Characterization of a Kinesin-Related Gene ATSV, within the Tuberous Sclerosis Locus (TSC1) Candidate Region on Chromosome 9Q34

In the search for candidate genes for the tuberous sclerosis (TSC1) disease locus on chromosome 9q34, we have isolated an overlapping series of 22 plasmid and phage cDNA clones covering nearly 7 kb and with an open reading frame of 5070 bp encoding a protein of 1690 amino acids. The putative protein product is a member of the kinesin superfamily and is homologous to the mouse KIF1A and theCaenorhabditas elegansunc-104 genes. Both KIF1A and unc-104 function in the anterograde axonal transport of synaptic vesicles. The human homolog is therefore termed H-ATSV (axonal transporter of synaptic vesicles, HGMW-approved nomenclature ATSV) Screening of DNA from 107 tuberous sclerosis patients and 80 unaffected individuals with H-ATSV cDNA probes by pulsed-field gel electrophoresis/Southern blotting following digestion by rare-cutting methylation-sensitive restriction enzymes showed variant banding patterns in three patients with tuberous sclerosis. However, further analysis indicated that these variant fragments represent a rare polymorphism probably associated with methylation of clustered restriction sites. There is no evidence to support H-ATSV as a candidate gene for TSC1.     

Loss of Tuberous Sclerosis Complex 2 (TSC2) as a Predictive Biomarker of Response to mTOR Inhibitor Treatment in Patients with Hepatocellular Carcinoma

BACKGROUND: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death globally. Mechanistic target of rapamycin (mTOR) is frequently up-regulated in HCC and plays an important role in HCC tumorigenesis. Tumors with loss of tuberous sclerosis complex 2 (TSC2), a negative regulator of mTOR signaling, tend to respond well to mTOR inhibitors. We analyzed TSC2 expression status in Korean patients with HCC and evaluated the correlation between TSC2 loss and response to the mTOR inhibitor, everolimus. METHODS: We retrospectively assessed 36 patients with advanced HCC who had received sorafenib at a single center in Korea between 2008 and 2014, and for whom tumor specimens were available for TSC2 immunohistochemical analysis (IHC). Three patient-derived tumor cell lines (PDCs) were analyzed by western blotting to determine TSC2 expression and drug sensitivity to mTOR. RESULTS: Twelve of 36 patients (33.3%) showed low to undetectable levels of TSC2 expression. No significant differences were observed in progression-free survival (PFS) or overall survival with sorafenib treatment based on TSC2 expression status. Two patients were treated with everolimus after sorafenib failure; one patient, with moderate TSC2 expression, experienced stable disease with a PFS of 5.8 months; the other, with high TSC2 expression, experienced rapid progression. PDC models demonstrated that the TSC2-low HCC PDC line was significantly more sensitive to everolimus than the TSC2-high HCC PDC lines. CONCLUSION: Loss of TSC2 may predict improved response to everolimus in HCC patients, but further studies are needed to confirm the predictive role of TSC2 expression for everolimus treatment.     

Vigabatrin Inhibits Seizures and mTOR Pathway Activation in a Mouse Model of Tuberous Sclerosis Complex

Epilepsy is a common neurological disorder and cause of significant morbidity and mortality. Although antiseizure medication is the first-line treatment for epilepsy, currently available medications are ineffective in a significant percentage of patients and have not clearly been demonstrated to have disease-specific effects for epilepsy. While seizures are usually intractable to medication in tuberous sclerosis complex (TSC), a common genetic cause of epilepsy, vigabatrin appears to have unique efficacy for epilepsy in TSC. While vigabatrin increases gamma-aminobutyric acid (GABA) levels, the precise mechanism of action of vigabatrin in TSC is not known. In this study, we investigated the effects of vigabatrin on epilepsy in a knock-out mouse model of TSC and tested the novel hypothesis that vigabatrin inhibits the mammalian target of rapamycin (mTOR) pathway, a key signaling pathway that is dysregulated in TSC. We found that vigabatrin caused a modest increase in brain GABA levels and inhibited seizures in the mouse model of TSC. Furthermore, vigabatrin partially inhibited mTOR pathway activity and glial proliferation in the knock-out mice in vivo, as well as reduced mTOR pathway activation in cultured astrocytes from both knock-out and control mice. This study identifies a potential novel mechanism of action of an antiseizure medication involving the mTOR pathway, which may account for the unique efficacy of this drug for a genetic epilepsy.     

Autophagy: an 'Achilles' heel of tumorigenesis in TSC and LAM

Mammalian target of rapamycin (mTOR) complex 1 (mTORC1), which is activated in tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM), is a master regulator of cell growth, cellular metabolism, and autophagy. Treatment of TSC and LAM patients with mTORC1 inhibitors partially decreases the size of brain and kidney tumors, and stabilizes pulmonary function. However, the tumors regrow and lung function continues to decline when treatment is discontinued. We hypothesized that dysregulation of autophagy plays a critical role in the pathogenesis of tumors with mTORC1 hyperactivation and in their response to mTORC1-targeted therapy. We found that cells lacking TSC2 have low levels of autophagy under basal and cellular stress conditions. Using genetic and pharmacological approaches, we discovered that the survival of Tsc2-deficient tumor cells is dependent on autophagy induction. Thus, autophagy inhibitors may have therapeutic potential in TSC and LAM, either as single agent therapy or in combination with mTORC1 inhibitors.     

A Quantitative Proteomic Approach to Identify Significantly Altered Protein Networks in the Serum of Patients with Lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM) is a rare and progressive cystic lung condition affecting approximately 3.4–7.5/million women, with an average lag time between symptom onset and diagnosis of upwards of 4 years. The aim of this work was to identify altered proteins in LAM serum which may be potential biomarkers of disease. Serum from LAM patient volunteers and healthy control volunteers were pooled and analysis carried out using quantitative 4-plex iTRAQ technology. Differentially expressed proteins were validated using ELISAs and pathway analysis was carried out using Ingenuity Pathway Analysis. Fourteen proteins were differentially expressed in LAM serum compared to control serum (p<0.05). Further screening validated the observed differences in extracellular matrix remodelling proteins including fibronectin (30% decrease in LAM, p = 0.03), von Willebrand Factor (40% reduction in LAM, p = 0.03) and Kallikrein III (25% increase in LAM, p = 0.03). Pathway networks elucidated the relationships between the ECM and cell trafficking in LAM. This study was the first to highlight an imbalance in networks important for remodelling in LAM, providing a set of novel potential biomarkers. These understandings may lead to a new effective treatment for LAM in the future.     

Mis-regulation of Mammalian Target of Rapamycin (mTOR) Complexes Induced by Albuminuria in Proximal Tubules

High albumin concentrations in the proximal tubule of the kidney causes tubulointerstitial injury, but how this process occurs is not completely known. To address the signal transduction pathways mis-regulated in renal injury, we studied the modulation of mammalian target of rapamycin (mTOR) complexes by physiologic and pathophysiologic albumin concentrations in proximal tubule cells. Physiologic albumin concentrations activated the PI3K/mTORC2/PKB/mTORC1/S6 kinase (S6K) pathway, but pathophysiologically high albumin concentrations overactivated mTORC1 and inhibited mTORC2 activity. This control process involved the activation of ERK1/2, which promoted the inhibition of TSC2 and activation of S6K. Furthermore, S6K was crucial to promoting the over activation of mTORC1 and inhibition of mTORC2. Megalin expression at the luminal membrane is reduced by high concentrations of albumin. In addition, knockdown of megalin mimicked all the effects of pathophysiologic albumin concentrations, which disrupt normal signal transduction pathways and lead to an overactivation of mTORC1 and inhibition of mTORC2. These data provide new perspectives for understanding the molecular mechanisms behind the effects of albumin on the progression of renal disease.     

Tuberous sclerosis-2 (TSC2) regulates the stability of death-associated protein kinase-1 (DAPK) through a lysosome-dependent degradation pathway

We previously identified a novel interaction between tuberous sclerosis-2 (TSC2) and death-associated protein kinase-1 (DAPK), the consequence being that DAPK catalyses the inactivating phosphorylation of TSC2 to stimulate mammalian target of rapamycin complex 1 (mTORC1) activity. We now report that TSC2 binding to DAPK promotes the degradation of DAPK. We show that DAPK protein levels, but not gene expression, inversely correlate with TSC2 expression. Furthermore, altering mTORC1 activity does not affect DAPK levels, excluding indirect effects of TSC2 on DAPK protein levels through changes in mTORC1 translational control. We provide evidence that the C-terminus regulates TSC2 stability and is required for TSC2 to reduce DAPK protein levels. Importantly, using a GTPase-activating protein-dead missense mutation of TSC2, we demonstrate that the effect of TSC2 on DAPK is independent of GTPase-activating protein activity. TSC2 binds to the death domain of DAPK and we show that this interaction is required for TSC2 to reduce DAPK protein levels and half-life. Finally, we show that DAPK is regulated by the lysosome pathway and that lysosome inhibition blocks TSC2-mediated degradation of DAPK. Our study therefore establishes important functions of TSC2 and the lysosomal-degradation pathway in the control of DAPK stability, which taken together with our previous findings, reveal a regulatory loop between DAPK and TSC2 whose balance can either promote: (a) TSC2 inactivation resulting in mTORC1 stimulation, or (b) DAPK degradation via TSC2 signalling under steady-state conditions. The fine balance between DAPK and TSC2 in this regulatory loop may have subtle but important effects on mTORC1 steady-state function.     

MicroRNA-21 (miR-21) expression promotes growth, metastasis, and chemo- or radioresistance in non-small cell lung cancer cells by targeting PTEN

MicroRNAs (miRNAs) regulate gene expression by binding to target sites and initiating translational repression and/or mRNA degradation. In our previous study, we have shown that expression of serum microRNA (miR)-21 is correlated with TNM stage and lymph node metastasis and might be an independent prognostic factor for NSCLC patients. However, the roles of miR-21 overexpression in NSCLC development are still unclear. The purpose of this study is to investigate the effect of miR-21 and determine whether miR-21 can be a therapeutic target for human NSCLC. Taqman real-time quantitative RT-PCR assay was performed to detect miR-21 expression in NSCLC cell lines and tissues. Next, the effects of miR-21 expression on NSCLC cell characteristics including growth, invasion, and chemo- or radioresistance were also determined. Results showed that miR-21 is commonly upregulated in NSCLC cell lines and tissues with important functional consequences. In addition, we found that anti-miR-21 could significantly inhibit growth, migration and invasion, and reverse chemo- or radioresistance of NSCLC cells, while miR-21 mimics could increase growth, promote migration and invasion, and enhance chemo- or radioresistance of NSCLC cells. Meanwhile, miR-21 mimics could inhibit expression of PTEN mRNA and protein and the luciferase activity of a PTEN 3??-untranslated region (UTR)-based reporter construct in A549 cells, while anti-miR-21 could increase expression of PTEN mRNA and protein and the luciferase activity of a PTEN 3??-UTR-based reporter construct in A549 cells. Furthermore, overexpression of PTEN could mimic the same effects of anti-miR-21 in NSCLC cells, and siRNA-mediated downregulation of PTEN could rescue the effects on NSCLC cells induced by anti-miR-21. Taken together, these results provide evidence to show the promotion role of miR-21 in NSCLC development through modulation of the PTEN signaling pathway.     

Clinical Testing and Spinal Cord Removal in a Mouse Model for Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder resulting in progressive degeneration of motoneurons. Peak of onset is around 60 years for the sporadic disease and around 50 years for the familial disease. Due to its progressive course, 50% of the patients die within 30 months of symptom onset. In order to evaluate novel treatment options for this disease, genetic mouse models of ALS have been generated based on human familial mutations in the SOD gene, such as the SOD1 (G93A) mutation. Most important aspects that have to be evaluated in the model are overall survival, clinical course and motor function. Here, we demonstrate the clinical evaluation, show the conduction of two behavioural motor tests and provide quantitative scoring systems for all parameters. Because an in depth analysis of the ALS mouse model usually requires an immunohistochemical examination of the spinal cord, we demonstrate its preparation in detail applying the dorsal laminectomy method. Exemplary histological findings are demonstrated. The comprehensive application of the depicted examination methods in studies on the mouse model of ALS will enable the researcher to reliably test future therapeutic options which can provide a basis for later human clinical trials.     

Rapamycin Inhibition of Polyposis and Progression to Dysplasia in a Mouse Model

Familial adenomatous polyposis (FAP) is often due to adenomatous polyposis coli (APC) gene germline mutations. Somatic APC defects are found in about 80% of colorectal cancers (CRCs) and adenomas. Rapamycin inhibits mammalian target of rapamycin (mTOR) protein, which is often expressed in human adenomas and CRCs. We sought to assess the effects of rapamycin in a mouse polyposis model in which both Apc alleles were conditionally inactivated in colon epithelium. Two days after inactivating Apc, mice were given rapamycin or vehicle in cycles of two weeks on and two weeks off. Polyps were scored endoscopically. Mice were euthanized at time points or when moribund, and tissue analyses were performed. In other studies, mice with demonstrable Apc-defective colon polyps were given rapamycin, followed by analysis of their colon tissues. The median survival of mice receiving rapamycin treatment cycles was 21.5 versus 6.5 weeks in control mice (p = 0.03), and rapamycin-treated mice had a significantly lower percentage of their colon covered with polyps (4.3+/− 2 vs 56.5+/− 10.8 percent, p = 0.001). Mice with Apc-deficient colon tissues that developed high grade dysplasia treated with rapamycin underwent treatment for significantly longer than mice treated with vehicle (15.8 vs 5.1 weeks, p = 0.003). In Apc-defective colon tissues, rapamycin treatment was linked to decreased levels of β-catenin and Sox9 at 7 weeks. Other effects of rapamycin in Apc-defectivecolon tissues included decreased proliferation and increased numbers of differentiated goblet cells at 7 weeks. Rapamycin did not affect β-catenin-regulated gene expression in cultured intestinal epithelial cells. Rapamycin has potent inhibitory effects in a mouse colon polyposis model, and mTOR inhibition is linked to decreased proliferation and increased expression of differentiation markers in Apc-mutant colon epithelium and delays development of dysplasia. Our findings highlight the possibility that mTOR inhibitors may have relevance for polyposis inhibition approaches in FAP patients.     

MicroRNA-21 Knockout Improve the Survival Rate in DSS Induced Fatal Colitis through Protecting against Inflammation and Tissue Injury

Background

MicroRNA-21 (miR-21) is overexpressed in most inflammatory diseases, but its physiological role in gut inflammation and tissue injury is poorly understood. The goal of this work is to understand the role of miR-21 in colitis and damage progression of intestine in a genetically modified murine model.

Methods

Experimental colitis was induced in miR-21 KO and wild-type (WT) mice by 3.5% dextran sulphate sodium (DSS) administration for 7 days. Disease activity index(DAI), blood parameters, intestinal permeability, histopathologic injury, cytokine and chemokine production, and epithelial cells apoptosis were examined in colons of miR-21 KO and WT mice.

Results

miR-21 was overexpressed in intestine of inflammatory bowel diseases (IBD) and acute intestinal obstruction (AIO) patients when compared with normal intestinal tissues. Likewise, miR-21 was up-regulated in colon of IL-10 KO mice when compared with control mice. WT mice rapidly lost weight and were moribund 5 days after treatment with 3.5% DSS, while miR-21 KO mice survived for at least 6 days. Elevated leukocytes and more severe histopathology were observed in WT mice when compared with miR-21 KO mice. Elevated levels of TNF-α and macrophage inflammatory protein-2(MIP-2) in colon culture supernatants from WT mice exhibited significant higher than miR-21 KO mice. Furthermore, CD3 and CD68 positive cells, intestinal permeability and apoptosis of epithelial cells were significantly increased in WT mice when compared with miR-21 KO mice. Finally, we found that miR-21 regulated the intestinal barrier function through modulating the expression of RhoB and CDC42.

Conclusion

Our results suggest that miR-21 is overexpressed in intestinal inflammation and tissue injury, while knockout of miR-21 in mice improve the survival rate in DSS-induced fatal colitis through protecting against inflammation and tissue injury. Therefore, attenuated expression of miR-21 in gut may prevent the onset or progression of inflammatory bowel disease in patients.     

microRNA－21在肿瘤中异常表达的意义

microRNA（miRNA）是由18～26个核苷酸组成的内源性非编码的单链RNA分子,其通过与mRNA的结合来抑制其翻译过程从而调节相应基因的表达,在人体一系列生物学过程发挥着作用。miR-21在众多肿瘤组织中表达上调,临床试验证实miR-21的表达水平与肿瘤的临床分期,转移,预后存在密切联系,因此miR－21成为了癌症基因治疗的新靶点。     

Induction of Thoracic Aortic Remodeling by Endothelial-Specific Deletion of MicroRNA-21 in Mice

MicroRNAs (miRs) are known to have an important role in modulating vascular biology. MiR21 was found to be involved in the pathogenesis of proliferative vascular disease. The role of miR21 in endothelial cells (ECs) has well studied in vitro, but the study in vivo remains to be elucidated. In this study, miR21 endothelial-specific knockout mice were generated by Cre/LoxP system. Compared with wild-type mice, the miR21 deletion in ECs resulted in structural and functional remodeling of aorta significantly, such as diastolic pressure dropping, maximal tension depression, endothelium-dependent relaxation impairment, an increase of opening angles and wall-thickness/inner diameter ratio, and compliance decrease, in the miR21 endothelial-specific knockout mice. Furthermore, the miR21 deletion in ECs induced down-regulation of collagen I, collagen III and elastin mRNA and proteins, as well as up-regulation of Smad7 and down-regulation of Smad2/5 in the aorta of miR21 endothelial-specific knockout mice. CTGF and downstream MMP/TIMP changes were also identified to mediate vascular remodeling. The results showed that miR21 is identified as a critical molecule to modulate vascular remodeling, which will help to understand the role of miR21 in vascular biology and the pathogenesis of vascular diseases.     

Neuroprotective Effects of (-)-Epigallocatechin-3-gallate in a Transgenic Mouse Model of Amyotrophic Lateral Sclerosis

The purpose of this study is to evaluate neuroprotective effects of (-)-Epigallocatechin-3-gallate (EGCG) in a transgenic mouse model of Amyotrophic lateral sclerosis (ALS). SOD1-G93A transgenic mice and wild-type mice were randomly divided into EGCG-treated groups (10 mg/kg, p.o) and vehicle-treated control groups. Rotarod measurement was performed to assess the motor function of mice starting at the age of 70 days. Nissl staining to examine the number of motor neurons and CD11b immunohistochemical staining to evaluate activation of microglia in the lumbar spinal cords were conducted at the age of 120 days. In addition, for further observation of regulation of cell signaling pathways by EGCG, we used immunohistochemical analysis for nuclear factor kappa B (NF-κB) and cleaved caspase-3 as well as western blot analysis to determine the expression of nitric oxide synthase (iNOS) and NF-κB in the spinal cord. This study demonstrated that oral administration of EGCG beginning from a pre-symptomatic stage significantly delayed the onset of disease, and extended life span. Furthermore, EGCG-treated transgenic mice showed increased number of motor neurons, diminished microglial activation, reduced immunohistochemical reaction of NF-κB and cleaved caspase-3 as well as reduced protein level of iNOS and NF-κB in the spinal cords. In conclusion, this study provides further evidences that EGCG has multifunctional therapeutic effects in the mouse model of ALS.     

MicroRNA-23a Participates in Estrogen Deficiency Induced Gap Junction Remodeling of Rats by Targeting GJA1

Increased incidence of arrhythmias in women after menopause has been widely documented, which is considered to be related to estrogen (E₂) deficiency induced cardiac electrophysiological abnormalities. However, its molecular mechanism remains incompletely clear. In the present study, we found cardiac conduction blockage in post-menopausal rats. Thereafter, the results showed that cardiac gap junctions were impaired and Connexin43 (Cx43) expression was reduced in the myocardium of post-menopausal rats. The phenomenon was also observed in ovariectomized (OVX) rats, which was attenuated by E₂ supplement. Further study displayed that microRNA-23a (miR-23a) level was significantly increased in both post-menopausal and OVX rats, which was reversed by daily E₂ treatment after OVX. Importantly, forced overexpression of miR-23a led to gap junction impairment and Cx43 downregulation in cultured cardiomyocytes, which was rescued by suppressing miR-23a by transfection of miR-23a specific inhibitory oligonucleotide (AMO-23a). GJA1 was identified as the target gene of miR-23a by luciferase assay and miRNA-masking antisense ODN (miR-Mask) assay. We also found that E₂ supplement could reverse cardiac conduction blockage, Cx43 downregulation, gap junction remodeling and miR-23a upregulation in post-menopausal rats. These findings provide the evidence that miR-23a mediated repression of Cx43 participates in estrogen deficiency induced damages of cardiac gap junction, and highlights a new insight into molecular mechanism of post-menopause related arrhythmia at the microRNA level.