Homozygosity Mapping and Targeted Sanger Sequencing Identifies Three Novel CRB1 [Crumbs homologue 1] Mutations in Iranian Retinal Degeneration Families

Background: Inherited retinal diseases [IRDs] are a group of genetic disorders with high degrees of clinical, genetic and allelic heterogeneity. IRDs generally show progressive retinal cell death resulting in gradual vision loss

IRDs constitute a broad spectrum of disorders including retinitis pigmentosa and Leber congenital amaurosis. In this study, we performed genotyping studies to identify the underlying mutations in three Iranian families

Methods: Having employed homozygosity mapping and Sanger sequencing, we identified the underlying mutations in the crumbs homologue 1 gene. The CRB1 protein is a part of a macromolecular complex with a vital role in retinal cell polarity, morphogenesis, and maintenance

Results: We identified a novel homozygous variant [c.1053-1061del; p.Gly352-Cys354del] in one family, a combination of a novel [c.2086T>C; p.Cys696Arg] and a known variant [c.2234C>T, p.Thr745Met] in another family and a homozygous novel variant [c.3090T>A; p.Asn!030Lys] in a third family

Conclusion: This study shows that mutations in CRB1 are relatively common in Iranian non-syndromic IRD patients

Senior-Loken syndrome: a novel NPHP5 gene mutation in a family from Kuwait

Rare autosomal recessive disorders of variable severity are segregating in many highly consanguineous families from the Arab population. One of these deleterious diseases is Senior-Loken syndrome, a hereditary heterogeneous multiorgan disorder, which combines nephronophthisis with retinal dystrophy, leading to blindness and eventually end stage renal failure. This disorder has been reported in many cases worldwide, including two unrelated families from Arabian Gulf countries, which share the gene pool with Kuwait. Here, we are reporting two children from an Arab family with a novel frameshift mutation found in IQCB1/NPHP5 gene; c.1241-1242delTC, predicted to cause protein termination p.Leu414HisfsStop4, and describing the associated clinical features. Identification of this pathogenic mutation helped in confirmation of the clinical diagnosis and in providing a proper pre-marital genetic counselling and testing for a couple embarking on marriage from this highly consanguineous high-risk family

gene therapy revolution in ophthalmology

The advances in gene therapy hold significant promise for the treatment of ophthalmic conditions. Several studies using animal models have been published. Animal models on retinitis pigmentosa, Leber's Congenital Amaurosis [LCA], and Stargardt disease have involved the use of adeno-associated virus [AAV] to deliver functional genes into mice and canines. Mice models have been used to show that a mutation in cGMP phosphodiesterase that results in retinitis pigmentosa can be corrected using rAAV vectors. Additionally, rAAV vectors have been successfully used to deliver ribozyme into mice with a subsequent improvement in autosomal dominant retinitis pigmentosa. By using dog models, researchers have made progress in studying X-linked retinitis pigmentosa which results from a RPGR gene mutation. Mouse and canine models have also been used in the study of LCA. The widely studied form of LCA is LCA2, resulting from a mutation in the gene RPE65. Mice and canines that were injected with normal copies of RPE65 gene showed signs such as improved retinal pigment epithelium transduction, visual acuity, and functional recovery. Studies on Stargardt disease have shown that mutations in the ABCA4 gene can be corrected with AAV vectors, or nanoparticles. Gene therapy for the treatment of red-green color blindness was successful in squirrel monkeys. Plans are at an advanced stage to begin clinical trials. Researchers have also proved that CD[59] can be used with AMD. Gene therapy is also able to treat primary open angle glaucoma [POAG] in animal models, and studies show it is economically viable

Gene therapy: light is finally in the tunnel

After two decades of ups and downs, gene therapy has recently achieved a milestone in treating patients with Leber's congenital amaurosis (LCA). LCA is a group of inherited blinding diseases with retinal degeneration and severe vision loss in early infancy. Mutations in several genes, including RPE65, cause the disease. Using adeno-associated virus as a vector, three independent teams of investigators have recently shown that RPE65 can be delivered to retinal pigment epithelial cells of LCA patients by subretinal injections resulting in clinical benefits without side effects. However, considering the whole field of gene therapy, there are still major obstacles to clinical applications for other diseases. These obstacles include innate and immune barriers to vector delivery, toxicity of vectors and the lack of sustained therapeutic gene expression. Therefore, new strategies are needed to overcome these hurdles for achieving safe and effective gene therapy. In this article, we shall review the major advancements over the past two decades and, using lung gene therapy as an example, discuss the current obstacles and possible solutions to provide a roadmap for future gene therapy research.

Terapia gênica: o que é, o que não é e o que será / Gene therapy: what is, what is not and what will be

Terapia gênica é o tratamento baseado na introdução de genes sadios com uso de técnicas de DNA recombinante. O primeiro teste clínico bem-sucedido dessa técnica foi divulgado em 1990. Em que pese a ocorrência, em certos estudos clínicos, de efeitos adversos, alguns dos quais graves, laboratórios de pesquisa e empresas vêm continuamente desenvolvendo novos materiais e procedimentos mais seguros e eficazes. Embora ainda em estágio experimental, progressos recentes indicam oportunidades crescentes de investimento pela indústria, bem como justificam a expectativa de que, em alguns casos, essa tecnologia poderá chegar à prática clínica dentro de poucos anos.

Gene therapy is the therapeutic procedure based on the introduction of healthy genes using recombinant DNA techniques. The first successful clinical trial of this technique was published in 1990. Despite the occurrence, in certain clinical trials, of adverse effects, some of which serious, both laboratories and companies are continuously developing novel materials and establishing both safer and more effective procedures. Although still in experimental stages, recent progress both points to growing opportunities for investment by industry, as well as justify the expectation that, in some cases, this technology may reach clinical practice within a few years.

Brain Imaging Studies in Leber's Congenital Amaurosis: New Radiologic Findings Associated with the Complex Trait

PURPOSE: To report the incidence and new findings of abnormal brain imaging studies associated with patients initially diagnosed with Leber's congenital amaurosis (LCA) without definite systemic abnormalities and to determine the need for brain imaging studies in these patients. METHODS: A retrospective review of medical records was performed in 83 patients initially diagnosed as LCA and without definite systemic abnormalities before the age of 6 months in 2 tertiary referral centers. Brain magnetic resonance imaging was performed in 31 of 83 patients (37.3%). RESULTS: Six of 31 patients (19%) had radiologically documented brain abnormalities. Two patients had cerebellar vermis hypoplasia, 1 patient showed an absence of septum pellucidum, 2 subjects showed mild external hydrocephalus, and 1 patient was found to have a small cerebellum. CONCLUSIONS: Approximately one fifth of the LCA patients in whom brain imaging was performed were associated with brain abnormalities, including the absence of septum pellucidum, which has not been documented in the literature. Brain imaging is mandatory in patients primarily diagnosed with LCA, even without definite neurologic or systemic abnormalities.

Molecular confirmation of the causes of inherited visual impairment in northern Pakistan

Families with inherited visual impairment were identified and examined from January 2000 to December 2005 and given a clinical diagnosis. Known genes and loci were screened for mutations or linkage at Institute of Ophthalmology and Neurosciences, University of Leeds, in order to provide molecular confirmation. Inherited retinal disease was the most common cause of inherited visual impairment in 38 of 57 families [66.6%] with Leber's congenital amaurosis, rod-cone dystrophy and cone-rod dystrophy being the most common diagnoses in 22, 8 and 3 families respectively. Anterior segment dysgenesis was diagnosed in 8 families [14%]. Mutations in known genes or linkage to known loci were identified in 23 of 57 families [40%]. All families had molecular confirmation of autosomal recessive inheritance or a pedigree consistent with this mode of inheritance, with evidence of first-cousin marriage. Knowledge of carrier status and genetic counseling may allow families to make an informed decision regarding marriage, and thus begin to plan a way of reducing the incidence of inherited visual impairment

Two Cases of Senior-Loken Syndrome in Siblings

Although juvenile nephronophthisis(NPHP) is one of the most frequent genetic causes of chronic renal failure, it has very rarely been reported in Korean children. Most NPHP patients are found to have chronic renal failure, since there are no distinct clinical symptoms for NPHP except polydipsia, polyuria and enuresis in the early stage of disease. Ten percent of NPHP patients manifest retinitis pigmentosa, called Senior-Loken syndrome. We experienced 2 cases of Senior-Loken syndrome that occurred in siblings(a 10 year-old boy and a 14-year-old girl) who were diagnosed with Leber's amaurosis. They were found to have severe renal impairment without polydipsia and polyuria. However, no large homogenous deletion of the NPHP1(2q13) gene was not identified in these patients. We report here on these cases and we review the literature to emphasize the association between Leber's amaurosis and the development of chronic renal failure.