Mettl3 regulates the proliferation, migration and invasion of glioma cells by inhibiting PI3K/Akt signaling pathway.

OBJECTIVE: Methyltransferase-like 3 (Mettl3), one of "writers" for N6-methyladenosine RNA methylation is determined to participate in a variety of cell biological functions. However, the functions of Mettl3 on tumor growth of glioma remain unknown. Here, we conducted a research to explore the contribution of Mettl3 in the progression of glioma. PATIENTS AND METHODS: To detect the expression level of RNAs, quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed. To access the relative level of proteins, Western blot was conducted. The proliferative ability of glioma cells was detected by CCK-8 assay and colony formation assay. The migration and invasion of glioma cells were determined by wound healing assay and transwell invasion assay. RESULTS: The expression of Mettl3 was significantly downregulated in tumor tissues compared to the adjacent normal tissues. The downregulation of Mettl3 led to the enhancement of glioma cell proliferation, migration, and invasion in vitro, and promoted the tumor growth of glioma cells in vivo. In addition, further investigation confirmed that Mettl3 plays critical roles in the development of glioma by targeting PI3K/Akt pathway. CONCLUSIONS: Our study proves that Mettl3 plays a critical role in the proliferation, migration, and invasion of glioma cells by inactivating PI3K/Akt signaling pathway, providing a novel mechanism of glioma tumorigenesis and raising a new target for the treatment of glioma.

APP/PS1 transgenic mice treated with aluminum: an update of Alzheimer's disease model.

There is still no animal model available that can mimic all the cognitive, behavioral, biochemical, and histopathological abnormalities observed in patients with Alzheimer's disease (AD). We undertook to consider the interaction between genetic factors, including amyloid precursor protein (APP) and presenilin-1 (PS1), and environmental factors, such as Aluminum (Al) in determining susceptibility outcomes when studying the pathogenesis of AD. In this article, we provide an AD model in APP/PS1 transgenic mice triggered by Al. The animal model was established via intracerebral ventricular microinjection of aluminum chloride once a day for 5 days in APP/PS1 transgenic mice. Twenty wild type (WT) mice and 20 APP/PS1 transgenic (TG) mice were separately divided into 2 groups (control and Al group), and a stainless steel injector with stopper was used for microinjection into the left-lateral cerebral ventricle of each mouse. The Morris water maze task was used to evaluate behavioral function of learning and memory ability on the 20th day after the last injection. This AD model's brain was analyzed by: (1) amyloid beta immunohistochemical staining; (2) Tunnel staining; (3) apoptotic rates; (4) caspase-3 gene expression. Here, decrease of cognitive ability and neural cells loss were shown in APP/PS1 transgenic mice exposed to Al, which were more extensive than those in APP/PS1 TG alone and WT mice exposed to Al alone. These findings indicate that there is a close relationship between over-expression of APP and PS1 genes and Al overload. It is also suggested that APP/PS1 TG mice exposed to Al have potential value for improving AD models.

In vivo toxicity of nano-alumina on mice neurobehavioral profiles and the potential mechanisms.

The rapid development and expanding applications of nanotechnology have led to enhanced exposure of human body to nanoparticles. It is, therefore, necessary to address the safety issue via rigorous toxicological evaluation and to understand the underlying interaction mechanism. However, only a few studies to date have evaluated the safety of nano-sized materials and their potential adverse effects on biological systems. In this study, we sought to investigate the potential toxicity of aluminum oxide (alumina) nanoparticles in ICR strained mice, focusing on potential neurobehavioral defects and the possible mechanisms. The results demonstrated that nano-alumina impaired neurobehavioral functions, including lengthened escape latency, shorter time spent in the target quadrant and reductions in the number of platform crossing. In addition, it induced cell necrosis and apoptosis, which were likely mediated by the reduction of MMP and ROS, and the induction of the caspase-3 gene. Our results implicated that mitochondrial impairment plays a key role in neurotoxicity of nano-alumina, sequent oxidative damage and neural cell loss, especially necrosis, may be direct causes for the neurobehavioral defects. Collectively, nano-alumina presents a strong pro-cell death effect on ICR mice in vivo, suggesting that nano-alumina may serve as an inducer for neural toxicology. Findings in the present study indicating that surface chemical characteristics and nanoscale sizes of nano-alumina could co-contribute significantly to neurotoxicity. The impaired neurobehavioral patterns indicate that nano-alumina particles are more toxic to the cerebrum than those of nano-carbon with the same nanoparticle size and micro-alumina with the same surface chemical characteristics.

Cloning of the human homologue of the TGF beta-stimulated clone 22 gene.

We have isolated the human homologue if the TGF beta-stimulated clone 22 gene from a human embryo cDNA library. This gene maps to the q14 region of chromosome 13. Its deduced amino acid sequence is almost 99% identical to that of mouse or rat proteins and includes a putative leucine zipper motif. An abundant major transcript of 1.8 kb and in some instances an additional 5 kb transcript were detected by Northern blotting of several human tissues. The TSC-22 protein has been shown to be well conserved across evolution as evidenced by the existence of a Drosophila homologue. These observations prompt discussion on the strong conservation of TSC-22 during evolution but also on its general function as a primary response gene expressed either when stimulated by several different factors during early human development, or in the adult in response to inducing differentiation signals.

In vitro activity of the transcription activation functions of the progesterone receptor. Evidence for intermediary factors.

The human progesterone receptor (hPR) is a ligand-dependent transcription factor which contains two distinct transcription activation functions (TAFs). The full-length hPR and its individual TAFs were overexpressed in the baculovirus system and tested in a HeLa cell-derived in vitro transcription system. hPR stimulated transcription in a ligand-independent manner. When the two TAFs fused to the DNA-binding domain of GAL4 were tested, only the constitutive TAF-1 was functional in vitro, strongly suggesting that the transcriptional activity of baculovirus-expressed hPR comes solely from TAF-1. The GAL-TAF-1 activator was found to self-squelch without affecting basal transcription. A partially purified fraction relieved this self-squelching and, moreover, stimulated transcriptional activation by GAL-TAF-1, while having no influence on basal transcription. These results strongly suggest that the transcriptional activity of GAL-TAF-1 requires a factor(s) distinct from the general transcription factors.

Agonistic and antagonistic activities of RU486 on the functions of the human progesterone receptor.

RU486 induced the binding to a palindromic progestin responsive element (PRE) in vitro of homo- and heterodimers of the human progesterone receptor (hPR) isoforms A and B, present in T47D breast cancer cells or in HeLa cells transiently expressing the recombinant proteins. The resulting complexes were indistinguishable from those induced with the agonist R5020 with respect to specificity, affinity and stability. Ligand exposure was a necessary prerequisite to observe PR/PRE complexes. Antagonist-induced complexes migrated more rapidly during electrophoresis than agonist-induced ones, and no 'mixed' PR/RU486-PR/R5020 complexes were observed, suggesting that the dimerization interfaces of agonist- and antagonist-bound molecules are non-compatible. The analysis of a series of deletion mutants and chimeric receptors revealed the presence of two transcription activation functions (TAFs), located in the N-terminal region A/B (TAF-1) and the hormone binding domain (TAF-2). In the presence of agonists, both TAFs were active in HeLa cells. In the presence of RU486 TAF-2 was inactive, while TAF-1 within the hPR form B/RU486 complex activated transcription from a reporter gene containing a single palindromic PRE. We consider this to be the most convincing evidence that the receptor/RU486-complex does in fact bind to PREs in vivo. No transcriptional activation was observed in the presence of RU486 from a reporter gene containing the complex MMTV-LTR PRE. In contrast to hPR form B, form A was not able to activate transcription from PRE/GRE-tk-CAT in the presence of RU486. In vivo competition between hPR/RU486 and either cPR/R5020 or the human glucocorticoid receptor/dexamethasone (hGR/Dex) complex further supported that hPR/RU486 bound in vivo to its cognate responsive element. Indeed, the observed inhibition of transcription was shown to be due to competition for the MMTV PRE, since no transcriptional interference by the hPR/RU486 was observed, and since no heterodimers were formed between hPR/RU486 and cPR/R5020 or hGR/Dex. That the ligand-free hPR, however, was unable to compete, demonstrated that ligand binding is the prerequisite for DNA binding of hPR in vivo.