Epigenetics refers to the changes in gene expression level and function caused by non-genetic sequence changes. It can provide the time, location and mode of the genetic information for the execution of DNA sequences, including DNA methylation, histone modification, non-coding RNA and chromatin remodeling. Studies had shown that epigenetics plays an important role in the development of diabetic retinopathy (DR), and it had been found that epigenetic-related treatment regimens had a certain effect on the treatment of DR through animal experiments and in vitro experiments. It was benefit to regulate the development of diabetes and its complications by depth study of DNA methylation, histone modification, miRNA and metabolic memory. An understanding of changes in gene transcriptional mechanisms at the epigenetic level could help us to further study the prevention and control of diabetes and its complications, and to provide new ideas for treatment.
ObjectiveTo observe the disease-causing genes and the inheritance in sporadic retinitis pigmentosa (sRP) in Ningxia region. Methods49 sRP patients and 128 family members were recruited for this study. All the patients and family members received complete ophthalmic examinations including best corrected visual acuity, slit-lamp microscope, indirect ophthalmoscopy, fundus color photography, visual field, optic coherence tomography, full view electroretinogram. DNA was extracted from patients and family members. Using exon combined target region capture sequencing chip to screen the 230 candidate disease-causing gene mutations, polymerase chain reaction and direct sequencing were used to confirm the disease-causing mutations. Results24/49 patients (49.0%) had identified disease-causing genes, totally 16 genes were involved. There were 41 mutation sites were found, including 32 new mutations (78.0%). The disease-causing genes include USH2A, C2orf71, GNGA1, RPGR1, IFT140, TULP1, CLRN1, RPE65, ABCA4, GUCA1, EYS, CYP4V2, GPR98 and ATXN7. Based on pedigree analysis, 20 patients were autosomal recessive retinitis pigmentosa, 3 patients were autosomal dominant retinitis pigmentosa and 1 patient was X linked retinitis pigmentosa. 3/7 patients with USH2A mutations were identified as Usher syndrome. ConclusionsUSHZA is the main disease-causing of sRP patients in Ningxia region. 83.3% of sRP in this cohort are autosomal recessive retinitis pigmentosa.
Objective To investigate the relationship between diabetic retinopathy (DR) and insertion/deletion (a/b) polymorphism of a 27 base pair variable number tandem repeat (VNTR) in intron 4 of the endothelial nitric oxide synthase (eNOS) gene. Methods 321 patients of type 2 diabetes mellitus with over 10 years duration (case group) and 146 normal subjects (control group) were enrolled in this study. All the clients are Han Chinese. The case group was divided into DR subgroup (154 patients) and non-DR (NDR) subgroup (167 patients) according to the results of indirect ophthalmoscope and fundus fluorescent angiography. The VNTR polymorphism in eNOS gene was determined by polymerase chain reaction (PCR) combined with 8% agarose gel electrophoresis. Then the b, a allele frequency and b/b, a/a, b/a allele frequency of two groups were compared, and its correlation with diseases were analyzed. Results The b allele frequency of the VNTR in intron 4 of eNOS gene in the DR group was significantly higher than that in the NDR group（chi;2=4.745，P=0.029；OR=1.685，95%CI=1.050-3.905）and control group（chi;2=6.958，P=0.008；OR=1.891，95%CI=1.172-4.437）; b/b allele frequency in the DR group was also significantly higher than that in the NDR group（chi;2=4.811，P=0.028；OR=1.790，95%CI=1.060-4.645）and control group（chi;2= 5.203，P=0.023；OR=1.859，95%CI=1.087-4.952）. Conclusions The b allele and b/b genotype in intron 4 of eNOS gene in the Han Chinese are closely related to DR.
ObjectiveTo identify the pathogenic genes and mutations in a family with Usher syndrome type 2.MethodsA three-generation family including 7 individuals was enrolled in this study. There were 2 male patients and 5 unaffected individuals. All participants was underwent related ophthalmologic examination, including best corrected visual acuity, slit-lamp, indirect ophthalmoscopy, electroretinogram (ERG), optical coherence tomography and visual field test. DNA was extracted from 3 ml peripheral venous blood of all participants. A total of 136 hereditary retinal disease target genes were screened and the DNA sequence was performed by Next-generation sequence analysis. Then the suspected mutations compared with databases to identify the suspected mutations, which should be verified with non-affected family members and 100 normal subjects by PCR and Sanger sequence.ResultsThe sequence result showed that 2 patients, the proband and his brother, carried complex heterozygous mutations in the USH2A gene: c.5459T＞C (p.M1820T) in exon 27, c.802G＞A (p.G268R) in exon 5 and c.1190T＞A (p.I397K) in exon 7. The c.5459T＞C and c.1190T＞A mutations in USH2A have not been reported in the literature and database. Although their mother carried c.5459T＞C (p.M1820T) and c.802G＞A (p.G268R), and their father carried c.1190T＞A (p.I397K) heterozygous mutations, the parents did not present phenotype. These mutations were not detected in other normal family members. The result was supported by co-segregation analysis.ConclusionThe heterozygous mutations c.5459T＞C (p.M1820T), c.1190T＞A (p.I397K) and c.802G＞A (p.G268R) in USH2A gene cause Usher syndrome in this family.
Familial exudative vitreoretinopathy (FEVR) is a rare inherited disorder of retinal angiogenesis, including autosomal dominant, autosomal recessive, or X-linked forms. Zinc finger protein 408 (ZNF408) was recently found to be associated with FEVR. Cell transfection showed that it was a dominant negative regulator of FEVR pathogenesis. Knocking down ZNF408 in zebrafish by antisense morpholino oligonucleotides indicated it involved in retinal blood vessel development. Understanding the protein structure, gene localization, basic functions and the role of ZNF408 in retinal development will contribute to uncover the pathogenesis of FEVR.
Optogenetics is a novel technique which combines optics with genetics. Using genetic means, a selected opsin protein is ectopically expressed in target neurons, which are then stimulated by light to moderate the neuronal circuit, as a consequence to regulate the animal's behaviors. Retinal degeneration like retinitis pigmentosa and aged macular degeneration causes visual impairment and eventual blindness. Optogenetics techniques have opened the door to creating artificial photoreceptors in the remaining retinal circuits of retinal degeneration retinas via gene therapy. However, there are still limitations in optogenetics technique, for example, potential risk in virus infection, the choice of target cells and the low visual resolution of the experiment animal. It has been reported that vision was successfully restored to a certain extent in animal model using optogenetics technique. With higher photosensitivity of opsin protein, longer activation kinetics and higher transfection efficiency of virus vector, optogenetics techniques' application in ophthalmology will be improved.