Brown, A. K. | bioRxiv Science

bioRxiv2020

Infanticide by females is a leading source of juvenile mortality in a large social carnivore

Social animals benefit from their groupmates, so why do they sometimes kill each others offspring? Using 30 years of data from multiple groups of wild spotted hyenas, we address three critical aims for understanding infanticide in any species: (1) quantify the contribution of infanticide to overall mortality (2) describe the circumstances under which infanticide occurs and (3) evaluate hypotheses about the evolution of infanticide. We find that, although observed only rarely, infanticide is in fact a leading source of juvenile mortality. Infanticide accounted for 24% of juvenile mortality, and 1 in 10 hyenas born in our population perished due to infanticide. In all observed cases of infanticide, killers were adult females, but victims could be of both sexes. Of four hypotheses regarding the evolution of infanticide, we found the most support for the hypothesis that infanticide in spotted hyenas reflects competition over social status among matrilines.

animal behavior and cognition↗

bioRxiv2020

Changing and stable chromatin accessibility supports transcriptional overhaul during neural stem cell activation

Adult neural stem cells are largely quiescent, and require transcriptional reprogramming to reenter the cell cycle and undergo neurogenesis. However, the precise mechanisms that underlie the rapid transcriptional overhaul during NSC activation remain undefined. Here, we identify the genome-wide chromatin accessibility differences between primary neural stem and progenitor cells in quiescent and activated states. We show that these distinct cellular states exhibit both shared and unique chromatin profiles, which are both associated with gene regulation. Interestingly, we find that accessible chromatin states specific to quiescent or activated cells are active enhancers bound by pro-neurogenic and quiescence factors, ASCL1 and NFI. In contrast, shared sites are gene promoters harboring constitutively accessible chromatin enriched for particular core promoter elements that are functionally associated with translation and metabolic functions. Together, our findings reveal how accessible chromatin states regulate a transcriptional overhaul and drive the switch between quiescence and proliferation in NSC activation.

molecular biology↗