Epigenetic modifications such as DNA methylation, histone post-translational modifications, non-coding RNA are reversible, heritable alterations which are induced by environmental stimuli. Major risk factors of diabetes and diabetic complications including hyperglycemia, oxidative stress and advanced glycation end products, can lead to abnormal epigenetic modifications in retinal vascular endothelial cells and retinal pigment epithelium cells. Epigenetic mechanisms are involved in the pathogenesis of macular edema and neovascularization of diabetic retinopathy (DR), as well as diabetic metabolic memory. The heritable nature of epigenetic marks also playsakey role in familial diabetes mellitus. Further elucidation of epigenetic mechanisms in DR can open the way for the discovery of novel therapeutic targets to prevent DR progression.
ObjectiveTo observe the transthyretin (TTR) gene mutation, protein and mRNA expression in patients with familial vitreous amyloidosis. MethodsSubjects were divided into three groups: (1) illness group: seven patients with familial vitreous amyloidosis. (2) No-illness group: 9 unaffected family members. (3) Control group: 9 healthy individuals in same area. Subjects' peripheral venous blood were collected and DNA were extracted, 4 exons of TTR gene were amplified by reverse transcription polymerase chain reaction(RT-PCR), the gene fragments were sequencing by the fluorescence labelling method. Serum TTR protein expression was detected by Western blot, and TTR mRNA in leukocyte was assayed by RT-PCR. Results4 exons of TTR gene of all samples were amplified, and DNA sequencing data showed that 7 patients and 3 subjects DNA from unaffected family members had mutated in the 3rd exon of 107th base, changing from G to C. Heterozygous mutation occurred in codon of the 83th amino acid in exon 3, namely, Gly83Arg, resulted in the change of GGC to CGC. The protein and mRNA expression of TTR was lower in illness group than no-illness group and control groups(P < 0.05). Compared with control group, TTR mRNA expression in unaffected family members groups was significant decreased(P < 0.05). ConclusionHeterozygous mutation occurred in codon of the 83th amino acid in exon 3, namely Gly83Arg, and suggested that Gly83Arg is connected with the change of TTR mRNA and protein expression.
PURPOSE:To investigate the status and detailed structure of Rb gene in primary tumors and somatic cells of patients with retinoblastoma. To identify the character, origin and transmission of oncogenie point mutations. METHODS:DNA hybridization,SSCP analysis and PCR-associated direct sequencing. RESULTS:Among 108 RB patients examined 80 cases were found to have subtle alterations affecting Rb locus,including 44 cases with homozygous Rb point mutations, 20 cases with two independent heterozygous Rb point mutations, 16 cases with heterozygous mutations involved in one allele of Rb gene. Majority of bilateral RB patients and a small fraction of unilateral RB patients were detected to have a germline mutation. In addition the higher frequency of new germline mutation and parental origin of mutation were observed. CONCLUSION :Rb gene is closely associated with retinoblastoma. Two mutation events and resulting inaetivations of both Rb alleles are required for RB tumorigenesis. Based on our own data,the first event is exclusively point mutation. As for the second event,LOH accounts for two third of cases,point mutation for one third of cases. （Chin J Ocul Fundus Dis,1997,13: 12- 16）
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.
Epigenetics has become one of the major research directions of human genome after genome sequencing, and plays an important role in many complex pathophysiological processes such as tumor, biological development, aging and neuropathy. The metabolic memory phenomenon in diabetic retinopathy (DR) suggests that the pathogenesis of DR has a complicated relationship with epigenetic factors. Many studies show the changes and roles of histone modification, DNA methylation and non-coding RNA in the development of DR. However, the current understanding of how epigenetic modifications affect diseases is limited, and most studies on histone modifications have not been carried out in DR. There is still a lot of room for development in epigenetic research on DR. At the same time, epigenetic modification is very complicated, and how to integrate the interaction of different modifications in the development stage of DR is the focus of future research work.
ObjectiveTo investigate the difference of DNA methylation before and after bariatric surgery.MethodThe relevant literatures of the research on the changes of DNA methylation level and gene expression regulation in blood and tissues before and after bariatric surgery were retrieved and reviewed.ResultsDNA methylation was an important method of epigenetic regulation in organisms and its role in bariatric surgery had been paid more and more attention in recent years. Existing studies had found that there were changes of DNA methylation in blood and tissues before and after bariatric surgery. The degree of methylation varies with different follow-up time after bariatric surgery and the same gene had different degrees of methylation in different tissues, and some even had the opposite results.ConclusionsDNA methylation levels before and after bariatric surgery are different in different tissues. And studies with larger sample size and longer follow-up time are needed, to further reveal relationship among DNA methylation, obesity, and bariatric surgery.
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 observe the relationship between endothelial constitutive nitric oxide synthase (ecNOS) genetic polymorphism and diabetic retinopathy（DR）of non insulindependent diabetes mellitus (NIDDM) patients of the Han nationality.Methods A total of 166 patients who clinical diagnosed with NIDDM as case group, 85 cases of patients (cataract or fracture) and healthy subjects without diabetes, hypertension and kidney disease,over 40 years old of age and without consanguinity between each other were selected as normal control group. Case group were divided into non-DR (NDR) group, nonproliferative-DR (BDR) group and proliferativeDR (PDR) group according to the result of fundus fluorescein angiography. Case group and normal control group subjects all were Han nationality. DNA was extracted from peripheral venous blood; the fourth 27 base pairs (bp) repeat polymorphism of ecNOS gene by was measured by polymerase chain reaction (PCR). Results The 27 bp repeat sequences within the ecNOS gene present in the Han nationality,allele b repeat 5 times, alleles a repeat 4 times. PCR results showed that there are 2 alleles and 3 genotypes in normal control, NDR, BDR and PDR group. The frequency of genotype bb、ab、aa were 80%, 16.5%, 3.5% in normal subjects; 77.2％, 13.9%, 8.9％ in NDR group; 80.5％, 17.1%,2.4％ in BDR group;78.3％, 13%, 8.7％ in PDR group,respectively. The allele frequency (chi;2 =1.841) and gene frequency (chi;2=3.847) were not statistically significant (P＞0.5) in normal control,NDR,BDR and PDR group. Logistic regression analysis showed that there is no relation between DR and ecNOS duplicated gene polymorphism. Conclusions There is 27 bp repeated polymorphism in 4th intron of ecNOS gene, which may not be associated with the DR of NIDDM in the Han nationality.
Objective To investigate the disease-causing gene of Stargardt disease. Method Fifteen patients with Stargardt disease were analyzed with 11 primers of the 11 exons of ABCR gene by using PCR-SSCP and DNA direct sequencing techniques. Results Three newly detected disease-causing mutations were found. Among those mutations, one is a frameshift mutation and others are single base transition. Conclusion This research confirmed that ABCR gene is associated with Stargardt disease, and 3 new mutations of ABCR gene were found. (Chin J Ocul Fundus Dis,2000,16:240-243)
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.