Nuclear receptor TLX regulates islet beta cell proliferation via E2F6

PPP3R1 Promoter Polymorphism (Allelic Variation) Affects Tacrolimus Treatment Efficacy by Modulating E2F6 Binding Affinity

BACKGROUND

Tacrolimus is widely used as a first-line immunosuppressant in transplant immunology; however, its clinical application is constrained by the narrow therapeutic index and considerable interindividual variability. In this study, we identified the potential regulatory role of a novel PPP3R1 promoter polymorphism, rs4519508 C > T, in the tacrolimus pharmacodynamic pathway.

METHODS

Dual-luciferase reporter assays and bioinformatic analysis were applied to assess the impact of allelic variation. Electrophoretic mobility shift assays (EMSA) validated the altered binding of transcription factors. Quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA) and Western blots were used to determine the immunosuppressive effect of tacrolimus.

RESULTS

Assays revealed that rs4519508 C > T markedly enhanced PPP3R1 promoter activity. EMSA assays validated the binding of E2F6 to rs4519508 C (wild-type) and the binding was significantly weaker to the rs4519508 T (mutant-type). The overexpression of E2F6 significantly reduced the transcriptional activity and expression of PPP3R1 when the rs4519508 site presented as major C allele, an effect that was not observed with the rs4519508 T allele. Furthermore, the downregulation of E2F6 raises the level of downstream immune cytokines inhibited by TAC.

CONCLUSIONS

This study proposed that E2F6 suppresses the expression of PPP3R1, while rs4519508 C > T impairs the binding of E2F6, and thus elevates the level of PPP3R1, so that the inhibition of the downstream immune cytokines by TAC is attenuated. Our findings reported the potential regulatory role of a novel polymorphism, PPP3R1 rs4519508 C > T, which may serve as pharmacodynamic-associated pharmacogenetic biomarker indicating individual response variability of tacrolimus, and thus aid the clinical management of transplant immunology.

Lack of Nr2e1 expression in hepatocytes impaired cell survival and aggravated palmitate-induced oxidative stress

PURPOSE

Nuclear receptor subfamily 2 group E member 1 (Nr2e1) has been regarded as an essential regulator in neural stem cells. However, its function is still not clear in hepatocytes. This study aimed to clarify the effects of Nr2e1-deficiency in hepatocytes in lipotoxic conditions.

MATERIALS/METHODS

Nr2e1-knockdown AML12 ​cells were generated by lentiviral vector transfection. The influences of Nr2e1-deficiency on hepatocyte survival were determined by cell cycle progression and cell apoptosis rate using flow cytometry. Real-time quantitative PCR and Western blot were used to examine the genes and protein expression related to apoptosis, lipid metabolism, and oxidative stress. Meanwhile, RNA sequencing was adopted in liver samples from Nr2e1-knockout (Nr2e1-KO) mice.

RESULTS

Nr2e1 expression was observed with a significant decrease in AML12 ​cells after palmitic acid-stimulation. Knockdown of Nr2e1 in AML12 ​cells resulted in increased sensitivity to lipotoxicity, evidenced by a partial G0/G1 cell-cycle arrest and higher rates of cell apoptosis. Moreover, Nr2e1-knockdown AML12 ​cells presented increased gene expressions relative to lipid synthesis but decreased levels of β-oxidation related genes. Lack of Nr2e1 augmented palmitate-induced oxidative stress in hepatocytes. In vivo, differential genes in Nr2e1-KO mice liver were enriched in pathways associated with liver regeneration and cell proliferation.

CONCLUSIONS

This study indicated that hepatocytes lacking Nr2e1 were more susceptible to lipotoxic-mediated damage. Nr2e1 may serve as a potential target for the development of novel therapies for lipotoxicity-induced liver injury.

Adapting Physiology in Functional Human Islet Organogenesis

Generation of three-dimensional (3D)-structured functional human islets is expected to be an alternative cell source for cadaveric human islet transplantation for the treatment of insulin-dependent diabetes. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), offer infinite resources for newly synthesized human islets. Recent advancements in hPSCs technology have enabled direct differentiation to human islet-like clusters, which can sense glucose and secrete insulin, and those islet clusters can ameliorate diabetes when transplanted into rodents or non-human primates (NHPs). However, the generated hPSC-derived human islet-like clusters are functionally immature compared with primary human islets. There remains a challenge to establish a technology to create fully functional human islets in vitro, which are functionally and transcriptionally indistinguishable from cadaveric human islets. Understanding the complex differentiation and maturation pathway is necessary to generate fully functional human islets for a tremendous supply of high-quality human islets with less batch-to-batch difference for millions of patients. In this review, I summarized the current progress in the generation of 3D-structured human islets from pluripotent stem cells and discussed the importance of adapting physiology for in vitro functional human islet organogenesis and possible improvements with environmental cues.

The COX10-AS1/miR-641/E2F6 Feedback Loop Is Involved in the Progression of Glioma

Glioma is the most common primary tumour of the central nervous system and is considered one of the greatest challenges for neurosurgery. Mounting evidence has shown that lncRNAs participate in various biological processes of tumours, including glioma. This study aimed to reveal the role and relevant mechanism of COX10-AS1 in glioma. The expression of COX10-AS1, miR-641 and E2F6 was measured by qRT-PCR and/or western blot. Clone formation assays, EdU assays, Transwell assays and tumour xenograft experiments were performed to evaluate the effects of COX10-AS1, miR-641 and E2F6 on glioma proliferation, migration and invasion. Luciferase reporter assays, RNA pull-down assays and ChIP assays were conducted to analyse the relationship among COX10-AS1, miR-641 and E2F6. We demonstrated that COX10-AS1 was upregulated in glioma tissues and cell lines, which was related to the grade of glioma and patient survival. Next, through functional assays, we found that COX10-AS1 influenced the proliferation, migration and invasion of glioma cell lines. Then, with the help of bioinformatics analysis, we confirmed that COX10-AS1 regulated glioma progress by acting as a sponge of miR-641 to regulate E2F6. Moreover, further study indicated that E2F6 could promote COX10-AS1 expression by binding to its promoter region. Taken together, the data indicated that COX10-AS1 acts as an oncogene in combination with COX10-AS1/miR-641/E2F6 in glioma, which may be beneficial to the diagnosis and treatment of glioma.