 hours postmortem and processed for histopathology and immunocytochemistry.ResultsGrossly, the macula was atrophic with a bull's-eye appearance. The remaining retina showed postmortem edema but no intraretinal pigment. Microscopically, the macular retinal pigment epithelium was absent focally and had pigmentary changes elsewhere. Cones and rods were absent from the perifovea and reduced with shortened outer segments elsewhere in the macula. In the remainder of the retina, cones but not rods were reduced and all photoreceptor outer segments were shortened.ConclusionsThe abnormalities in both cone and rod photoreceptors confirm the importance of RPGR in both cell types but leaves unresolved how various exon ORF15 mutations lead to different clinical phenotypes

X-Linked Cone-Rod Dystrophy (Locus COD1): Identification of Mutations in RPGR Exon ORF15

X-linked cone-rod dystrophy (COD1) is a retinal disease that primarily affects the cone photoreceptors; the disease was originally mapped to a limited region of Xp11.4. We evaluated the three families from our original study with new markers and clinically reassessed all key recombinants; we determined that the critical intervals in families 2 and 3 overlapped the RP3 locus and that a status change (from affected to probably unaffected) of a key recombinant individual in family 1 also reassigned the disease locus to include RP3 as well. Mutation analysis of the entire RPGR coding region identified two different 2-nucleotide (nt) deletions in ORF15, in family 2 (delAG) and in families 1 and 3 (delGG), both of which result in a frameshift leading to altered amino acid structure and early termination. In addition, an independent individual with X-linked cone-rod dystrophy demonstrated a 1-nt insertion (insA) in ORF15. The presence of three distinct mutations associated with the same disease phenotype provides strong evidence that mutations in RPGR exon ORF15 are responsible for COD1. Genetic heterogeneity was observed in three other families, including the identification of an in-frame 12-nt deletion polymorphism in ORF15 that did not segregate with the disease in one of these families