Gomes, A. C. | bioRxiv Science

bioRxiv2021

Competition between hematopoietic stem and progenitor cells controls hematopoietic stem cell compartment size.

Cellular competition for limiting hematopoietic factors is a physiologically regulated but poorly understood process. Here, we studied this phenomenon by hampering hematopoietic progenitor access to Leptin receptor+ mesenchymal stem/progenitor cells (MSPCs) and endothelial cells (ECs). We show that HSC numbers increased by 2-fold when multipotent and lineage-restricted progenitors failed to respond to CXCL12 produced by MSPCs and ECs. HSCs were qualitatively normal, and HSC expansion only occurred when early hematopoietic progenitors but not differentiated hematopoietic cells lacked CXCR4. Furthermore, the MSPC and EC transcriptomic heterogeneity was remarkably stable, suggesting that it is impervious to dramatic changes in hematopoietic progenitor interactions. Instead, HSC expansion was caused by increased availability of membrane-bound stem cell factor (mSCF) on MSPCs and ECs due to reduced consumption by cKit-expressing hematopoietic progenitors. These studies revealed an intricate homeostatic balance between HSCs and proximal hematopoietic progenitors regulated by cell competition for limited amounts of mSCF.

immunology↗

bioRxiv2018

Profiles of cooperative brains: A discriminant analysis of cleaner and client fish monoaminergic responses to different social contexts

Vertebrate cognitive function requires a dynamic coordination of multiple specialized areas of the brain. The challenge here is to understand how these brain areas respond in dependence to the neurophysiological mechanisms in place, as to enable the successful processing of information. For instance, social and cooperative behaviour has been linked to the activation of some specific brain areas, mostly associated with reward processing. Here we evaluated a classic model system of cooperation between species of fish and compared datasets of brain monoaminergic response. We analysed by using multivariate discriminant analysis the exposure of cleaners, Labroides dimidiatus, to several social-related conditions, as well as the response of one client species, Naso elegans, to similar contexts. We demonstrate that the variable appraisal of each social challenge contributes to brain dopaminergic and serotonergic changes, in cleaners and clients, with both showing the diencephalon and optic tectum as main areas of metabolite response. The role of the serotoninergic system activation was mostly demonstrated at the diencephalon and cerebellum of cleaners, a response that was driven by mutualistic interaction, contact with client. Our current evidence is the first to jointly demonstrate the level of selective similarity in brain monoaminergic mechanisms that underlie fish mutualistic and social engagement, for both sides of these partnerships.

neuroscience↗