Bhim B. Biswa 1,2, Bharathi Venkatachalam 1,2, Hiroshi Mori 2,3, Atsushi Toyoda 4, Ken Kurokawa 2,5, Tsuyoshi Koide 1,2

Domestication, a longstanding process of selective breeding for human benefits, fundamentally alters the behaviour of animals, with tameness being a key trait. In order to study factors associated with domestication, we have applied selective breeding for higher motivation to approach humans (active tameness) using genetically diverse wild-derived heterogeneous stock (WHS) mice from eight wild strains. As a result, the selected groups exhibit higher active tameness than the non-selected groups. Furthermore, the selected groups exhibit higher sociability as well as higher levels of blood oxytocin, a hormone associate with social behavior, than the non-selected groups. We examined gut microbiota in mice selectively bred for increased human interaction (active tameness) compared to control groups. We analysed faecal samples from 80 mice, comprising 40 from the selected groups and 40 controls, through shotgun metagenomic analysis. Leveraging our shotgun metagenomic data, we compiled a collection of 374 high-quality metagenome-assembled genomes (MAGs) of bacteria across 11 phyla. The results indicate that selection for tameness does not significantly alter the taxonomic and functional diversity of the gut microbiota, but there is a notable increase in the abundance of Limosilactobacillus reuteri in the selected groups. We isolated multiple lines of L. reuteri from the faeces obtained from the selected mice. When one of these lines was administered to control mice via drinking water, an increase in tameness behaviour was observed with higher blood oxytocin levels. Our findings suggest that gut microbiota, particularly species like L. reuteri, can influence active tameness or social behavior in mice.

1 Mouse Genomics Resource Laboratory, National Institute of Genetics (NIG), Japan. 2 Graduate Institute for Advanced Studies (SOKENDAI), Japan. 3 Genome Diversity Laboratory, NIG, Japan. 4 Comparative Genomics Laboratory, NIG, Japan. 5 Genome Evolution Laboratory, NIG, Japan

SM Heyworth1, F Cortesi1,2, M Lührmann1,2, R Carew1, KL Cheney1

Seahorses hunt using pivot feeding, a highly effective strategy relying on advanced visual capabilities to identify planktonic prey against the background, maintain focus despite movement, and crucially, perceive depth allowing accurate strike. However, the retinal structure of the seahorse visual system remains largely unstudied. Here, we present our findings of how the seahorse retina supports targeted prey capture.

In all five species studied, we identified multiple retinal regions characterised by differences in morphology and gene expression. Histological analysis and MRI scans revealed the presence of multiple foveae, while slicing and wholemount techniques confirmed changes in cell density throughout the retina, extending beyond the foveal regions. Transcriptome sequencing revealed the expression of three opsin genes in the retina: sws2 (blue), rh2a (green) and lws (red). Notably, fluorescent in situ hybridisation showed distinct differences in opsin gene expression and co-expression within the same cone photoreceptor cells across the dorsal-ventral and nasal-temporal axes, including expression of only one opsin per cone within the fovea and a ventronasal absence of lws. These differences demonstrate support for dichromatic, trichromatic, and potentially tetrachromatic retinal regions. To further investigate the role of retinal regionalisation in prey strike, we conducted feeding trials on Hippocampus whitei to determine the effect on foraging when ambient light matched the sensitivity of the foveal single cones. Our study reveals that seahorses have one of the most complex fish visual systems to date, highlighting the benefit of multi-technique, multi-species comparisons in sensory ecology.

1School of the Environment, The University of Queensland, 2The Queensland Brain Institute, The University of Queensland

Funding Support: Australian Research Council Future Fellowship (FT190100313; awarded to KLC); Holsworth Wildlife Research Endowment, The Ecological Society of Australia (awarded to SMH).

Jingjing Yan, Kelsey Mainard, Fumihiro Ito, Yangyuan Li, Andrew Nguyen, Aabha Vora, Lijuan Feng and Wanhe Li

The molecular clock drives the circadian rhythm and its behavioral and physiological outputs through tightly regulated gene expression. Histone post-translational modifications (PTMs) alter chromatin structure and recruitments of transcriptional factors, thereby epigenetically regulating gene expression. Many types of PTMs, including acetylation and methylation, exhibit rhythms at promoters, enhancers, and gene bodies, hence modifying the accessibility of genes to transcriptional machinery. Histone monoaminylation is a recently recognized kind of PTM, where neurotransmitters, such as excessive dopamine or serotonin resulting from pathological conditions, are covalently bonded to the histone tail. This process regulates neuronal transcription. Most recently, a previously unreported histone monoaminylation called histaminylation was identified. Characterized as a PTM, histaminylation cycles in mice’s hypothalamic tuberomammillary nucleus (TMN) throughout their sleep/wake cycle. The functions of these emerging types of PTMs in epigenetic regulation in the nervous system, both in healthy and diseased brain states, are being uncovered, making them highly intriguing.

In this study, we built a neurogenetics toolbox to study histone modifications using the model organism Drosophila melanogaster. We found that perturbing histone monoaminylation resulted in a unique sleep phenotype. This phenotype reflects a defect in sleep maintenance during the nighttime but not sleep initiation, because sleep deprivation can induce normal sleep rebound. Subsequently, we employed a comprehensive set of molecular, genetics, and genomics approaches to further explore histone monoaminylation-dependent sleep regulation. We identified the neural circuit in which the dynamics of gene expression are regulated through epigenetic mechanisms. Since the monoamine biochemistry and histone proteins are remarkably conserved between humans and flies, the discovery of histone monoaminylation-dependent sleep regulation may reveal a conserved sleep regulatory mechanism in an epigenetic setting.

Center for Biological Clocks Research, Department of Biology, Texas A&M University

AM Barkley-Levenson1 , ALS Borges1,2, R Sultana1 , D-J Paredes1 , V Cordova3

Recent genome wide association studies (GWAS) have identified numerous novel hits for problematic alcohol use and alcohol consumption. However, follow-up studies are still needed to demonstrate a causal relationship between implicated genes and alcohol-related traits. Here, we describe the functional validation of a novel genetic association for problematic alcohol use and alcohol drinking (Fut2). In humans, common nonfunctional FUT2 variants are associated with increased risk of inflammatory bowel disease and may worsen alcohol-related liver disease, but these variants have not been investigated in relation to alcohol intake. We found that male Fut2 homozygous knockout mice have greater binge-like ethanol consumption in a drinking in the dark (DID) test than wild type littermates, and knockout mice of both sexes show greater ethanol conditioned place preference. To begin to investigate a potential mechanism underlying the role of Fut2 in binge-like drinking, we also examined gut microbiota composition before and after three cycles of ethanol or water DID in the homozygous knockout and wild type mice. We found reduced alpha diversity in the Fut2 knockout mice compared to wild type animals in both drinking groups. Additionally, the ethanol drinking knockout mice had increased relative abundance of Prevotella compared to wild types, which has been associated with increased inflammatory responses. Taken together, these findings provide evidence for a causal role of Fut2 in ethanol consumption and reward sensitivity. The identification of a gene x alcohol interaction effect on gut microbiota composition suggests a possible mechanism by which Fut2 genotype can impact alcohol-related traits. Funding: NIH-NIAAA grant R00AA027835, NIH-NIGMS grant P20GM103451, University of New Mexico College of Pharmacy Pilot Project Research Award, 1Department of Pharmaceutical Sciences, University of New Mexico College of Pharmacy, Albuquerque, NM, USA. 2Biomedical Sciences Graduate Program, University of New Mexico Health Sciences Center, Albuquerque, NM, USA. 3New Mexico IMBRE Student Experience, New Mexico State University, Las Cruses, NM, USA.