Identification of Novel Mutation in CNGA3 gene by Whole-Exome Sequencing and In-Silico Analyses for Genotype-Phenotype Assessment with Autosomal Recessive Achromatopsia in Pakistani families.

OBJECTIVE: To identify the underlying genetic anomalies in two consanguineous Pakistani families with autosomal recessive achromatopsia. METHODS: The exploratory study was conducted under the patronage of International Islamic University, Islamabad, Pakistan, and Sungshin Women University, Seoul, South Korea, after two families coded PKCN-02 and PKCN-07 belonging to different ethnic groups were recruited from different areas of Khyber Pakhtunkhawa province of Pakistan in July 2016. The families were originally diagnosed with nystagmus upon medical examination. Exome sequencing was performed to identify the possible causative gene which was found to be cyclic nucleotide-gated channel alpha-3. Sanger sequencing was performed to confirm the mutations. After genetic analysis, clinical analysis was re-evaluated for colour vision using Ishihara 26 plates. Pathogenic potential of these mutations was evaluated using algorithmic mutation prediction tools. In-silico analysis was performed to predict effect of these mutations on protein structure of the gene in question. RESULTS: Exome sequencing revealed a reported missense mutation c .1306C>T (p.R436W) in family PKCN-02 and a novel missense mutation c.1540G>A (p.D514N) in family PKCN-07. After mutational analysis, clinical re-evaluation revealed that both families were segregating autosomal recessive achromatopsia. Further, the topological model of the cyclic nucleotide-gated channel alpha-3 polypeptide describes these missense mutations primarily affecting the C-linker and cyclic guanosine monophosphate-binding sites, respectively. Protein structure modelling of cyclic nucleotide-gated channel alpha-3 protein revealed abnormal structure produced by p.R436W and p.D514N.. CONCLUSIONS: Exome sequencing approach was used to first identify the genetic alteration in families with nystagmus. Two mutations in cyclic nucleotide-gated channel alpha-3gene were uncovered, including one novel mutation. Clinical re-evaluation uncovered that both families had achromatopsia.

Prevalence of Color Blindness in Undergraduates of Kathmandu University.

INTRODUCTION: Color blindness is X-linked recessive inherited disorder that occurs mostly in males and is transmitted through females. Many people with color blindness may remain undetected. Thus the present study aims to evaluate the incidence of color blindness among undergraduates of Kathmandu University. METHODS: A cross-sectional study was conducted among 825 undergraduates, aged 17-25 years, from June to August 2018, in Kathmandu University, Kavre, Nepal. The Ishihara plates were used to evaluate the color vision of students under natural day light condition. RESULTS: Study revealed that 24 (2.9%) undergraduates were color blind which include 24 male (5%) and no female. Among the color blind, five (20.3%), three (12.5%), two (8.33%) and 14 (58.33%) males were the victims of deuteranomaly, deuteranopia, protanomalia and total color blindness respectively. Color blindness is prevalent among the Brahmin 10 (3.9%), followed by Chettri 10 (2.72%) and Newar 4 (2.24%). CONCLUSIONS: Prevalence of color blindness is found to be higher in males than females. Total color blindness is the most prevalent in our study. Screening enables the students to become aware of limitations and devise ways of overcoming them.

Color vision deficiency in preschool children: the multi-ethnic pediatric eye disease study.

PURPOSE: To determine the sex- and ethnicity-specific prevalence of color vision deficiency (CVD) in black, Asian, Hispanic, and non-Hispanic white preschool children. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: The Multi-Ethnic Pediatric Eye Disease Study is a population-based evaluation of the prevalence of vision disorders in children in Southern California. A total of 5960 subjects 30 to 72 months of age were recruited for the study, of whom 4177 were able to complete color vision testing (1265 black, 812 Asian, 1280 Hispanic, and 820 non-Hispanic white). METHODS: Color vision testing was performed using Color Vision Testing Made Easy color plates (Home Vision Care, Gulf Breeze, FL), and diagnostic confirmatory testing was performed using the Waggoner HRR Diagnostic Test color plates (Home Vision Care). MAIN OUTCOME MEASURES: Testability of color vision in preschool children between 30 and 72 months of age and prevalence of CVD stratified by age, sex, and ethnicity. RESULTS: Testability was 17% in children younger than 37 months of age, increasing to 57% in children 37 to 48 months of age, 89% in children 49 to 60 months of age, and 98% in children 61 to 72 months of age. The prevalence of CVD among boys was 1.4% for black, 3.1% for Asian, 2.6% for Hispanic, and 5.6% for non-Hispanic white children; the prevalence in girls was 0.0% to 0.5% for all ethnicities. The ethnic difference in CVD was statistically significant between black and non-Hispanic white children (P = 0.0003) and between Hispanic and non-Hispanic white children (P = 0.02). In boys, most CVD cases were either deutan (51%) or protan (34%); 32% were classified as mild, 15% as moderate, and 41% as severe. CONCLUSIONS: Testability for CVD in preschool children is high by 4 years of age. The prevalence of CVD in preschool boys varies by ethnicity, with the highest prevalence in non-Hispanic white and lowest in black children.

Molecular genetics of achromatopsia in Newfoundland reveal genetic heterogeneity, founder effects and the first cases of Jalili syndrome in North America.

Achromatopsia (ACHM) is a severe retinal disorder characterized by an inability to distinguish colors, impaired visual acuity, photophobia and nystagmus. This rare autosomal recessive disorder of the cone photoreceptors is best known for its increased frequency due to founder effect in the Pingelapese population of the Pacific islands. Sixteen patients from Newfoundland, Canada were sequenced for mutations in the four known achromatopsia genes CNGA3, CNGB3, GNAT2, and PDE6C. The majority (n = 12) of patients were either homozygotes or compound heterozygotes for known achromatopsia alleles, two in CNGB3 (p.T383fsX and p.T296YfsX9) and three in CNGA3 (p.R283Q, p.R427C and p.L527R). Haplotype reconstruction showed that recurrent mutations p.T383fsX and p.L527R were due to a founder effect. Aggregate data from exome sequencing, segregation analysis and archived medical records support a rediagnosis of Jalili syndrome in affected siblings (n = 4) from Family 0094, which to our knowledge is the first family identified with Jalili Syndrome in North America.

Worldwide prevalence of red-green color deficiency.

Literature that describes the prevalence of inherited red-green color deficiency in different populations is reviewed. Large random population surveys show that the prevalence of deficiency in European Caucasians is about 8% in men and about 0.4% in women and between 4% and 6.5% in men of Chinese and Japanese ethnicity. However, the male: female prevalence ratio is markedly different in Europeans and Asians. Recent surveys suggest that the prevalence is rising in men of African ethnicity and in geographic areas that have been settled by incoming migrants. It is proposed that founder events and genetic drift, rather than natural selection, are the cause of these differences.

Prevalence of congenital color vision defects in Saudi females of Arab origin.

BACKGROUND: Inherited color vision deficiencies (CVD) vary in prevalence by population and by sex. The most common CVD is X chromosome-linked anomalous trichromacy. Prevalence varies significantly by sex and race. The frequency of color vision defects in Saudi females has not been studied previously. This study surveyed the prevalence of congenital color vision defects in Saudi females of Arab origin. METHODS: Seven thousand four hundred sixty-seven female subjects (N = 7,467) from the Kingdom of Saudi Arabia were screened using both Ishihara pseudoisochromatic plates and the Farnsworth Dichotomous test (D-15). CVD subjects were tested further with the Farnsworth-Munsell 100 Hue test. RESULTS: Of 7,467 female subjects tested, 26 subjects were found to have defective color vision, for a prevalence of 0.35%. Sixteen subjects had a deutan defect, and 10 had a protan defect. Arab females have significantly lower prevalence of CVD when compared with published data from females of other races. Analysis of the 5 regions of Saudi Arabia showed no significant difference between the regions. CONCLUSION: Prevalence of CVD among Saudi females of Arab origin is 0.35% and is among the lowest of all published data.

[Comparison of congenital color vision deficiencies prevalence between Han and Uygur high-school students].

OBJECTIVE: A population-based study was conducted to compare the prevalence of congenital color vision deficiencies (CVD) in high-school students of Uygur and Han nationalities in Xinjiang Uygur autonomous region. METHODS: Students from 7 high schools were examined with pseudoisochromatic color plates and further with Farnsworth Munsell 100 test. The chi-square test was applied to compare categorical variables, and the independent-samples t test was used to compare the measure data. RESULTS: In the study population of 3764 Uygur students, 88 students had CVD, including 69 males and 19 females. 48 of 2055 Han students were diagnosed with CVD, including 46 males and 2 females. No significant difference existed in the prevalence of CVD in boys between two nationalities. The prevalence of CVD in Uygur girls was higher than that in Han girls. CONCLUSIONS: No significant difference was found in the prevalence of CVD in boys between two nationalities. The prevalence of CVD in Uygur girls was higher than that in Han girls.

Red-green colour blindness in Singaporean children.

PURPOSE: X-linked red-green colour blindness is the most common form of colour blindness. Various studies suggest that, worldwide, 2-8% of men are afflicted with this condition. The purpose of this study is to determine the prevalence of red-green colour blindness in Singaporean schoolchildren. METHOD: A total of 1249 children aged 13-15 years were screened using the Ishihara 24-plate edition book during the School Cohort study of the Risk factors for Myopia visit. RESULTS: A total of 1210 children (96.8%) managed to correctly identify at least 13 of the initial 15 plates and were deemed to have normal colour vision.Thirty-three children (32 boys, one girl) were only able to identify nine or less plates and were considered to be colour blind. Overall, 5.4% (95% confidence interval 3%, 7%) of Chinese, 4.9% (1%, 9%) of Malay and 4.9% (2%, 11%) of Indian boys were colour blind (P = 0.97). Classification plates 16-17 were useful in determining deutran or protan tendencies in only 14 (43%) of the 33 children identified as being colour blind. CONCLUSION: 5.3% of boys and 0.2% of girls were found to be colour blind in this Singapore-based study. Although the Ishihara test proved useful in identifying colour-blind children, other tests are required to accurately classify the types of red-green colour blindness in these children.

[Low prevalence of dyschromatopsia using the fourth edition of HRR (Hardy, Rand and Rittler) pseudoisochromatic plate test among the Indian population of Lalima village, Terena]. / Baixa prevalência de discromatopsia, pela 4a edição do teste pseudoisocromático HRR (Hardy, Rand e Rittler), da população indígena de etnia terena da aldeia lalima na região de Miranda: Mato Grosso do Sul.

PURPOSE: to evaluate the frequency of dyschromatopsias among the 10 to 45-year-old male Indian population of Lalima village, Terena ethnicity, in Miranda-MS, using the fourth edition of the pseudoisochromatic HRR test (Hardy, Rand and Rittler). METHODS: Lalima village in Miranda-MS was visited in January and February 2005. The visits only occurred after the approval of the project by the Committee of Ethics and Research of UFMS, by the National Committee of Ethics and Research, by the Indian National Foundation, and by the chief of Lalima village. The test was applied in 226 Indians who had been previously submitted to ophthalmologic examination for the detection of abnormalities that could doubt the applicability of the test. The test was performed under natural illumination, in sunny days, however with no direct sunlight. The test was applied and analyzed by the same experimenter in all the Indians. RESULTS: Two hundred and twenty-six men were examined (60.1%) of the total male population of 376 individuals between 10 and 45 years old who live in Lalima village. No cases of dyschromatopsia were found in this population examined with the HRR test. CONCLUSIONS: Once it is known that incidence of dyschromatopsias among the white male Caucasian population is about 6-8%, the results of the present study indicate a low prevalence of dyschromatopsias in this Indian population of Terena ethnicity, since no cases were detected in the examined sample. Other studies using different methods must be made to reinforce the present results. It would also be interesting to genetically examine this population and verify the genes that code for photopigments.

Baixa prevalência de discromatopsia, pela 4ª edição do teste pseudoisocromático HRR (Hardy, Rand e Rittler), da população indígena de etnia terena da aldeia lalima na região de Miranda: Mato Grosso do Sul / Low prevalence of dyschromatopsia using the fourth edition of HRR (Hardy, Rand and Rittler) pseudoisochromatic plate test among the Indian population of Lalima village, Terena

OBJETIVO: Avaliar a freqüência de discromatopsias através da 4ª edição do teste pseudoisocromático HRR (Hardy, Rand and Rittler) entre a população indígena masculina da aldeia Lalima, etnia Terena, na região de Miranda-MS. MÉTODOS: Foram realizadas viagens à aldeia Lalima em Miranda-MS, nos meses de janeiro e fevereiro de 2005. As viagens para realizar os exames só foram iniciadas após o projeto ter sido avaliado e aprovado pelos Comitê de Ética e Pesquisa da UFMS, Comitê Nacional de Ética e Pesquisa, Fundação Nacional do índio e do cacique da aldeia Lalima. O teste HRR foi aplicado em 226 índios após terem sido submetidos a exame oftalmológico para detecção de anormalidades que pudessem comprometer a aplicabilidade do teste. O teste foi realizado sob luz natural, em dias ensolarados, sem incidência direta de sol. O teste foi aplicado e interpretado pelo mesmo examinador em todos os índios. RESULTADOS: Realizaram-se 226 exames (60,1 por cento) de uma população de 376 homens entre 10 e 45 anos de idade, que vivem na Aldeia Lalima. Não foi encontrado nenhum caso de discromatopsia na população examinada com o teste HRR. CONCLUSÃO: O resultado do presente estudo mostra a baixa prevalência de discromatopsia nesta população indígena de etnia Terena, uma vez que não se detectou nenhum caso de discromatopsia na população estudada, sendo a prevalência de discromatopsia entre homens caucasianos de 6 a 8 por cento. A ausência de discromatopsia na população estudada, no entanto, deve ser mais bem avaliada tentando aumentar o tamanho da amostra, utilização de outros testes e, principalmente, por estudos genéticos para verificar os genes codificadores dos fotopigmentos para melhor compreensão das condições relacionadas à visão de cores dessa comunidade indígena.

PURPOSE: to evaluate the frequency of dyschromatopsias among the 10 to 45-year-old male Indian population of Lalima village, Terena ethnicity, in Miranda-MS, using the fourth edition of the pseudoisochromatic HRR test (Hardy, Rand and Rittler). METHODS: Lalima village in Miranda-MS was visited in January and February 2005. The visits only occurred after the approval of the project by the Committee of Ethics and Research of UFMS, by the National Committee of Ethics and Research, by the Indian National Foundation, and by the chief of Lalima village. The test was applied in 226 Indians who had been previously submitted to ophthalmologic examination for the detection of abnormalities that could doubt the applicability of the test. The test was performed under natural illumination, in sunny days, however with no direct sunlight. The test was applied and analyzed by the same experimenter in all the Indians. RESULTS: Two hundred and twenty-six men were examined (60.1 percent) of the total male population of 376 individuals between 10 and 45 years old who live in Lalima village. No cases of dyschromatopsia were found in this population examined with the HRR test. CONCLUSIONS: Once it is known that incidence of dyschromatopsias among the white male Caucasian population is about 6-8 percent, the results of the present study indicate a low prevalence of dyschromatopsias in this Indian population of Terena ethnicity, since no cases were detected in the examined sample. Other studies using different methods must be made to reinforce the present results. It would also be interesting to genetically examine this population and verify the genes that code for photopigments.

Clinical and genetic features of Hungarian achromatopsia patients.

PURPOSE: To describe the clinical features and molecular genetic findings in a collection of Hungarian achromatopsia patients. METHODS: Twelve patients with congenital achromatopsia from nine Hungarian families were analyzed in this study. The patients underwent standard ophthalmological examination including detailed full-field electroretinography and color vision testing. In two patients, dark adaptation and spectral luminosity tests were also performed. PCR/RFLP analysis and DNA sequencing was applied for mutation screening of CNGA3 and CNGB3. Heterologous minigene expression was used to evaluate transcript splicing of a new intronic mutation in CNGB3. RESULTS: Mutations in CNGA3 were present in four families and mutations in CNGB3 in the remaining five families, including mutations known from Western European patient samples and two new CNGB3 mutations: c.112C>T/Gln38X and c.1663-5T>G. Heterologous expression in COS7 cells shows that the latter induces a splicing defect through the activation of a cryptic splice site 4 bases upstream of the genuine splice site. The patients presented with a clinical picture typical for congenital achromatopsia and there was no significant difference in the phenotype of subjects with either CNGA3 or CNGB3 mutations based on standard ophthalmological examination. However, we assume residual cone function in a subject homozygous for the Phe547Leu mutation in CNGA3 based on prior detailed psychophysical testing (i.e., dark adaptation and spectral luminosity). CONCLUSIONS: Mutations in CNGA3 and CNGB3 account for achromatopsia in Hungarian patients including known mutations and a few new CNGB3 mutations. While standard ophthalmological examination revealed a phenotype of complete achromatopsia, we show that thorough psychophysical testing can help to identify subjects with some minute cone function.

Correlation of gene structure and psychophysical measurement in red-green color vision deficiency in Chinese.

PURPOSE: To study the correlation of genotype for X-linked red-green gene array with color vision phenotype in 58 subjects with red-green color vision deficiency. METHODS: The molecular structure of red and green pigment genes on 58 X chromosomes was studied exon-by-exon by using heteroduplex-SSCP analysis and sequencing. The color vision of these subjects was determined by a Neitz anomaloscope. RESULTS: Variations in the red and green pigment genes were detected in 43 subjects and a hybrid gene was found in 27 subjects. About 50% of the fusion sites occurred at intron 2-3. All 3 anomalous trichromats with intron 4 fusion were mild type but another 3 with intron 2-3 fusion were severe type. No subjects with mild type of color vision defects had a fusion site at intron 2-3 or its upstream. Three subjects with complete deletion of the green pigment gene manifested deuteranomaly. CONCLUSIONS: Protans can be differentiated from deutans on the basis of genotype. It is still difficult to establish a clear correlation of different anomalous trichromats with genotype. The fusion site of a hybrid gene affects the phenotype to some degree. Intron 2-3 is the common place for gene crossover.

Homozygosity mapping of the Achromatopsia locus in the Pingelapese.

Achromatopsia, or total color blindness (also referred to as "rod monochromacy"), is a severe retinal disorder characterized clinically by an inability to distinguish colors, impaired visual acuity in daylight, photophobia, and nystagmus. Inherited as an autosomal recessive trait, achromatopsia is rare in the general population (1:20,000-1:50,000). Among the Pingelapese people of the Eastern Caroline Islands, however, the disorder occurs at an extremely high frequency, as recounted in Oliver Sacks's popular book The Island of the Colorblind: 4%-10% of this island population have the disorder and approximately 30% carry the gene. This extraordinary enrichment of the disease allele most likely resulted from a sharp reduction in population in the late 18th century, in the aftermath of a typhoon and subsequent geographic and cultural isolation. To obtain insights into the genetic basis of achromatopsia, as well as into the genetic history of this region of Micronesia, a genomewide search for linkage was performed in three Pingelapese kindreds with achromatopsia. A two-step search was used with a DNA pooling strategy, followed by genotyping of individual family members. Genetic markers that displayed a shift toward homozygosity in the affected DNA pool were used to genotype individual members of the kindreds, and an achromatopsia locus was identified on 8q21-q22. A maximal multipoint LOD score of 9.5 was observed with marker D8S1707. Homozygosity was seen for three adjacent markers (D8S275, D8S1119, and D8S1707), whereas recombination was observed with the flanking markers D8S1757 and D8S270, defining the outer boundaries of the disease-gene locus that spans a distance of <6.5cM.

Prevalence of congenital colour blindness among Inuit in East Greenland.

PURPOSE: To establish whether congenital colour blindness among males is still rare in Inuit (Eskimos) as indicated previously in 1893 and 1930, especially in East Greenland, as demonstrated by Erik Skeller in 1950. METHODS: The study was comprised mainly of school children. 540 Inuit in East Greenland were compared to 545 controls in East Greenland and Denmark examined by three sets of pseudoisochromatic plates (Ishihara 1932, original plate used by Skeller), Ishihara (1994), and standard P.P. 2 part Igaku-Shoin (1994). RESULTS: Only 1.0% of male Inuit (3/290) are colour blind, a significantly lower incidence than the 8.7% among Danish males in Denmark (15/173). The prevalence was the same in the three control groups, Danes in East Greenland, immigrants and Danes in Denmark. Deuteranopia is the most common type. Females showed the same low prevalence in all four groups. MAJOR CONCLUSIONS: Colour blindness is still remarkably low among Inuit in East Greenland as compared with the present three control groups.

G6PD haplotypes spanning Xq28 from F8C to red/green color vision.

The most telomeric region of the human X chromosome within band Xq28 consists of a gene-rich region of about 3 Mb which contains the genes for coagulation factor VIIIc, glucose-6-phosphate dehydrogenase (G6PD), and red/green color vision. We have studied five polymorphic sites from this region, in a sample of normal people from the Cosenza province of Southern Italy. These sites, which span a distance of some 350 kb, are in strong linkage disequilibrium. Of the 32 possible haplotypes only 10 were found, and 4 of these account for 80% of all X chromosomes analyzed. In addition, we found that all G6PD-deficient people with the G6PD Mediterranean mutation belong to only two haplotypes. One of these (Med 1) is found only within a small subregion of the area investigated, west of the Appennine mountain range. Most remarkably, all Med 1 G6PD-deficient individuals also had red/green color blindness. The more frequent haplotype (Med 2) is the same in Calabria and in Sardinia, where it accounts for about 90% of the G6PD Mediterranean mutations, despite the fact that gene flow between the populations of Sardinia and Southern Italy must have been limited. These data do not enable us to determine whether the two types of G6PD Mediterranean have arisen through two separate identical mutational events or through a single mutational event followed by recombination. However, the data indicate relatively little recombination over an extended region of the X chromosome and they suggest that the G6PD Mediterranean mutation is recent by comparison to the other polymorphisms investigated.

[Frequency of color blindness and glucose-6-phosphate dehydrogenase enzyme deficiency in non-industrialized populations in the state of Nuevo León, México]. / Frecuencia de la ceguera para los colores y de la deficiencia a la enzima glucosa-6-fosfato-deshidrogenasa en poblaciones no industrializadas del Estado de Nuevo León, México.

In order to know if there would be genetic structural differences among non industrial and industrial populations, two genetic markers were studied: color-blindness (CPC) and glucose-6-phosphate dehydrogenase deficiency (G6PD), in students, males and females that were resident in five non industrial populations in the State of Nuevo Leon. The results were compared with the information for industrial zone from the Monterrey Metropolitan area (AMM). It was found that the frequencies of CPC and G6PD in non industrial populations (2.57 and 0.00 per cent), were lower than the ones in the industrial AMM (4.0 and 0.66 per cent), probably as a result that in the first populations, with minor urbanization, the main factors that influence are: natural selection, interacial mixed or genetic drift and the second population is the immigration, since 1940 to present time, of Mexican populations with greater influence from the Indians and Africans.

Colour blindness (CB) distribution in the male population of Albanian and Croatian communities of Molise, Italy (with a review of the published Caucasoid CB gene frequencies).

All the secondary school students of the Albanian and Croatian communities of Molise were tested for colour vision. Percent frequencies of red-green colour blindness were 5.91 +/- 1.73 and 7.02 +/- 3.38. These figures are in agreement with those found for Central Italy thus confirming the similarity of these communities with the rest of Italy as described for several other autosomal polymorphisms. The distribution of red-green CB genes in Europe shows that they are slightly more frequent in Northern Europe than in Southern Europe and Northern Africa.