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PubMed1990

Mapping of the X-linked recessive retinitis pigmentosa gene. A review.

X-linked retinitis pigmentosa is caused by (a) mutation(s) on the X chromosome. One of the problems encountered in the genetic counselling of this disease is the identification of carrier females who appear ophthalmologically and electrodiagnostically normal. Despite normal testing these women are at risk of transmitting the XLRP gene to their children. Since the biochemical basis of XLRP is unknown, prenatal diagnosis and definitive carrier detection remain elusive. Existing methods of diagnosis and carrier detection are subject to limitations and are dependent on X-inactivation. The application of recombinant DNA probes to families with XLRP has provided a large number of genetic marker loci at the level of DNA. These markers are called restriction fragment length polymorphisms (RFLPs). By analysis of linkage relationships in affected kindreds, the XLRP gene(s) has (have) been localized to two subregions of the short arm of the X chromosome, Xp11 and Xp21. These findings suggest that there may be more than one retinitis pigmentosa gene on the X chromosome. Until further families are studied to clarify the localization(s) of XLRP, neither locus can be excluded if prenatal diagnosis and accurate carrier detection is to be established.

Chromosome Mapping↗
PubMed2004

A novel PRPF31 splice-site mutation in a Chinese family with autosomal dominant retinitis pigmentosa.

PURPOSE: The autosomal dominant form of retinitis pigmentosa (ADRP) can be caused by mutations in 13 genes and a further locus for which the gene remains to be identified. This study was intended to identify mutations in a large Chinese pedigree with ADRP. METHODS: A genome scan was conducted in the family. The whole coding sequences and the intron-exon boundaries of candidate genes were amplified and sequenced. The reverse transcriptase polymerase chain reaction (RT-PCR) was performed to amplify the mutated mRNA. RESULTS: The strongest evidence of linkage was detected with three adjacent microsatellite markers genotyped between D19S902 and D19S210 on chromosome 19q13.33-13.43. Within the region, a single nucleotide change (G>A) at position -1 of Intron 5 of PRPF31 was found. The consensus AG doublet of the Intron 5 splice acceptor was changed to AA. The mutation co-segregated with the disease phenotype, suggesting that it was the disease-causing mutation in this family. This splicing site mutation is predicted to cause an erroneous splicing of Exon 6. By RT-PCR, we found the mutated nucleotide of Intron 5 (A) and the first nucleotide of Exon 6 (G) was regarded as a new splice acceptor, resulting in 1 bp deletion of the first codon of Exon 6 (GAG-to-AG) at the mRNA level. This change led to a frameshift and truncated protein of 196 amino acids with 56 novel amino acids prior to a premature stop. CONCLUSIONS: A novel splicing mutation (IVS5-1G>A) in the pre-mRNA splicing-factor gene PRPF31 causes retinitis pigmentosa in a large Chinese family. The mutation results in a truncated protein of PRPF31.

Asian People↗
PubMed1987

Genetic study of retinitis pigmentosa in China.

A total of 190 patients (379 eyes), from 169 families, with retinitis pigmentosa were studied in four genetic aspects in China. A large percentage (58.9%) of affected patients appear to be sporadic cases with no family history of disease. In dermatoglyphic analysis, comparing with the controls, the increment of eight or more whorls, the increase of the number of simian and the value of atd angle in 110 patients with retinitis pigmentosa were statistically significant. In addition, the incidence of G6PD deficiency in retinitis pigmentosa (7.89%) is higher than that (3.5%) of a nonaffected population in the same area. However, there is no significant difference of ABO blood typing between 176 patients with retinitis pigmentosa and the normal population of China.

ABO Blood-Group System↗
PubMed1998

TULP1 mutation in two extended Dominican kindreds with autosomal recessive retinitis pigmentosa.

The RP14 autosomal recessive Retinitis pigmentosa (arRP) locus has been mapped to a 2cM region of chromosome 6p21.3. TULP1 (the gene encoding tubby-like protein 1) is a candidate target for the disease mutation because it maps to the RP14 minimum genetic region and because a mutation in the highly homologous mouse tub gene leads to obesity, deafness and early progressive retinal degeneration. Here we report a splice-site mutation (IVS14+1, G-->A) that is homozygous in all affected individuals (N=33) and heterozygous in all obligate carriers (N=50) from two RP14-linked kindreds. The mutation was not observed in 210 unrelated controls. The data indicate that impairment of TULP1 protein function is a rare cause of arRP and that the normal protein plays an essential role in the physiology of the retina.

Animals↗
PubMed1978

Prevention of blindness from retinitis pigmentosa.

Prevention of blindness from retinitis pigmentosa is considered in three stages: what can be done at present; what is likely to be achieved within the next few years; and what can be envisaged for the more distant future.

Blindness↗
PubMed1977

Functional evaluation in central retinitis pigmentosa.

Three patients with central retinitis pigmentosa were investigated in a 5-year follow-up study. The psychophysical and electrophysiological data show the involement of both the central and peripheral photoreceptors and their continuous functional deterioration with time. This conclusion could be demonstrated under all conditions of testing indicating the polymorphism of the disease. The results and the lack of genetical involvement make it difficult to relate this condition to the classical pigmentary retinal degeneration. This data emphasizes the importance of clinical reevaluations and serial electrophysiological testing in order to differentiate between the stationary periods and the progressive deterioration in this disease.

Adaptation, Ocular↗
PubMed1990

Analysis of genes coding for S-antigen, interstitial retinol binding protein, and the alpha-subunit of cone transducin in patients with retinitis pigmentosa.

We screened 526 unrelated patients with autosomal dominant, autosomal recessive, or simplex retinitis pigmentosa for evidence of mutations of the genes encoding S-antigen (S-Ag), interstitial retinol binding protein (IRBP), and the alpha-subunit of cone-specific transducin. Restriction fragment length polymorphisms (RFLPs) were identified at each of these loci. Within each set of patients with a particular genetic type of retinitis pigmentosa, RFLP alleles at each of these loci showed no departure from Hardy-Weinberg equilibrium. No gene deletions or rearrangements could be detected in any patient. Furthermore, in each of six pedigrees (one autosomal dominant, one autosomal recessive, three Usher's syndrome type I, and one Laurence-Moon-Bardet-Biedl syndrome) there was no co-segregation of the disease with alleles determined by RFLPs at the locus for S-antigen. At the IRBP locus, lack of co-segregation was seen in one autosomal dominant, two autosomal recessive, and three Usher's syndrome type I pedigrees. Finally, one pedigree with autosomal recessive retinitis pigmentosa showed no co-segregation of the disease with alleles at the locus for the alpha-subunit of the cone-specific transducin. These data support the idea that the genes coding for S-Ag, IRBP, and the alpha-subunit of the cone-specific transducin do not play an etiologic role in the families with retinitis pigmentosa so far studied.

Alleles↗
PubMed2005

Retinitis pigmentosa in mevalonate kinase deficiency.

Retinitis pigmentosa can occur as a complication of mevalonate kinase deficiency. This may be due to the unique isoprenoid metabolism in the retina. Early detection requires awareness on the part of the treating physician.

Child, Preschool↗
PubMed1987

Diurnal rhythm in the human rod ERG: retinitis pigmentosa.

Rod ERGs were measured at three times of day over an extensive range of retinal illuminances in six light-entrained patients with autosomal recessive or isolate forms of retinitis pigmentosa and at five times of day in six light-entrained normal volunteers. B-wave amplitude versus retinal illuminance functions from each time of day were described by determining the parameters of the best-fit Naka-Rushton function. Results from normal subjects showed that rod ERG threshold (defined as the log retinal illuminance necessary to elicit a 2.0 microV response) was elevated 1 1/2 hr after daily light-onset due to both an increase in log k (semi-saturation constant) and a decrease in log Vmax (maximum rod amplitude). The magnitude of the threshold elevation 1 1/2 hr after light-onset was comparable in patients with retinitis pigmentosa and normal subjects. Whereas thresholds returned to pre-light exposure levels rapidly during the light-phase of the daily cycle in normal subjects, thresholds continued to rise in patients with retinitis pigmentosa due primarily to a further increase in log k. These findings are consistent with abnormal rod photoreceptor disc renewal mechanisms in retinitis pigmentosa.

Adolescent↗
PubMed1989

Posterior chamber intraocular lens implantation in patients with retinitis pigmentosa.

20 eyes of 12 Retinitis Pigmentosa patients underwent extracapsular cataract extraction followed by I.O.L. implantation. No unusual intra or post operative complications were encountered. All pseudophakic eyes showed improvement in visual acuity whereas the V.F. remained unaltered. Subjectively all 12 patients reported a benefit from surgery despite the Visual Field impairment.

Adult↗
PubMed1987

Associated retinitis pigmentosa and fundus flavimaculatus.

A family is described with 2 members, father and son, affected by associated retinitis pigmentosa and fundus flavimaculatus, whereas 1 other member had a combination of retinitis pigmentosa and unilateral central areolar atrophy, 1 member a fundus flavimaculatus with electroretinographic findings indicative of a subclinical form of retinitis pigmentosa and the last one with electroretinographic findings indicative of a subclinical form of retinitis pigmentosa.

Adult↗
PubMed1998

Investigation of retinitis pigmentosa using the multifocal electroretinogram.

Retinitis pigmentosa (RP) patients have pathological changes in both the macula and the periphery, and are known to have abnormal electroretinograms (ERGs). The response densities measured by the multifocal electroretinogram (MERG) in the macula and pericentral retina were greatly reduced in RP. In photopic conditions, some patients had relatively better ERG responses in the macula than in the pericentral retina, and this agreed with the finding that there is usually relatively well-preserved macular function in RP. In scotopic conditions, both macula and pericentral retina gave poor responses. There was very little increase in response as stimulus luminance increased in RP. The topographical mapping of the MERG results can provide objective, localized assessment of retinal function.

Adult↗
PubMed1998

Mental effort required for walking: effects of retinitis pigmentosa.

PURPOSE: To determine whether retinitis pigmentosa (RP) increases the mental effort required for walking. METHODS: A dual-task methodology was used; walking speed and reaction time (RT) to randomly emitted tones were measured in 13 persons with RP and 29 persons with normal vision. Measures of RT were used to estimate the mental effort required for walking. In a second experiment, 15 persons with RP and 17 persons with normal vision navigated a "simple" and a "complex" route. RESULTS: The RP subjects had longer RT compared with the normal-vision subjects when walking the complex but not the simple route. Normalized to each person's baseline, RT while walking the complex route was significantly correlated with log contrast sensitivity (r = -0.63) and log retinal area (r = -0.64) in the RP group. The amount of mental effort required for walking was shown to also depend on familiarity with the route. CONCLUSIONS: Route complexity is critical in determining whether walking requires more mental effort for persons with RP than for persons with normal vision. The magnitude of mental effort required for mobility covaries with the visual impairment measures which correlate with mobility performance in RP.

Adult↗
PubMed1998

Positional cloning of the gene for X-linked retinitis pigmentosa 2.

X-linked retinitis pigmentosa (XLRP) results from mutations in at least two different loci, designated RP2 and RP3, located at Xp11.3 and Xp21.1, respectively. The RP3 gene was recently isolated by positional cloning, whereas the RP2 locus was mapped genetically to a 5-cM interval. We have screened this region for genomic rearrangements by the YAC representation hybridization (YRH) technique and detected a LINE1 (L1) insertion in one XLRP patient. The L1 retrotransposition occurred in an intron of a novel gene that consisted of five exons and encoded a polypeptide of 350 amino acids. Subsequently, nonsense, missense and frameshift mutations, as well as two small deletions, were identified in six additional patients. The predicted gene product shows homology with human cofactor C, a protein involved in the ultimate step of beta-tubulin folding. Our data provide evidence that mutations in this gene, designated RP2, are responsible for progressive retinal degeneration.

Amino Acid Sequence↗
PubMed1999

Retinal degeneration in retinitis pigmentosa and neuronal ceroid lipofuscinosis: An overview.

Retinal degeneration is an early consequence of the group of lysosomal storage diseases collectively referred to as the neuronal ceroid lipofuscinoses (NCLs). This review details specialized techniques that have evolved for retinal assessment in patients with hereditary retinal degeneration. A standard ERG protocol is described for assessing rod- and cone-mediated function. Standardization will be crucial for planning and implementing multicenter trials as rational therapeutic intervention becomes available. In recent years, there has been a dramatic increase in knowledge of the molecular biological bases of retinitis pigmentosa and allied retinal degenerations. Rather than attempting a comprehensive summary, this review stresses the concepts of genetic, allelic, and clinical heterogeneity, which have obvious parallels in the NCLs. Many of the mutations that cause retinal degeneration are in genes that encode photoreceptor cascade proteins; others are in genes that encode photoreceptor structural proteins. Recent advances in linking the retinal degeneration slow (RDS) and ATP-binding cassette transporter retina (ABCR) genes to a variety of disease phenotypes will be summarized. Clinical heterogeneity even among family members with the same mutation raises the possibility that modifying factors, either genetic or environmental, could influence the severity of the disease. Here, we focus on vitamin A and docosahexaenoic acid, two potential nutritional modifiers that have received considerable attention in recent years.

Child↗
PubMed1988

Rod ERG diurnal rhythm in some patients with dominant retinitis pigmentosa.

Five patients with dominant retinitis pigmentosa who were monocularly entrained to a 14 hr light: 10 hr dark cycle showed an abnormal diurnal rhythm in the rod electroretinogram of the entrained eye. These patients as a group showed larger-than-normal reductions in b-wave sensitivity 1.5 hr and 8 hr after light onset relative to other times of day. The findings raise the possibility that these patients have an abnormality in rod photoreceptor function associated with the process of outer segment renewal.

Adult↗