A multifunctional locus controls motor neuron differentiation through short and long noncoding RNAs.

The transition from dividing progenitors to postmitotic motor neurons (MNs) is orchestrated by a series of events, which are mainly studied at the transcriptional level by analyzing the activity of specific programming transcription factors. Here, we identify a post-transcriptional role of a MN-specific transcriptional unit (MN2) harboring a lncRNA (lncMN2-203) and two miRNAs (miR-325-3p and miR-384-5p) in this transition. Through the use of in vitro mESC differentiation and single-cell sequencing of CRISPR/Cas9 mutants, we demonstrate that lncMN2-203 affects MN differentiation by sponging miR-466i-5p and upregulating its targets, including several factors involved in neuronal differentiation and function. In parallel, miR-325-3p and miR-384-5p, co-transcribed with lncMN2-203, act by repressing proliferation-related factors. These findings indicate the functional relevance of the MN2 locus and exemplify additional layers of specificity regulation in MN differentiation.

Divergent roles for STAT4 in shaping differentiation of cytotoxic ILC1 and NK cells during gut inflammation.

Natural killer (NK) cells and type 1 innate lymphoid cells (ILC1) require signal transducer and activator of transcription 4 (STAT4) to elicit rapid effector responses and protect against pathogens. By combining genetic and transcriptomic approaches, we uncovered divergent roles for STAT4 in regulating effector differentiation of these functionally related cell types. Stat4 deletion in Ncr1-expressing cells led to impaired NK cell terminal differentiation as well as to an unexpected increased generation of cytotoxic ILC1 during intestinal inflammation. Mechanistically, Stat4-deficient ILC1 exhibited upregulation of gene modules regulated by STAT5 in vivo and an aberrant effector differentiation upon in vitro stimulation with IL-2, used as a prototypical STAT5 activator. Moreover, STAT4 expression in NCR+ innate lymphocytes restrained gut inflammation in the dextran sulfate sodium-induced colitis model limiting pathogenic production of IL-13 from adaptive CD4+ T cells in the large intestine. Collectively, our data shed light on shared and distinctive mechanisms of STAT4-regulated transcriptional control in NK cells and ILC1 required for intestinal inflammatory responses.

Cereblon regulates NK cell cytotoxicity and migration via Rac1 activation.

Rearrangement of the actin cytoskeleton is critical for cytotoxic and immunoregulatory functions as well as migration of natural killer (NK) cells. However, dynamic reorganization of actin is a complex process, which remains largely unknown. Here, we investigated the role of the protein Cereblon (CRBN), an E3 ubiquitin ligase complex co-receptor and the primary target of the immunomodulatory drugs, in NK cells. We observed that CRBN partially colocalizes with F-actin in chemokine-treated NK cells and is recruited to the immunological synapse, thus suggesting a role for this protein in cytoskeleton reorganization. Accordingly, silencing of CRBN in NK cells results in a reduced cytotoxicity that correlates with a defect in conjugate and lytic synapse formation. Moreover, CRBN depletion significantly impairs the ability of NK cells to migrate and reduces the enhancing effect of lenalidomide on NK cell migration. Finally, we provided evidence that CRBN is required for activation of the small GTPase Rac1, a critical mediator of cytoskeleton dynamics. Indeed, in CRBN-depleted NK cells, chemokine-mediated or target cell-mediated Rac1 activation is significantly reduced. Altogether our data identify a critical role for CRBN in regulating NK cell functions and suggest that this protein may mediate the stimulatory effect of lenalidomide on NK cells.

Granzyme A and CD160 expression delineates ILC1 with graded functions in the mouse liver.

Type 1 innate lymphoid cells (ILC1) are tissue-resident lymphocytes that provide early protection against bacterial and viral infections. Discrete transcriptional states of ILC1 have been identified in homeostatic and pathological contexts. However, whether these states delineate ILC1 with different functional properties is not completely understood. Here, we show that liver ILC1 are heterogeneous for the expression of distinct effector molecules and surface receptors, including granzyme A (GzmA) and CD160, in mice. ILC1 expressing high levels of GzmA are enriched in the liver of adult mice, and represent the main hepatic ILC1 population at birth. However, the heterogeneity of GzmA and CD160 expression in hepatic ILC1 begins perinatally and increases with age. GzmA+ ILC1 differ from NK cells for the limited homeostatic requirements of JAK/STAT signals and the transcription factor Nfil3. Moreover, by employing Rorc(γt)-fate map (fm) reporter mice, we established that ILC3-ILC1 plasticity contributes to delineate the heterogeneity of liver ILC1, with RORγt-fm+ cells skewed toward a GzmA- CD160+ phenotype. Finally, we showed that ILC1 defined by the expression of GzmA and CD160 are characterized by graded cytotoxic potential and ability to produce IFN-γ. In conclusion, our findings help deconvoluting ILC1 heterogeneity and provide evidence for functional diversification of liver ILC1.

Identification and in vitro characterization of a new series of potent and highly selective G9a inhibitors as novel anti-fibroadipogenic agents.

A new series of in vitro potent and highly selective histone methyl transferase enzyme G9a inhibitors was obtained. In particular, compound 2a, one the most potent G9a inhibitor identified, was endowed with >130-fold selectivity over GLP and excellent ligand efficiency. Therefore, it may represent a valuable tool compound to validate the role of highly selective G9a inhibitors in different pathological conditions. When 2a was characterized in vitro in cellular models of skeletal muscle differentiation, a relevant increase of myofibers' size and reduction of the fibroadipogenic infiltration were observed, further confirming the therapeutic potential of selective G9a inhibitors for the treatment of Duchenne muscle dystrophy.

OMIP-079: Cell cycle of CD4+ and CD8+ naïve/memory T cell subsets, and of Treg cells from mouse spleen.

A multicolor flow cytometry panel was designed and optimized to define the following nine mouse T cell subsets: Treg (CD3+ CD4+ CD8- FoxP3+ ), CD4+ T naïve (CD3+ CD4+ CD8- FoxP3- CD44int/low CD62L+ ), CD4+ T central memory (CD3+ CD4+ CD8- FoxP3- CD44high CD62L+ ), CD4+ T effector memory (CD3+ CD4+ CD8- FoxP3- CD44high CD62L- ), CD4+ T EMRA (CD3+ CD4+ CD8- FoxP3- CD44int/low CD62L- ), CD8+ T naïve (CD3+ CD8+ CD4- CD44int/low CD62L+ ), CD8+ T central memory (CD3+ CD8+ CD4- CD44high CD62L+ ), CD8+ T effector memory (CD3+ CD8+ CD4- CD44high CD62L- ), and CD8+ T EMRA (CD3+ CD8+ CD4- CD44int/low CD62L- ). In each T cell subset, a dual staining for Ki-67 expression and DNA content was employed to distinguish the following cell cycle phases: G0 (Ki67- , with 2n DNA), G1 (Ki67+ , with 2n DNA), and S-G2 /M (Ki67+ , with 2n < DNA ≤ 4n). This panel was established for the analysis of mouse (C57BL/6J) spleen.

Design and Synthesis of Piperazine-Based Compounds Conjugated to Humanized Ferritin as Delivery System of siRNA in Cancer Cells.

Gene expression regulation by small interfering RNA (siRNA) holds promise in treating a wide range of diseases through selective gene silencing. However, successful clinical application of nucleic acid-based therapy requires novel delivery options. Herein, to achieve efficient delivery of negatively charged siRNA duplexes, the internal cavity of "humanized" chimeric Archaeal ferritin (HumAfFt) was specifically decorated with novel cationic piperazine-based compounds (PAs). By coupling these rigid-rod-like amines with thiol-reactive reagents, chemoselective conjugation was efficiently afforded on topologically selected cysteine residues properly located inside HumAfFt. The capability of PAs-HumAfFt to host and deliver siRNA molecules through human transferrin receptor (TfR1), overexpressed in many cancer cells, was explored. These systems allowed siRNA delivery into HeLa, HepG2, and MCF-7 cancer cells with improved silencing effect on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression with respect to traditional transfection methodologies and provided a promising TfR1-targeting system for multifunctional siRNA delivery to therapeutic applications.

Genetically driven CD39 expression shapes human tumor-infiltrating CD8+ T-cell functions.

In our study, we investigated the role of CD39 on tumor-infiltrating CD8+ T lymphocytes (CD8+ TILs) in colorectal, head and neck and pancreatic cancers. Partially confirming recent observations correlating the CD39 expression with T-cell exhaustion, we demonstrated a divergent functional activity in CD39+ CD8+ TILs. On the one hand, CD39+ CD8+ TILs (as compared to their CD39- counterparts) produced significantly lower IFN-γ and IL-2 amounts, expressed higher PD-1, and inversely correlated with perforin and granzyme B expression. On the other, they displayed a significantly higher proliferative capacity ex vivo that was inversely correlated with the PD-1 expression. Therefore, CD39+ CD8+ TILs, including those co-expressing the CD103 (a marker of T resident memory [TRM] cells), were defined as partially dysfunctional T cells that correlate with tumor patients with initial progression stages. Interestingly, our results identified for the first time a single nucleotide polymorphism (SNP rs10748643 A>G), as a genetic factor associated with CD39 expression in CD8+ TILs. Finally, we demonstrated that compounds inhibiting CD39-related ATPases improved CD39+ CD8+ T-cell effector function ex vivo, and that CD39+ CD8+ TILs displayed effective suppression function in vitro. Overall these data suggest that the SNP analysis may represent a suitable predictor of CD39+ CD8+ T-cell expression in cancer patients, and propose the modulation of CD39 as a new strategy to restore partially exhausted CD8+ TILs.

Discovery of a pyrimidine compound endowed with antitumor activity.

Recently, some synthetic nitrogen-based heterocyclic molecules, such as PJ34, have shown pronounced antitumor activity. Therefore, we designed and synthesized new derivatives characterized by a nitrogen-containing scaffold and evaluated their antiproliferative properties in tumor cells. We herein report the effects of three newly synthesized compounds on cell lines from three different human cancers: triple-negative breast cancer, colon carcinoma and glioblastoma. We found that two of these compounds did not affect proliferation, while the third significantly inhibited replication of the three cell lines. Moreover, this third molecule at 20 µM led to the upregulation of p21 and p27 and blockage of the cell cycle at G0/G1; in addition, it induced apoptosis in all three cell lines when used at higher concentrations (30-50 µM). The results demonstrate that this compound is a potent inhibitor of replication, an inducer of apoptosis and a negative regulator of cell cycle progression for cancer cells of different histotypes. Our data suggest a potential role for this new molecule as an interesting and powerful tool for new approaches in treating various cancers.

An optimized retinoic acid-inducible gene I agonist M8 induces immunogenic cell death markers in human cancer cells and dendritic cell activation.

RIG-I is a cytosolic RNA sensor that recognizes short 5' triphosphate RNA, commonly generated during virus infection. Upon activation, RIG-I initiates antiviral immunity, and in some circumstances, induces cell death. Because of this dual capacity, RIG-I has emerged as a promising target for cancer immunotherapy. Previously, a sequence-optimized RIG-I agonist (termed M8) was generated and shown to stimulate a robust immune response capable of blocking viral infection and to function as an adjuvant in vaccination strategies. Here, we investigated the potential of M8 as an anti-cancer agent by analyzing its ability to induce cell death and activate the immune response. In multiple cancer cell lines, M8 treatment strongly activated caspase 3-dependent apoptosis, that relied on an intrinsic NOXA and PUMA-driven pathway that was dependent on IFN-I signaling. Additionally, cell death induced by M8 was characterized by the expression of markers of immunogenic cell death-related damage-associated molecular patterns (ICD-DAMP)-calreticulin, HMGB1 and ATP-and high levels of ICD-related cytokines CXCL10, IFNß, CCL2 and CXCL1. Moreover, M8 increased the levels of HLA-ABC expression on the tumor cell surface, as well as up-regulation of genes involved in antigen processing and presentation. M8 induction of the RIG-I pathway in cancer cells favored dendritic cell phagocytosis and induction of co-stimulatory molecules CD80 and CD86, together with increased expression of IL12 and CXCL10. Altogether, these results highlight the potential of M8 in cancer immunotherapy, with the capacity to induce ICD-DAMP on tumor cells and activate immunostimulatory signals that synergize with current therapies.

Reversible Cavitation-Induced Junctional Opening in an Artificial Endothelial Layer.

Targeting pharmaceuticals through the endothelial barrier is crucial for drug delivery. In this context, cavitation-assisted permeation shows promise for effective and reversible opening of intercellular junctions. A vessel-on-a-chip is exploited to investigate and quantify the effect of ultrasound-excited microbubbles-stable cavitation-on endothelial integrity. In the vessel-on-a-chip, the endothelial cells form a complete lumen under physiological shear stress, resulting in intercellular junctions that exhibit barrier functionality. Immunofluorescence microscopy is exploited to monitor vascular integrity following vascular endothelial cadherin staining. It is shown that microbubbles amplify the ultrasound effect, leading to the formation of interendothelial gaps that cause barrier permeabilization. The total gap area significantly increases with pressure amplitude compared to the control. Gap opening is fully reversible with gap area distribution returning to the control levels 45 min after insonication. The proposed integrated platform allows for precise and repeatable in vitro measurements of cavitation-enhanced endothelium permeability and shows potential for validating irradiation protocols for in vivo applications.

Counter-regulation of regulatory T cells by autoreactive CD8+ T cells in rheumatoid arthritis.

The mechanisms whereby autoreactive T cells escape peripheral tolerance establishing thus autoimmune diseases in humans remain an unresolved question. Here, we demonstrate that autoreactive polyfunctional CD8+ T cells recognizing self-antigens (i.e., vimentin, actin cytoplasmic 1, or non-muscle myosin heavy chain 9 epitopes) with high avidity, counter-regulate Tregs by killing them, in a consistent percentage of rheumatoid arthritis (RA) patients. Indeed, these CD8+ T cells express a phenotype and gene profile of effector (eff) cells and, upon antigen-specific activation, kill Tregs indirectly in an NKG2D-dependent bystander fashion in vitro. This data provides a mechanistic basis for the finding showing that AE-specific (CD107a+) CD8+ T killer cells correlate, directly with the disease activity score, and inversely with the percentage of activated Tregs, in both steady state and follow-up studies in vivo. In addition, multiplex immunofluorescence imaging analyses of inflamed synovial tissues in vivo show that a remarkable number of CD8+ T cells express granzyme-B and selectively contact FOXP3+ Tregs, some of which are in an apoptotic state, validating hence the possibility that CD8+ Teff cells can counteract neighboring Tregs within inflamed tissues, by killing them. Alternatively, the disease activity score of a different subset of patients is correlated with the expansion of a peculiar subpopulation of autoreactive low avidity, partially-activated (pa)CD8+ T cells that, despite they conserve the conventional naïve (N) phenotype, produce high levels of tumor necrosis factor (TNF)-α and exhibit a gene expression signature of a progressive activation state. Tregs directly correlate with the expansion of this autoreactive (low avidity) paCD8+ TN cell subset in vivo, and efficiently control their differentiation rather their proliferation in vitro. Interestingly, autoreactive high avidity CD8+ Teff cells or low avidity paCD8+ TN cells are significantly expanded in RA patients who would become non-responders or patients who would become responders to TNF-α inhibitor therapy, respectively. These data provide evidence of a previously undescribed role of such mechanisms in the progression and therapy of RA.

Natural killer cell activity and dysfunction in Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) encompasses disorders with abnormal function of lysosomes and lysosome-related organelles, and some patients who develop immunodeficiency. The basic mechanisms contributing to immune dysfunction in HPS are ill-defined. We analysed natural killer (NK) cells from patients diagnosed with HPS-1, HPS-2, HPS-4, and an unreported HPS subtype. NK cells from an HPS-2 and an unreported HPS subtype share a similar cellular phenotype with defective granule release and cytotoxicity, but differ in cytokine exocytosis. Defining NK cell activity in several types of HPS provides insights into cellular defects of the disorder and understanding of mechanisms contributing to HPS pathogenesis.

Manipulation of lipoplex concentration at the cell surface boosts transfection efficiency in hard-to-transfect cells.

To date, efficiency upon non-viral DNA delivery remains low and this implies the existence of unidentified transfection barriers. Here we explore the mechanisms of action of multicomponent (MC) cationic liposome/DNA complexes (lipoplexes) by a combination of reporter technologies, dynamic light scattering (DLS), synchrotron small angle X-ray scattering (SAXS), fluorescence activated cell sorting (FACS) analysis and laser scanning confocal microscopy (LSCM) in live cells. Lipofectamine - the gold standard among transfection reagents - was used as a reference. On the basis of our results, we suggest that an additional transfection barrier impairs transfection efficiency, that is: low lipoplex concentration at the cell surface. Based on the acquired knowledge we propose an optimized transfection protocol that allowed us to efficiently transfect DND41, JURKAT, MOLT3, P12-ICHIKAWA, ALL-SILL, TALL-1 human T-cell acute lymphoblastic leukemia (T-ALL) cell lines known to be difficult-to-transfect by using non-viral vectors and where LFN-based technologies fail to give satisfactory results.

Chediak-Higashi syndrome: Lysosomal trafficking regulator domains regulate exocytosis of lytic granules but not cytokine secretion by natural killer cells.

BACKGROUND: Mutations in lysosomal trafficking regulator (LYST) cause Chediak-Higashi syndrome (CHS), a rare immunodeficiency with impaired cytotoxic lymphocyte function, mainly that of natural killer (NK) cells. Our understanding of NK cell function deficiency in patients with CHS and how LYST regulates lytic granule exocytosis is very limited. OBJECTIVE: We sought to delineate cellular defects associated with LYST mutations responsible for the impaired NK cell function seen in patients with CHS. METHODS: We analyzed NK cells from patients with CHS with missense mutations in the LYST ARM/HEAT (armadillo/huntingtin, elongation factor 3, protein phosphatase 2A, and the yeast kinase TOR1) or BEACH (beige and Chediak-Higashi) domains. RESULTS: NK cells from patients with CHS displayed severely reduced cytotoxicity. Mutations in the ARM/HEAT domain led to a reduced number of perforin-containing granules, which were significantly increased in size but able to polarize to the immunologic synapse; however, they were unable to properly fuse with the plasma membrane. Mutations in the BEACH domain resulted in formation of normal or slightly enlarged granules that had markedly impaired polarization to the IS but could be exocytosed on reaching the immunologic synapse. Perforin-containing granules in NK cells from patients with CHS did not acquire certain lysosomal markers (lysosome-associated membrane protein 1/2) but were positive for markers of transport vesicles (cation-independent mannose 6-phosphate receptor), late endosomes (Ras-associated binding protein 27a), and, to some extent, early endosomes (early endosome antigen 1), indicating a lack of integrity in the endolysosomal compartments. NK cells from patients with CHS had normal cytokine compartments and cytokine secretion. CONCLUSION: LYST is involved in regulation of multiple aspects of NK cell lytic activity, ranging from governance of lytic granule size to control of their polarization and exocytosis, as well as regulation of endolysosomal compartment identity. LYST functions in the regulated exocytosis but not in the constitutive secretion pathway.

Loss of miR-107, miR-181c and miR-29a-3p Promote Activation of Notch2 Signaling in Pediatric High-Grade Gliomas (pHGGs).

The mechanisms by which microRNAs control pediatric high-grade gliomas (pHGGs) have yet to be fully elucidated. Our studies of patient-derived pHGG tissues and of the pHGG cell line KNS42 revealed down-regulation in these tumors of three microRNAs, specifically miR-107, miR-181c, and miR-29a-3p. This down-regulation increases the proliferation of KNS42 cells by de-repressing expression of the Notch2 receptor (Notch2), a validated target of miR-107 and miR-181c and a putative target of miR-29a-3p. Inhibition (either pharmacologic or genetic) of Notch2 or re-expression of the implicated microRNAs (all three combined but also individually) significantly reduced KNS42 cell proliferation. These findings suggest that Notch2 pathway activation plays a critical role in pHGGs growth and reveal a direct epigenetic mechanism that controls Notch2 expression, which could potentially be targeted by novel forms of therapy for these childhood tumors characterized by high-morbidity and high-mortality.

Reactive oxygen species- and DNA damage response-dependent NK cell activating ligand upregulation occurs at transcriptional levels and requires the transcriptional factor E2F1.

Increasing evidence indicates that cancer cell stress induced by chemotherapeutic agents promote antitumor immune responses and contribute to their full clinical efficacy. In this article, we identify the signaling events underlying chemotherapy-induced NKG2D and DNAM-1 ligand expression on multiple myeloma (MM) cells. Our findings indicate that sublethal doses of doxorubicin and melphalan initiate a DNA damage response (DDR) controlling ligand upregulation on MM cell lines and patient-derived malignant plasma cells in Chk1/2-dependent and p53-independent manner. Drug-induced MICA and PVR gene expression are transcriptionally regulated and involve DDR-dependent E2F1 transcription factor activity. We also describe the involvement of changes in the redox state in the control of DDR-dependent upregulation of ligand surface expression and gene transcriptional activity by using the antioxidant agent N-acetyl-L-cysteine. Finally, in accordance with much evidence indicating that DDR and oxidative stress are major determinants of cellular senescence, we found that redox-dependent DDR activation upon chemotherapeutic treatment is critical for MM cell entry in premature senescence and is required for the preferential ligand upregulation on senescent cells, which are preferentially killed by NK cells and trigger potent IFN-γ production. We propose immunogenic senescence as a mechanism that promotes the clearance of drug-treated tumor cells by innate effector lymphocytes, including NK cells.

LAMP1/CD107a is required for efficient perforin delivery to lytic granules and NK-cell cytotoxicity.

Secretory lysosomes of natural killer (NK) cells, containing perforin and granzymes, are indispensable for NK-cell cytotoxicity because their release results in the induction of target-cell apoptosis. Lysosome-associated membrane protein (LAMP) 1/CD107a is used as a marker for NK-cell degranulation, but its role in NK-cell biology is unknown. We show that LAMP1 silencing causes inhibition of NK-cell cytotoxicity, as LAMP1 RNA interference (RNAi) cells fail to deliver granzyme B to target cells. Reduction of LAMP1 expression affects the movement of lytic granules and results in decreased levels of perforin, but not granzyme B, in the granules. In LAMP1 RNAi cells, more perforin is retained outside of lysosomal compartments in trans-Golgi network-derived transport vesicles. Disruption of expression of LAMP1 binding partner, adaptor protein 1 (AP-1) sorting complex, also causes retention of perforin in the transport vesicles and inhibits cytotoxicity, indicating that the interaction between AP-1 sorting complex and LAMP1 on the surface of the transport vesicles is important for perforin trafficking to lytic granules. We conclude that the decreased level of perforin in lytic granules of LAMP1-deficient cells, combined with disturbed motility of the lytic granules, leads to the inability to deliver apoptosis-inducing granzyme B to target cells and to inhibition of NK-cell cytotoxicity.

Membrane-type 6 matrix metalloproteinase regulates the activation-induced downmodulation of CD16 in human primary NK cells.

CD16 (FcγRIIIa), the low-affinity receptor for IgG, expressed by the majority of human NK cells, is a potent activating receptor that facilitates Ab-dependent cell-mediated cytotoxicity (ADCC). ADCC dysfunction has been linked to cancer progression and poor prognosis for chronic infections, such as HIV; thus, understanding how CD16 expression is regulated by NK cells has clinical relevance. Importantly, CD16 cell-surface expression is downmodulated following NK cell activation and, in particular, exposure to stimulatory cytokines (IL-2 or IL-15), likely owing to the action of matrix metalloproteinases (MMPs). In this article, we identify membrane-type 6 (MT6) MMP (also known as MMP25) as a proteinase responsible for CD16 downmodulation. IL-2-induced upregulation of MT6/MMP25 cell-surface expression correlates with CD16 downmodulation. MT6/MMP25, sequestered in intracellular compartments in unstimulated NK cells, translocates to the cell surface after stimulation; moreover, it polarizes to the effector-target cell interface of the CD16-mediated immunological synapse. siRNA-mediated disruption of MT6/MMP25 expression enhances the ADCC capacity of NK cells, emphasizing the important functional role of MT6/MMP25 in the regulation of ADCC activity. Thus, this study uncovers a previously unknown role of MT6/MMP25 in human NK cells, and suggests that inhibition of MT6/MMP25 activity could improve ADCC efficacy of therapeutically administered NK cells that require IL-2 for culture and expansion.

miRNA-27a-3p is involved in the plasticity of differentiated hepatocytes.

BACKGROUND: Epigenetic mechanisms, including DNA methylation, histone modifications, and chromatin remodeling, are highly involved in the regulation of hepatocyte viability, proliferation, and plasticity. We have previously demonstrated that repression of H3K27 methylation in differentiated hepatic HepaRG cells by treatment with GSK-J4, an inhibitor of JMJD3 and UTX H3K27 demethylase activity, changed their phenotype, inducing differentiated hepatocytes to proliferate. In addition to the epigenetic enzymatic role in the regulation of the retro-differentiation process, emerging evidence indicate that microRNAs (miRNAs) are involved in controlling hepatocyte proliferation during liver regeneration. Hence, the aim of this work is to investigate the impact of H3K27 methylation on miRNAs expression profile and its role in the regulation of the differentiation status of human hepatic progenitors HepaRG cells. METHODS: A miRNA-sequencing was carried out in differentiated HepaRG cells treated or not with GSK-J4. Target searching and Gene Ontology analysis were performed to identify the molecular processes modulated by differentially expressed miRNAs. The biological functions of selected miRNAs was further investigated by transfection of miRNAs inhibitors or mimics in differentiated HepaRG cells followed by qPCR analysis, albumin ELISA assay, CD49a FACS analysis and EdU staining. RESULTS: We identified 12 miRNAs modulated by GSK-J4; among these, miR-27a-3p and miR- 423-5p influenced the expression of several proliferation genes in differentiated HepaRG cells. MiR-27a-3p overexpression increased the number of hepatic cells reentering proliferation. Interestingly, both miR-27a-3p and miR-423-5p did not affect the expression levels of genes involved in the differentiation of progenitors HepaRG cells. CONCLUSIONS: Modulation of H3K27me3 methylation in differentiated HepaRG cells, by GSK-J4 treatment, influenced miRNA' s expression profile pushing liver cells towards a proliferating phenotype. We demonstrated the involvement of miR-27a-3p in reinducing proliferation of differentiated hepatocytes suggesting a potential role in liver plasticity.