Hepatic Snai1 and Snai2 promote liver regeneration and suppress liver fibrosis in mice.

Liver injury stimulates hepatocyte replication and hepatic stellate cell (HSC) activation, thereby driving liver regeneration. Aberrant HSC activation induces liver fibrosis. However, mechanisms underlying liver regeneration and fibrosis remain poorly understood. Here, we identify hepatic Snai1 and Snai2 as important transcriptional regulators for liver regeneration and fibrosis. Partial hepatectomy or CCl4 treatment increases occupancies of Snai1 and Snai2 on cyclin A2 and D1 promoters in the liver. Snai1 and Snai2 in turn increase promoter H3K27 acetylation and cyclin A2/D1 expressions. Hepatocyte-specific deletion of both Snai1 and Snai2, but not one alone, suppresses liver cyclin A2/D1 expression and regenerative hepatocyte proliferation after hepatectomy or CCl4 treatments but augments CCl4-stimulated HSC activation and liver fibrosis. Conversely, Snai2 overexpression in the liver enhances hepatocyte replication and suppresses liver fibrosis after CCl4 treatment. These results suggest that hepatic Snai1 and Snai2 directly promote, via histone modifications, reparative hepatocyte replication and indirectly inhibit liver fibrosis.

Minimally Invasive Delivery of Percutaneous Ablation Agent via Magnetic Colloidal Hydrogel Injection for Treatment of Hepatocellular Carcinoma.

Percutaneous thermotherapy, a minimally invasive operational procedure, is employed in the ablation of deep tumor lesions by means of target-delivering heat. Conventional thermal ablation methods, such as radiofrequency or microwave ablation, to a certain extent, are subjected to extended ablation time as well as biosafety risks of unwanted overheating. Given its effectiveness and safety, percutaneous thermotherapy gains a fresh perspective, thanks to magnetic hyperthermia. In this respect, an injectable- and magnetic-hydrogel-construct-based thermal ablation agent is likely to be a candidate for the aforementioned clinical translation. Adopting a simple and environment-friendly strategy, a magnetic colloidal hydrogel injection is introduced by a binary system comprising super-paramagnetic Fe3O4 nanoparticles and gelatin nanoparticles. The colloidal hydrogel constructs, unlike conventional bulk hydrogel, can be easily extruded through a percutaneous needle and then self-heal in a reversible manner owing to the unique electrostatic cross-linking. The introduction of magnetic building blocks is exhibited with a rapid magnetothermal response to an alternating magnetic field. Such hydrogel injection is capable of generating heat without limitation of deep penetration. The materials achieve outstanding therapeutic results in mouse and rabbit models. These findings constitute a new class of locoregional interventional thermal therapies with minimal collateral damages.

miR-30e-5p regulates leukemia stem cell self-renewal through the Cyb561/ROS signaling pathway.

Leukemia stem cells (LSC) represent a crucial and rare subset of cells present in acute myeloid leukemia (AML); they play a pivotal role in the initiation, maintenance, and relapse of this disease. Targeting LSC holds great promise for preventing AML relapse and improving long-term outcomes. However the precise molecular mechanisms governing LSC self-renewal are still poorly understood. Here, we present compelling evidence that the expression of miR-30e-5p, a potential tumor-suppressive microRNA, is significantly lower in AML samples than in healthy bone marrow samples. Forced expression of miR- 30e effectively inhibits leukemogenesis, impairs LSC self-renewal, and delays leukemia progression. Mechanistically, Cyb561 acts as a direct target of miR-30e-5p in LSC, and its deficiency restricts the self-renewal of LSC by activating reactive oxygen series signaling and markedly prolongs recipients' survival. Moreover, genetic or pharmacological overexpression of miR-30e-5p or knockdown of Cyb561 suppresses the growth of human AML cells. In conclusion, our findings establish the crucial role of the miR-30e-5p/Cyb561/ROS axis in finely regulating LSC self-renewal, highlighting Cyb561 as a potential therapeutic target for LSC-directed therapies.

LepRb+ cell-specific deletion of Slug mitigates obesity and nonalcoholic fatty liver disease in mice.

Leptin exerts its biological actions by activating the long-form leptin receptor (LepRb). LepRb signaling impairment and leptin resistance are believed to cause obesity. The transcription factor Slug - also known as Snai2 - recruits epigenetic modifiers and regulates gene expression by an epigenetic mechanism; however, its epigenetic action has not been explored in leptin resistance. Here, we uncover a proobesity function of neuronal Slug. Hypothalamic Slug was upregulated in obese mice. LepRb+ cell-specific Slug-knockout (SlugΔLepRb) mice were resistant to diet-induced obesity, type 2 diabetes, and liver steatosis and experienced decreased food intake and increased fat thermogenesis. Leptin stimulated hypothalamic Stat3 phosphorylation and weight loss to a markedly higher level in SlugΔLepRb than in Slugfl/fl mice, even before their body weight divergence. Conversely, hypothalamic LepRb+ neuron-specific overexpression of Slug, mediated by AAV-hSyn-DIO-Slug transduction, induced leptin resistance, obesity, and metabolic disorders in mice on a chow diet. At the genomic level, Slug bound to and repressed the LepRb promoter, thereby inhibiting LepRb transcription. Consistently, Slug deficiency decreased methylation of LepRb promoter H3K27, a repressive epigenetic mark, and increased LepRb mRNA levels in the hypothalamus. Collectively, these results unravel what we believe to be a previously unrecognized hypothalamic neuronal Slug/epigenetic reprogramming/leptin resistance axis that promotes energy imbalance, obesity, and metabolic disease.

Hepatic Slug epigenetically promotes liver lipogenesis, fatty liver disease, and type 2 diabetes.

De novo lipogenesis is tightly regulated by insulin and nutritional signals to maintain metabolic homeostasis. Excessive lipogenesis induces lipotoxicity, leading to nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Genetic lipogenic programs have been extensively investigated, but epigenetic regulation of lipogenesis is poorly understood. Here, we identified Slug as an important epigenetic regulator of lipogenesis. Hepatic Slug levels were markedly upregulated in mice by either feeding or insulin treatment. In primary hepatocytes, insulin stimulation increased Slug expression, stability, and interactions with epigenetic enzyme lysine-specific demethylase-1 (Lsd1). Slug bound to the fatty acid synthase (Fasn) promoter where Slug-associated Lsd1 catalyzed H3K9 demethylation, thereby stimulating Fasn expression and lipogenesis. Ablation of Slug blunted insulin-stimulated lipogenesis. Conversely, overexpression of Slug, but not a Lsd1 binding-defective Slug mutant, stimulated Fasn expression and lipogenesis. Lsd1 inhibitor treatment also blocked Slug-stimulated lipogenesis. Remarkably, hepatocyte-specific deletion of Slug inhibited the hepatic lipogenic program and protected against obesity-associated NAFLD, insulin resistance, and glucose intolerance in mice. Conversely, liver-restricted overexpression of Slug, but not the Lsd1 binding-defective Slug mutant, had the opposite effects. These results unveil an insulin/Slug/Lsd1/H3K9 demethylation lipogenic pathway that promotes NAFLD and type 2 diabetes.

A Cdh1-FoxM1-Apc axis controls muscle development and regeneration.

Forkhead box M1 (FoxM1) transcriptional factor has a principal role in regulating cell proliferation, self-renewal, and tumorigenesis. However, whether FoxM1 regulates endogenous muscle development and regeneration remains unclear. Here we found that loss of FoxM1 in muscle satellite cells (SCs) resulted in muscle atrophy and defective muscle regeneration. FoxM1 functioned as a direct transcription activator of adenomatous polyposis coli (Apc), preventing hyperactivation of wnt/ß-catenin signaling during muscle regeneration. FoxM1 overexpression in SCs promoted myogenesis but impaired muscle regeneration as a result of spontaneous activation and exhaustion of SCs by transcriptional regulation of Cyclin B1 (Ccnb1). The E3 ubiquitin ligase Cdh1 (also termed Fzr1) was required for FoxM1 ubiquitylation and subsequent degradation. Loss of Cdh1 promoted quiescent SCs to enter into the cell cycle and the SC pool was depleted by serial muscle injuries. Haploinsufficiency of FoxM1 ameliorated muscle regeneration of Cdh1 knock-out mice. These data demonstrate that the Cdh1-FoxM1-Apc axis functions as a key regulator of muscle development and regeneration.

Inhibition of Slug effectively targets leukemia stem cells via the Slc13a3/ROS signaling pathway.

Leukemia stem cells (LSCs) are the rare populations of acute myeloid leukemia (AML) cells that are able to initiate, maintain, and propagate AML. Targeting LSCs is a promising approach for preventing AML relapse and improving long-term outcomes. While Slug, a zinc-finger transcription repressor, negatively regulates the self-renewal of normal hematopoietic stem cells, its functions in AML are still unknown. We report here that Slug promotes leukemogenesis and its loss impairs LSC self-renewal and delays leukemia progression. Mechanistically, Slc13a3, a direct target of Slug in LSCs, restricts the self-renewal of LSCs and markedly prolongs recipient survival. Genetic or pharmacological inhibition of SLUG or forced expression of Slc13a3 suppresses the growth of human AML cells. In conclusion, our studies demonstrate that Slug differentially regulates self-renewal of LSCs and normal HSCs, and both Slug and Slc13a3 are potential therapeutic targets of LSCs.

The transcription factor Slug represses p16Ink4a and regulates murine muscle stem cell aging.

Activation of the p16Ink4a-associated senescence pathway during aging breaks muscle homeostasis and causes degenerative muscle disease by irreversibly dampening satellite cell (SC) self-renewal capacity. Here, we report that the zinc-finger transcription factor Slug is highly expressed in quiescent SCs of mice and functions as a direct transcriptional repressor of p16Ink4a. Loss of Slug promotes derepression of p16Ink4a in SCs and accelerates the entry of SCs into a fully senescent state upon damage-induced stress. p16Ink4a depletion partially rescues defects in Slug-deficient SCs. Furthermore, reduced Slug expression is accompanied by p16Ink4a accumulation in aged SCs. Slug overexpression ameliorates aged muscle regeneration by enhancing SC self-renewal through active repression of p16Ink4a transcription. Our results identify a cell-autonomous mechanism underlying functional defects of SCs at advanced age. As p16Ink4a dysregulation is the chief cause for regenerative defects of human geriatric SCs, these findings highlight Slug as a potential therapeutic target for aging-associated degenerative muscle disease.

Application of TALE-Based Approach for Dissecting Functional MicroRNA-302/367 in Cellular Reprogramming.

MicroRNAs are small 18-24 nt single-stranded noncoding RNA molecules involved in many biological processes, including stemness maintenance and cellular reprogramming. Current methods used in loss-of-function studies of microRNAs have several limitations. Here, we describe a new approach for dissecting miR-302/367 functions by transcription activator-like effectors (TALEs), which are natural effector proteins secreted by Xanthomonas and Ralstonia bacteria. Knockdown of the miR-302/367 cluster uses the Kruppel-associated box repressor domain fused with specific TALEs designed to bind the miR-302/367 cluster promoter. Knockout of the miR-302/367 cluster uses two pairs of TALE nucleases (TALENs) to delete the miR-302/367 cluster in human primary cells. Together, both TALE-based transcriptional repressor and TALENs are two promising approaches for loss-of-function studies of microRNA cluster in human primary cells.

CRISPR/Cas9-Mediated Genome Editing Corrects Dystrophin Mutation in Skeletal Muscle Stem Cells in a Mouse Model of Muscle Dystrophy.

Muscle stem cells (MuSCs) hold great therapeutic potential for muscle genetic disorders, such as Duchenne muscular dystrophy (DMD). The CRISP/Cas9-based genome editing is a promising technology for correcting genetic alterations in mutant genes. In this study, we used fibrin-gel culture system to selectively expand MuSCs from crude skeletal muscle cells of mdx mice, a mouse model of DMD. By CRISP/Cas9-based genome editing, we corrected the dystrophin mutation in expanded MuSCs and restored the skeletal muscle dystrophin expression upon transplantation in mdx mice. Our studies established a reliable and feasible platform for gene correction in MuSCs by genome editing, thus greatly advancing tissue stem cell-based therapies for DMD and other muscle disorders.

Selective Expansion of Skeletal Muscle Stem Cells from Bulk Muscle Cells in Soft Three-Dimensional Fibrin Gel.

Muscle stem cells (MuSCs) exhibit robust myogenic potential in vivo, thus providing a promising curative treatment for muscle disorders. Ex vivo expansion of adult MuSCs is highly desired to achieve a therapeutic cell dose because of their scarcity in limited muscle biopsies. Sorting of pure MuSCs is generally required for all the current culture systems. Here we developed a soft three-dimensional (3D) salmon fibrin gel culture system that can selectively expand mouse MuSCs from bulk skeletal muscle preparations without cell sorting and faithfully maintain their regenerative capacity in culture. Our study established a novel platform for convenient ex vivo expansion of MuSCs, thus greatly advancing stem cell-based therapies for various muscle disorders. Stem Cells Translational Medicine 2017;6:1412-1423.

Zfp281 Coordinates Opposing Functions of Tet1 and Tet2 in Pluripotent States.

Pluripotency is increasingly recognized as a spectrum of cell states defined by their growth conditions. Although naive and primed pluripotency states have been characterized molecularly, our understanding of events regulating state acquisition is wanting. Here, we performed comparative RNA sequencing of mouse embryonic stem cells (ESCs) and defined a pluripotent cell fate (PCF) gene signature associated with acquisition of naive and primed pluripotency. We identify Zfp281 as a key transcriptional regulator for primed pluripotency that also functions as a barrier toward achieving naive pluripotency in both mouse and human ESCs. Mechanistically, Zfp281 interacts with Tet1, but not Tet2, and its direct transcriptional target, miR-302/367, to negatively regulate Tet2 expression to establish and maintain primed pluripotency. Conversely, ectopic Tet2 alone, but not Tet1, efficiently reprograms primed cells toward naive pluripotency. Our study reveals a molecular circuitry in which opposing functions of Tet1 and Tet2 control acquisition of alternative pluripotent states.

SLUG is a direct transcriptional repressor of PTEN tumor suppressor.

BACKGROUND: PTEN/AKT signaling plays a key role in prostate cancer development and maintenance of prostate cancer stem cells. How other oncogenes or tumor suppressors interact with this pathway remain to be elucidated. SLUG is an zinc finger transcription factor of the Snail superfamily, and it promotes cancer metastasis and determines the mammary stem cell state. METHODS: SLUG was overexpressed in cells by retroviral vector and knockdown of SLUG and PTEN was mediated by shRNAs-expressing lentiviruses. Expression level of SLUG and PTEN was examined by Western blot, RT-PCR, and qPCR analyses. PTEN promoter activity was measured by luciferase reporter assay. ChIP assay was used to measure the binding between SLUG and the PTEN promoter in vivo. RESULT: We showed that overexpression of SLUG decreased expression of PTEN tumor repressor in prostate cancer cell lines 22RV1 and DU145; conversely, knockdown of SLUG expression elevated PTEN expresson at both protein and RNA level in these cells. We demonstrated that SLUG overexpression inhibits PTEN promoter activity through the proximal promoter region in prostate cancer cells. By ChIP assay, we confirmed that SLUG directly binds to the PTEN promoter region covering the E-box sites. We also showed that Slug deficiency leads to an increased expression of PTEN in mouse embryo fibroblasts and prostate tissues. Importantly, we found that overexpression of SLUG increases drug resistance of DU145 prostate cancer cell line and knockdown of SLUG by shRNA sensitizes DU145 cell line to chemotherapeutic drugs. We further demonstrated that PTEN knockdown converts drug sensitivity of DU145 cells expressing SLUG shRNA to anticancer drugs. CONCLUSION: We provide compelling evidence showing that PTEN is a direct functional target of SLUG. Our findings offer new insight in the regulation of the PTEN/AKT pathway and provide a molecular basis for potential targeted therapies of prostate cancer Prostate 75:907-916, 2015. © 2015 Wiley Periodicals, Inc.

MicroRNA-302/367 cluster governs hESC self-renewal by dually regulating cell cycle and apoptosis pathways.

miR-302/367 is the most abundant miRNA cluster in human embryonic stem cells (hESCs) and can promote somatic cell reprogramming. However, its role in hESCs remains poorly understood. Here, we studied functional roles of the endogenous miR-302/367 cluster in hESCs by employing specific TALE-based transcriptional repressors. We revealed that miR-302/367 cluster dually regulates hESC cell cycle and apoptosis in dose-dependent manner. Gene profiling and functional studies identified key targets of the miR-302/367 cluster in regulating hESC self-renewal and apoptosis. We demonstrate that in addition to its role in cell cycle regulation, miR-302/367 cluster conquers apoptosis by downregulating BNIP3L/Nix (a BH3-only proapoptotic factor) and upregulating BCL-xL expression. Furthermore, we show that butyrate, a natural compound, upregulates miR-302/367 cluster expression and alleviates hESCs from apoptosis induced by knockdown of miR-302/367 cluster. In summary, our findings provide new insights in molecular mechanisms of how miR-302/367 cluster regulates hESCs.

A multicolor panel of TALE-KRAB based transcriptional repressor vectors enabling knockdown of multiple gene targets.

Stable and efficient knockdown of multiple gene targets is highly desirable for dissection of molecular pathways. Because it allows sequence-specific DNA binding, transcription activator-like effector (TALE) offers a new genetic perturbation technique that allows for gene-specific repression. Here, we constructed a multicolor lentiviral TALE-Kruppel-associated box (KRAB) expression vector platform that enables knockdown of multiple gene targets. This platform is fully compatible with the Golden Gate TALEN and TAL Effector Kit 2.0, a widely used and efficient method for TALE assembly. We showed that this multicolor TALE-KRAB vector system when combined together with bone marrow transplantation could quickly knock down c-kit and PU.1 genes in hematopoietic stem and progenitor cells of recipient mice. Furthermore, our data demonstrated that this platform simultaneously knocked down both c-Kit and PU.1 genes in the same primary cell populations. Together, our results suggest that this multicolor TALE-KRAB vector platform is a promising and versatile tool for knockdown of multiple gene targets and could greatly facilitate dissection of molecular pathways.

Sodium butyrate facilitates reprogramming by derepressing OCT4 transactivity at the promoter of embryonic stem cell-specific miR-302/367 cluster.

Small-molecule inhibitors and microRNAs (miRNAs) are two newly emerging classes of tools for optimizing induced pluripotent stem cell (iPSC) generation. We report here that sodium butyrate (NaB), a small-molecule inhibitor of histone deacetylases (HDACs), upregulates transcriptional levels of the miR-302/367 cluster by enhancing Oct4 transcriptional activity at the miR-302/367 cluster promoter. NaB does not affect the OCT4 DNA-binding domain; instead it enhances transactivity of the OCT4 transactivation domains. We elucidate that OCT4 transcriptional activity is usually dampened by its associated HDACs in cells and can be derepressed by NaB by impairing the interaction between Oct4 and HDACs, which leads to an elevated expression of the miR-302/367 cluster. Our new findings suggest a novel molecular mechanism for NaB in promoting somatic cell reprogramming via the miR-302/367 cluster.

Dissecting the roles of miR-302/367 cluster in cellular reprogramming using TALE-based repressor and TALEN.

MicroRNAs are important gene regulators involved in many biological processes, including stemness maintenance and cellular reprogramming. Current methods used in loss-of-function studies of microRNAs mainly include locked nucleic acid (LNA) oligonucleotides and miRZip inhibitors, which have several limitations. Due to their unique gene structures and small sizes, there is no efficient or simple strategy to knock down or knock out microRNAs or whole microRNA clusters. Here, we demonstrate knockdown of the miR-302/367 cluster by using the Kruppel-associated box repressor domain fused with specific transcription activator-like effectors (TALEs) designed to bind the miR-302/367 cluster promoter. We also designed two pairs of TALE nucleases (TALENs) to efficiently delete the miR-302/367 cluster in primary human fibroblasts and determined that knockout of the miR-302/367 cluster completely blocked induced pluripotent stem cell (iPSC) generation. Together, our results demonstrate that TALE-based transcriptional repressor and TALENs are two promising approaches for loss-of-function studies of microRNA clusters in somatic cells and pluripotent stem cells.

MYBL2 is a sub-haploinsufficient tumor suppressor gene in myeloid malignancy.

A common deleted region (CDR) in both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) affects the long arm of chromosome 20 and has been predicted to harbor a tumor suppressor gene. Here we show that MYBL2, a gene within the 20q CDR, is expressed at sharply reduced levels in CD34+ cells from most MDS cases (65%; n = 26), whether or not they harbor 20q abnormalities. In a murine competitive reconstitution model, Mybl2 knockdown by RNAi to 20-30% of normal levels in multipotent hematopoietic progenitors resulted in clonal dominance of these 'sub-haploinsufficient' cells, which was reflected in all blood cell lineages. By 6 months post-transplantation, the reconstituted mice had developed a clonal myeloproliferative/myelodysplastic disorder originating from the cells with aberrantly reduced Mybl2 expression. We conclude that downregulation of MYBL2 activity below levels predicted by classical haploinsufficiency underlies the clonal expansion of hematopoietic progenitors in a large fraction of human myeloid malignancies. DOI:http://dx.doi.org/10.7554/eLife.00825.001.

Sodium butyrate promotes generation of human induced pluripotent stem cells through induction of the miR302/367 cluster.

Small molecules (SM) can greatly enhance the efficiency of induced pluripotent stem (iPS) cell generation, but the mechanisms by which they act have not been fully explored. We show here that an SM cocktail (NaB, PD03259, and SB431542) significantly promotes iPS cell generation from human fibroblasts, and NaB is more potent than the other two common histone deacetylase inhibitors (valproic acid and Trichostatin A) in promoting cellular reprogramming. Our data indicate that the SM cocktail substantially upregulates the miR302/367 cluster expression by increasing the stability and transcriptional level of this microRNA (miRNA) cluster in a manner dependent on the four defined transcription factors (TFs). Among the four TFs, Oct4 in particular appears to be required for the induction of the miR302/367 cluster by the SM cocktail. We also found that NaB alone can enhance the TFs-dependent upregulation of the miR302/367 cluster. Using a promoter reporter assay, we show that the SM cocktail remarkably enhanced the transcriptional activity of the four TFs in the miR302/367 promoter. Notably, attenuation of miRNA302/367 using a miRZip impairs the ability of the SM cocktail in promoting reprogramming. Collectively, these findings suggest that the SM cocktail promotes reprogramming at least partly through the induction of the miR302/367 cluster expression. Further insights into this process may pave the way for the generation of iPS cells using only SM cocktails.