Biology subjects

Rigo, P.

Publications and source records attributed to Rigo, P..

4 recordsLinked to original sources

bioRxiv2024

Sequential transcriptional programs underpin activation of quiescent hippocampal stem cells.

Postnatal neural stem cells are primarily quiescent, which is a cellular state that exists as a continuum from deep to shallow quiescence. The molecular changes that occur along this continuum are beginning to be understood but the transcription factor network governing these changes has not been defined. We show that these transitions are regulated by sequential transcription factor programs. Single-cell transcriptomic analyses of mice with loss- or gain-of-function of the essential activation factor Ascl1, reveal that Ascl1 promotes the activation of hippocampal neural stem cells by driving these cells out of deep quiescence, despite its low protein expression. Subsequently, during the transition from deep to shallow quiescence, Ascl1 induces the expression of Mycn, which drives progression through shallow states of quiescence towards an active state. Together, these results define the required sequence of transcription factors during hippocampal neural stem cell activation.

neuroscience↗

bioRxiv2020

Wnt/beta-catenin signalling is dispensable for adult neural stem cell homeostasis and activation.

Adult mouse hippocampal neural stem cells (NSCs) generate new neurons that integrate into existing hippocampal networks and modulate mood and memory. These NSCs are largely quiescent and are stimulated by niche signals to activate and produce neurons. Wnt/{beta}-catenin signalling acts at different steps along the hippocampal neurogenic lineage and has been shown to promote the proliferation of intermediate progenitor cells. However, whether it has a direct role in the regulation of NSCs still remains unclear. Here we used Wnt/{beta}-catenin reporters and transcriptomic data from in vivo and in vitro models to show that both active and quiescent adult NSCs respond to Wnt/{beta}-catenin signalling. Wnt/{beta}-catenin stimulation instructed neuronal differentiation of active NSCs and promoted the activation or differentiation of quiescent NSCs in a dose-dependent manner. However, we found that inhibiting NSCs response to Wnt, by conditionally deleting {beta}-catenin, did not affect their activation or maintenance of their stem cell characteristics. Together, our results indicate that whilst NSCs do respond to Wnt/{beta}-catenin stimulation in a dose-dependent and state-specific manner, Wnt/{beta}-catenin signalling is not cell-autonomously required to maintain NSC homeostasis, which could reconcile some of the contradictions in the literature as to the role of Wnt/{beta}-catenin signalling in adult hippocampal NSCs.

developmental biology↗

bioRxiv2020

Enlarged Ingroup Effect: How a Shared Culture Shapes In-Group Perception

Increasing levels of migration and constant redefinition of a sense of belonging characterize modern societies. Thus, social perception of people from different ethnicities as in-group or out-group members is influenced by a shared culture that might go beyond ethnicity. Using functional magnetic resonance imaging, we aim to study how sharing a common culture changes the social perceptions of in-groups and out-groups. We presented same- and different-race faces to young adults living in an integrated multicultural society. Same- and different-race faces were primed by images of environmental context that promotes identification with the participants ethnicity or a common shared culture. We found that same and different-race faces recruit similar brain networks only when associated with an environmental context, which promoted identification with a common shared culture. These results support a possible emergent phenomenon in multicultural societies that we call enlarged multi-ethnic in-group effect, which may form the basis of a potential new way to categorize oneself and others in terms of membership.

neuroscience↗

bioRxiv2020

Progressive changes in hippocampal stem cell properties ensure lifelong neurogenesis

Neural stem cell numbers fall rapidly in the hippocampus of juvenile mice but stabilise during adulthood, ensuring lifelong hippocampal neurogenesis. We show that this reduction in stem cell depletion rate is the result of multiple coordinated changes in stem cell behaviour. In particular, while active neural stem cells divide only once or twice before differentiating rapidly in juveniles, they increasingly return to a resting state of shallow quiescence and progress through additional self-renewing divisions in adulthood. Single-cell transcriptomic, mathematical modelling and label-retention analyses indicate that resting cells have a higher activation rate and greater contribution to neurogenesis than dormant cells, which have not left quiescence. These progressive changes in stem cell behaviour result from reduced expression of the pro-activation protein ASCL1 due to increased post-translational degradation. These mechanisms help reconcile current contradictory models of hippocampal NSC dynamics and may contribute to the different rates of decline of hippocampal neurogenesis in mammalian species including humans.

developmental biology↗