Review and update on the molecular basis of Leber congenital amaurosis

Inherited retinal diseases are uncommon pathologies and one of the most harmful causes of childhood and adult blindness. Leber congenital amaurosis(LCA) is the most severe kind of these diseases accounting for approximately 5% of the whole retinal dystrophies and 20% of the children that study on blind schools. Clinical ophthalmologic findings including severe vision loss, nystagmus and ERG abnormalities should be suspected through the first year of life in this group of patients. Phenotypic variability is found when LCA patients have a full ophthalmologic examination. However, a correct diagnosis may be carried out; the determination of ophthalmologic clues as light sensibility, night blindness, fundus pigmentation, among other, join with electroretinographics findings, optical coherence tomography, and new technologies as molecular gene testing may help to reach to a precise diagnosis. Several retinal clinical features in LCA may suggest a genetic or gene particular defect; thus genetic-molecular tools could directly corroborate the clinical diagnosis. Currently, approximately 20 genes have been associated to LCA. In this review, historical perspective, clinical ophthalmological findings, new molecular-genetics technologies, possible phenotype-genotypes correlations, and gene therapy for some LCA genes are described.

Comprehensive analysis of genetic variations in strictly-defined Leber congenital amaurosis with whole-exome sequencing in Chinese

AIM：To make a comprehensive analysis of the potential pathogenic genes related with Leber congenital amaurosis（LCA） in Chinese.METHODS：LCA subjects and their families were retrospectively collected from 2013 to 2015.Firstly,whole-exome sequencing was performed in patients who had underwent gene mutation screening with nothing found,and then homozygous sites was selected,candidate sites were annotated,and pathogenic analysis was conducted using softwares including Sorting Tolerant from Intolerant（SIFT）,Polyphen-2,Mutation assessor,Condel,and Functional Analysis through Hidden Markov Models（FATHMM）.Furthermore,Gene Ontology function and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of pathogenic genes were performed followed by co-segregation analysis using Fisher exact Test.Sanger sequencing was used to validate single-nucleotide variations（SNVs）.Expanded verification was performed in the rest patients.RESULTS：Totally 51 LCA families with 53 patients and24 family members were recruited.A total of 104 SNVs（66 LCA-related genes and 15 co-segregated genes）were submitted for expand verification.The frequencies of homozygous mutation of KRT12 and CYP1A1 were simultaneously observed in 3 families.Enrichment analysis showed that the potential pathogenic genes were mainly enriched in functions related to cell adhesion,biological adhesion,retinoid metabolic process,and eye development biological adhesion.Additionally,WFS7 and STAU2 had the highest homozygous frequencies.CONCLUSION：LCA is a highly heterogeneous disease.Mutations in KRT12,CVP1A1,WFS1,and STAU2 may be involved in the development of LCA.

Leber's congenital amaurosis and the role of gene therapy in congenital retinal disorders

Leber＇s congenital amaurosis（LCA）and recent gene therapy advancement for treating inherited retinopathies were extensive literature reviewed using MEDLINE,Pub Med and EMBASE. Adeno-associated viral vectors were the most utilised vectors for ocular gene therapy. Cone photoreceptor cells might use an alternate pathway which was not reliant of the retinal pigment epithelium（RPE）derived retinoid isomerohydrolase（RPE65）to access the 11-cis retinal dehydechromophore. Research efforts dedicated on the progression of a gene-based therapy for the treatment of LCA2. Such gene therapy approaches were extremely successful in canine,porcine and rodent LCA2 models. The recombinant AAV2.h RPE65v2 adenoassociated vector contained the RPE65 cDNA and was replication deficient. Its in vitro injection in target cells induced RPE65 protein production. The gene therapy trials that were so far conducted for inherited retinopathies have generated promising results. Phase I clinical trials to cure LCA and choroideremia demonstrated that adeno-associated viral vectors containing RPE genes and photoreceptors respectively,could be successfully administered to inherited retinopathy patients. A phase III trial is presently ongoing and if successful,it will lead the way to additional gene therapy attempts to cure monogenic,inherited retinopathies.

Blunt Traumatic Pericardial Rupture with Traumatic Amaurosis Fugax Presenting as Massive Haemothorax: A Conundrum?

Introduction: Blunt traumatic pericardial rupture (BTPR) or traumatic pericardiotomy is a rare typical trauma. It is usually discovered at autopsy. Surgical repair is mandatory especially if prompt diagnosis is made because of the associated high mortality. Clinical Case: We report the successful management and survival of BTPR patient after chest trauma presenting with massive haemothorax and transient loss of vision, necessitating urgent surgical treatment. The patient was involved in a road traffic accident having a head-on collision with the rear of the vehicle ahead whiles trying to overtake it. Discussion: It is usually discovered at autopsy or during emergent surgical exploration through either sternotomy or thoracotomy [1] due to its delayed diagnosis, unusual presentation, association with other major cardiopulmonary injuries and complications such as cardiac herniation, fatal arrhythmias, cardiogenic shock and cardiac arrest. Conclusion: Blunt traumatic pericardial rupture should be suspected in any patient in whom hemodynamic instability occurs rapidly after trauma without evidence of major bleeding. Prompt surgical exploration may yield excellent results.

医学期刊中Amaurosis的中文名称辨析

Amaurosis,是一个医学常用名词,指眼球内外无明显病变,瞳孔对光反射存在,而单眼或双眼暂时性或永久性失明的病理状态。在国内医学期刊的相关文献中,其对应的中文名称存在＂黑矇＂＂黑朦＂＂黑蒙＂＂黑曚＂＂黑濛＂等多种写法,而且还存在相同期刊写法不统一,甚至在同一刊期、同一文章内都有不同写法的情况。

Clinical exome sequencing facilitates the understanding of genetic heterogeneity in Leber congenital amaurosis patients with variable phenotype in southern India

Background:Leber congenital amaurosis(LCA),primarily characterized by retinal degeneration is the most severe form of inherited retinal dystrophy(IRD)responsible for congenital blindness.The presence of phenotypic heterogeneity makes the diagnosis of LCA challenging,especially in the absence of pronounced disease pathognomonic,yet it can be well comprehended by employing molecular diagnosis.Therefore,the present study aimed to reveal the causative mutations in ten LCA patients with variable phenotypes using clinical exome sequencing(CES).Methods:CES was performed in ten unrelated LCA patients.Ophthalmic information and family history of all patients were obtained to make a meaningful interpretation.The clinical exome data was analyzed and prioritized using a bioinformatics pipeline to identify mutations,which was further validated by Sanger sequencing.Segregation analysis was also performed on available family members.Results:CES led to the identification of causative mutations in nine LCA patients.Seven patients harbored a mutation in six LCA candidate genes,including RPE65,LCA5(n=2),CRX,PRPH2,CEP290,and ALMS1,while two patients possess a mutation in IFT80 and RP1,known to cause other diseases.Three novel mutations in LCA5(c.1823del),CRX(c.848del)and CEP290(c.2483G>T)were identified.The current study reports for the first time,a mutation in PRPH2,CEP290,and ALMS1 from the Indian population.Additionally,we observed a novel association of LCA phenotype with IFT80 known to cause Jeune syndrome.Based on the genetic finding,the patient AS09,who harbored a mutation in the RP1 gene,was re-diagnosed with early-onset retinitis pigmentosa.Conclusion:In conclusion,the results underline the importance of CES in clinically diagnosed LCA patients with variable phenotypes.The correlation between mutations in candidate genes and clinical phenotypes,helps to refine the clinical diagnosis.However,molecular evaluation with a larger cohort of LCA patients is needed for better understanding of the mutational spectrum in southern India.

Does amaurosis fugax after retrobulbar injection need any treatment？

Many potential complications resulting from .retrobulbar injection have been reported, from themore commonly encountered retrobulbar hemorrhage to the life-threatening respiratory arrest. As one of the major complications, the occurrence of amaurosis fugax may not be noted by the doctor during surgery since the patient may take it as normal and not report it to the surgeon after injection. Fortunately, in most of the cases the visual loss is transient and the patients with amaurosis fugax may recover their vision soon after an injection.

A Gene Scan Study of RPE65 in Chinese Patients with Leber Congenital Amaurosis

Background： Leber congenital anaaurosis （LCA） is a visual disease which is caused by RPE65 mutations and results in retinal degeneration and severe vision loss in early infancy. According to previous researches, mutations of the RPE65 gene account for 16% of all cases of LCA. This study aimed to identify RPE65 gene mutations in Chinese patients with LCA. Methods： We recruited 52 sporadic patients from Peking University Third Hospital in 2016 and applied Sanger sequencing to identil＇y variants among exons responsible for the disease. The genomic DNAs from blood leukocytes of these patients were isolated, and tile entire coding region of the RPE65 gene was amplified by polymerase chain reaction. We then deterrnined the sequence of RPE65 using ABI 3100 Genetic Analyzer. Results： Our study identified that only 1 out of the 52 patients with LCA carried the previously unreported homozygosis missense mutation c1174A〉C （T392P） of the RPE65 gene. However, the mutation was associated with the disease phenotype and not detected in 100 normal controls. Conclusions： Though we identified a novel missense mutation in the RPE65 gene that causes LCA, our result indicates that RPE65 mutations may not play a major role in the LCA patients in China since only 1 out of the 52 patients carried mutation in the RPE65 gene.

New Screening Approach for Ocular Diseases

Objective: Present a new screening approach for ocular diseases. Method: Transversal, retrospective, single center study that analyzed medical records of patients from a social project on the prevention of blindness and amblyopia, which aimed at: 1) Detect the main ocular disorders such as amblyopia, primary angle-closure suspect (PACS);glaucoma suspect (GS);predisposing retinal detachment lesions (PRDL);age-related macular degeneration (AMD), and diabetic retinopathy (DR);2) Perform cataract diagnosis;3) Provide guidance and treatment for allergic conjunctivitis. 4) Prescribe glasses for children until 14 years of age. Participants were examined by a single specialist, holder of a post-doctoral degree in ophthalmology, with 36 years of experience and a sub-specialization in retina and vitreous. All data were analyzed in 2022. Results: The examiner diagnosed 42 cases of PACS, 21 of GS, 8 of PRDL, 14 of AMD, 3 of DR, 40 of cataract and 31 cases of allergic conjunctivitis. Thirty-three participants younger than 14 were prescribed glasses. Other pathologies included retinal detachment, papilledema, corneal ulcer, suspected conjunctival squamous cell carcinoma, retinal vasculitis, strabismus, uveitis, bilateral papilla paleness and lacrimal duct obstruction. Out of the 297 cases examined, 168 participants presented some type of alteration that could compromise their vision. Conclusion: The examiner’s experience and knowledge were decisive factors for the quick diagnosis, advice, screening and/or treatment of several ocular diseases. The social project results reveal that the primary care and/or the screening performed by a specialist are likely to reduce blindness cases.

Targeting molecular pathways for the treatment of inherited retinal degeneration

Inherited retinal degeneration is a major cause of incurable blindness characterized by loss of retinal photoreceptor cells.Inherited retinal degeneration is characterized by high genetic and phenotypic heterogeneity with several genes mutated in patients affected by these genetic diseases.The high genetic heterogeneity of these diseases hampers the development of effective therapeutic interventions for the cure of a large cohort of patients.Common cell demise mechanisms can be envisioned as targets to treat patients regardless the specific mutation.One of these targets is the increase of intracellular calcium ions,that has been detected in several murine models of inherited retinal degeneration.Recently,neurotrophic factors that favor the efflux of calcium ions to concentrations below toxic levels have been identified as promising molecules that should be evaluated as new treatments for retinal degeneration.Here,we discuss therapeutic options for inherited retinal degeneration and we will focus on neuroprotective approaches,such as the neuroprotective activity of the Pigment epithelium-derived factor.The characterization of specific targets for neuroprotection opens new perspectives together with many questions that require deep analyses to take advantage of this knowledge and develop new therapeutic approaches.We believe that minimizing cell demise by neuroprotection may represent a promising treatment strategy for retinal degeneration.

Applications of CRISPR/Cas9 in retinal degenerative diseases

Gene therapy is a potentially effective treatment for retinal degenerative diseases.Clustered regularly interspaced short palindromic repeats（CRISPR）/CRISPR-associated protein 9（Cas9） system has been developed as a new genome-editing tool in ophthalmic studies.Recent advances in researches showed that CRISPR/Cas9 has been applied in generating animal models as well as gene therapy in vivo of retinitis pigmentosa（RP） and leber congenital amaurosis（LCA）.It has also been shown as a potential attempt for clinic by combining with other technologies such as adeno-associated virus（AAV） and induced pluripotent stem cells（i PSCs）.In this review,we highlight the main points of further prospect of using CRISPR/Cas9 in targeting retinal degeneration.We also emphasize the potential applications of this technique in treating retinal degenerative diseases.

Retinal imaging in inherited retinal diseases

Inherited retinal diseases(IRD)are a leading cause of blindness in the working age population.The advances in ocular genetics,retinal imaging and molecular biology,have conspired to create the ideal environment for establishing treatments for IRD,with the first approved gene therapy and the commencement of multiple therapy trials.The scope of this review is to familiarize clinicians and scientists with the current landscape of retinal imaging in IRD.Herein we present in a comprehensive and concise manner the imaging findings of:(I)macular dystrophies(MD)[Stargardt disease(ABCA4),X-linked retinoschisis(RS1),Best disease(BEST1),pattern dystrophy(PRPH2),Sorsby fundus dystrophy(TIMP3),and autosomal dominant drusen(EFEMP1)],(II)cone and cone-rod dystrophies(GUCA1A,PRPH2,ABCA4 and RPGR),(III)cone dysfunction syndromes[achromatopsia(CNGA3,CNGB3,PDE6C,PDE6H,GNAT2,ATF6],blue-cone monochromatism(OPN1LW/OPN1MW array),oligocone trichromacy,bradyopsia(RGS9/R9AP)and Bornholm eye disease(OPN1LW/OPN1MW),(IV)Leber congenital amaurosis(GUCY2D,CEP290,CRB1,RDH12,RPE65,TULP1,AIPL1 and NMNAT1),(V)rod-cone dystrophies[retinitis pigmentosa,enhanced S-Cone syndrome(NR2E3),Bietti crystalline corneoretinal dystrophy(CYP4V2)],(VI)rod dysfunction syndromes(congenital stationary night blindness,fundus albipunctatus(RDH5),Oguchi disease(SAG,GRK1),and(VII)chorioretinal dystrophies[choroideremia(CHM),gyrate atrophy(OAT)].