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Results for “Cone dystrophy”

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PubMed1998

A mutation in guanylate cyclase activator 1A (GUCA1A) in an autosomal dominant cone dystrophy pedigree mapping to a new locus on chromosome 6p21.1.

We report a mutation (Y99C) in guanylate cyclase activator 1A (GUCA1A), the gene for guanylate cyclase activating protein (GCAP1), in a family with autosomal dominant cone dystrophy. Linkage analysis excluded all the known cone and cone-rod dystrophy loci, except the chromosome 6p21.1 region. This is known to contain the RDS gene, which is associated with dominant cone-rod dystrophy. Screening of the RDS gene by heteroduplex analysis and direct sequencing failed to demonstrate sequence changes in the coding region of this gene. The gene for GCAP1, a calcium binding protein which is highly expressed in photoreceptor outer segments, is also located in 6p21.1. It was screened for mutations, and all affected individuals showed a single base pair missense mutation (A-->G) at codon 99 in exon 2 of this gene generating a tyrosine-to-cysteine change in the GCAP1 protein. This change was absent from 206 unrelated normal controls. We propose that this change would at least disrupt the EF3handof GCAP1 thereby preventing calcium binding and consequently interfere with activation. The resulting effect on cGMP production would predictably modify the number of open cGMP gated cation channels, and could explain the ultimate demise of cone photoreceptor cells.

Amino Acid Sequence↗

PubMed1988

Treatment of low vision in the progressive cone dystrophies.

Twenty-three patients suffering from the progressive cone dystrophies (PCD) were evaluated retrospectively, after they had undergone treatment for low vision. All patients were able to read 1 M or smaller print with magnification, despite poor central acuity. Eighteen (78%) patients achieved their primary rehabilitation goal, and 86% of the low vision devices prescribed were used at follow-up. Photosensitivity was reported by a large number of patients. Seven patients indicated that alleviating this problem was their primary rehabilitation goal. Eight (35%) found sun filters to be helpful. Our successful experience with patients with these disorders suggests that examination for, and trial of, low vision devices is warranted.

Adolescent↗

PubMed2000

[Cone dystrophy associated with Alport syndrome].

BACKGROUND: Alport's syndrome is a hereditary disease with renal, cochlear, and ocular involvement. We report a patient with Alport's syndrome who exhibited morphologic macular changes similar to cone dystrophy. HISTORY AND SIGNS: A 46-year-old man was evaluated for peculiar macular changes, which have caused a significant decrease in visual acuity over the last years. His general history was remarkable for the presence of sensorineural hearing impairment since infancy as well as end stage renal failure followed by renal transplantation. The ophthalmological findings in this patient included circumscribed macular lesions consisting of atrophy of the retinal pigment epithelium and bilateral anterior lenticonus. CONCLUSION: Alport's syndrome is a characteristic prototype of a genetic basement membrane disease with ocular, renal, and cochlear involvement. Common ocular findings are the dot-and-fleck retinopathy and the anterior lenticonus. In contrary to the anterior lenticonus retinal changes are rarely associated with visual impairment. An association with a macular lesion similar to the cone dystrophy has only infrequently been reported.

Electroretinography↗

PubMed2006

The crystal structure of GCAP3 suggests molecular mechanism of GCAP-linked cone dystrophies.

Absorption of light by visual pigments initiates the phototransduction pathway that results in degradation of the intracellular pool of cyclic-GMP (cGMP). This hydrolysis promotes the closing of cGMP-gated cation channels and consequent hyperpolarization of rod and cone photoreceptor cell membranes. Guanylate cyclase-activating proteins (GCAPs) are a family of proteins that regulate retinal guanylate cyclase (GC) activity in a Ca2+-dependent manner. At high [Ca2+], typical of the dark-adapted state (approximately 500 nM), GCAPs inhibit retinal GCs. At the low [Ca2+] (approximately 50 nM) that occurs after the closing of cGMP-gated channels, GCAPs activate retinal GCs to replenish dark-state cGMP levels. Here, we report the crystal structure of unmyristoylated human GCAP3 with Ca2+ bound. GCAP3 is an EF-hand Ca2+-binding protein with Ca2+ bound to EF2, 3 and 4, while Ca2+ binding to EF-hand 1 is disabled. GCAP3 contains two domains with the EF-hand motifs arranged in a tandem array similar to GCAP2 and members of the recoverin subfamily of Ca2+-binding proteins. Residues not involved in Ca2+ binding, but conserved in all GCAPs, cluster around EF1 in the N-terminal domain and may represent the interface with GCs. Five point mutations in the closely related GCAP1 have been linked to the etiology of cone dystrophies. These residues are conserved in GCAP3 and the structure suggests important roles for these amino acids. We present a homology model of GCAP1 based on GCAP3 that offers insight into the molecular mechanism underlying the autosomal dominant cone dystrophies produced by GCAP1 mutations.

Calcium↗

PubMed1987

Progressive cone dystrophy.

Psychophysical, reflectometric, and electrophysiological studies were performed on four members of a dominant pedigree with progressive cone dystrophy. The two youngest individuals were asymptomatic at the initial examination, and none of the subjects complained of problems associated with night vision. Absent or grossly reduced cone-mediated ERG responses revealed the widespread loss of cone function. Moderate elevations (1 log unit) in absolute threshold together with reductions in rhodopsin levels in the midperipheral retina provided evidence of a mild impairment of the rod system also, although not to the degree seen in a cone-rod dystrophy. The progressive nature of the disease was apparent from the case histories and the changes in visual performance that occurred on re-test after a 5-year interval. Likewise, the results of incremental threshold measurements at several retinal loci suggested that peripheral cones may be affected earlier and more severely than those in the central retina.

Adolescent↗

PubMed2004

Progressive cone dystrophy and sensorineural hearing loss.

A 39-year old man presented 13 years ago with a history of progressive loss of vision and photophobia. A full ophthalmological and ENT work-up during several years of follow-up, including psychophysical as well as electrophysiological tests, revealed a progressive cone dystrophy in combination with sensorineural hearing loss. His younger sister presented with very similar features and underwent the same work-up. A novel syndrome of progressive cone dystrophy and sensorineural hearing loss is described in both siblings. Both also suffered from non-ocular disease possibly related to ciliary dysfunction. The condition is likely to be inherited as an autosomal recessive trait.

Adult↗

PubMed2006

Mutation in the auxiliary calcium-channel subunit CACNA2D4 causes autosomal recessive cone dystrophy.

Retinal signal transmission depends on the activity of high voltage-gated l-type calcium channels in photoreceptor ribbon synapses. We recently identified a truncating frameshift mutation in the Cacna2d4 gene in a spontaneous mouse mutant with profound loss of retinal signaling and an abnormal morphology of ribbon synapses in rods and cones. The Cacna2d4 gene encodes an l-type calcium-channel auxiliary subunit of the alpha (2) delta type. Mutations in its human orthologue, CACNA2D4, were not yet known to be associated with a disease. We performed mutation analyses of 34 patients who received an initial diagnosis of night blindness, and, in two affected siblings, we detected a homozygous nucleotide substitution (c.2406C-->A) in CACNA2D4. The mutation introduces a premature stop codon that truncates one-third of the corresponding open reading frame. Both patients share symptoms of slowly progressing cone dystrophy. These findings represent the first report of a mutation in the human CACNA2D4 gene and define a novel gene defect that causes autosomal recessive cone dystrophy.

Adult↗

PubMed1999

Previously apparently undescribed autosomal recessive MCA/MR syndrome with light fixation, retinal cone dystrophy, and seizures: the M syndrome.

We report on two sisters from healthy families with a syndrome of severe developmental delay, ataxia, impaired social interaction, a seizure disorder with early onset but without epileptiform electroencephalogram changes, and a striking light-fixating behavior which was associated with retinal cone dystrophy. Additionally, they have minor anomalies including peripheral iris hypoplasia, bluish sclerae, mild anteversion of nostrils, micrognathia, ear anomalies, broad halluces and thumbs, hypoplastic toenails, short perineal body, "Mongolian spots," mild hirsutism, hypoplastic ridges in the hypothenar area, and distal axial triradii. Growth and general health are normal in both, but one also had tetralogy of Fallot and vesicoureteral reflux. Because this condition appears to be previously undescribed we postulate a new autosomal recessive disorder with light-fixating behavior and retinal cone dystrophy as leading symptom.

Abnormalities, Multiple↗

PubMed2005

Abnormal distribution of red/green cone opsins in a patient with an autosomal dominant cone dystrophy.

PURPOSE: To define the distribution of the red/green and blue opsins in cones from donor eyes from an affected member of a clinically well-characterized family with an autosomal dominant form of cone dystrophy. METHODS: Tissue was fixed and processed for immunohistochemistry. Cryosections were studied by indirect immunofluorescence, using well-characterized antibodies to cone cytoplasm, rhodopsin, and cone opsins. The cone-associated matrix was also labeled with the lectin PNA. The affected donor eyes were compared to a postmortem matched normal eye. RESULTS: Electroretinogram (ERG) testing three years prior to the affected member's death showed normal rod function, while the cone b-wave amplitude was reduced 40% below the lower limit of normal. Fundus exam showed only isolated drusen within the macula. Either a normal-appearing or only nonspecific macular findings were noted in the other affected family members who were examined. Immunofluorescence studies showed that blue cone opsin was restricted to the outer segments of blue cones in the affected retina. Red/green opsins were distributed along the entire plasma membrane of these cone types, from the tip of the outer segment to the synaptic base. Cone-associated matrix displayed a heterogeneous distribution. These patterns were observed both in the macula and in the periphery of the affected retina. Cone pedicles appeared larger than normal. In contrast, rhodopsin staining appeared normal. CONCLUSIONS: The immunocytochemical data obtained suggest that the clinical manifestation of this dystrophy is associated with an abnormal distribution of cone red/green opsins. Additionally, changes in the cone pedicles could have contributed to the abnormal cone ERG in this patient.

Aged↗

PubMed1978

Familial syndrome of progressive cone dystrophy, degenerative liver disease, and endocrine dysfunction. III. Genetic studies.

A syndrome of progressive cone dystrophy, endocrine dysfunctions and degenerative liver diseases has been observed in seven patients, six of whom belonged to one extensive kindred. Genetic analyses revealed a segregation ratio indicating autosomal recessive inheritance of the syndrome, and the kindred from which six of the seven patients originated was heavily inbred. Thus, the results of the segregation analyses as well as of the inbreeding analyses provide evidence that this previously unrecognized disorder is inherited as an autosomal recessive trait. Genetic marker analyses were conducted with respect to 22 marker systems, and linkage information was obtained with respect to 15 of them. No strong suggestion of linkage emerged from the analyses, but very close linkage could be excluded for several of genetic marker systems. Pedigree analysis was helpful in establishing the spectrum of clinical manifestations belonging to the syndrome proper. The data presently available suggest that elevated levels of creatine phosphokinase, which were found in all patients, may be useful in tracing heterozygotes for this disorder. This possibility will be further examined.

Abnormalities, Multiple↗

PubMed1987

Progressive cone dystrophy.

Psychophysical, reflectometric, and electrophysiologic studies were done on four members of a dominant pedigree with progressive cone dystrophy. The two youngest individuals were asymptomatic at the initial examination, and none of the subjects complained of problems associated with night vision. Nevertheless, absent or grossly reduced cone-mediated electroretinographic (ERG) responses showed the widespread loss of cone function, and moderate elevations (less than 1 log unit) in absolute threshold together with reductions in rhodopsin levels in the mid-peripheral retina provided evidence of impairment of the rod system. The progressive nature of the disease was apparent from the case histories and the changes in visual performance that occurred on re-test after a 5-year interval. Moreover, the results of increment threshold measurements at several retinal loci suggested that peripheral cones may be affected earlier and more severely than those in the central retina.

Adolescent↗

PubMed1990

Cone dystrophy and supernormal dark-adapted b-waves in the electroretinogram.

A male patient suffering from cone dystrophy was followed over 9 years. In addition to the typical clinical and electrophysiologic signs, supernormal b-waves were found in the dark-adapted electroretinogram. Our case is compared with 12 similar patients described in the literature. Our patient differed from the other patients in the following aspects: he was male and had a congenital stationary disease with a small pigment epithelial scar in the left eye only and no other fundus changes up to the age of 22 years. He did not complain of night blindness. The dark-adapted electroretinogram of our patient showed a normal b-wave threshold with increased b-wave amplitudes and markedly prolonged b-wave latencies and implicit times. This combination of signs has not been reported to date in any other patient and points towards a postreceptoral defect of the interneuronal connection.

Adolescent↗

PubMed1993

Rod-cone dystrophy, sensorineural deafness, and renal dysfunction: an autosomal recessive syndrome?

An autosomal recessive syndrome of progressive rod-cone dystrophy, sensorineural deafness, and renal dysfunction was identified in 14 children in 9 Afrikaner families in South Africa. The renal involvement, which is of the Fanconi type, leads to rickets-like skeletal changes and kidney failure. Each of the children was initially misdiagnosed as having retinitis pigmentosa or Usher syndrome, on a basis of minor retinal pigmentation. This condition, which appears to be a hitherto undocumented entity, warrants differentiation from these disorders.

Adolescent↗

PubMed2001

Identification and functional consequences of a new mutation (E155G) in the gene for GCAP1 that causes autosomal dominant cone dystrophy.

Mutations in the gene for guanylate cyclase-activating protein-1 (GCAP1) (GUCA1A) have been associated with autosomal dominant cone dystrophy (COD3). In the present study, a severe disease phenotype in a large white family was initially shown to map to chromosome 6p21.1, the location of GUCA1A. Subsequent single-stranded conformation polymorphism analysis and direct sequencing revealed an A464G transition, causing an E155G substitution within the EF4 domain of GCAP1. Modeling of the protein structure shows that the mutation eliminates a bidentate amino acid side chain essential for Ca2+ binding. This represents the first disease-associated mutation in GCAP1, or any neuron-specific calcium-binding protein within an EF-hand domain, that directly coordinates Ca2+. The functional consequences of this substitution were investigated in an in vitro assay of retinal guanylate cyclase activation. The mutant protein activates the cyclase at low Ca2+ concentrations but fails to inactivate at high Ca2+ concentrations. The overall effect of this would be the constitutive activation of guanylate cyclase in photoreceptors, even at the high Ca2+ concentrations of the dark-adapted state, which may explain the dominant disease phenotype.

Amino Acid Sequence↗

PubMed1986

X-linked recessive cone dystrophy with tapetal-like sheen. A newly recognized entity with Mizuo-Nakamura phenomenon.

We encountered a new X-linked recessive cone dystrophy in which patients have a greenish-golden tapetal-like sheen of the retina; while the retinal sheen and electroretinographic abnormalities are present from childhood, patients are not symptomatic until adult years. All of the male patients tested showed evidence of cone dysfunction on color vision testing, dark adaptometry, and electroretinography. After three hours of dark adaptation, the tapetal-like sheen disappeared, with most areas changing from greenish-golden shades to orange-red hues (Mizuo-Nakamura phenomenon). One male patient had a retinal detachment from atrophic round holes in the equatorial retina.

Adolescent↗

PubMed1997

Localization of a novel X-linked progressive cone dystrophy gene to Xq27: evidence for genetic heterogeneity.

Clinical reexamination and DNA linkage analysis were carried out in an X-linked progressive cone dystrophy (XLPCD) family, previously described by Pinckers and Timmerman in 1981. In a large pedigree segregating XLPCD, by use of > or = 27 markers spanning the entire X chromosome, a novel locus for XLPCD was identified in Xq27. All other regions on the chromosome could be excluded. Since this novel locus is distinct from previously identified genes or regions involved in XLPCD, we further establish genetic heterogeneity underlying this disease entity.

Chromosome Mapping↗

PubMed1989

X-linked progressive cone dystrophy. Clinical characteristics of affected males and female carriers.

The authors evaluated nine affected males and six female carriers from a four-generation family with X-linked cone dystrophy. As the affected males grew older, visual acuity deteriorated, central scotomas deepened, and macular changes became more prominent. There was granularity of the macula in younger individuals and bull's eye lesions and central geographic atrophy of the retinal pigment epithelium (RPE) in the older subjects. The retinas of some affected males had a bronze-green tapetal-like sheen. Color vision was impaired in all affected males and resembled an acquired type II defect (Verriest classification). One younger subject had paradoxical pupillary constriction to darkness. Visual-evoked potential (VEP) latencies were prolonged in some affected males, suggesting that photoreceptor degeneration caused transsynaptic degeneration of ganglion cells. All female carriers had visual acuities of 20/30 or better, but some showed mild ophthalmoscopic changes and abnormalities of color vision, electroretinograms (ERGs), and VEPs.

Adolescent↗

PubMed1992

Fundus albipunctatus associated with cone dystrophy.

We describe five unrelated patients in whom the typical signs of fundus albipunctatus were accompanied by colour vision defects, bull's eye or similar macular lesions, and severely diminished full-field cone electroretinograms indicating widespread damage to cones outside the macula. All patients had noticed night blindness from childhood. Signs of retinitis punctata albescens, a disease of similar appearance but with characteristics resembling retinitis pigmentosa, were absent. We cannot be sure whether these patients represent a process of fundus albipunctatus or a distinct disease entity or a casual combination of fundus albipunctatus and cone dystrophy.

Adult↗