Elf5-centered transcription factor hub controls trophoblast stem cell self-renewal and differentiation through stoichiometry sensitive shifts in target gene networks

Latos, P. A., Sienerth, A. R., Murray, A., Senner, C. E., Muto, M., Ikawa, M., . . . Hemberger, M. (2015). Elf5-centered transcription factor hub controls trophoblast stem cell self-renewal and differentiation through stoichiometry sensitive shifts in target gene networks. Genes and Development, 29(23), 2435-2448. doi:10.1101/gad.268821.11

Polycomb Group Protein Bmi1 Is Required for Growth of RAF Driven Non-Small-Cell Lung Cancer

Background: We have previously described a RAF oncogene driven transgenic mouse model for non small cell lung cancer (NSCLC). Here we examine whether tumor initiation and growth requires the stem cell self-renewal factor Bmi1. Principal Findings: In order to evaluate Bmi1 function in NSCLC two founder lines that differ in incidence and latency of tumor formation were compared. Ablation of Bmi1 expression in both lines had a dramatically decreased tumor growth. As the line with shorter latency matched the life span of Bmi1 knock out mice, these mice were chosen for further study. The absence of Bmi1 did not decrease the number of tumor initiation in these mice as only the size and not the number of tumors decreased. Reduction in tumor growth resulted from an increase in cell death and decrease in cell cycle progression that corresponded with up-regulation of the p16 INK4a and p19 ARF. Significance: The data identifies Bmi1 as an important factor for expansion but not initiation of RAF driven NSCLC

Placentation defects are highly prevalent in embryonic lethal mouse mutants.

Large-scale phenotyping efforts have demonstrated that approximately 25-30% of mouse gene knockouts cause intrauterine lethality. Analysis of these mutants has largely focused on the embryo and not the placenta, despite the crucial role of this extraembryonic organ for developmental progression. Here we screened 103 embryonic lethal and sub-viable mouse knockout lines from the Deciphering the Mechanisms of Developmental Disorders program for placental phenotypes. We found that 68% of knockout lines that are lethal at or after mid-gestation exhibited placental dysmorphologies. Early lethality (embryonic days 9.5-14.5) is almost always associated with severe placental malformations. Placental defects correlate strongly with abnormal brain, heart and vascular development. Analysis of mutant trophoblast stem cells and conditional knockouts suggests that a considerable number of factors that cause embryonic lethality when ablated have primary gene function in trophoblast cells. Our data highlight the hugely under-appreciated importance of placental defects in contributing to abnormal embryo development and suggest key molecular nodes that govern placenta formation

Regulation des anti-inflammatorischen Zytokines Il-10 durch das Polycomb Group Protein Bmi1

Macrophages are important effector cells of the innate and adaptive immune response and exert a wide variety of immunological functions which necessitates a high level of plasticity on the chromatin level. In response to pathogen-associated molecular patterns (PAMPs) or inflammatory signals macrophages undergo a process of cellular activation which is associated with morphologic, functional and biochemical changes. Toll-like receptors (TLR) are able to sense many different PAMPs. TLR4 is an important sensor for lipopolysaccharide (LPS) which elicits a major portion of the host’s inflammatory response through the activation of many different signaling pathways such as the NF-κB and the MAPK protein kinase pathways RASRAF- MEK-ERK, p38 and JNK. Polycomb group (PcG) proteins are well known chromatin modifiers which function in large complexes and are required to maintain chromatin structure in a transcriptionally repressed state. It has previously been shown that the PcG protein Bmi1 is phosphorylated by 3pK, a downstream effector kinase of the MAPK protein kinase pathways RAS-RAF-MEK-ERK, p38 and JNK. In this work I analyzed the role of Bmi1 as a downstream effector of MAPK signaling during macrophage activation. Unexpectedly a rapid up-regulation on the Bmi1 protein level was observed in bone marrow derived macrophages (BMDMs) after LPS treatment. The Bmi1 induction was associated with transient protein phosphorylation that occured downstream of MAPK signaling. LPS treatment of BMDMs in the absence of Bmi1 resulted in a pronounced increase of IL-10 secretion. This secretion of the anti-inflammatory cytokine IL-10 was associated with increased IL-10 mRNA levels. Furthermore, siRNA mediated knock down of Bmi1 in J774A.1 macrophages also resulted in elevated IL-10 mRNA levels in response to LPS. ChIP analysis revealed that Bmi1 binds to throughout the il-10 locus. Alternative activation of wild type BMDMs via concomitant TLR4 and FcγR activation which triggers high IL-10 expression is paralleled by an attenuated Bmi1 protein expression. These results identify Bmi1 as a repressor of IL-10 expression during activation of macrophages.Makrophagen sind wichtige Effektorzellen der angeborenen und adaptiven Immunantwort und üben eine große Fülle von immunologischen Funktionen aus. Deshalb benötigen sie eine hohe Plastizität auf Chromatinebene. Als Antwort auf pathogen-assoziierte molekulare Muster (PAMPs) oder andere inflammatorische Signale machen Makrophagen einen zellulären Aktivierungsprozess durch, der mit morphologischen, funktionellen und biochemischen Veränderungen assoziiert ist. Toll-like Rezeptoren (TLR) sind fähig, solche PAMPs zu erkennen. Der TLR4 ist ein wichtiger Sensor für Lipopolysaccharid (LPS). LPS löst eine inflammatorische Antwort des Wirtes durch die Aktivierung vieler verschiedener Signalwege wie zum Beispiel des NF-κB Signalwegs und der MAPK Proteinkinasensignalwege RAS-RAFMEK- ERK, p38 und JNK aus. Polycomb Gruppen (PcG) Proteine arbeiten in großen Proteinkomplexen zusammen und werden benötigt, um das Chromatin in einem transkriptionell reprimierten Zustand beizubehalten. Es konnte gezeigt werden, dass das PcG Protein Bmi1 von 3pK, einer Effektorkinase der MAPK Proteinkinasensignalwege RAS-RAF-MEK-ERK, p38 und JNK, phosphoryliert wird. In meiner Doktorabeit analysierte ich die Rolle von Bmi1 als downstream-Effektor der MAPKSignaltransduktion während der Makrophagenaktivierung. Es wurde unerwarteterweise eine schnelle Induktion von Bmi1 auf Proteinebene in Knochenmarks-Makrophagen (BMDMs) beobachtet. Diese Induktion war MAPK-abhängig und mit einer transienten Proteinphosphorylierung assoziiert. Die LPS-Behandlung der BMDMs in Abwesenheit von Bmi1 hatte erhöhte IL-10 Sekretion zur Folge. Diese erhöhte Sekretion des antiinflammatorischen Zytokines IL-10 war mit erhöhten IL-10 mRNA Expression verbunden. Des Weiteren hatte ein Bmi1 siRNA-vermittelter Gen-Knockdown in J774A.1 Makrophagen eine erhöhte IL-10 mRNA-Expression zur Folge. ChIP Analysen haben gezeigt, dass Bmi1 am ganzen il-10-Locus verteilt binden kann. Eine TLR4 und FcγR vermittelte alternative Aktivierung von BMDMs, die mit hoher IL-10 Expression verbunden ist, führte zu einer attenuierten Bmi1 Proteinexpression. Diese Ergebnisse zusammengenommen weisen Bmi1 als Repressor von IL-10 während der Makrophagenaktivierung aus