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CONTENTS YEAR 2006
Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 1-14
Clinical and Genetic Analysis of Coloboma : A Review
Ramakrishna Prasad Alur and Brian P. Brooks
National Institute of Eye, NIH, 10 Center Drive, MSC-1860, Bldg 10, Rm 10b16, Bethesda, MD 20892.
Abstract: This review focuses on uveal coloboma, which encompasses any defect in the iris, retina/uvea/choroid and/or optic nerve due to the faulty closure of optic fissure during the 5th to 7th week of fetal life (7-20 mm stage of development). The terms “choroidal fissure” and “embryonic fissure” are used interchangeably with “optic fissure” in the literature and should be considered synonymous. Uveal colobomas, in general, tend to be inferonasal, which is the normal position of the optic fissure in eye development. Involvement may be continuous or involve “skip lesions” and may be unilateral or bilateral. It is unclear whether lesions that have “colobomatous” appearance, but that are not in the inferonasal quadrant are developmentally related to true uveal coloboma. Often, these other ophthalmic anomalies of the optic nerve, the macula, and the uveal tract are referred to as ‘atypical’ colobomas. They may represent other developmental abnormalities such as aniridia or anterior segment dysgenesis.
Key-words : Uveal colobomas, inferonasal, inferonasal, colobomatous, uveal coloboma
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 15-28
Suganthalakshmi Balasubbu1, Anand Rajendran2, Kim Ramasamy2, Perumalsamy Namperumalsamy2 and Periasamy Sundaresan*1
1. Department of Genetics, Aravind Medical Research foundation, 2. Retina clinic, Aravind Eye Hospital, Madurai, India.625020
Abstract: Diabetic retinopathy (DR) is one of the most frequent complications of diabetes and the leading cause of acquired blindness in developed countries. More than 60% of type 2 diabetic patients are prone to the development of retinopathy. Although hyperglycemia is the prime factor associated with the pathogenesis of diabetic retinopathy, the exact mechanism by which retinal damage is inflicted upon is unknown. Studies suggest that many factors like type of diabetes, duration, onset, glycaemic control, environmental, biochemical, growth factors and high blood pressure are involved in the development and progression of diabetic retinopathy. However these factors alone do not explain the occurrence of retinopathy. Subsequently many candidate genes associated with the development and progression of diabetic retinopathy have been identified. This review highlights the molecular genetic aspects of diabetic retinopathy and the results emerging from molecular studies of the potentially involved genes.
Key words : Diabetic Rehinopathy, Polymurphism, Candidate gene.
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 29-43
Molecular Genetics of Human Cataract
P. D. Gupta, S. Rajkumar, Manasi Dave, and A. R. Vasavada
Iladevi Cataract and IOL Research Centre, Gurukul, Memnagar, Ahmedabad - 320058; India
Abstract : Exact molecular mechanism of aging and senile cataract has not yet been fully understood. Some of the genetic defects like alteration in gene sequence, deletions, up or down regulation of genes seems to have role in cataractogenesis. Genetic variation among individuals of the same ethnic group and between different ethnic groups may react differently in different ethnic groups depending on the environmental and genetic conditions. In addition to these genetic factors biochemical changes such as oxidative stress, protein modifications, and depletion of antioxidative enzymes due to aging have also been identified causative factors in cataractogenesis.
Many of the factors mentioned above for cataractogenesis are age related. The thinness of capsule during aging has been reported, which may also be responsible for the ocular disorders. Recent studies (Gupta et al., 2002, 05) have suggested that incidence of cataract in menopausal women is higher than menstruating women. The overall understanding of genetics mechanism of aging may also help in understanding and prevention of senile cataract.
Key- word : Aging, gene regulation, hormone cycle, antioxidents.
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Günther Rudolph
Eye Hospital, Ludwig-Maximilians-University D-80336 München, Mathildenstrasse 8, Germany
Abstract : Stargardt‘s disease (OMIM #248200/STGD1, chromosome 1p21-p13) and Best’s vitelliform macular dystrophy (OMIM #607854/VMD2, chromosome 11q13) are the most common forms of macular dystrophies. The onset of the disease is variable, but often symptoms become apparent in the first or second decade of life with reduced visual acuity. Stargardt’s disease is a recessive genetic disorder, while Best’s disease is inherited as a dominant trait. The underlying mechanisms of these two diseases are only partly understood until now. In Stargardt’s disease intraepithelial accumulation of a lipofuscin-like substance is a characteristic feature, creating retinal flecks and an so called “fundus flavimaculatus”. Mutations in the ABCA4 gene seem to be the origin of the disease. Even more striking is the fact, that mutations in the ABCA4 transporter gene not only cause Stargardt’s disease or fundus flavimaculatus, but also atypical retinitis pigmentosa or cone-rod dystrophy. Best's disease is characterized by subretinal accumulation of lipofuscin-like material resulting in an atrophic lesion at the posterior pole of the eye. The clinical expression is highly variable. The disease is the result of mutations in the VMD2-gene. VMD2 encodes bestrophin, a transmembrane protein with putative Ca2+-dependent chloride channel activity at the basolateral portion of the retinal pigment epithelium.
Key Words : Stargardt disease, STGD1, Best vitelliform macular dystroph, VMD2
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Genetics of Retinitis Pigmentosa
Francesco Testa, Settimio Rossi and Francesca Simonelli*
Department of Ophthalmology, Second University of Naples, Naples, Italy.
Abstract : Retinitis pigmentosa (RP) is one of the most genetically heterogeneous of hereditary conditions for which molecular pathologies have so far been elucidated. This group of hereditary conditions involving death of retinal photoreceptors, represents the prevalent cause of visual handicap among working populations in developed countries. Here we provide an overview of our research in Italy on the molecular pathologies associated with RP.
Key Words : Retinitis pigmentosa, gene, mutations, genotype/phenotype correlations
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 63-80
M. A. Nanavaty, A. R. Vasavada and P. D. Gupta*
Iladevi Cataract and IOL Research Centre, Gurukul, Memnagar, Ahmedabad
Abstract : Dry eye is not a disease but it is rather an annoyance, which may be because of varied causes including genetics. Dry eyes, eyelid abnormalities, naso-lacrimal drainage pathologies, neurological causes, corneal disorders, irritation of lashes and hypersecretion of tears are some the known causes. The article deals with the diagnostic, prevention and treatment paradigms for the same. Recent advances related to the cause and target oriented treatment of the tears have also been discussed. Dry eye syndrome is not very uncommon especially in old age. Depending on etiology varied treatment modalities are decided. Meticulous diagnosis is required for better management of the dry eye syndrome. The knowledge of influence of sex hormones on the etiology of tears in old age has opened new avenues for research, to find out specific treatment measures. (Gupta et al., 2005).
Key-words : Tears, old age, epiphora, dry eyes
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 81-96
Dietmar R. Lohmann
Department of Human Genetics, University of Duisburg-Essen, Germany Institut für Humangenetik Universitätsklinikum Essen Hufelandstrasse 55, IG1 45122 Essen, Germany
Abstract : Retinoblastoma (Rb) is a malignant tumor of the eye that originates from developing retinal cells. Diagnosis is based on clinical signs and symptoms and is usually made in children under age of five years. Tumor formation starts from cells with mutational loss of both normal alleles of the RB1, a tumor suppressor gene that is located on 13q14. In most patients with sporadic unilateral Rb, both mutations have occurred in somatic cells and are not passed to offspring (non-hereditary Rb). Almost all patients with sporadic bilateral and virtually all patients with familial Rb are heterozygous for an oncogenic RB1 mutation and transmit Rb predisposition as an autosomal dominant trait (hereditary Rb). Penetrance of hereditary Rb depends on the functional consequence of the predisposing RB1 mutation. Mutational mosaicism, which is relatively frequent in patients with sporadic Rb is also a cause of milder phenotypic expression. Additional genetic factors can modify genotype-phenotype associations. Known modifiers include parental origin of the mutant RB1 allele and genetic variation linked to RB1.
Key Words : Retinoblastoma, genotype-phenotype associations, genetic modification, genetic counselling, molecular risk prediction
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 97-112
Ashima Bhattacharjee1, Moulinath Acharya1, Suddhasil Mookherjee1, Sumedha Banerjee1, Arijit Mukhopadhyay1, Arun Kumar Banerjee2, Sanjay Kumar Daulat Thakur2, Abhijit Sen3 and Kunal Ray1
1. Human Genetics & Genomics Division, Indian Institute of Chemical Biology, Kolkata – 700 032, India 2. Regional Institute of Ophthalmology, Medical College, Kolkata – 700 073, India 3. Dristi Pradip, 385 Jodhpur Park, Kolkata – 700 068, India
Abstract : Glaucoma is a heterogeneous group of optic neuropathies, with a complex genetic basis. Among the established candidate genes known to be involved in the disease, myocilin has been reported to cause a small percentage of adult onset and a major percentage of juvenile onset cases of glaucoma. Mutations in different regions of the gene have been found to be associated with a wide spectrum of glaucoma phenotypes. The gene has also been implicated in primary congenital glaucoma as well as in digenic cases of the disease. The article intends to explore the functional aspects of the protein in normal trabecular meshwork (TM) and molecular basis of TM cell dysfunction as a result of mutation in the protein as revealed from the current studies. We also report occurrence in an Indian POAG family a mutation (Q368X), common among Caucasians, and the studies in progress on myocilin-related genes that could serve as candidates for glaucoma.
Key words: Myocilin, Glaucoma, Molecular defects, Aberrations, Pathogenesis
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Asian J. Exp. Sci., Vol. 20, Supplement, 2006, 113-132
Avneet Kaur1, Daljit Singh2 and Jai Rup Singh*1
1. Centre for Genetic Disorders Guru Nanak Dev University, Amritsar 2. Dr. Daljit Singh Eye Hospital Sheranwala Gate, Amritsar
Abstract : Glaucoma belongs to a group of diseases that share a common clinical phenotype characterized primarily by progressive degeneration of the optic nerve. It is the second major cause of irreversible blindness in the world that affects 67 million people worldwide. There are three major types of glaucoma; Primary Open Angle Glaucoma (POAG), Primary Congenital Glaucoma (PCG) and Primary Acute Closed Angle Glaucoma (PACG). Ten loci have been identified for their inherited forms, mutations in four genes – Myocilin, Optineurin, WDR36 and CYP1B1 have been implicated in the pathogenesis of glaucoma. However, the specific phenotype of glaucoma in an individual is determined by other associated genes as well as certain risk factors. Precise clinical documentation and classification of this disease is essential to understand etiology for proper diagnosis and management at the molecular level.
Keywords : Glaucoma, MYOC, CYP1B1, OPTN
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