Novel mutations in the gene for α-subunit of retinal cone cyclic nucleotide-gated channels in a Japanese patient with congenital achromatopsia.

PURPOSE: To present the characteristics and pathology of a patient with congenital achromatopsia. PATIENT AND METHODS: The patient was a 22-year-old Japanese woman who was 8 years old when she first visited our clinic. Comprehensive ophthalmic examinations including visual acuity measurements, perimetry, optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, electroretinography (ERG), and color vision tests were performed. Her genomic DNA was used as the template for the amplification of exons of five candidate genes for achromatopsia; CNGA3, CNGB3, GNAT2, PDE6C, and PDE6H, and the amplified products were sequenced. A missense mutation, found in the CNGA3, was studied both electrophysiologically and biochemically. RESULTS: Her phenotype was typical of congenital complete achromatopsia. She was followed for 14 years, and her vision and fundus findings were stable. However, the scotopic ERG b-waves at age 22 were smaller than those at age 8, and her FAF images showed increased autofluorescence in both maculae. Genetic examinations revealed combined heterozygous mutations of c.997_998delGA and p.M424V in the CNGA3 gene. The homomeric channel consisting of the CNGA3 subunit with the p.M424V mutation had a weak cGMP-activated current in patch-clamp recordings. In heterologous expression analyses, the expression at the cell surface of the mutant CNGA3 subunit was about 28 % of the wild type. CONCLUSIONS: The two novel mutations found in the CNGA3 gene, c.997_998delGA and p.M424V, can cause complete achromatopsia. The vision of the patient was stationary until the third decade of life although the FAF was altered at the age of 22 years.

Oscillatory potentials with repeated-flash electroretinography.

PURPOSE: To study the influence of retinal adaptation on oscillatory potential (OP) using repeated-flash electroretinography. METHODS: Subjects were 28 adult eyes with normal retinas. Four stimuli (four flashes) of white light from a light-emitting diode built into a contact lens that also served as the recording electrode were presented at 5-s intervals after 30 min of dark adaptation (DA) and then after 10 min of light adaptation (LA). Recordings were made without background light. RESULTS: Four OPs (O1, O2, O3, and O4) were recordable. After DA, amplitudes of O1 and O4 decreased with subsequent flashes, whereas those of O2 increased after the second flash. After LA, amplitudes of O3 and O4 were smaller than after DA. CONCLUSIONS: Amplitude and implicit time of OPs were influenced by retinal adaptation. Among all OPs, O2 showed unique characteristics in course of retinal adaptation.

Electroretinography of short-wavelength-sensitive cones with a LED built-in electrode and its normal values.

To record electroretinograms (ERG) produced by short-wavelength-sensitive cone mechanisms (SWS-cone ERG), the authors used three kinds (blue, green, and red) of light-emitting diode (LED) which were built into a contact lens electrode assembly. The LEDs were used as both stimulus and background light sources. ERG was recorded using blue LED after 10 min of yellow light adaptation produced by green and red LEDs. Duration of photo-stimulation was either 2 or 100 ms. ERG recorded in normal human subjects showed two positive waves with 2 ms photo-stimulation. Amplitude of the former positive wave (b1-wave) was attenuated when the luminance of yellow background increased, and the latter positive wave (b2-wave) was attenuated when the color of photo-stimulation was green or red. These findings suggest that middle-wavelength-sensitive and long-wavelength-sensitive cone mechanisms generated the former positive wave (b1-wave) and SWS-cone mechanisms generated the latter positive wave (b2-wave). Ratio of b2-wave-amplitude to b1-wave-amplitude with 2 ms photo-stimulation measured on 39 normal subjects ranged from 0.5 to 2.0. It was concluded that this three-colored LED built-in electrode was useful for recording SWS-cone ERG.

ABCA4 gene mutations in Japanese patients with Stargardt disease and retinitis pigmentosa.

PURPOSE: To evaluate photoreceptor cell-specific adenosine triphosphate (ATP)-binding cassette transporter (ABCA4) gene mutations in Japanese patients with Stargardt disease (STGD) and the correlation of these mutations to clinical phenotypes. METHODS: Serum was obtained from 10 unrelated Japanese patients with STGD and 96 unrelated Japanese patients with autosomal recessive retinitis pigmentosa (arRP). All 50 ABCA4 gene exons of the patients with STGD were screened for mutations by a combination of single-strand conformation polymorphism analysis and polymerase chain reaction (PCR) direct-sequencing techniques. By restriction enzyme digestion, primer extension analysis, and PCR direct sequencing techniques, the patients with arRP were screened for three segregated, presumably null ABCA4 gene mutations observed in Japanese patients with STGD. RESULTS: Three novel, presumably null mutations of the ABCA4 gene, IVS7-45_952delinsTCTGACC, IVS12+2T-->G, and 1894delA, were identified. The Arg2149stop mutation that had been found in a white patient with STGD in a prior study was also found in a Japanese patient. Two arRP-affected siblings and two unrelated patients with STGD were found to be homozygous for the same IVS12+2T-->G mutation, and three other arRP-affected siblings were carriers of the IVS12+2T-->G mutation and/or the IVS7-45_952delinsTCTGACC mutation. These three siblings with arRP showed only atrophic degeneration in the macula early after the onset of the disease, and STGD had been diagnosed. CONCLUSIONS: Three novel ABCA4 gene mutations were identified in Japanese patients with STGD and arRP. Mutations in the ABCA4 gene can cause panretinal degeneration that changes its clinical appearance from STGD to arRP over time.