GID complex regulates the differentiation of neural stem cells by destabilizing TET2 / 医学前沿

Brain development requires a delicate balance between self-renewal and differentiation in neural stem cells (NSC), which rely on the precise regulation of gene expression. Ten-eleven translocation 2 (TET2) modulates gene expression by the hydroxymethylation of 5-methylcytosine in DNA as an important epigenetic factor and participates in the neuronal differentiation. Yet, the regulation of TET2 in the process of neuronal differentiation remains unknown. Here, the protein level of TET2 was reduced by the ubiquitin-proteasome pathway during NSC differentiation, in contrast to mRNA level. We identified that TET2 physically interacts with the core subunits of the glucose-induced degradation-deficient (GID) ubiquitin ligase complex, an evolutionarily conserved ubiquitin ligase complex and is ubiquitinated by itself. The protein levels of GID complex subunits increased reciprocally with TET2 level upon NSC differentiation. The silencing of the core subunits of the GID complex, including WDR26 and ARMC8, attenuated the ubiquitination and degradation of TET2, increased the global 5-hydroxymethylcytosine levels, and promoted the differentiation of the NSC. TET2 level increased in the brain of the Wdr26+/- mice. Our results illustrated that the GID complex negatively regulates TET2 protein stability, further modulates NSC differentiation, and represents a novel regulatory mechanism involved in brain development.

Metformin inhibits apoptosis by regulating TET2-Foxo3a pathway after spinal cord injury / 中华骨科杂志

Objective:Through TTC staining, immunohistochemical analysis, RT-PCR and hind limb motor function evaluation and other experimental methods, to explore the regulatory mechanism of metformin on anti-apoptosis in rats with spinal cord injury (SCI).Methods:Establish a rat spinal cord injury model. Through Basso-Beattie -Bresnahan locomotor rating scale (BBB) and cant test to evaluate the recovery of hindlimb motor function in rats. The changes of necrotic area of spinal cord tissue were compared by TTC staining. Extraction of rat spinal cord tissue, by Dot blot analysis and immunohistochemical detection of the hydroxyl of DNA methylation level. By qPCR, Western Blot detection TET2mRNA and protein expression level, and the changes in the scope of spinal cord injury were detected by inhibiting the expression of TET2. The interaction between TET2 and Foxo3a was detected by immunoblotting and immunoprecipitation. Through RT-PCR assay Foxo3a downstream related changes in the level of gene expression.Results:Compared with the SCI+NS group, the necrotic area of the spinal cord tissue was reduced after metformin treatment, and the BBB score and the incline test score were higher ( P<0.05). At the same time, we found that the levels of TET2mRNA and protein increased significantly after SCI at 24 h, and the 5-hmC level of DNA increased. The levels of TET2mRNA and protein and 5-hmC increased further after the use of metformin. After using SC-1, compared with the SCI+MET group, the level of 5-hmC decreased and the area of infarction increased. After SCI, the mRNA levels of downstream genes Bim, P27kip, Bax increased significantly. After metformin treatment, the mRNA levels of Bim and Bax were lower than those in the SCI+NS group ( P<0.05). After SCI, the 5-hmC levels of downstream genes Bim, P27kip, Bax increased significantly. After metformin treatment, the 5-hmC levels of Bim and Bax were lower than those in the SCI+NS group ( P<0.05). Conclusion:Metformin can promote the interaction between TET2 and Foxo3a, increase the 5-hmC level of the overall DNA, and inhibit the activation of related apoptosis genes, thereby improving tissue damage and nerve function recovery after spinal cord injury.