RESUMO
The AML1/Runx1 transcription factor and its heterodimerization partner CBFß are essential regulators of myeloid differentiation. The chromosomal translocation t(8;21), fusing the DNA binding domain of AML1 to the corepressor eight-twenty-one (ETO), is frequently associated with acute myeloid leukemia and generates the AML1/ETO (AE) fusion protein. AE represses target genes usually activated by AML1 and also affects the endogenous repressive function of ETO at Notch target genes. In order to analyze the contribution of CBFß in AE-mediated leukemogenesis and deregulation of Notch target genes, we introduced two point mutations in a leukemia-initiating version of AE in mice, called AE9a, that disrupt the AML1/CBFß interaction (AE9aNT). We report that the AE9a/CBFß interaction is not required for the AE9a-mediated aberrant expression of AML1 target genes, while upregulation/derepression of Notch target genes does require the interaction with CBFß. Using retroviral transduction to express AE9a in murine adult bone marrow-derived hematopoietic progenitors, we observed that both AE9a and AE9aNT lead to increased myeloproliferation in vivo. However, both development of leukemia and long-term replating capacity are only observed with AE9a but not with AE9aNT. Thus, deregulation of both AML1 and Notch target genes is required for the development of AE9a-driven leukemia.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Subunidade beta de Fator de Ligação ao Core/metabolismo , Leucemia/patologia , Proteínas de Fusão Oncogênica/metabolismo , Proteína 1 Parceira de Translocação de RUNX1/metabolismo , Animais , Diferenciação Celular , Linhagem Celular , Dimerização , Humanos , Leucemia/genética , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Sepsis is known to be a severe systemic immune reaction based on an infection of various origins. The initial immune response is accompanied by excess activation of immune cells and release of proinflammatory cytokines. Simultaneously initiated compensatory mechanisms lead to high levels of anti-inflammatory mediators to counterbalance the generalized inflammatory reaction; however, the compensatory immunoreaction itself equally overreacts and results in a prolonged sepsis-induced immunosuppression. The underlying mechanisms for these exaggerated immune responses and the resulting global immunosuppression that increase the risk for secondary infection are still unknown. Recent findings indicate that epigenetic mechanisms change basic properties of important immune cells by mechanisms leading to changes in gene expression. Dynamic exchanges of histone modifications result in a variation of transcription and seem to play a key role in cell function of macrophages and other immune cells. This article provides a current overview of epigenetic sepsis research and the sepsis-induced effects on the immune system.
Assuntos
Epigênese Genética/genética , Epigênese Genética/imunologia , Imunidade Celular/genética , Imunidade Celular/imunologia , Sepse/genética , Sepse/imunologia , Animais , Humanos , Infecções/genética , Infecções/imunologia , Infecções/patologia , Sepse/patologia , Síndrome de Resposta Inflamatória Sistêmica/genética , Síndrome de Resposta Inflamatória Sistêmica/imunologiaRESUMO
During spermatogenesis, approximately 85% of histones are replaced by protamines. The remaining histones have been proposed to carry essential marks for the establishment of epigenetic information in the offspring. The aim of the present study was to analyse the expression pattern of histone H3 acetylated at lysine 9 (H3K9ac) during normal and impaired spermatogenesis and the binding pattern of H3K9ac to selected genes within ejaculates. Testicular biopsies, as well as semen samples, were used for immunohistochemistry. Chromatin immunoprecipitation was performed with ejaculated sperm chromatin. HeLa cells and prostate tissue served as controls. Binding of selected genes was evaluated by semiquantitative and real-time polymerase chain reaction. Immunohistochemistry of H3K9ac demonstrated positive signals in spermatogonia, spermatocytes, elongating spermatids and ejaculated spermatozoa of fertile and infertile men. H3K9ac was associated with gene promoters (CRAT, G6PD, MCF2L), exons (SOX2, GAPDH, STK11IP, FLNA, PLXNA3, SH3GLB2, CTSD) and intergenic regions (TH) in fertile men and revealed shifts of the distribution pattern in ejaculated spermatozoa of infertile men. In conclusion, H3K9ac is present in male germ cells and may play a role during the development of human spermatozoa. In addition, H3K9ac is associated with specific regions of the sperm genome defining an epigenetic code that may influence gene expression directly after fertilisation.
