Systemic Inflammation and Normocytic Anemia in DOCK11 Deficiency.

BACKGROUND: Increasing evidence links genetic defects affecting actin-regulatory proteins to diseases with severe autoimmunity and autoinflammation, yet the underlying molecular mechanisms are poorly understood. Dedicator of cytokinesis 11 (DOCK11) activates the small Rho guanosine triphosphatase (GTPase) cell division cycle 42 (CDC42), a central regulator of actin cytoskeleton dynamics. The role of DOCK11 in human immune-cell function and disease remains unknown. METHODS: We conducted genetic, immunologic, and molecular assays in four patients from four unrelated families who presented with infections, early-onset severe immune dysregulation, normocytic anemia of variable severity associated with anisopoikilocytosis, and developmental delay. Functional assays were performed in patient-derived cells, as well as in mouse and zebrafish models. RESULTS: We identified rare, X-linked germline mutations in DOCK11 in the patients, leading to a loss of protein expression in two patients and impaired CDC42 activation in all four patients. Patient-derived T cells did not form filopodia and showed abnormal migration. In addition, the patient-derived T cells, as well as the T cells from Dock11-knockout mice, showed overt activation and production of proinflammatory cytokines that were associated with an increased degree of nuclear translocation of nuclear factor of activated T cell 1 (NFATc1). Anemia and aberrant erythrocyte morphologic features were recapitulated in a newly generated dock11-knockout zebrafish model, and anemia was amenable to rescue on ectopic expression of constitutively active CDC42. CONCLUSIONS: Germline hemizygous loss-of-function mutations affecting the actin regulator DOCK11 were shown to cause a previously unknown inborn error of hematopoiesis and immunity characterized by severe immune dysregulation and systemic inflammation, recurrent infections, and anemia. (Funded by the European Research Council and others.).

Mediator complex proximal Tail subunit MED30 is critical for Mediator core stability and cardiomyocyte transcriptional network.

Dysregulation of cardiac transcription programs has been identified in patients and families with heart failure, as well as those with morphological and functional forms of congenital heart defects. Mediator is a multi-subunit complex that plays a central role in transcription initiation by integrating regulatory signals from gene-specific transcriptional activators to RNA polymerase II (Pol II). Recently, Mediator subunit 30 (MED30), a metazoan specific Mediator subunit, has been associated with Langer-Giedion syndrome (LGS) Type II and Cornelia de Lange syndrome-4 (CDLS4), characterized by several abnormalities including congenital heart defects. A point mutation in MED30 has been identified in mouse and is associated with mitochondrial cardiomyopathy. Very recent structural analyses of Mediator revealed that MED30 localizes to the proximal Tail, anchoring Head and Tail modules, thus potentially influencing stability of the Mediator core. However, in vivo cellular and physiological roles of MED30 in maintaining Mediator core integrity remain to be tested. Here, we report that deletion of MED30 in embryonic or adult cardiomyocytes caused rapid development of cardiac defects and lethality. Importantly, cardiomyocyte specific ablation of MED30 destabilized Mediator core subunits, while the kinase module was preserved, demonstrating an essential role of MED30 in stability of the overall Mediator complex. RNAseq analyses of constitutive cardiomyocyte specific Med30 knockout (cKO) embryonic hearts and inducible cardiomyocyte specific Med30 knockout (icKO) adult cardiomyocytes further revealed critical transcription networks in cardiomyocytes controlled by Mediator. Taken together, our results demonstrated that MED30 is essential for Mediator stability and transcriptional networks in both developing and adult cardiomyocytes. Our results affirm the key role of proximal Tail modular subunits in maintaining core Mediator stability in vivo.

Bromodomain-Containing Protein 9 Regulates Signaling Pathways and Reprograms the Epigenome in Immortalized Human Uterine Fibroid Cells.

Bromodomain-containing proteins (BRDs) are involved in many biological processes, most notably epigenetic regulation of transcription, and BRD dysfunction has been linked to many diseases, including tumorigenesis. However, the role of BRDs in the pathogenesis of uterine fibroids (UFs) is entirely unknown. The present study aimed to determine the expression pattern of BRD9 in UFs and matched myometrium and further assess the impact of a BRD9 inhibitor on UF phenotype and epigenetic/epitranscriptomic changes. Our studies demonstrated that the levels of BRD9 were significantly upregulated in UFs compared to matched myometrium, suggesting that the aberrant BRD expression may contribute to the pathogenesis of UFs. We then evaluated the potential roles of BRD9 using its specific inhibitor, I-BRD9. Targeted inhibition of BRD9 suppressed UF tumorigenesis with increased apoptosis and cell cycle arrest, decreased cell proliferation, and extracellular matrix deposition in UF cells. The latter is the key hallmark of UFs. Unbiased transcriptomic profiling coupled with downstream bioinformatics analysis further and extensively demonstrated that targeted inhibition of BRD9 impacted the cell cycle- and ECM-related biological pathways and reprogrammed the UF cell epigenome and epitranscriptome in UFs. Taken together, our studies support the critical role of BRD9 in UF cells and the strong interconnection between BRD9 and other pathways controlling the UF progression. Targeted inhibition of BRDs might provide a non-hormonal treatment option for this most common benign tumor in women of reproductive age.

HDAC6 regulates human erythroid differentiation through modulation of JAK2 signalling.

Among histone deacetylases, HDAC6 is unusual in its cytoplasmic localization. Its inhibition leads to hyperacetylation of non-histone proteins, inhibiting cell cycle, proliferation and apoptosis. Ricolinostat (ACY-1215) is a selective inhibitor of the histone deacetylase HDAC6 with proven efficacy in the treatment of malignant diseases, but anaemia is one of the most frequent side effects. We investigated here the underlying mechanisms of this erythroid toxicity. We first confirmed that HDAC6 was strongly expressed at both RNA and protein levels in CD34+ -cells-derived erythroid progenitors. ACY-1215 exposure on CD34+ -cells driven in vitro towards the erythroid lineage led to a decreased cell count, an increased apoptotic rate and a delayed erythroid differentiation with accumulation of weakly hemoglobinized immature erythroblasts. This was accompanied by drastic changes in the transcriptomic profile of primary cells as shown by RNAseq. In erythroid cells, ACY-1215 and shRNA-mediated HDAC6 knockdown inhibited the EPO-dependent JAK2 phosphorylation. Using acetylome, we identified 14-3-3ζ, known to interact directly with the JAK2 negative regulator LNK, as a potential HDAC6 target in erythroid cells. We confirmed that 14-3-3ζ was hyperacetylated after ACY-1215 exposure, which decreased the 14-3-3ζ/LNK interaction while increased LNK ability to interact with JAK2. Thus, in addition to its previously described role in the enucleation of mouse fetal liver erythroblasts, we identified here a new mechanism of HDAC6-dependent control of erythropoiesis through 14-3-3ζ acetylation level, LNK availability and finally JAK2 activation in response to EPO, which is crucial downstream of EPO-R activation for human erythroid cell survival, proliferation and differentiation.

Artificial intelligence to empower diagnosis of myelodysplastic syndromes by multiparametric flow cytometry.

The diagnosis of myelodysplastic syndromes (MDS) might be challenging and relies on the convergence of cytological, cytogenetic, and molecular factors. Multiparametric flow cytometry (MFC) helps diagnose MDS, especially when other features do not contribute to the decision-making process, but its usefulness remains underestimated, mostly due to a lack of standardization of cytometers. We present here an innovative model integrating artificial intelligence (AI) with MFC to improve the diagnosis and the classification of MDS. We develop a machine learning model through an elasticnet algorithm directed on a cohort of 191 patients, only based on flow cytometry parameters selected by the Boruta algorithm, to build a simple but reliable prediction score with five parameters. Our AI-assisted MDS prediction score greatly improves the sensitivity of the Ogata score while keeping an excellent specificity validated on an external cohort of 89 patients with an Area Under the Curve of 0.935. This model allows the diagnosis of both high- and low-risk MDS with 91.8% sensitivity and 92.5% specificity. Interestingly, it highlights a progressive evolution of the score from clonal hematopoiesis of indeterminate potential (CHIP) to highrisk MDS, suggesting a linear evolution between these different stages. By significantly decreasing the overall misclassification of 52% for patients with MDS and of 31.3% for those without MDS (P=0.02), our AI-assisted prediction score outperforms the Ogata score and positions itself as a reliable tool to help diagnose MDS.

Hormone Receptor Signaling and Breast Cancer Resistance to Anti-Tumor Immunity.

Breast cancers regroup many heterogeneous diseases unevenly responding to currently available therapies. Approximately 70-80% of breast cancers express hormone (estrogen or progesterone) receptors. Patients with these hormone-dependent breast malignancies benefit from therapies targeting endocrine pathways. Nevertheless, metastatic disease remains a major challenge despite available treatments, and relapses frequently ensue. By improving patient survival and quality of life, cancer immunotherapies have sparked considerable enthusiasm and hope in the last decade but have led to only limited success in breast cancers. In addition, only patients with hormone-independent breast cancers seem to benefit from these immune-based approaches. The present review examines and discusses the current literature related to the role of hormone receptor signaling (specifically, an estrogen receptor) and the impact of its modulation on the sensitivity of breast cancer cells to the effector mechanisms of anti-tumor immune responses and on the capability of breast cancers to escape from protective anti-cancer immunity. Future research prospects related to the possibility of promoting the efficacy of immune-based interventions using hormone therapy agents are considered.

Accurate classification of plasma cell dyscrasias is achieved by combining artificial intelligence and flow cytometry.

Monoclonal gammopathy of unknown significance (MGUS), smouldering multiple myeloma (SMM), and multiple myeloma (MM) are very common neoplasms. However, it is often difficult to distinguish between these entities. In the present study, we aimed to classify the most powerful markers that could improve diagnosis by multiparametric flow cytometry (MFC). The present study included 348 patients based on two independent cohorts. We first assessed how representative the data were in the discovery cohort (123 MM, 97 MGUS) and then analysed their respective plasma cell (PC) phenotype in order to obtain a set of correlations with a hypersphere visualisation. Cluster of differentiation (CD)27 and CD38 were differentially expressed in MGUS and MM (P < 0·001). We found by a gradient boosting machine method that the percentage of abnormal PCs and the ratio PC/CD117 positive precursors were the most influential parameters at diagnosis to distinguish MGUS and MM. Finally, we designed a decisional algorithm allowing a predictive classification ≥95% when PC dyscrasias were suspected, without any misclassification between MGUS and SMM. We validated this algorithm in an independent cohort of PC dyscrasias (n = 87 MM, n = 41 MGUS). This artificial intelligence model is freely available online as a diagnostic tool application website for all MFC centers worldwide (https://aihematology.shinyapps.io/PCdyscrasiasToolDg/).

Epidemiology and Effects of Bacterial Infections in Patients With Cirrhosis Worldwide.

BACKGROUND & AIMS: Bacterial infections are common and life-threatening in patients with cirrhosis. Little is known about the epidemiology of bacterial infections in different regions. We performed a multicenter prospective intercontinental study to assess the prevalence and outcomes of bacterial and fungal infections in patients with cirrhosis. METHODS: We collected data from 1302 hospitalized patients with cirrhosis and bacterial or fungal infections at 46 centers (15 in Asia, 15 in Europe, 11 in South America, and 5 in North America) from October 2015 through September 2016. We obtained demographic, clinical, microbiology, and treatment data at time of diagnosis of infection and during hospitalization. Patients were followed until death, liver transplantation, or discharge. RESULTS: The global prevalence of multidrug-resistant (MDR) bacteria was 34% (95% confidence interval 31%-37%). The prevalence of MDR bacteria differed significantly among geographic areas, with the greatest prevalence in Asia. Independent risk factors for infection with MDR bacteria were infection in Asia (particularly in India), use of antibiotics in the 3 months before hospitalization, prior health care exposure, and site of infection. Infections caused by MDR bacteria were associated with a lower rate of resolution of infection, a higher incidence of shock and new organ failures, and higher in-hospital mortality than those caused by non-MDR bacteria. Administration of adequate empirical antibiotic treatment was independently associated with improved in-hospital and 28-day survival. CONCLUSIONS: In a worldwide study of hospitalized patients, we found a high prevalence of infection with MDR bacteria in patients with cirrhosis. Differences in the prevalence of MDR bacterial infections in different global regions indicate the need for different empirical antibiotic strategies in different continents and countries. While we await new antibiotics, effort should be made to decrease the spread of MDR bacteria in patients with cirrhosis.

Reduction in acute kidney injury stage predicts survival in patients with type-1 hepatorenal syndrome.

BACKGROUND: Hepatorenal syndrome type 1 (HRS-1), a form of acute kidney injury (AKI) in cirrhosis, has a median survival of days to weeks if untreated. The impact of reduction in AKI stage on overall survival in cirrhosis, independent of HRS reversal, is unclear. METHODS: The Randomized, placEbo-controlled, double-blind study to confirm the reVERSal of HRS-1 with terlipressin study assessed terlipressin versus placebo, both with albumin, as treatment for HRS-1 for ≤14 days. Renal dysfunction severity was categorized by AKI stage at enrollment. Baseline patient characteristics were evaluated as predictors of AKI improvement using a multivariate model; the association between AKI stage reduction and 90-day survival was assessed using linear regression. RESULTS: A total of 184 patients (terlipressin: n = 91; placebo: n = 93) with similar numbers in AKI Stages 1-3 (terlipressin/placebo, Stage 1: n = 25/26; Stage 2: n = 35/33; Stage 3: n = 31/34) were included. Predictors of AKI improvement were absence of alcoholic hepatitis, baseline serum creatinine and male gender. Overall survival was not significantly different across AKI stages (range 53-65%). In patients with no AKI worsening, 90-day survival was consistently better when AKI improved independent of HRS reversal, regardless of the initial AKI stage, with patients with Stage 1 at initial diagnosis achieving the greatest clinical benefit. A significant association was observed between AKI reduction and overall 90-day survival (P = 0.0022). CONCLUSIONS: A reduction in AKI stage, independent of HRS reversal, was sufficient to improve overall survival in patients with HRS-1. The goal for HRS-1 treatment should be less stringent than absolute HRS reversal.

Biomarkers of Gemtuzumab Ozogamicin Response for Acute Myeloid Leukemia Treatment.

Gemtuzumab ozogamicin (GO, Mylotarg®) consists of a humanized CD33-targeted antibody-drug conjugated to a calicheamicin derivative. Growing evidence of GO efficacy in acute myeloid leukemia (AML), demonstrated by improved outcomes in CD33-positive AML patients across phase I to III clinical trials, led to the Food and Drug Administration (FDA) approval on 1 September 2017 in CD33-positive AML patients aged 2 years and older. Discrepancies in GO recipients outcome have raised significant efforts to characterize biomarkers predictive of GO response and have refined the subset of patients that may strongly benefit from GO. Among them, CD33 expression levels, favorable cytogenetics (t(8;21), inv(16)/t(16;16), t(15;17)) and molecular alterations, such as NPM1, FLT3-internal tandem duplications and other signaling mutations, represent well-known candidates. Additionally, in depth analyses including minimal residual disease monitoring, stemness expression (LSC17 score), mutations or single nucleotide polymorphisms in GO pathway genes (CD33, ABCB1) and molecular-derived scores, such as the recently set up CD33_PGx6_Score, represent promising markers to enhance GO response prediction and improve patient management.

Oncogenic exon 2 mutations in Mediator subunit MED12 disrupt allosteric activation of cyclin C-CDK8/19.

Somatic mutations in exon 2 of the RNA polymerase II transcriptional Mediator subunit MED12 occur at high frequency in uterine fibroids (UFs) and breast fibroepithelial tumors as well as recurrently, albeit less frequently, in malignant uterine leimyosarcomas, chronic lymphocytic leukemias, and colorectal cancers. Previously, we reported that UF-linked mutations in MED12 disrupt its ability to activate cyclin C (CycC)-dependent kinase 8 (CDK8) in Mediator, implicating impaired Mediator-associated CDK8 activity in the molecular pathogenesis of these clinically significant lesions. Notably, the CDK8 paralog CDK19 is also expressed in myometrium, and both CDK8 and CDK19 assemble into Mediator in a mutually exclusive manner, suggesting that CDK19 activity may also be germane to the pathogenesis of MED12 mutation-induced UFs. However, whether and how UF-linked mutations in MED12 affect CDK19 activation is unknown. Herein, we show that MED12 allosterically activates CDK19 and that UF-linked exon 2 mutations in MED12 disrupt its CDK19 stimulatory activity. Furthermore, we find that within the Mediator kinase module, MED13 directly binds to the MED12 C terminus, thereby suppressing an apparent UF mutation-induced conformational change in MED12 that otherwise disrupts its association with CycC-CDK8/19. Thus, in the presence of MED13, mutant MED12 can bind, but cannot activate, CycC-CDK8/19. These findings indicate that MED12 binding is necessary but not sufficient for CycC-CDK8/19 activation and reveal an additional step in the MED12-dependent activation process, one critically dependent on MED12 residues altered by UF-linked exon 2 mutations. These findings confirm that UF-linked mutations in MED12 disrupt composite Mediator-associated kinase activity and identify CDK8/19 as prospective therapeutic targets in UFs.

Detection of a new heterozygous germline ETV6 mutation in a case with hyperdiploid acute lymphoblastic leukemia.

ETV6 is a target of recurrent aberrations in sporadic and familial acute lymphoblastic leukemia (ALL). Here, we report on a new pedigree with a germline ETV6 mutation in which the index patient and his father developed high hyperdiploid (HeH) ALL and polycythemia vera at age 13 and 51, respectively. The index patient achieved durable complete remission without transplantation but had persistent moderate thrombocytopenia without bleeding tendency. To determine the prevalence of ETV6 alterations in HeH-ALL, we screened 81 unrelated subjects with HeH-ALL by single nucleotide polymorphism array and high-throughput sequencing for the ETV6 gene. Overall, ETV6 microdeletions and mutations were identified in 9% of cases, all of which were somatic and considered as secondary events. Apart from the index patient, no germline ETV6 aberration was identified. Finally, we reviewed the literature for ETV6 germline aberrations and predispositions to ALL.

Mediator kinase module and human tumorigenesis.

Mediator is a conserved multi-subunit signal processor through which regulatory informatiosn conveyed by gene-specific transcription factors is transduced to RNA Polymerase II (Pol II). In humans, MED13, MED12, CDK8 and Cyclin C (CycC) comprise a four-subunit "kinase" module that exists in variable association with a 26-subunit Mediator core. Genetic and biochemical studies have established the Mediator kinase module as a major ingress of developmental and oncogenic signaling through Mediator, and much of its function in signal-dependent gene regulation derives from its resident CDK8 kinase activity. For example, CDK8-targeted substrate phosphorylation impacts transcription factor half-life, Pol II activity and chromatin chemistry and functional status. Recent structural and biochemical studies have revealed a precise network of physical and functional subunit interactions required for proper kinase module activity. Accordingly, pathologic change in this activity through altered expression or mutation of constituent kinase module subunits can have profound consequences for altered signaling and tumor formation. Herein, we review the structural organization, biological function and oncogenic potential of the Mediator kinase module. We focus principally on tumor-associated alterations in kinase module subunits for which mechanistic relationships as opposed to strictly correlative associations are established. These considerations point to an emerging picture of the Mediator kinase module as an oncogenic unit, one in which pathogenic activation/deactivation through component change drives tumor formation through perturbation of signal-dependent gene regulation. It follows that therapeutic strategies to combat CDK8-driven tumors will involve targeted modulation of CDK8 activity or pharmacologic manipulation of dysregulated CDK8-dependent signaling pathways.

Terlipressin Improves Renal Function and Reverses Hepatorenal Syndrome in Patients With Systemic Inflammatory Response Syndrome.

BACKGROUND & AIMS: Patients with systemic inflammatory response syndrome (SIRS) along with decompensated cirrhosis and renal dysfunction have a poor prognosis and a lower response to treatment. We evaluated the effect of SIRS on the response of hepatorenal syndrome type 1 (HRS-1) to terlipressin. METHODS: We performed a retrospective study of data from a trial of the effects of terlipressin (1 mg every 6 hours or placebo with concomitant albumin) in 198 patients with HRS-1, performed at 50 investigational sites in the United States and 2 in Canada from October 2010 through February 2013. We identified patients with 2 or more criteria for SIRS, without untreated infections (28 received terlipressin and 30 received placebo), and patients with less than 2 criteria for SIRS (control subjects). Primary endpoints included HRS reversal (a decrease in serum level of creatinine to ≤1.5 mg/dL), confirmed HRS reversal (defined as 2 serum creatinine levels ≤1.5 mg/dL, ≥ 48 hours apart), and survival for 90 days after treatment. RESULTS: Baseline characteristics were similar between groups, apart from slightly higher white blood cell counts and heart rates, and slightly lower serum levels of bicarbonate in patients with SIRS versus without SIRS. HRS was reversed in 42.9% of patients who received terlipressin with SIRS (12/28) versus 6.7% of patients who received placebo (2/30) (P = .0018); confirmed HRS reversal occurred in 32.1% of patients who received terlipressin with SIRS (9/28) versus 3.3% who received placebo (1/30) (P = .0048). A larger proportion of patients with SIRS who received terlipressin survived for 90 days without a transplant (13/28; 46.4%) than patients with SIRS who received placebo (7/30; 23.3%) (P = .076). CONCLUSIONS: In an analysis of data from a placebo-controlled study, we found that terlipressin improved renal function and reversed HRS in a higher proportion of patients with HRS-1 and SIRS than patients who received albumin plus placebo. ClincialTrials.gov, number NCT 01143246.

Terlipressin Plus Albumin Is More Effective Than Albumin Alone in Improving Renal Function in Patients With Cirrhosis and Hepatorenal Syndrome Type 1.

BACKGROUND & AIMS: Hepatorenal syndrome type 1 (HRS-1) in patients with cirrhosis and ascites is a functional, potentially reversible, form of acute kidney injury characterized by rapid (<2 wk) and progressive deterioration of renal function. Terlipressin is a synthetic vasopressin analogue that acts, via vascular vasopressin V1 receptors, as a systemic vasoconstrictor. We performed a phase 3 study to evaluate the efficacy and safety of intravenous terlipressin plus albumin vs placebo plus albumin in patients with HRS-1. METHODS: Adult patients with cirrhosis, ascites, and HRS-1 (based on the 2007 International Club of Ascites criteria of rapidly deteriorating renal function) were assigned randomly to groups given intravenous terlipressin (1 mg, n = 97) or placebo (n = 99) every 6 hours with concomitant albumin. Treatment continued through day 14 unless the following occurred: confirmed HRS reversal (CHRSR, defined as 2 serum creatinine [SCr] values ≤1.5 mg/dL, at least 40 hours apart, on treatment without renal replacement therapy or liver transplantation) or SCr at or above baseline on day 4. The primary end point was the percentage of patients with confirmed CHRSR. Secondary end points included the incidence of HRS reversal (defined as at least 1 SCr value ≤1.5 mg/dL while on treatment), transplant-free survival, and overall survival. The study was performed at 50 investigational sites in the United States and 2 in Canada, from October 2010 through February 2013. RESULTS: Baseline demographic/clinical characteristics were similar between groups. CHRSR was observed in 19 of 97 patients (19.6%) receiving terlipressin vs 13 of 99 patients (13.1%) receiving placebo (P = .22). HRS reversal was achieved in 23 of 97 (23.7%) patients receiving terlipressin vs 15 of 99 (15.2%) receiving placebo (P = .13). SCr decreased by 1.1 mg/dL in patients receiving terlipressin and by only 0.6 mg/dL in patients receiving placebo (P < .001). Decreases in SCr and survival were correlated (r(2) = .882; P < .001). Transplant-free and overall survival were similar between groups. A significantly greater proportion of patients with CHRSR who received terlipressin survived until day 90 than patients who did not have CHRSR after receiving terlipressin (P < .001); this difference was not observed in patients who did vs did not have CHRSR after receiving placebo (P = .28). There were similar numbers of adverse events in each group, but patients in the terlipressin group had more ischemic events. CONCLUSIONS: Terlipressin plus albumin was associated with greater improvement in renal function vs albumin alone in patients with cirrhosis and HRS-1. Patients had similar rates of HRS reversal with terlipressin as they did with albumin. ClinicalTrials.gov no: NCT01143246.

Mediator subunit Med12 contributes to the maintenance of neural stem cell identity.

BACKGROUND: The RNA polymerase II transcriptional Mediator subunit Med12 is broadly implicated in vertebrate brain development, and genetic variation in human MED12 is associated with X-linked intellectual disability and neuropsychiatric disorders. Although prior studies have begun to elaborate the functional contribution of Med12 within key neurodevelopmental pathways, a more complete description of Med12 function in the developing nervous system, including the specific biological networks and cellular processes under its regulatory influence, remains to be established. Herein, we sought to clarify the global contribution of Med12 to neural stem cell (NSC) biology through unbiased transcriptome profiling of mouse embryonic stem (ES) cell-derived NSCs following RNAi-mediated Med12 depletion. RESULTS: A total of 240 genes (177 up, 73 down) were differentially expressed in Med12-knockdown versus control mouse NS-5 (mNS-5) NSCs. Gene set enrichment analysis revealed Med12 to be prominently linked with "cell-to-cell interaction" and "cell cycle" networks, and subsequent functional studies confirmed these associations. Targeted depletion of Med12 led to enhanced NSC adhesion and upregulation of cell adhesion genes, including Syndecan 2 (Sdc2). Concomitant depletion of both Sdc2 and Med12 reversed enhanced cell adhesion triggered by Med12 knockdown alone, confirming that Med12 negatively regulates NSC cell adhesion by suppressing the expression of cell adhesion molecules. Med12-mediated suppression of NSC adhesion is a dynamically regulated process in vitro, enforced in self-renewing NSCs and alleviated during the course of neuronal differentiation. Accordingly, Med12 depletion enhanced adhesion and prolonged survival of mNS-5 NSCs induced to differentiate on gelatin, effects that were bypassed completely by growth on laminin. On the other hand, Med12 depletion in mNS-5 NSCs led to reduced expression of G1/S phase cell cycle regulators and a concordant G1/S phase cell cycle block without evidence of apoptosis, resulting in a severe proliferation defect. CONCLUSIONS: Med12 contributes to the maintenance of NSC identity through a functionally bipartite role in suppression and activation of gene expression programs dedicated to cell adhesion and G1/S phase cell cycle progression, respectively. Med12 may thus contribute to the regulatory apparatus that controls the balance between NSC self-renewal and differentiation, with important implications for MED12-linked neurodevelopmental disorders.

Somatic MED12 mutations in prostate cancer and uterine leiomyomas promote tumorigenesis through distinct mechanisms.

BACKGROUND: Mediator is a multiprotein interface between eukaryotic gene-specific transcription factors and RNA polymerase II. Mutations in exon 2 of the gene encoding MED12, a key subunit of the regulatory kinase module in Mediator, are extremely frequent in uterine leiomyomas, breast fibroadenomas, and phyllodes tumors. These mutations disrupt kinase module interactions and lead to diminished Mediator-associated kinase activity. MED12 mutations in exon 26, resulting in a substitution of leucine 1224 to phenylalanine (L1224F), have been recurrently observed in prostate cancer. METHODS: To elucidate the molecular mechanisms leading to tumorigenesis in prostate cancer, we analyzed global interaction profiles of wild-type and L1224F mutant MED12 with quantitative affinity purification-mass spectrometry (AP-MS). Immunoprecipitation and kinase activity assay were used to further assess the interactions between Mediator complex subunits and kinase activity. The presence of L1224F mutation was analyzed in altogether 877 samples representing prostate hyperplasia, prostate cancer, and various tumor types in which somatic MED12 mutations have previously been observed. RESULTS: In contrast to N-terminal MED12 mutations observed in uterine leiomyomas, the L1224F mutation compromises neither the interaction of MED12 with kinase module subunits Cyclin C and CDK8/19 nor Mediator-associated CDK activity. Instead, the L1224F mutation was shown to affect interactions between MED12 and other Mediator components (MED1, MED13, MED13L, MED14, MED15, MED17, and MED24). Mutation screening revealed one mutation in a Finnish (Caucasian) prostate cancer patient, whereas no mutations in any other tumor type were observed. CONCLUSIONS: Specific somatic MED12 mutations in prostate cancer and uterine leiomyomas accumulate in two separate regions of the gene and promote tumorigenesis through clearly distinct mechanisms.

Mutations in MED12 cause X-linked Ohdo syndrome.

Ohdo syndrome comprises a heterogeneous group of disorders characterized by intellectual disability (ID) and typical facial features, including blepharophimosis. Clinically, these blepharophimosis-ID syndromes have been classified in five distinct subgroups, including the Maat-Kievit-Brunner (MKB) type, which, in contrast to the others, is characterized by X-linked inheritance and facial coarsening at older age. We performed exome sequencing in two families, each with two affected males with Ohdo syndrome MKB type. In the two families, MED12 missense mutations (c.3443G>A [p.Arg1148His] or c.3493T>C [p.Ser1165Pro]) segregating with the phenotype were identified. Upon subsequent analysis of an additional cohort of nine simplex male individuals with Ohdo syndrome, one additional de novo missense change (c.5185C>A [p.His1729Asn]) in MED12 was detected. The occurrence of three different hemizygous missense mutations in three unrelated families affected by Ohdo syndrome MKB type shows that mutations in MED12 are the underlying cause of this X-linked form of Ohdo syndrome. Together with the recently described KAT6B mutations resulting in Ohdo syndrome Say/Barber/Biesecker/Young/Simpson type, our findings point to aberrant chromatin modification as being central to the pathogenesis of Ohdo syndrome.