RESUMO
Sox2 is an important transcriptional regulator in embryonic and adult stem cells. Recently, Sox2 was identified as an oncogene in many endodermal cancers, including colon cancer. There is great interest in how Sox2 cooperates with other transcription factors to regulate stem cell renewal, differentiation, and reprogramming. However, we still lack a general understanding of Sox2 transcriptional action. To determine transcriptional partners of Sox2 in adult cells, we generated mice where gene expression could be induced by an externally applied stimulus. We analyzed the consequences in the intestine where cell turnover is rapid. Sox2 expression, but not Oct4, specifically increased the numbers of stem cells and repressed Cdx2, a master regulator of endodermal identity. In vivo studies demonstrated that Sox21, another member of the SoxB gene family, was a specific, immediate, and cell-autonomous target of Sox2 in intestinal stem cells. In vitro experiments showed that Sox21 was sufficient to repress Cdx2 in colon cancer cells and in pluripotent stem cells. Sox21 was also specifically induced by Sox2 in fibroblasts and inhibition of Sox21 blocked reprogramming to the pluripotent state. These results show that transcriptional induction of Sox21 is a rapid and general mediator of the effects of Sox2 on cell identity in a wide range of cell types.
Assuntos
Células-Tronco Pluripotentes/metabolismo , Fatores de Transcrição SOXB1/metabolismo , Fatores de Transcrição SOXB2/metabolismo , Ativação Transcricional , Animais , Fator de Transcrição CDX2 , Diferenciação Celular/genética , Linhagem Celular , Neoplasias do Colo/genética , Neoplasias do Colo/metabolismo , Fibroblastos/metabolismo , Regulação da Expressão Gênica , Proteínas de Homeodomínio/antagonistas & inibidores , Mucosa Intestinal/metabolismo , Intestinos/citologia , Camundongos , Camundongos Transgênicos , Fator 3 de Transcrição de Octâmero/biossíntese , Células-Tronco Pluripotentes/citologia , Fatores de Transcrição SOXB2/antagonistas & inibidores , Fatores de Transcrição/antagonistas & inibidores , Transcrição GênicaRESUMO
Reactive oxygen species (ROS) are mediators of brain injury in ischemia/reperfusion. An involvement of the NADPH oxidase Nox2 has been demonstrated. In contrast, only little is known about the contribution of the Nox1 homologue in this context. Thus, we studied the role of Nox1 in early cerebral reperfusion injury in the middle cerebral artery filament occlusion model using Nox1 knockout mice. Genetic deletion of a functional Nox1 lead to a 55% attenuation in lesion size at 24h after induction of 1h ischemia (p<0.05). This result was paralleled by a significant improvement of neurological outcome, preservation of blood-brain barrier integrity and reduced cerebral edema in Nox1(y/)(-) compared to WT mice. Interestingly, no difference in infarct size between WT and Nox1(y/)(-) was observed with an occlusion time of 2h and longer. Apoptosis rate as measured by TUNEL staining was similar between the groups. Moreover, infusion of the antioxidant TEMPOL as well as of the unspecific NO-synthase inhibitor l-NAME elicited similar changes with respect to ischemic tissue damage between WT and Nox1-deficient mice. In conclusion, Nox1 is involved in the pathophysiology of cerebral ischemia. Our data however indicate that ROS-mediated direct cellular injury is unlikely to explain the protective effect achieved by genetic deletion of the enzyme.
Assuntos
Isquemia Encefálica/enzimologia , Infarto da Artéria Cerebral Média/enzimologia , NADH NADPH Oxirredutases/fisiologia , Acidente Vascular Cerebral/enzimologia , Animais , Infarto Encefálico/enzimologia , Infarto Encefálico/genética , Infarto Encefálico/patologia , Isquemia Encefálica/genética , Isquemia Encefálica/patologia , Células Cultivadas , Modelos Animais de Doenças , Feminino , Infarto da Artéria Cerebral Média/genética , Infarto da Artéria Cerebral Média/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NADH NADPH Oxirredutases/deficiência , NADH NADPH Oxirredutases/genética , NADPH Oxidase 1 , Degeneração Neural/enzimologia , Degeneração Neural/genética , Degeneração Neural/patologia , Acidente Vascular Cerebral/genética , Acidente Vascular Cerebral/patologiaRESUMO
The generation of new neurons in the olfactory bulb (OB) persists into adulthood and is a multistep process that includes proliferation, fate choice, migration, survival, and differentiation. Neural precursor cells destined to form olfactory interneurons arise in the subventricular zone (SVZ) and migrate along the rostral migratory stream (RMS) to the OB. Recently, some factors classically known from their effects on the vascular system have been found to influence different steps of adult neurogenesis. In the present study, we report a modulatory function for the vascular endothelial growth factor receptor-1 (VEGFR-1) in adult olfactory neurogenesis. We identified expression of VEGFR-1 in GFAP-positive cells within regions involved in neurogenesis of the adult mouse brain. To determine functions for VEGFR-1 in adult neurogenesis, we compared neural progenitor cell proliferation, migration, and differentiation from wild-type and VEGFR-1 signaling-deficient mice (Flt-1TK(-/-) mice). Our data show that VEGFR-1 signaling is involved in the regulation of proliferation of neuronal progenitor cells within the SVZ, migration along the RMS, and in neuronal differentiation and anatomical composition of interneuron subtypes within the OB. RMS migration in Flt-1TK(-/-) mice was altered mainly as a result of increased levels of its ligand VEGF-A, which results in an increased phosphorylation of VEGFR-2 in neuronal progenitor cells within the SVZ and the RMS. This study reveals that proper RMS migration is dependent on endogenous VEGF-A protein.