Sirtuin 1 regulation of developmental genes during differentiation of stem cells

The longevity-promoting NAD+-dependent class III histone deacetylase Sirtuin 1 (SIRT1) is involved in stem cell function by controlling cell fate decision and/or by regulating the p53-dependent expression of NANOG. We show that SIRT1 is down-regulated precisely during human embryonic stem cell differentiation at both mRNA and protein levels and that the decrease in Sirt1 mRNA is mediated by a molecular pathway that involves the RNA-binding protein HuR and the arginine methyltransferase coactivator-associated arginine methyltransferase 1 (CARM1). SIRT1 down-regulation leads to reactivation of key developmental genes such as the neuroretinal morphogenesis effectors DLL4, TBX3, and PAX6, which are epigenetically repressed by this histone deacetylase in pluripotent human embryonic stem cells. Our results indicate that SIRT1 is regulated during stem cell differentiation in the context of a yet-unknown epigenetic pathway that controls specific developmental genes in embryonic stem cells

Cancer Genes Hypermethylated in Human Embryonic Stem Cells

Developmental genes are silenced in embryonic stem cells by a bivalent histone-based chromatin mark. It has been proposed that this mark also confers a predisposition to aberrant DNA promoter hypermethylation of tumor suppressor genes (TSGs) in cancer. We report here that silencing of a significant proportion of these TSGs in human embryonic and adult stem cells is associated with promoter DNA hypermethylation. Our results indicate a role for DNA methylation in the control of gene expression in human stem cells and suggest that, for genes repressed by promoter hypermethylation in stem cells in vivo, the aberrant process in cancer could be understood as a defect in establishing an unmethylated promoter during differentiation, rather than as an anomalous process of de novo hypermethylation

Consumo de sustancias psicoactivas de tipo legal e ilegal, y calidad de vida en adolescentes

77 Páginas.Algunos investigadores aseguran que son pocas las investigaciones a nivel mundial, con respecto a la Calidad de Vida y al consumo de Sustancias Psicoactivas (SPA) en niños y adolescentes. Teniendo en cuenta lo anterior la presente investigación de diseño descriptivo-comparativo, tiene como objetivo general identificar sí existen diferencias significativas en la calidad de vida entre adolescentes que no consumen SPA, aquellos que consumen SPA de tipo Legal y quienes consumen SPA de tipo legal e ilegal. La muestra estuvo compuesta por 69 adolescentes entre 14-18 años de edad, estudiantes de un colegio público de la ciudad de Villavicencio-Meta