REST maintains self-renewal and pluripotency of embryonic stem cells.

The neuronal repressor REST (RE1-silencing transcription factor; also called NRSF) is expressed at high levels in mouse embryonic stem (ES) cells, but its role in these cells is unclear. Here we show that REST maintains self-renewal and pluripotency in mouse ES cells through suppression of the microRNA miR-21. We found that, as with known self-renewal markers, the level of REST expression is much higher in self-renewing mouse ES cells than in differentiating mouse ES (embryoid body, EB) cells. Heterozygous deletion of Rest (Rest+/-) and its short-interfering-RNA-mediated knockdown in mouse ES cells cause a loss of self-renewal-even when these cells are grown under self-renewal conditions-and lead to the expression of markers specific for multiple lineages. Conversely, exogenously added REST maintains self-renewal in mouse EB cells. Furthermore, Rest+/- mouse ES cells cultured under self-renewal conditions express substantially reduced levels of several self-renewal regulators, including Oct4 (also called Pou5f1), Nanog, Sox2 and c-Myc, and exogenously added REST in mouse EB cells maintains the self-renewal phenotypes and expression of these self-renewal regulators. We also show that in mouse ES cells, REST is bound to the gene chromatin of a set of miRNAs that potentially target self-renewal genes. Whereas mouse ES cells and mouse EB cells containing exogenously added REST express lower levels of these miRNAs, EB cells, Rest+/- ES cells and ES cells treated with short interfering RNA targeting Rest express higher levels of these miRNAs. At least one of these REST-regulated miRNAs, miR-21, specifically suppresses the self-renewal of mouse ES cells, corresponding to the decreased expression of Oct4, Nanog, Sox2 and c-Myc. Thus, REST is a newly discovered element of the interconnected regulatory network that maintains the self-renewal and pluripotency of mouse ES cells.

Skills training and social influences for violence prevention in middle schools: A curriculum evaluation

This pilot study evaluated the effect of skills training and of social influences on self-reported aggressive behavior in a sample of 239 sixth-grade students. The effect of two intervention groups and one control group were compared. In the first intervention group, a 15-session, violence-prevention curriculum was taught by the teacher. In the second intervention group, the same curriculum was taught by the teacher with the assistance of peer leaders trained to modify social norms about violence. The control group was evaluated but did not receive any training. The design included four schools. In two schools, three classes were assigned to one of the two interventions or to the control group. In the other two schools, two classes were assigned to either intervention (teacher only) or control. Students were evaluated before and after the implementation of the curriculum using a standardized questionnaire.^ The primary outcome was the effect of the curriculum and peer leaders on self-reported aggressive behaviors. The secondary outcome was their impact on intervening variables: knowledge about violence, conflict-resolution skills, self-efficacy, and attitudes.^ The intervention had a moderate effect on reducing self-reported aggressive behaviors among boys in two of the six classes that received the curriculum. Both classes with peer leaders reduced their aggressive behavior, but this reduction was significant in only one. A peer leader selection problem could probably explain this lack of effect.^ In three of the four schools, both interventions had an overall significant effect on increasing knowledge about violence and skills to reduce violence. Students also developed a more negative attitude toward violence after the intervention. As hypothesized, attitude change was stronger among students from the teacher plus peer leader group. No intervention effect was observed on self-efficacy nor on attitudes toward skills to reduce violence. Limitations of the study and implications for violence prevention in schools are discussed. ^