Hormonal regulation of miRNA during mammary gland development.

The mammary gland is a unique organ as most of its development occurs after birth through stages of proliferation, differentiation and apoptosis that are tightly regulated by circulating hormones and growth factors. Throughout development, hormonal cues induce the regulation of different pathways, ultimately leading to differential transcription and expression of genes involved in this process, but also in the activation or inhibition of post-transcriptional mechanisms of regulation. However, the role of microRNAs (miRNAs) in the different phases of mammary gland remodeling is still poorly understood. The objectives of this study were to analyze the expression of miRNA in key stages of mammary gland development in mice and to determine whether it could be associated with hormonal variation between stages. To do so, miRNAs were isolated from mouse mammary glands at stages of adulthood, pregnancy, lactation and involution, and sequenced. Results showed that 490, 473, 419, and 460 miRNAs are detected in adult, pregnant, lactating and involuting mice, respectively, most of them being common to all four groups, and 58 unique to one stage. Most genes could be divided into six clusters of expression, including two encompassing the highest number of miRNA (clusters 1 and 3) and showing opposite profiles of expression, reaching a peak at adulthood and valley at lactation, or showing the lowest expression at adulthood and peaking at lactation. GO and KEGG analyses suggest that the miRNAs differentially expressed between stages influence the expression of targets associated with mammary gland homeostasis and hormone regulation. To further understand the links between miRNA expression and hormones involved in mammary gland development, miRNAs were then sequenced in breast cells exposed to estradiol, progesterone, prolactin and oxytocin. Four, 38, 24 and 66 miRNAs were associated with progesterone, estradiol, prolactin, and oxytocin exposure, respectively. Finally, when looking at miRNAs modulated by the hormones, differentially expressed during mammary gland development, and having a pattern of expression that could be correlated with the relative levels of hormones known to be found in vivo, 16 miRNAs were identified as likely regulated by circulating hormones. Overall, our study brings a better understanding of the regulation of miRNAs throughout mammary gland development and suggests that there is a relationship between their expression and the main hormones involved in mammary gland development. Future studies will examine this role more in detail.

It takes two: examining the dynamic nature of cooperative behavior in adolescents.

Cooperating with those around us is an important facet of functioning in modern-day society. Forming successful cooperative relationships requires trust, reciprocity, and other interpersonal skills that continue to develop during adolescence. This study examined the dynamic nature of how trust is formed and broken among 248 adolescents (Males = 110, M Age = 15.1 years) throughout an iterative cooperative task (i.e., the Trust Game) and the interindividual differences that alter the success of their relationships. In our study, adolescents from the same classroom were anonymously paired and played a 10-trial version of the Trust Game, which examines trust and reciprocity. We found that trust is formed in the first half of the game and decreases as the threat of defection nears in the last trial. As the game progressed, the relationship between trial number and investments on the subsequent trial was mediated by percent return (ab = -0.09, 95% CI = [-0.15, -0.02]). Importantly, this relationship was moderated by social skills (p = 0.003) and impulsivity (p = 0.001), such that increases in either were associated with decreased percent return and investments on future trials. Overall, we found that cooperation is an adaptive behavior which requires trust and reciprocity, and adolescents need to exhibit both of these behaviors to have fruitful interactions. These findings suggest that interventions to help students think about their partner's perspective and stress the longer-term nature of interactions with peers would foster successful cooperation in social situations.

Understanding boys' underrepresentation in private and enriched programmes during the transition to secondary school.

BACKGROUND: In the past decades, there has been a growing concern to understand why boys struggle in school. One of the turning points in students' educational trajectories likely to exacerbate boys' academic difficulties is students' enrolment in private or enriched school programmes, as boys are underrepresented in such programmes. METHOD: To better understand this gender imbalance, our research draws on a longitudinal design to examine whether grade 6 students' externalizing behaviours, school engagement and school grades in mathematics and language arts relate to secondary school programme attendance, among a sample size of 577 students (277 boys). RESULTS: Path analysis showed that only language arts grades predicted enrolment in private or selective public programmes and contributed to boys' underrepresentation in these programmes. CONCLUSIONS: Such findings have important implications for understanding boys' underachievement and low persistence in school as well as to guide interventions to promote gender and overall educational equity in school.

Learning to embrace one's stress: the selective effects of short videos on youth's stress mindsets.

BACKGROUND AND OBJECTIVES: Stress is not inherently negative. As youth will inevitably experience stress when facing the various challenges of adolescence, they can benefit from developing a stress-can-be-enhancing mindset rather than learning to fear their stress responses and avoid taking on challenges. We aimed to verify whether a rapid intervention improved stress mindsets and diminished perceived stress and anxiety sensitivity in adolescents. DESIGN AND METHODS: An online experimental design randomly exposed 233 Canadian youths aged 14-17 (83% female) to four videos of the Stress N' Go intervention (how to embrace stress) or to control condition videos (brain facts). Validated questionnaires assessing stress mindsets, perceived stress, and anxiety sensitivity were administered pre- and post-intervention, followed by open-ended questions. RESULTS: The intervention content successfully instilled a stress-can-be-enhancing mindset compared to the control condition. Although Bayes factor analyses showed no main differences in perceived stress or anxiety sensitivity between conditions, a thematic analysis revealed that the intervention helped participants to live better with their stress. CONCLUSIONS: Overall, these results suggest that our intervention can rapidly modify stress mindsets in youth. Future studies are needed to determine whether modifying stress mindsets is sufficient to alter anxiety sensitivity in certain adolescents and contexts.