Transcriptional coactivation of NRF2 signaling in cardiac fibroblasts promotes resistance to oxidative stress.

We recently discovered that steroid receptor coactivators (SRCs) SRCs-1, 2 and 3, are abundantly expressed in cardiac fibroblasts (CFs) and their activation with the SRC small molecule stimulator MCB-613 improves cardiac function and dramatically lowers pro-fibrotic signaling in CFs post-myocardial infarction. These findings suggest that CF-derived SRC activation could be beneficial in the mitigation of chronic heart failure after ischemic insult. However, the cardioprotective mechanisms by which CFs contribute to cardiac pathological remodeling are unclear. Here we present studies designed to identify the molecular and cellular circuitry that governs the anti-fibrotic effects of an MCB-613 derivative, MCB-613-10-1, in CFs. We performed cytokine profiling and whole transcriptome and proteome analyses of CF-derived signals in response to MCB-613-10-1. We identified the NRF2 pathway as a direct MCB-613-10-1 therapeutic target for promoting resistance to oxidative stress in CFs. We show that MCB-613-10-1 promotes cell survival of anti-fibrotic CFs exposed to oxidative stress by suppressing apoptosis. We demonstrate that an increase in HMOX1 expression contributes to CF resistance to oxidative stress-mediated apoptosis via a mechanism involving SRC co-activation of NRF2, hence reducing inflammation and fibrosis. We provide evidence that MCB-613-10-1 acts as a protectant against oxidative stress-induced mitochondrial damage. Our data reveal that SRC stimulation of the NRF2 transcriptional network promotes resistance to oxidative stress and highlights a mechanistic approach toward addressing pathologic cardiac remodeling.

A GREB1-steroid receptor feedforward mechanism governs differential GREB1 action in endometrial function and endometriosis.

Cellular responses to the steroid hormones, estrogen (E2), and progesterone (P4) are governed by their cognate receptor's transcriptional output. However, the feed-forward mechanisms that shape cell-type-specific transcriptional fulcrums for steroid receptors are unidentified. Herein, we found that a common feed-forward mechanism between GREB1 and steroid receptors regulates the differential effect of GREB1 on steroid hormones in a physiological or pathological context. In physiological (receptive) endometrium, GREB1 controls P4-responses in uterine stroma, affecting endometrial receptivity and decidualization, while not affecting E2-mediated epithelial proliferation. Of mechanism, progesterone-induced GREB1 physically interacts with the progesterone receptor, acting as a cofactor in a positive feedback mechanism to regulate P4-responsive genes. Conversely, in endometrial pathology (endometriosis), E2-induced GREB1 modulates E2-dependent gene expression to promote the growth of endometriotic lesions in mice. This differential action of GREB1 exerted by a common feed-forward mechanism with steroid receptors advances our understanding of mechanisms that underlie cell- and tissue-specific steroid hormone actions.

Correction to: Funding of research & innovation in the field of medical technologies and biomedical engineering over the different European framework programmes.

[This corrects the article DOI: 10.1007/s13534-023-00320-9.].

Funding of research & innovation in the field of medical technologies and biomedical engineering over the different European framework programmes.

To demonstrate the role of the European Framework Programmes for Research & Innovation in supporting the field of Medical Technologies and Biomedical Engineering and to show which types of medical technologies and which funding instruments are the preferred ones. Based on data available in the European Commission data warehouse for the past two Framework Programmes, funded projects addressing a Medical Technology were identified. This enabled to categorize the projects according to the intended use and to classify into different types. Moreover, the main instruments in the Framework Programme acting as funding sources were explored. The increase in R&I support led to 1961 projects and a total financing of € 3.2 bllion under the last Framework Programme. The categorization showed a balanced funding in terms of intended use, the detailed classification revealed that in-vitro-diagnostics and imaging equipment prevail in the diagnostic category, tissue-engineering products, implants and robotics in the therapeutic domain and ICT or software-based technologies in the miscellaneous category. As to funding sources, the classical health-oriented collaborative research scheme was on top, followed by instruments like the European Research Council, the Future and Emerging Technologies activities and the European Innovation Council, and completed by the Public-Private Partnerships. The European Framework Programmes are key on the global landscape for financing Research & Innovation of Medical Technology and the breadth of supported technologies is equally reflected by the different funding instruments involved.

Steroid receptor coactivator 3 is a key modulator of regulatory T cell-mediated tumor evasion.

Steroid receptor coactivator 3 (SRC-3) is most strongly expressed in regulatory T cells (Tregs) and B cells, suggesting that it plays an important role in the regulation of Treg function. Using an aggressive E0771 mouse breast cell line syngeneic immune-intact murine model, we observed that breast tumors were "permanently eradicated" in a genetically engineered tamoxifen-inducible Treg-cell-specific SRC-3 knockout (KO) female mouse that does not possess a systemic autoimmune pathological phenotype. A similar eradication of tumor was noted in a syngeneic model of prostate cancer. A subsequent injection of additional E0771 cancer cells into these mice showed continued resistance to tumor development without the need for tamoxifen induction to produce additional SRC-3 KO Tregs. SRC-3 KO Tregs were highly proliferative and preferentially infiltrated into breast tumors by activating the chemokine (C-C motif) ligand (Ccl) 19/Ccl21/chemokine (C-C motif) receptor (Ccr)7 signaling axis, generating antitumor immunity by enhancing the interferon-γ/C-X-C motif chemokine ligand (Cxcl) 9 signaling axis to facilitate the entrance and function of effector T cells and natural killer cells. SRC-3 KO Tregs also show a dominant effect by blocking the immune suppressive function of WT Tregs. Importantly, a single adoptive transfer of SRC-3 KO Tregs into wild-type E0771 tumor-bearing mice can completely abolish preestablished breast tumors by generating potent antitumor immunity with a durable effect that prevents tumor reoccurrence. Therefore, treatment with SRC-3-deleted Tregs represents an approach to completely block tumor growth and recurrence without the autoimmune side effects that typically accompany immune checkpoint modulators.

Steroid Receptor Coactivator-3 is a Key Modulator of Regulatory T Cell-Mediated Tumor Evasion.

Steroid receptor coactivator 3 (SRC-3) is most strongly expressed in regulatory T cells (Tregs) and B cells, suggesting that it plays an important role in the regulation of Treg function. Using an aggressive E0771 mouse breast cell line syngeneic immune-intact murine model, we observed that breast tumors were 'permanently eradicated' in a genetically engineered tamoxifen-inducible Treg-cell specific SRC-3 knockout (KO) female mouse that does not possess a systemic autoimmune pathological phenotype. A similar eradication of tumor was noted in a syngeneic model of prostate cancer. A subsequent injection of additional E0771 cancer cells into these mice showed continued resistance to tumor development without the need for tamoxifen induction to produce additional SRC-3 KO Tregs. SRC-3 KO Tregs were highly proliferative and preferentially infiltrated into breast tumors by activating the Chemokine (C-C motif) ligand (Ccl) 19/Ccl21/ Chemokine (C-C motif) Receptor (Ccr)7 signaling axis, generating antitumor immunity by enhancing the interferon-γ/C-X-C Motif Chemokine Ligand (Cxcl) 9 signaling axis to facilitate the entrance and function of effector T cells and Natural Killer cells. SRC-3 KO Tregs also show a dominant effect by blocking the immune suppressive function of WT Tregs. Importantly, a single adoptive transfer of SRC-3 KO Tregs into wild-type E0771 tumor-bearing mice can completely abolish pre-established breast tumors by generating potent antitumor immunity with a durable effect that prevents tumor reoccurrence. Therefore, treatment with SRC-3 deleted Tregs represents a novel approach to completely block tumor growth and recurrence without the autoimmune side-effects that typically accompany immune checkpoint modulators. Significance statement: Tregs are essential in restraining immune responses for immune homeostasis. SRC-3 is a pleiotropic coactivator, the second-most highly expressed transcriptional coactivator in Tregs, and a suspect in Treg function. The disruption of SRC-3 expression in Tregs leads to a 'complete lifetime eradication' of tumors in aggressive syngeneic breast cancer mouse models because deletion of SRC-3 alters the expression of a wide range of key genes involved in efferent and afferent Treg signaling. SRC-3KO Tregs confer this long-lasting protection against cancer recurrence in mice without an apparent systemic autoimmune pathological phenotype. Therefore, treatment with SRC-3 deleted Tregs could represent a novel and efficient future target for eliminating tumor growth and recurrence without the autoimmune side-effects that typically accompany immune checkpoint modulators.

SOX7 deficiency causes ventricular septal defects through its effects on endocardial-to-mesenchymal transition and the expression of Wnt4 and Bmp2.

SOX7 is a transcription factor-encoding gene located in a region on chromosome 8p23.1 that is recurrently deleted in individuals with ventricular septal defects (VSDs). We have previously shown that Sox7-/- embryos die of heart failure around E11.5. Here, we demonstrate that these embryos have hypocellular endocardial cushions with severely reduced numbers of mesenchymal cells. Ablation of Sox7 in the endocardium also resulted in hypocellular endocardial cushions, and we observed VSDs in rare E15.5 Sox7flox/-;Tie2-Cre and Sox7flox/flox;Tie2-Cre embryos that survived to E15.5. In atrioventricular explant studies, we showed that SOX7 deficiency leads to a severe reduction in endocardial-to-mesenchymal transition (EndMT). RNA-seq studies performed on E9.5 Sox7-/- heart tubes revealed severely reduced Wnt4 transcript levels. Wnt4 is expressed in the endocardium and promotes EndMT by acting in a paracrine manner to increase the expression of Bmp2 in the myocardium. Both WNT4 and BMP2 have been previously implicated in the development of VSDs in individuals with 46,XX sex reversal with dysgenesis of kidney, adrenals and lungs (SERKAL) syndrome and in individuals with short stature, facial dysmorphism and skeletal anomalies with or without cardiac anomalies 1 (SSFSC1) syndrome, respectively. We now show that Sox7 and Wnt4 interact genetically in the development of VSDs through their additive effects on endocardial cushion development with Sox7+/-;Wnt4+/- double heterozygous embryos having hypocellular endocardial cushions and perimembranous and muscular VSDs not seen in their Sox7+/- and Wnt4+/- littermates. These results provide additional evidence that SOX7, WNT4 and BMP2 function in the same pathway during mammalian septal development and that their deficiency can contribute to the development of VSDs in humans.

Polyploid giant cancer cells and ovarian cancer: new insights into mitotic regulators and polyploidy†.

Current first-line treatment of patients with high-grade serous ovarian cancer (HGSOC) involves the use of cytotoxic drugs that frequently lead to recurrent tumors exhibiting increased resistance to the drugs and poor patient survival. Strong evidence is accumulating to show that HGSOC tumors and cell lines contain a subset of cells called polyploidy giant cancer cells (PGCCs) that act as stem-like, self-renewing cells. These PGCCs appear to play a key role in tumor progression by generating drug-resistant progeny produced, in part, as a consequence of utilizing a modified form of mitosis known as endoreplication. Thus, developing drugs to target PGCCs and endoreplication may be an important approach for reducing the appearance of drug-resistant progeny. In the review, we discuss newly identified regulatory factors that impact mitosis and which may be altered or repurposed during endoreplication in PGCCs. We also review recent papers showing that a single PGCC can give rise to tumors in vivo and spheroids in culture. To illustrate some of the specific features of PGCCs and factors that may impact their function and endoreplication compared to mitosis, we have included immunofluorescent images co-localizing p53 and specific mitotic regulatory, phosphoproteins in xenografts derived from commonly used HGSOC cell lines.

Cell lineage tracing links ERα loss in Erbb2-positive breast cancers to the arising of a highly aggressive breast cancer subtype.

HER2-positive (HER2+) breast cancers (BrCs) contain approximately equal numbers of ERα+HER2+ and ERα-HER2+ cases. An enduring obstacle is the unclear cell lineage-related characteristics of these BrCs. Although ERα+HER2+ BrCs could lose ERα to become ERα-HER2+ BrCs, direct evidence is missing. To investigate ERα dependencies and their implications during BrC growth and metastasis, we generated ERαCreRFP-T mice that produce an RFP-marked ERα+ mammary gland epithelial cell (MGEC) lineage. RCAS virus-mediated expression of Erbb2, a rodent Her2 homolog, first produced comparable numbers of ERα+RFP+Erbb2+ and ERα-RFP-Erbb2+ MGECs. Early hyperplasia developed mostly from ERα+RFP+Erbb2+ cells and ERα-RFP-Erbb2+ cells in these lesions were rare. The subsequently developed ductal carcinomas in situ had 64% slow-proliferating ERα+RFP+Erbb2+ cells, 15% fast-proliferating ERα-RFP+Erbb2+ cells derived from ERα+RFP+Erbb2+ cells, and 20% fast-proliferating ERα-RFP-Erbb2+ cells. The advanced tumors had mostly ERα-RFP+Erbb2+ and ERα-RFP-Erbb2+ cells and only a very small population of ERα+RFP+Erbb2+ cells. In ERα-RFP+Erbb2+ cells, GATA3 and FoxA1 decreased expression and ERα promoter regions became methylated, consistent with the loss of ERα expression. Lung metastases consisted of mostly ERα-RFP+Erbb2+ cells, a few ERα-RFP-Erbb2+ cells, and no ERα+RFP+Erbb2+ cells. The high metastatic capacity of ERα-RFP+Erbb2+ cells was associated with ERK1/2 activation. These results show that the slow-proliferating, nonmetastatic ERα+RFP+Erbb2+ cells progressively lose ERα during tumorigenesis to become fast-proliferating, highly metastatic ERα-RFP+Erbb2+ cells. The ERα-Erbb2+ BrCs with an ERα+ origin are more aggressive than those ERα-Erbb2+ BrCs with an ERα- origin, and thus, they should be distinguished and treated differently in the future.

Constitutive expression of progesterone receptor isoforms promotes the development of hormone-dependent ovarian neoplasms.

Differences in the relative abundances of the progesterone receptor (PGR) isoforms PGRA and PGRB are often observed in women with reproductive tract cancers. To assess the importance of the PGR isoform ratio in the maintenance of the reproductive tract, we generated mice that overexpress PGRA or PGRB in all PGR-positive tissues. Whereas few PGRA-overexpressing mice developed reproductive tract tumors, all PGRB-overexpressing mice developed ovarian neoplasms that were derived from ovarian luteal cells. Transcriptomic analyses of the ovarian tumors from PGRB-overexpressing mice revealed enhanced AKT signaling and a gene expression signature similar to those of human ovarian and endometrial cancers. Treating PGRB-overexpressing mice with the PGR antagonist RU486 stalled tumor growth and decreased the expression of cell cycle-associated genes, indicating that tumor growth and cell proliferation were hormone dependent in addition to being isoform dependent. Analysis of the PGRB cistrome identified binding events at genes encoding proteins that are critical regulators of mitotic phase entry. This work suggests a mechanism whereby an increase in the abundance of PGRB relative to that of PGRA drives neoplasia in vivo by stimulating cell cycling.

The International Prospective Glanzmann Thrombasthenia Registry: Pediatric Treatment and Outcomes.

Background Standard treatment for Glanzmann thrombasthenia (GT), a severe inherited bleeding disorder, is platelet transfusion. Recombinant activated factor VII (rFVIIa) is reported to be effective in GT with platelet antibodies and/or refractoriness to platelet transfusions. Methods We evaluated rFVIIa effectiveness and safety for the treatment and prevention of surgical and nonsurgical bleeding in children <18 years old, with or without platelet antibodies and/or refractoriness, as reported in the GT Registry (GTR). Data were used from the GTR, an international, multicenter, observational, postmarketing study of rFVIIa that prospectively collected data on the treatment and outcomes of bleeds in patients with GT. Only patients with a diagnosis of congenital GT were included in the registry. Results Between 2007 and 2011, 27 children were treated for 44 surgical procedures (minor: 36; major: 8); nonsurgical bleeds occurred in 104 patients (599 episodes: severe, 145; moderate, 454; spontaneous, 423; posttraumatic, 176). The effectiveness of treatment for minor procedures, major procedures, nonsurgical bleeds was 6/6, 1/1, and 75/84 for rFVIIa, 6/6, 2/2, and 64/76 for rFVIIa + antifibrinolytics (AF), 11/12, 1/1, and 162/214 for platelets ± AF, and 5/6, 0/3, and 33/45 for rFVIIa + platelets ± AF. In all, 25 adverse events were reported in children; no thromboembolic events were reported. Conclusion For all patients, regardless of platelet antibody or refractoriness status, rFVIIa, administered with or without platelets (± AF), provided effective hemostasis with a low frequency of adverse events in surgical, as well as nonsurgical, bleeding in patients with GT. clinicaltrials.gov identifier: NCT01476423.

Early growth response 1 transcriptionally primes the human endometrial stromal cell for decidualization.

Mouse studies support a role for endometrial early growth response 1 (EGR1) in uterine receptivity and decidualization, which are processes controlled by estrogen and progesterone. However, the importance of this transcription factor in similar cellular processes in human is unclear. Analysis of clinical samples indicate that endometrial EGR1 levels are decreased in the endometrium of women with recurrent implantation failure, suggesting that tight control of EGR1 levels are necessary for normal endometrial function. Therefore, we used siRNA-mediated knockdown of EGR1 expression in cultured human endometrial stromal cells (hESCs) to assess the functional role of EGR1 in hESC decidualization. Protein expression studies revealed that EGR1 is highly expressed in pre-decidual hESCs. However, EGR1 protein levels rapidly decrease following administration of an established deciduogenic hormone stimulus containing estradiol, medroxyprogesterone acetate, and cyclic adenosine monophosphate. Intriguingly, EGR1 knockdown in pre-decidual hESCs blocks the ability of these cells to decidualize later, indicating that EGR1 is required to transcriptionally program pre-decidual hESCs for decidualization. Support for this proposal comes from the analysis of transcriptome and cistrome datasets, which shows that EGR1 target genes are primarily involved in transcriptional regulation, cell signaling, and proliferation. Collectively, our studies provide translational support for an evolutionary conserved role for human endometrial stromal EGR1 in the early events of pregnancy establishment.

The von Willebrand factor Tyr2561 allele is a gain-of-function variant and a risk factor for early myocardial infarction.

The frequent von Willebrand factor (VWF) variant p.Phe2561Tyr is located within the C4 domain, which also harbors the platelet GPIIb/IIIa-binding RGD sequence. To investigate its potential effect on hemostasis, we genotyped 865 patients with coronary artery disease (CAD), 915 with myocardial infarction (MI), and 417 control patients (Ludwigshafen Risk and Cardiovascular Health Study) and performed functional studies of this variant. A univariate analysis of male and female carriers of the Tyr2561 allele aged 55 years or younger revealed an elevated risk for repeated MI (odds ratio, 2.53; 95% confidence interval [CI], 1.07-5.98). The odds ratio was even higher in females aged 55 years or younger, at a value of 5.93 (95% CI, 1.12-31.24). Cone and plate aggregometry showed that compared with Phe2561, Tyr2561 was associated with increased platelet aggregate size both in probands' blood and with the recombinant variants. Microfluidic assays revealed that the critical shear rate for inducing aggregate formation was decreased to 50% by Tyr2561 compared with Phe2561. Differences in C-domain circular dichroism spectra resulting from Tyr2561 suggest an increased shear sensitivity of VWF as a result of altered association of the C domains that disrupts the normal dimer interface. In summary, our data emphasize the functional effect of the VWF C4 domain for VWF-mediated platelet aggregation in a shear-dependent manner and provide the first evidence that a functional variant of VWF plays a role in arterial thromboembolism.

FOXO1 regulates uterine epithelial integrity and progesterone receptor expression critical for embryo implantation.

Successful embryo implantation requires a receptive endometrium. Poor uterine receptivity can account for implantation failure in women who experience recurrent pregnancy loss or multiple rounds of unsuccessful in vitro fertilization cycles. Here, we demonstrate that the transcription factor Forkhead Box O1 (FOXO1) is a critical regulator of endometrial receptivity in vivo. Uterine ablation of Foxo1 using the progesterone receptor Cre (PgrCre) mouse model resulted in infertility due to altered epithelial cell polarity and apoptosis, preventing the embryo from penetrating the luminal epithelium. Analysis of the uterine transcriptome after Foxo1 ablation identified alterations in gene expression for transcripts involved in the activation of cell invasion, molecular transport, apoptosis, ß-catenin (CTNNB1) signaling pathway, and an increase in PGR signaling. The increase of PGR signaling was due to PGR expression being retained in the uterine epithelium during the window of receptivity. Constitutive expression of epithelial PGR during this receptive period inhibited expression of FOXO1 in the nucleus of the uterine epithelium. The reciprocal expression of PGR and FOXO1 was conserved in human endometrial samples during the proliferative and secretory phase. This demonstrates that expression of FOXO1 and the loss of PGR during the window of receptivity are interrelated and critical for embryo implantation.

Retinoid signaling controlled by SRC-2 in decidualization revealed by transcriptomics

Establishment of a successful pregnancy requires not only implantation of a healthy embryo into a receptive uterus but also progesterone receptor (PGR)-dependent transformation of endometrial stromal cells (ESCs) into specialized decidual cells. Decidual cells support the developing embryo and are critical for placentation. We have previously shown that a known transcriptional coregulator of the PGR, steroid receptor coactivator-2 (SRC-2), is a critical driver of endometrial decidualization in both human and mouse endometrium. However, the full spectrum of genes transcriptionally controlled by SRC-2 in decidualizing ESCs has not been identified. Therefore, using an RNA- and chromatin immunoprecipitation-sequencing approach, we have identified the transcriptome of decidualizing human ESCs (hESCs) that requires SRC-2. We revealed that the majority of hESC genes regulated by SRC-2 are associated with decidualization. Over 50% of SRC-2-regulated genes are also controlled by the PGR. While ontology analysis showed that SRC-2-dependent genes are functionally linked to signaling processes known to underpin hESC decidualization, cell membrane processes were significantly enriched in this analysis. Follow-up studies showed that retinoid signaling is dependent on SRC-2 during hESC decidualization. Specifically, SRC-2 is required for full induction of the retinol transporter, stimulated by retinoic acid 6 (STRA6), which is essential for hESC decidualization. Together our findings show that a critical subset of genes transcriptionally reprogramed by PGR during hESC decidualization requires SRC-2. Among the multiple genes, pathways and networks that are dependent on SRC-2 during hESC decidualization, first-line analysis supports a critical role for this coregulator in maintaining retinoid signaling during progesterone-driven decidualization.

SOX17 regulates uterine epithelial-stromal cross-talk acting via a distal enhancer upstream of Ihh.

Mammalian pregnancy depends on the ability of the uterus to support embryo implantation. Previous studies reveal the Sox17 gene as a downstream target of the Pgr-Gata2-dependent transcription network that directs genomic actions in the uterine endometrium receptive for embryo implantation. Here, we report that ablating Sox17 in the uterine epithelium impairs leukemia inhibitory factor (LIF) and Indian hedgehog homolog (IHH) signaling, leading to failure of embryo implantation. In vivo deletion of the SOX17-binding region 19 kb upstream of the Ihh locus by CRISPR-Cas technology reduces Ihh expression specifically in the uterus and alters proper endometrial epithelial-stromal interactions, thereby impairing pregnancy. This SOX17-binding interval is also bound by GATA2, FOXA2, and PGR. This cluster of transcription factor binding is common in 737 uterine genes and may represent a key regulatory element essential for uterine epithelial gene expression.

Steroid Receptor Coactivator-2 Controls the Pentose Phosphate Pathway through RPIA in Human Endometrial Cancer Cells.

Steroid receptor coactivator-2 (SRC-2) is a transcriptional coregulator that modulates the activity of many transcription factors. Levels of SRC-2 are elevated in endometrial biopsies from polycystic ovary syndrome patients, a population predisposed to endometrial cancer (EC). Increased expression of SRC-2 is also detected in neoplastic endometrium suggesting a causal link between elevated SRC-2 expression and the emergence of endometrial disorders that can lead to cancer. Here, we reveal that SRC-2 knockdown reduces EC cell proliferation and anchorage-independence. Additionally, SRC-2 is required to maintain cellular glycolytic capacity and oxidative phosphorylation, processes essential for EC cell proliferation. Importantly, SRC-2 is critical for the normal performance of the pentose phosphate pathway (PPP). Perturbation of the PPP due to loss of SRC-2 expression may result from the depletion of ribose-5-P isomerase (RPIA), a key enzyme of the PPP. As with SRC-2, RPIA knockdown reduces EC cell proliferation, which is accompanied by a decrease in glycolytic capacity and oxidative phosphorylation. Glucose metabolite tracking experiments confirmed that knockdown of SRC-2 and RPIA downregulates the metabolic rate of both glycolysis and the PPP, highlighting a novel regulatory cross-talk between glycolysis and the PPP modulated by SRC-2.

Maf1 and Repression of RNA Polymerase III-Mediated Transcription Drive Adipocyte Differentiation.

RNA polymerase (pol) III transcribes a variety of small untranslated RNAs involved in transcription, RNA processing, and translation. RNA pol III and its components are altered in various human developmental disorders, yet their roles in cell fate determination and development are poorly understood. Here we demonstrate that Maf1, a transcriptional repressor, promotes induction of mouse embryonic stem cells (mESCs) into mesoderm. Reduced Maf1 expression in mESCs and preadipocytes impairs adipogenesis, while ectopic Maf1 expression in Maf1-deficient cells enhances differentiation. RNA pol III repression by chemical inhibition or knockdown of Brf1 promotes adipogenesis. Altered RNA pol III-dependent transcription produces select changes in mRNAs with a significant enrichment of adipogenic gene signatures. Furthermore, RNA pol III-mediated transcription positively regulates long non-coding RNA H19 and Wnt6 expression, established adipogenesis inhibitors. Together, these studies reveal an important and unexpected function for RNA pol III-mediated transcription and Maf1 in mesoderm induction and adipocyte differentiation.