Genome-wide association study of open field behavior in outbred heterogeneous stock rats identifies multiple loci implicated in psychiatric disorders

Many personality traits are influenced by genetic factors. Rodents models provide an efficient system for analyzing genetic contribution to these traits. Using 1,246 adolescent heterogeneous stock (HS) male and female rats, we conducted a genome-wide association study (GWAS) of behaviors measured in an open field, including locomotion, novel object interaction, and social interaction. We identified 30 genome-wide significant quantitative trait loci (QTL). Using multiple criteria, including the presence of high impact genomic variants and co-localization of cis-eQTL, we identified 13 candidate genes (Adarb2, Ankrd26, Cacna1c, Clock, Crhr1, Ctu2, Cyp26b1, Eva1a, Fam114a1, Kcnj9, Mlf2, Rab27b, Sec11a) for these traits. Most of these genes have been implicated by human GWAS of various psychiatric traits. For example, Cacna1c, a gene known to be critical for social behavior in rodents and implicated in human schizophrenia and bipolar disorder, is a candidate gene for distance to the social zone. In addition, the QTL region for total distance to the novel object zone, on Chr1 at 144 Mb, is syntenic to a hotspot on human Chr15 (82.5-90.8 Mb) that contains 14 genes associated with psychiatric or substance abuse traits. Although some of the genes identified by this study appear to replicate findings from prior human GWAS, others likely represent novel findings that can be the catalyst for future molecular and genetic insights into human psychiatric diseases. Together, these findings provide strong support for the use of the HS population to study psychiatric disorders.

Failure of Diphtheria Toxin Model to Induce Parkinson-like Behavior in Mice

Rodent models of Parkinson’s disease are based on transgenic expression of mutant synuclein, deletion of PD genes, injections of MPTP or rotenone, or seeding of synuclein fibrils. The models show histopathologic features of PD such as Lewi bodies but mostly only subtle in vivo manifestations or systemic toxicity. The models only partly mimic a predominant loss of dopaminergic neurons in the substantia nigra. We therefore generated mice that express the transgenic diphtheria toxin receptor (DTR) specifically in DA neurons by crossing DAT-Cre mice with Rosa26 loxP-STOP-loxP DTR mice. After defining a well-tolerated DTx dose, DAT-DTR and DTR-flfl controls were subjected to non-toxic DTx treatment (5 × 100 pg/g) and subsequent histology and behavioral tests. DAT protein levels were reduced in the midbrain, and tyrosine hydroxylase-positive neurons were reduced in the substantia nigra, whereas the pan-neuronal marker NeuN was not affected. Despite the promising histologic results, there was no difference in motor function tests or open field behavior. These are tests in which double mutant Pink1−/−SNCAA53T Parkinson mice show behavioral abnormalities. Higher doses of DTx were toxic in both groups. The data suggest that DTx treatment in mice with Cre/loxP-driven DAT-DTR expression leads to partial ablation of DA-neurons but without PD-reminiscent behavioral correlates.

Thigmotaxis in a virtual human open field test

Animal models are used to study neurobiological mechanisms in mental disorders. Although there has been significant progress in the understanding of neurobiological underpinnings of threat-related behaviors and anxiety, little progress was made with regard to new or improved treatments for mental disorders. A possible reason for this lack of success is the unknown predictive and cross-species translational validity of animal models used in preclinical studies. Re-translational approaches, therefore, seek to establish cross-species translational validity by identifying behavioral operations shared across species. To this end, we implemented a human open field test in virtual reality and measured behavioral indices derived from animal studies in three experiments ($$\textit{N}=31$$ N = 31 , $$\textit{N}=30$$ N = 30 , and $$\textit{N}=80$$ N = 80 ). In addition, we investigated the associations between anxious traits and such behaviors. Results indicated a strong similarity in behavior across species, i.e., participants in our study—like rodents in animal studies—preferred to stay in the outer region of the open field, as indexed by multiple behavioral parameters. However, correlational analyses did not clearly indicate that these behaviors were a function of anxious traits of participants. We conclude that the realized virtual open field test is able to elicit thigmotaxis and thus demonstrates cross-species validity of this aspect of the test. Modulatory effects of anxiety on human open field behavior should be examined further by incorporating possible threats in the virtual scenario and/or by examining participants with higher anxiety levels or anxiety disorder patients.

Deep Behavioral Phenotyping of Mouse Autism Models using Open-Field Behavior

Autism is noted for both its genotypic and phenotypic diversity. Repetitive action, resistance to environmental change, and motor disruptions vary from individual to individual. In animal models, conventional behavioral phenotyping captures such fine-scale variations incompletely. Here we use advances in computer vision and deep learning to develop a framework for characterizing mouse behavior on multiple time scales using a single popular behavioral assay, the open field test. We observed male and female C57BL/6J mice to develop a dynamic baseline of adaptive behavior over multiple days. We then examined two rodent models of autism, a cerebellum-specific model, L7-Tsc1, and a whole-brain knockout model, Cntnap2. Both Cntnap2 knockout and L7-Tsc1 mutants showed forelimb lag during gait. L7-Tsc1 mutants showed complex defects in multi-day adaptation, lacking the tendency of wild-type mice to spend progressively more time in corners of the arena. In L7-Tsc1 mutant mice, failure-to-adapt took the form of maintained ambling, turning, and locomotion, and an overall decrease in grooming. Adaptation in Cntnap2 knockout mice more broadly resembled that of wild-type. L7-Tsc1 mutant and Cntnap2 knockout mouse models showed different patterns of behavioral state occupancy. Our automated pipeline for deep phenotyping successfully captures model-specific deviations in adaptation and movement as well as differences in the detailed structure of behavioral dynamics.

Gait-level analysis of mouse open field behavior using deep learning-based pose estimation

1.AbstractGait and whole body posture are sensitive measures of the proper functioning of numerous neural circuits, and are often perturbed in many neurological, neuromuscular, and neuropsychiatric illnesses. Rodents provide a tractable model for elucidating disease mechanisms and interventions, however, studying gait and whole body posture in rodent models requires specialized methods and remains challenging. Here, we develop a simple assay that allows adoption of the commonly used open field apparatus for gait and whole body posture analysis. We leverage modern neural networks to abstract a mouse into keypoints and extract gait and whole body coordination metrics of the animal. Gait-level analysis allows us to detect every step of the animal’s movement and provides high resolution information about the animal’s behavior. We quantitate gait and whole body posture with high precision and accuracy across 62 highly visually diverse strains of mice. We validate our approach using four genetic mutants with known gait deficits. In extended analysis, we demonstrate that multiple autism spectrum disorder (ASD) models show gait and posture deficits, implying this is a general feature of ASD. We conduct a large strain survey of over 1898 mice, and find that gait and whole body posture measures are highly heritable in the laboratory mouse, and fall into three classes. Furthermore, the reference mouse strain, C57BL/6J, has a distinctly different gait and posture compared to other standard laboratory and wild-derived strains. We conduct a genome wide association study (GWAS) to define the genetic architecture of mouse movement in the open field. Combined, we describe a simple, sensitive, accurate, scalable, and ethologically relevant method of mouse gait and whole body posture analysis for behavioral neurogenetics. These results provide one of the largest laboratory mouse gait-level data resources for the research community and show the utility of automated machine learning approaches for biological insights.

Methamphetamine-Induced Open Field Behavior and LD50 in Periplaneta americana Cockroaches (Blattodea: Blattidae)

Invertebrate animal studies of methamphetamine (METH) could allow for high throughput, inexpensive, and high-animal number pharmacology and toxicology studies. We hypothesized that in Periplaneta americana cockroaches, METH would increase locomotion compared to saline and produce lethality. Lethal dose, 50% (LD50) was determined with 0–1,780 µg/g (mg/kg) METH (n = 15–16/group) using logit analysis. Locomotor activity after METH (0–560 mg/kg, intra-abdominal, n = 8 per group) administration and spontaneous locomotor activity in surviving cockroaches in an open field 24 h after LD50 study doses was measured with Noldus Ethovision. The LD50 of METH was 823.1 mg/kg (more than 10-fold greater than the value in rats). There were significant decreases in spontaneous locomotor activity in surviving cockroaches after administration of 650 and 750 mg/kg METH (P < 0.05). While 100 mg/kg METH did not significantly increase METH locomotor activity relative to saline, 300 mg/kg METH significantly increased locomotor activity compared to saline (P < 0.05), and 560 mg/kg METH resulted in most of the cockroaches slowly moving around the open field in the supine position for most of the trial. In conclusion, METH produces pharmacological and toxicological effects in P. americana. The high availability, low cost, and relative ease of use of these animals makes them a potential, very accessible option for studying METH use disorder.

Sex-specific gut microbiota modulation of aversive conditioning and basolateral amygdala dendritic spine density

ABSTRACTGut microbiota influence numerous aspects of host biology, including brain structure and function. Growing evidence implicates gut microbiota in aversive conditioning and anxiety-related behaviors, but research has focused almost exclusively on males. To investigate sex-specific effects of gut dysbiosis on aversive learning and memory, adult female and male C57BL/6N mice were orally administered a moderate dose of non-absorbable antimicrobial medications (ATMs; neomycin, bacitracin, pimaricin) or a control over 10 days. Changes in gut microbiome composition were analyzed by 16S rRNA sequencing. Open field behavior, cued aversive learning, context recall, and cued recall were assessed. Following behavioral testing, the morphology of basolateral amygdala (BLA) principal neuron dendrites and spines was characterized. Results revealed that ATMs induced distinct but overlapping patterns of gut dysbiosis across sex, with stronger effects in females. There were also sex-specific effects on behavior and neuroanatomy. Treated males but not females exhibited altered locomotor and anxiety-like behavior in the novel open field test. Treated females but not males showed impairments in aversive memory acquisition and cued recall. Context recall remained intact in both sexes, as did dendritic structure of BLA principal neurons. However, ATMs exerted sex-specific effects on spine density. A second experiment was conducted to isolate gut perturbation to cued recall. Results revealed no effect of ATMs on recall of a previously consolidated fear memory, suggesting that gut dysbiosis preferentially impacts aversive learning. These data shed new light on how gut microbiota interact with sex to influence aversive conditioning, anxiety-like behavior, and BLA dendritic spine architecture.SignificanceGut microbiota can influence brain function and behavior, including trauma and anxiety-related disorders. Although these disorders disproportionately affect women, preclinical research has focused almost exclusively on male rodent models. We investigated the impact of antimicrobial administration on gut microbiome structure, aversive conditioning, open field behavior, and basolateral amygdala principal neuron morphology in female and male mice. Results showed that treatment exerted wide-ranging effects, many of which were sex-specific. Our findings underscore the importance of studying sex differences and support a role for microbial modulation of aversive learning, anxiety-like behavior, and amygdala spine patterning.