Scaling law in free walking of mice in circular open fields of various diameters

Genetics of behavioural evolution in giant mice from Gough Island

The evolution of behaviour on islands is a pervasive phenomenon that contributed to Darwin's theory of natural selection. Island populations frequently show increased boldness and exploration compared with their mainland counterparts. Despite the generality of this pattern, the genetic basis of island-associated behaviours remains a mystery. To address this gap in knowledge, we genetically dissected behaviour in 613 F2s generated by crossing inbred mouse strains from Gough Island (where they live without predators or human commensals) and a mainland conspecific. We used open field and light/dark box tests to measure seven behaviours related to boldness and exploration in juveniles and adults. Across all assays, we identified a total of 41 quantitative trait loci (QTL) influencing boldness and exploration. QTL have moderate effects and are often unique to specific behaviours or ages. Function-valued trait mapping revealed changes in estimated effects of QTL during assays, providing a rare dynamic window into the genetics of behaviour often missed by standard approaches. The genomic locations of QTL are distinct from those found in laboratory strains of mice, indicating different genetic paths to the evolution of similar behaviours. We combine our mapping results with extensive phenotypic and genetic information available for laboratory mice to nominate candidate genes for the evolution of behaviour on islands.

A hierarchical 3D-motion learning framework for animal spontaneous behavior mapping

Animal behavior usually has a hierarchical structure and dynamics. Therefore, to understand how the neural system coordinates with behaviors, neuroscientists need a quantitative description of the hierarchical dynamics of different behaviors. However, the recent end-to-end machine-learning-based methods for behavior analysis mostly focus on recognizing behavioral identities on a static timescale or based on limited observations. These approaches usually lose rich dynamic information on cross-scale behaviors. Here, inspired by the natural structure of animal behaviors, we address this challenge by proposing a parallel and multi-layered framework to learn the hierarchical dynamics and generate an objective metric to map the behavior into the feature space. In addition, we characterize the animal 3D kinematics with our low-cost and efficient multi-view 3D animal motion-capture system. Finally, we demonstrate that this framework can monitor spontaneous behavior and automatically identify the behavioral phenotypes of the transgenic animal disease model. The extensive experiment results suggest that our framework has a wide range of applications, including animal disease model phenotyping and the relationships modeling between the neural circuits and behavior.

Evolution of Boldness and Exploratory Behavior in Giant Mice from Gough Island

Island populations are hallmarks of extreme phenotypic evolution. Radical changes in resource availability and predation risk accompanying island colonization drive changes in behavior, which Darwin likened to tameness in domesticated animals. Although many examples of animal boldness are found on islands, the heritability of observed behaviors, a requirement for evolution, remains largely unknown. To fill this gap, we profiled anxiety and exploration in island and mainland inbred strains of house mice raised in a common laboratory environment. The island strain was descended from mice on Gough Island, the largest wild house mice on record. Experiments utilizing open environments across two ages showed that Gough Island mice are bolder and more exploratory, even when a shelter is provided. Concurrently, Gough Island mice retain an avoidance response to predator urine. F1 offspring from crosses between these two strains behave more similarly to the mainland strain for most traits, suggesting recessive mutations contributed to behavioral evolution on the island. Our results provide a rare example of novel, inherited behaviors in an island population and demonstrate that behavioral evolution can be specific to different forms of perceived danger. Our discoveries pave the way for a genetic understanding of how island populations evolve unusual behaviors.

Long term breeding of the Lmna G609G progeric mouse: Characterization of homozygous and heterozygous models

The transgenic Lmna^G609G progeric mouse represents an outstanding animal model for studying the human Hutchinson-Gilford Progeria Syndrome (HGPS) caused by a mutation in the LMNA gene, coding for the nuclear envelope protein Lamin A/C, and, as an important, more general scope, for studying the complex process governing physiological aging in humans. Here we give a comprehensive description of the peculiarities related to the breeding of Lmna^G609G mice over a prolonged period of time, and of many features observed in a large colony for a 2-years period. We describe the breeding and housing conditions underlining the possible interference of the genetic background on the phenotype expression. This information represents a useful tool when planning and interpreting studies on the Lmna^G609G mouse model, complementing any specific data already reported in the literature about this model since its production. It is also particularly relevant for the heterozygous mouse, which mirrors the genotype of the human pathology however requires an extended time to manifest symptoms and to be carefully studied.

Altered synaptic phospholipid signaling in PRG-1 deficient mice induces exploratory behavior and motor hyperactivity resembling psychiatric disorders

Plasticity related gene 1 (PRG-1) is a neuron specific membrane protein located at the postsynaptic density of glutamatergic synapses. PRG-1 modulates signaling pathways of phosphorylated lipid substrates such as lysophosphatidic acid (LPA). Deletion of PRG-1 increases presynaptic glutamate release probability leading to neuronal over-excitation. However, due to its cortical expression, PRG-1 deficiency leading to increased glutamatergic transmission is supposed to also affect motor pathways. We therefore analyzed the effects of PRG-1 function on exploratory and motor behavior using homozygous PRG-1 knockout (PRG-1^-/-) mice and PRG-1/LPA₂-receptor double knockout (PRG-1^-/-/LPA₂^-/-) mice in two open field settings of different size and assessing motor behavior in the Rota Rod test. PRG-1^-/- mice displayed significantly longer path lengths and higher running speed in both open field conditions. In addition, PRG-1^-/- mice spent significantly longer time in the larger open field and displayed rearing and self-grooming behavior. Furthermore PRG-1^-/- mice displayed stereotypical behavior resembling phenotypes of psychiatric disorders in the smaller sized open field arena. Altogether, this behavior is similar to the stereotypical behavior observed in animal models for psychiatric disease of autistic spectrum disorders which reflects a disrupted balance between glutamatergic and GABAergic synapses. These differences indicate an altered excitation/inhibition balance in neuronal circuits in PRG-1^-/- mice as recently shown in the somatosensory cortex [38]. In contrast, PRG-1^-/-/LPA₂^-/- did not show significant changes in behavior in the open field suggesting that these specific alterations were abolished when the LPA₂-receptor was lacking. Our findings indicate that PRG-1 deficiency led to over-excitability caused by an altered LPA/LPA₂-R signaling inducing a behavioral phenotype typically observed in animal models for psychiatric disorders.