The role of Tet3 DNA dioxygenase in epigenetic reprogramming by oocytes.

Sperm and eggs carry distinctive epigenetic modifications that are adjusted by reprogramming after fertilization. The paternal genome in a zygote undergoes active DNA demethylation before the first mitosis. The biological significance and mechanisms of this paternal epigenome remodelling have remained unclear. Here we report that, within mouse zygotes, oxidation of 5-methylcytosine (5mC) occurs on the paternal genome, changing 5mC into 5-hydroxymethylcytosine (5hmC). Furthermore, we demonstrate that the dioxygenase Tet3 (ref. 5) is enriched specifically in the male pronucleus. In Tet3-deficient zygotes from conditional knockout mice, paternal-genome conversion of 5mC into 5hmC fails to occur and the level of 5mC remains constant. Deficiency of Tet3 also impedes the demethylation process of the paternal Oct4 and Nanog genes and delays the subsequent activation of a paternally derived Oct4 transgene in early embryos. Female mice depleted of Tet3 in the germ line show severely reduced fecundity and their heterozygous mutant offspring lacking maternal Tet3 suffer an increased incidence of developmental failure. Oocytes lacking Tet3 also seem to have a reduced ability to reprogram the injected nuclei from somatic cells. Therefore, Tet3-mediated DNA hydroxylation is involved in epigenetic reprogramming of the zygotic paternal DNA following natural fertilization and may also contribute to somatic cell nuclear reprogramming during animal cloning.

Gadd45a promotes DNA demethylation through TDG.

Growth arrest and DNA-damage-inducible protein 45 (Gadd45) family members have been implicated in DNA demethylation in vertebrates. However, it remained unclear how they contribute to the demethylation process. Here, we demonstrate that Gadd45a promotes active DNA demethylation through thymine DNA glycosylase (TDG) which has recently been shown to excise 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) generated in Ten-eleven-translocation (Tet)-initiated oxidative demethylation. The connection of Gadd45a with oxidative demethylation is evidenced by the enhanced activation of a methylated reporter gene in HEK293T cells expressing Gadd45a in combination with catalytically active TDG and Tet. Gadd45a interacts with TDG physically and increases the removal of 5fC and 5caC from genomic and transfected plasmid DNA by TDG. Knockout of both Gadd45a and Gadd45b from mouse ES cells leads to hypermethylation of specific genomic loci most of which are also targets of TDG and show 5fC enrichment in TDG-deficient cells. These observations indicate that the demethylation effect of Gadd45a is mediated by TDG activity. This finding thus unites Gadd45a with the recently defined Tet-initiated demethylation pathway.

Changes of Regulatory T Cells in the Early Stage of Obesity Mice and Their Modulation on Macrophage Subtypes in Visceral Adipose Tissue.

Objective To investigate the changes of regulatory T cells (Tregs) and whether Tregs can modulate the distribution of macrophage subtypes in visceral adipose tissue in the early stage of obesity.Methods After C57BL/6 mice obesity models were successfully established,metabolic parameters and numbers of Tregs and M1/M2 macrophage were measured at 4,10,and 20 weeks.The changes of metabolic parameters and adipose tissue inflammation in obesity mice after rapamycin intervention were evaluated. Results The early-stage obesity models were successfully established.Compared with normal diet mice,high fat diet mice had significantly higher epididymal adipose tissue mass and serum leptin levels(P<0.05).However,there was no statistical difference in blood glucose and insulin levels between these two groups(All P>0.05). Macrophages infiltration in adipose tissue in high fat diet mice gradually increased with time,coincident with decrease in Treg numbers. Increased numbers of Treg,improved metabolic parameters,and decreased ratio of M1/M2 can be seen after rapamycin intervention in mice.Conclusion The decrease of Tregs in the early stage of obesity may contribute to abnormal distribution of macrophage subtypes in visceral adipose.

Effect of high-fat or high-glucose diet on obesity and visceral adipose tissue in mice.

OBJECTIVE: To investigate the effect of high-fat or high-glucose diet on obesity and visceral adipose tissue in C57BL/6 mice. METHODS: Four-week-old C57BL/6 mice were allocated into normal diet group,high-fat diet group,and high-glucose diet group according to the random number table until 20 weeks old. Body weight,epididymal adipose tissue weight,blood leptin,fat infiltration in liver,M1/M2 macrophage subtypes,and monocyte chemoattractant protein-1 mRNA in epididymal adipose tissues were measured. RESULTS: Compared with normal diet group,body weight,epididymal adipose tissue weight,and leptin concentration in high fat diet group at 20 weeks were significantly increased (P < 0.05),and oil red O staining showed more prominent adipocyte infiltration in liver in high-fat diet group than those in normal diet and high-glucose diet group. However,no apparent differences were seen in high-glucose diet group at 20 weeks in terms of body weight,epididymal adipose tissue weight and leptin concentration. In high-fat diet group,the macrophages infiltration in epididymal adipose tissue increased with time and the percentage of M2 macrophage decreased in high-fat diet group than that in high-glucose diet group(P<0.05). Compared with normal diet group,monocyte chemoattractant protein-1 mRNA expression increased significantly in high-fat diet group(P<0.05). In high-glucose group,however,no significant differences were discerned (P > 0.05). CONCLUSION: High-fat diet,rather than 60% high glucose diet,will lead to obesity and macrophage infiltration in adipose tissues.

Myricetin mitigates motor disturbance and decreases neuronal ferroptosis in a rat model of Parkinson's disease.

Ferroptosis is an iron-dependent cell death form characterized by reactive oxygen species (ROS) overgeneration and lipid peroxidation. Myricetin, a flavonoid that exists in numerous plants, exhibits potent antioxidant capacity. Given that iron accumulation and ROS-provoked dopaminergic neuron death are the two main pathological hallmarks of Parkinson's disease (PD), we aimed to investigate whether myricetin decreases neuronal death through suppressing ferroptosis. The PD models were established by intraperitoneally injecting 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into rats and by treating SH-SY5Y cells with 1-methyl-4-phenylpyridinium (MPP+), respectively. Ferroptosis was identified by assessing the levels of Fe2+, ROS, malondialdehyde (MDA), and glutathione (GSH). The results demonstrated that myricetin treatment effectively mitigated MPTP-triggered motor impairment, dopamine neuronal death, and α-synuclein (α-Syn) accumulation in PD models. Myricetin also alleviated MPTP-induced ferroptosis, as evidenced by decreased levels of Fe2+, ROS, and MDA and increased levels of GSH in the substantia nigra (SN) and serum in PD models. All these changes were reversed by erastin, a ferroptosis activator. In vitro, myricetin treatment restored SH-SY5Y cell viability and alleviated MPP+-induced SH-SY5Y cell ferroptosis. Mechanistically, myricetin accelerated nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) and subsequent glutathione peroxidase 4 (Gpx4) expression in MPP+-treated SH-SY5Y cells, two critical inhibitors of ferroptosis. Collectively, these data demonstrate that myricetin may be a potential agent for decreasing dopaminergic neuron death by inhibiting ferroptosis in PD.

[Mutation screening of MLH1 and MSH2 genes in two Chinese families with hereditary nonpolyposis colorectal cancer].

OBJECTIVE: To identify the MLH1 and MSH2 gene mutation in two hereditary nonpolyposis colorectal cancer (HNPCC) families. METHODS: Polymerase chain reaction and DNA sequencing were used to screen for MLH1 and MSH2 gene mutation, and PCR-restriction fragment length polymorphism and DNA sequencing were performed to confirm the mutation. RESULTS: By DNA sequencing, a novel mutation of c.243_244insA located at the exon 3 of MLH1 gene was detected in family A, while c.1215_1218dupCCGA mutation located at the exon 7 of MSH2 gene was detected in family B. These two mutations can cause the formation of premature proteins. CONCLUSION: The novel mutations c.243_244insA in MLH1 gene and c.1215_1218dupCCGA in MSH2 gene were the disease-causing mutations in the two HNPCC families.

[Mapping of pathogenic genes in two families with autosomal dominant ichthyosis vulgaris].

To localize the pathogenic genes of autosomal dominant ichthyosis vulgaris, we ascertained two ichthyosis vulgaris families from Hunan Province. Venous blood samples were collected from affected and unaffected family members and genomic DNA was extracted. We then performed genome scan and linkage analysis using microsatellite markers around known ichthyosis vulgaris loci in chromosomes 1 and 10. In family 1, the locus linked to ichthyosis vulgaris was located near D1S498 (1q21), which overlapped with known ichthyosis vulgaris loci. In family 2, however, all known loci for ichthyosis vulgaris were excluded and the new locus remains to be identified.

Two novel mutations of the LDL receptor gene associated with familial hypercholesterolemia in a Chinese family.

BACKGROUND: Familial hypercholesterolemia (FH) is a type of dominant autosomal disease that causes high levels of plasma low-density lipoprotein cholesterol (LDL-C). In the past years, molecular data related to FH were limited in China. Now, to gain more information about FH, we analyzed one proband with a severe FH phenotype as well as his relatives. METHODS: After the entire coding sequence and the intron-exon junctions of the low-density lipoprotein receptor (LDLR) gene were amplified using PCR, we sequenced the LDLR gene of a Chinese FH family. RT-PCR was used to detect changes in the mRNA. RESULTS: Two novel mutations were identified in the LDLR gene of this family. One, W165X, was a G > A substitution at the third nucleotide of codon 165. The other, IVS5-1G > A, was also a G > A substitution at the acceptor splice site of intron 5. The most striking discovery is that the proband was heterozygous for W165X but homozygous for IVS5-1G > A. The cDNA sequencing showed that the IVS5-1G > A mutation caused the insertion of 10 nucleotides, namely GCTCTCACAA, between exon 5 and exon 6. CONCLUSIONS: The two nucleotide variations are thought to be the FH-causing mutations because the co-segregation of the mutant allele with the phenotype of FH has been shown in this Chinese family. These data show an increase in the mutational spectrum of FH in China and verify a scarce mutational form in the LDLR gene.

[Mutation analysis of GCH1 gene in Chinese patients with dopa responsive dystonia].

OBJECTIVE: To detect mutations of guanosine triphosphate cyclohydrolase I (GCH1) gene in Chinese patients with dopa responsive dystonia (DRD). METHODS: Six sporadic patients with DRD were examined. GCH1 gene mutations were detected using polymerase chain reaction (PCR), DNA sequence analysis and restriction enzyme digestion analysis. One hundred normal people were detected using PCR and restriction enzyme digestion analysis. RESULTS: A new point mutation, 151(G-->A) in exon one was found in a patient. It lead to substitution of a methionine for isoleucine at amino acid 1(M1I). This mutation was not found in normal control people. CONCLUSION: The authors report a new heterozygotic point mutation 151(G-->A) in GCH1 gene. There are GCH1 gene mutations in Chinese sporadic patients with DRD.

[Mapping of pathogenic genes in a pedigree with autosomal dominant ichthyosis vulgaris].

OBJECTIVE: To elucidate the pathogenic genes in a pedigree with autosomal dominant ichthyosis vulgaris (IV). METHODS: Linkage analysis was performed by using STR markers in chromosome 1, and mutation detection was used to screen for FLG gene mutation. RESULTS: A maximum two-point Lod score of 3.46 (theta=0) was obtained at D1S2696. Haplotype analysis placed the critical region in a 15-CM interval defined by D1S2726 and D1S305, but no mutation of FLG was found in our IV patients. CONCLUSION: The pathologic gene of the IV family locates near D1S2696, and the FLG gene may not ruled out from the pathologic genes.

[Novel mutation of Y271H in EXT1 gene causes multiple exostoses].

OBJECTIVE: To explore the disease associated gene mutation of multiple exostoses by family analysis. METHODS: Polymerase chain reaction and DNA sequencing were used to detect the mutation hot spot regions of EXT1 and EXT2 gene, while restriction fragment length polymorphism was performed to screen the mutation. RESULTS: We found a novel heterozygous mutation c.811T ->C in EXT1 gene of patients, which resulted in the substitution of histidine for tyrosine at codon 271 in this hereditary multiple exostoses family. The mutation was not found in the unaffected family members, nor in the 100 unrelated normal individual, which was unreported before. CONCLUSION: The novel mutation Y271H is the disease-causing mutation in the hereditary multiple exostoses family.

[Clinical and mutational analysis of KCNQ3 gene in a Chinese family with benign familial neonatal convulsions].

OBJECTIVE: To study the clinical and genetic characteristics of a Chinese family with benign familial convulsions (BFNC). METHODS: The clinical data of this family was analyzed. The blood samples were collected from 13 members of this family. By four microsatellite markers which are located in the gene loci of both K+ channel KCNQ2 and KCNQ3, the linkage analysis was performed in the family. With DNA direct sequencing and restriction endonuclease cutting analysis, the mutation analysis of KCNQ3 gene was made for the proband, other 12 family members and 76 unrelated normal individuals. RESULTS: There were 7 patients with BFNC observed in the three generation of family. The BFNC seizures of all patients disappeared during one month and no recurrence of seizures was found. The linkage analysis suggested the disease gene linked to KCNQ3 gene locus in the family. The mutation 988(C to T) of KCNQ3 gene was found in the proband by DNA-direct sequencing. Cosegregation of this mutation with BFNC was confirmed by restriction endonuclease cutting analysis. CONCLUSION: Chinese patients with BFNC can be caused by KCNQ3 gene mutation.

[A mutation 1633-26(C-->A) in EXT1 gene causes multiple exostoses].

OBJECTIVE: To study the gene mutation in a patient with multiple exostoses, identify the disease-causing gene mutation. METHODS: Polymerase chain reaction and DNA sequencing were used to screen the EXT1 or EXT2 gene mutation, while mismatch primer amplification and restriction endonuclease digestion were performed to confirm the mutation. RESULTS: By DNA sequencing, a mutation in the seventh intron was detected and located at 26 bp of 3' splice site upstream in EXT1 gene, which was unreported before. Mismatch primer amplification and restriction fragment length polymorphism analysis suggested that this mutation was not detected in the normal control. CONCLUSION: The mutation 1633-26(C-->A) may be the disease-causing mutation in this patient with multiple exostoses.

A novel splicing mutation of KIT results in piebaldism and auburn hair color in a Chinese family.

Piebaldism is a rare autosomal dominant disorder of melanocyte development, which is mostly caused by KIT gene. The key characteristics of piebaldism include localized poliosis, congenital leukoderma, and other variable manifestations. The previous study has illustrated that the homogeneous MC1R (a gene which is associated with the hair color) variant (p.I120T) coordinating with KIT mutation may lead to auburn hair color and piebaldism. In this study, we have investigated a Chinese family with piebaldism and auburn hair color; the mutation screening of KIT and MC1R genes identified that only a splicing mutation (c. 2484+1G>A) of KIT gene cosegregated with the auburn hair color and piebaldism. The data of this study and others suggests that the KIT mutation may causes of the auburn hair color in the piebaldism patients.