Biology subjects

Milewski, T. M.

Publications and source records attributed to Milewski, T. M..

5 recordsLinked to original sources

bioRxiv2026

Socially dominant male mice in social hierarchies identified via automated RFID tracking exhibit elevated activity levels and circulating markers of higher metabolic demand

Dominance hierarchies are a fundamental aspect of social organization, enabling animals to minimize aggression and optimize access to resources. Previous studies have highlighted the energetic and physiological demands of dominant status, as well as the behavioral flexibility required of subordinates to navigate these hierarchies. Despite advancements in automated behavior tracking, limitations persist in tracking fine-scale, real-time interactions within complex social environments. Here, we developed and validated a novel RFID-based system to continuously monitor dominance hierarchies in group-housed male mice over 10 days. This system enabled unbiased behavioral inference across light phases and revealed spatial and temporal patterns of dominance behavior undetectable through traditional live-scored methods. Automated tracking accurately identified alpha individuals and consistently inferred linear hierarchies across cohorts, with greater precision for higher-ranked individuals. Behavioral metrics, such as transition frequencies and proximity to food zones, were consistent with dominance driven activity. Hormonal analyses revealed that higher-ranked mice exhibited increased leptin and peptide YY, consistent with heightened activity and satiety signaling, while lower C-peptide levels reflected greater metabolic demands of dominance. Furthermore, dominance rank was associated with differences in light-dark activity, which were in turn related to circulating hormone profiles. This study demonstrates the utility of automated RFID tracking in capturing dominance hierarchies with temporal and spatial granularity, while revealing links between social rank, metabolic regulation, and activity patterns advancing our understanding of social behavior dynamics.

animal behavior and cognition↗

bioRxiv2026

Single-Nucleus Transcriptomics of the Mouse Medial Preoptic Area Reveals Sex-Dependent Molecular Signatures of Social Dominance

Social dominance hierarchies are a common form of social organization across animal species. We have previously shown that both male and female CD-1 mice form highly linear dominance hierarchies. In mice and other vertebrates, the medial preoptic area (mPOA) is a key hypothalamic sub-region regulating aggressive and defensive behaviors that support hierarchical social structures, but the transcriptional mechanisms in mPOA neurons underlying dominance behaviors and the influence of sex on these neuron populations in the context of social dominance hierarchies remain largely unresolved. Using single-nucleus RNA sequencing (snRNA-seq) to profile mPOA neurons from dominant and subordinate mice, we identified highly consistent social status-dependent changes in the transcriptomes of neuronal nuclei expressing neuropeptide transcripts. Oxytocin expression was remarkably widespread across mPOA neurons, and we found it to be the primary driver of group differences in neuropeptide co-expression networks. Overall, dominant males and females exhibited markedly decreased expression of oxytocin and vasopressin and had a lower proportion of neurons co-expressing multiple neuropeptide transcripts compared to subordinate individuals. In contrast, subordinates displayed widespread reorganization of the transcriptomic neuropeptidome and strikingly enhanced coupling of neuropeptide expression in mPOA neurons. Despite the strong pattern of concordant gene expression in dominant and subordinate individuals, the number of genes that were differentially expressed by status was substantially reduced in males compared to females. In sum, these results demonstrate that maintenance of social status dynamically reconfigures hypothalamic transcriptomic neuropeptidome in a sex-dependent manner and establishes how social status is encoded at a single-cell resolution.

neuroscience↗

bioRxiv2025

Rapid changes in cholinergic signaling, myelination and thyroid signaling pathway gene expression in amygdala subnuclei in response to social status maintenance and reorganization

Male CD-1 mice form linear social hierarchies and can rapidly reform them following social reorganization. Through Tag-based sequencing in the medial amygdala (MeA), we identified several genes regulating cholinergic signaling, myelination, and thyroid signaling that rapidly shift expression 70 minutes after animals change social status. Here, we further characterize the expression patterns of individual genes within these pathways in both stable and reorganized hierarchies. We find that genes related to cholinergic signaling show higher expression in the MeA of dominant males in stable hierarchies as well as when reestablishing dominance in reorganized hierarchies. Dominant males also show higher levels of myelination related genes than socially descending males when reestablishing their social status during social reorganization but less so in stable groups. Conversely, thyroid signaling genes show higher expression in the MeA in subordinate males and previously dominant males who are socially descending. Using RNAscope, we were able to demonstrate broadly similar patterns of gene expression immediately following social reorganization across the MeA, basolateral, and central amygdala for 7 genes of interest (chat, slc5a7, ache, mbp, mog, crym, mybpc1). High levels of co-expression of cholinergic signaling and myelination gene expression in dominant males suggest that these processes work together to promote resilience to the social challenge and promote dominance. In summary, we demonstrate that rapid changes in amygdala gene expression in each pathway are associated with the formation and maintenance of dominance and subordinate social status in stable and reorganized environments.

neuroscience↗

bioRxiv2024

Rapid changes in plasma corticosterone and medial amygdala transcriptome profiles during social status change reveal molecular pathways associated with a major life history transition in mouse dominance hierarchies

Social hierarchies are a common form of social organization across species. Although hierarchies are largely stable across time, animals may socially ascend or descend within hierarchies depending on environmental and social challenges. Here, we develop a novel paradigm to study social ascent and descent within male CD-1 mouse social hierarchies. We show that mice of all social ranks rapidly establish new stable social hierarchies when placed in novel social groups with animals of equivalent social status. Seventy minutes following social hierarchy formation, previously socially dominant animals exhibit higher increases in plasma corticosterone and vastly greater transcriptional changes in the medial amygdala (MeA), which is central to the regulation of social behavior, compared to previously subordinate animals. Specifically, social descent is associated with reductions in MeA expression of myelination and oligodendrocyte differentiation genes. Maintaining high social status is associated with high expression of genes related to cholinergic signaling in the MeA. Conversely, social ascent is related to relatively few unique rapid changes in the MeA. We also identify novel genes associated with social transition that show common changes in expression when animals undergo either social descent or social ascent compared to maintaining their status. Two genes, Myosin binding protein C1 (Mybpc1) and -Crystallin (Crym), associated with vasoactive intestinal polypeptide (VIP) and thyroid hormone pathways respectively, are highly upregulated in socially transitioning individuals. Further, increases in genes associated with synaptic plasticity, excitatory glutamatergic signaling and learning and memory pathways were observed in transitioning animals suggesting that adaptations in these processes may support rapid social status changes. Author SummaryWe investigate how male CD-1 mice behaviorally, physiologically, and molecularly respond to changes in their social hierarchies. We found that mice rapidly reform social hierarchies when placed into novel social groups. Formerly dominant mice experience the greatest increase in stress hormone levels and the largest shifts in gene expression in the medial amygdala, a brain region crucial for regulating social behavior. Specifically, we observed reduced expression of genes related to myelin production and maintenance as well as cholinergic functioning in formerly dominant males who socially descended. In contrast, formerly subordinate males who socially ascended displayed fewer genomic changes. Moreover, we identified a set of genes that change expression when animals transition their social status regardless of whether they rise or fall in rank. These social transition genes provide new insights into the biological mechanisms underpinning social plasticity. Our findings demonstrate the distinct molecular mechanisms that are shared between socially ascending versus descending mice, as well as those that are unique to each type of social transition.

neuroscience↗

bioRxiv2021

Distinct inflammatory and transcriptomic profiles in dominant versus subordinate males in mouse social hierarchies

Social status is a critical factor determining health outcomes in human and nonhuman social species. In social hierarchies with reproductive skew, individuals compete to monopolize resources and increase mating opportunities. This can come at a significant energetic cost leading to trade-offs between different physiological systems. Particularly, changes in energetic investment in the immune system can have significant short and long-term effects on fitness and health. We have previously found that dominant alpha male mice living in social hierarchies have increased metabolic demands related to territorial defense. In this study, we tested the hypothesis that high-ranking male mice favor energetically inexpensive adaptive immunity, while subordinate mice show higher investment in innate immunity. We housed 12 groups of 10 outbred CD-1 male mice in a social housing system. All formed linear social hierarchies and subordinate mice had higher concentrations of plasma corticosterone (CORT) than alpha males. This difference was heightened in highly despotic hierarchies. Using flow cytometry, we found that dominant status was associated with a significant shift in immunophenotypes towards favoring adaptive versus innate immunity. Using Tag-Seq to profile hepatic and splenic transcriptomes of alpha and subordinate males, we identified genes that regulate metabolic and immune defense pathways that are associated with status and/or CORT concentration. In the liver, dominant animals showed an up-regulation of specific genes involved in major urinary production and catabolic processes, whereas subordinate animals showed an up-regulation of genes promoting biosynthetic processes, wound healing, and proinflammatory responses. In spleen, subordinate mice showed up-regulation of genes facilitating oxidative phosphorylation and DNA repair and CORT was negatively associated with genes involved in lymphocyte proliferation and activation. Together, our findings suggest that dominant and subordinate animals adaptively shift energy investment in immune functioning and gene expression to match their contextual energetic demands. HighlightsO_LIImmunity is shaped by stress and energetic pressures associated with social status C_LIO_LIDominant and subordinate mice favor adaptive and innate immunity, respectively C_LIO_LIDominants increase expression of genes involved in energy production C_LIO_LIWound healing and DNA repair genes are upregulated in subordinates C_LIO_LIGenes related to maintaining and signaling social status are upregulated in dominants C_LI

immunology↗