Biology subjects

Hegarty, B. E.

Publications and source records attributed to Hegarty, B. E..

6 recordsLinked to original sources

bioRxiv2024

Tracking Microcystis viruses and infection dynamics across distinct phases of a Microcystis-dominated bloom

Given the impact of viruses on microbial community composition and function, viruses have the potential to play a significant role in the fate of freshwater cyanobacterial harmful algal blooms (cHABs). Yet the role of viruses in cHABs remains poorly understood. We sought to address this knowledge gap with a metagenomic analysis of viruses of bloom-forming Microcystis aeruginosa across cHAB phases in the western basin of Lake Erie. Size-fractionation of the water allowed us to identify significant fraction-specific trends in viral diversity, which corresponded with Microcystis genetic diversity. Using a new machine-learning model, we predicted infections between viral and microbial host populations. We predicted hundreds of viral populations with infection histories including Microcystis and non-Microcystis hosts, suggesting extensive interconnectivity and the potential for virus-mediated cross-species exchange of genetic material within cHABs communities. Infection predictions revealed a broad host range for Lake Erie Microcystis viruses, challenging previous notions of "narrow" host-virus interactions in cHABs. Abundant viral genes belonging to predicted Microcystis viruses revealed their potential role in key metabolic pathways and adaptation to environmental changes. We observed significant turnover of predicted Microcystis virus populations across time. Viral diversity was highest in the viral fraction and lowest in the colony-associated fraction, suggesting that Microcystis colony formation and growth during cHABs leads to bottlenecks in viral diversity. These findings advance our understanding of uncultivated Microcystis virus diversity, their potential effects on host metabolism, potential influence on species interactions, and potential coevolutionary processes between microbial hosts and their viral predators within Microcystis-dominated cHABs. ImportanceUnderstanding interactions between viruses, their hosts, and environmental parameters may be key to identifying the mechanisms underlying the persistence and demise of cyanobacterial harmful algal blooms (cHABs). In this study we describe the viral diversity and host ranges of viruses predicted to infect Microcystis, describing the distribution of these properties across time, space, and different bloom-associated size fractions. Additionally, the study highlights abundant genes belonging to predicted Microcystis viruses and their potential roles in key metabolic pathways and adaptation to environmental changes. The observed turnover of Microcystis virus populations, with the highest diversity in viral fractions and the lowest in colony-associated fractions, suggests that Microcystis colony formation during blooms plays an important role in shaping viral diversity and community turnover. These findings contribute to a better understanding of the interplay between viruses, Microcystis, and their accompanying bacterial communities, shedding light on mechanisms driving bloom dynamics, species interactions, and coevolutionary processes.

microbiology↗

bioRxiv2024

Adult sex change leads to extensive forebrain reorganization in clownfish

Sexual differentiation of the brain occurs in all major vertebrate lineages but is not well understood at a molecular and cellular level. Unlike most vertebrates, sex-changing fishes have the remarkable ability to change reproductive sex during adulthood in response to social stimuli, offering a unique opportunity to understand mechanisms by which the nervous system can initiate and coordinate sexual differentiation. This study explores sexual differentiation of the forebrain using single nucleus RNA-sequencing in the anemonefish Amphiprion ocellaris, producing the first cellular atlas of a sex-changing brain. We uncover extensive sex differences in cell type-specific gene expression, relative proportions of cells, baseline neuronal excitation, and predicted inter-neuronal communication. Additionally, we identify the cholecystokinin, galanin, and estrogen systems as central molecular axes of sexual differentiation. Supported by these findings, we propose a model of neurosexual differentiation in the conserved vertebrate social decision-making network spanning multiple subtypes of neurons and glia, including neuronal subpopulations within the preoptic area that are positioned to regulate gonadal differentiation. This work deepens our understanding of sexual differentiation in the vertebrate brain and defines a rich suite of molecular and cellular pathways that differentiate during adult sex change in anemonefish. Significance StatementThis study provides key insights into brain sex differences in sex-changing anemonefish (Amphiprion ocellaris), a species that changes sex in adulthood in response to the social environment. Using single nucleus RNA-sequencing, the study provides the first brain cellular atlas showing sex differences in two crucial reproductive areas: the preoptic area and telencephalon. The research identifies notable sex-differences in cell-type proportions and gene expression, particularly in radial glia and glutamatergic neurons that co-express the neuropeptide cholecystokinin. It also highlights differences in preoptic area neurons likely involved in gonadal regulation. This work deepens our understanding of sexual differentiation of the brain in vertebrates, especially those capable of adult sex change, and illuminates key molecular and cellular beginning and endpoints of the process.

neuroscience↗

bioRxiv2023

Natural variation in oxytocin receptor signaling causes widespread changes in brain transcription: a link to the natural killer gene complex

Oxytocin (OXT) is a highly conserved neuropeptide that modulates social cognition, and genetic variation in its receptor gene (Oxtr) is linked to divergent social phenotypes. However, the molecular mechanisms connecting Oxtr genotype to behavioral outcomes remain obscure. Here, we leverage naturally occurring Oxtr polymorphisms in the prairie vole that associate with striatal-specific OXTR density to investigate how OXTR signaling influences brain function. Specifically, we identify OXTR-dependent transcriptomic changes in the natural killer gene complex (NKC) - a genomic region classically associated with peripheral immune function. Centrally, OXTR-regulated NKC genes are positioned to influence microglia-neuron interactions. Consistent with a role for these genes in shaping neuronal connectivity, we show that genetic reduction of OXTR levels leads to increased dendritic spine density on striatal Oxtr-expressing neurons. In addition, we provide support for a similar relation between variation in OXTR mRNA levels and NKC transcription in humans. Together, our findings suggest a role for OXTR signaling in the shaping of neural circuits through transcriptional control of the NKC, outlining a mechanism via which variation in OXTR signaling may influence circuit connectivity to generate diversity in social behaviors.

neuroscience↗

bioRxiv2023

Spatially resolved cell atlas of the teleost telencephalon and deep homology of the vertebrate forebrain

The telencephalon has undergone remarkable diversification and expansion throughout vertebrate evolution, exhibiting striking differences in structural and functional complexity. Nevertheless, fundamental features are shared across vertebrate taxa, such as the presence of distinct regions including the pallium, subpallium, and olfactory structures. Teleost fishes have a uniquely everted telencephalon, which has made it challenging to compare brain regions in fish to those in other vertebrates. Here we combine spatial transcriptomics and single-nucleus RNA-sequencing to generate a spatially-resolved transcriptional atlas of the cichlid fish telencephalon. We then compare cell-types and anatomical regions in the cichlid telencephalon with those in amphibians, reptiles, birds, and mammals. We uncover striking transcriptional similarities between cell populations in the fish telencephalon and subpallial, hippocampal, and cortical cell populations in tetrapods. Ultimately, our work lends new insights into the organization and evolution of conserved cell-types and regions in the vertebrate forebrain.

neuroscience↗

bioRxiv2022

Cellular profiling of a recently-evolved social behavior

Social behaviors are essential for survival and reproduction and vary within and among species. We integrate single nucleus RNA-sequencing (snRNA-seq), comparative genomics, and automated behavior analysis to investigate a recently-evolved social "bower building" behavior in Lake Malawi cichlid fishes. We functionally profile telencephalic nuclei matched to 38 paired behaving/control individuals. Our data suggest bower behavior has evolved in part through divergence in a gene module selectively expressed in a subpopulation of glia lining the pallium. Downregulation of the module is associated with glial departure from quiescence and rebalancing of neuronal subpopulation proportions in the putative homologue of the hippocampus. We show further evidence that behavior-associated excitation of neuronal populations that project to the putative hippocampus mediate glial function and rebalancing. Our work suggests that bower behavior has evolved through changes in glia and region-specific neurogenesis, and more broadly shows how snRNA-seq can generate insight into uncharted behaviors and species.

neuroscience↗

bioRxiv2021

A Snapshot of the Global Drinking Water Virome: Diversity and Metabolic Potential Vary with Residual Disinfectant Use

Viruses are important drivers of microbial community ecology and evolution, influencing microbial mortality, metabolism, and horizontal gene transfer. However, the effects of viruses remain largely unknown in many environments, including in drinking water systems. Drinking water metagenomic studies have offered a whole community perspective of bacterial impacts on water quality, but have not yet considered the influences of viruses. In this study, we address this gap by mining viral DNA sequences from publicly available drinking water metagenomes from distribution systems in six countries around the world. These datasets provide a snapshot of the taxonomic diversity and metabolic potential of the global drinking water virome; and provide an opportunity to investigate the effects of geography, climate, and drinking water treatment practices on viral diversity. Both environmental conditions and differences in sample processing were found to influence the viral composition. Using free chlorine as the residual disinfectant was associated with clear differences in viral taxonomic diversity and metabolic potential, with significantly fewer viral populations and less even viral community structures than observed in distribution systems without residual disinfectant. Additionally, drinking water viruses carry antibiotic resistance genes (ARGs), as well as genes to survive oxidative stress and nitrogen limitation. Through this study, we have demonstrated that viral communities are diverse across drinking water systems and vary with the use of residual disinfectant. Our findings offer directions for future research to develop a more robust understanding of how virus-bacteria interactions in drinking water distribution systems affect water quality.

microbiology↗