Development of the social behavior of two mice species with contrasting social systems

miRNA-mediated inhibition of an actomyosin network in hippocampal pyramidal neurons restricts sociability in adult male mice

Social deficits are frequently observed in patients suffering from neurodevelopmental disorders, but the molecular mechanisms regulating sociability are still poorly understood. We recently reported that the loss of the microRNA (miRNA) cluster miR-379-410 leads to hypersocial behavior and anxiety in mice. Here, we show that ablating miR-379-410 in excitatory neurons of the postnatal mouse hippocampus recapitulates hypersociability, but not anxiety. At the cellular level, miR-379-410 loss in excitatory neurons leads to larger dendritic spines, increased excitatory synaptic transmission, and upregulation of an actomyosin gene network. Re-expression of three cluster miRNAs, as well as pharmacological inhibition of the actomyosin activator ROCK, is sufficient to reinstate normal sociability in miR-379-410 knockout mice. Several actomyosin genes and miR-379-410 family members are reciprocally dysregulated in isogenic human induced pluripotent stem cell (iPSC)-derived neurons harboring a deletion present in patients with Williams-Beuren syndrome, characterized by hypersocial behavior. Together, our results show an miRNA-actomyosin pathway involved in social behavior regulation.

Neural basis of unfamiliar conspecific recognition in domestic chicks (Gallus Gallus domesticus)

Domestic chickens are able to distinguish familiar from unfamiliar conspecifics, however the neuronal mechanisms mediating this behaviour are almost unknown. Moreover, the lateralisation of chicks' social recognition has only been investigated at the behavioural level, but not at the neural level. The aim of the present study was to test the hypothesis that exposure to unfamiliar conspecifics will selectively activate septum, hippocampus or nucleus taeniae of the amygdala of young domestic chicks. Moreover we also wanted to test the lateralisation of this response. For this purpose, we used the immediate early gene product c-Fos to map neural activity. Chicks were housed in pairs for one week. At test, either one of the two chicks was exchanged by an unfamiliar individual (experimental 'unfamiliar' group) or the familiar individual was briefly removed and then placed back in its original cage (control 'familiar' group). Analyses of chicks' interactions with the familiar/unfamiliar social companion revealed a higher number of social pecks directed towards unfamiliar individuals, compared to familiar controls. Moreover, in the group exposed to the unfamiliar individual a significantly higher activation was present in the dorsal and ventral septum of the left hemisphere and in the ventral hippocampus of the right hemisphere, compared to the control condition. These effects were neither present in other subareas of hippocampus or septum, nor in the nucleus taeniae of the amygdala. Our study thus indicates selective lateralised involvement of domestic chicks' septal and hippocampal subregions in responses to unfamiliar conspecific.

Ectoparasites burden of House mouse (Mus musculus linnaeus, 1758) from Hai'l region, Kingdom of Saudi Arabia

The House mice (Mus musculus Linnaeus, 1758), play an important role in the transmission of diseases, both in humans and livestock, through ectoparasite carried on their feces, urine and hair remnants. The purpose of this study was to investigate the ectoparasites infestation, as well as their quantitative and qualitative abundance and, prevalence in the house mice captured from Hai’l region, Kingdom of Saudi Arabia (KSA). Parasitological investigations were performed on 70 house mice trapped during 2012–2013 from two localities (Hai’l City residential area and Al-Khitah agricultural farm habitats in Hai’l region). Captured mice were identified as males (34.3% and 48.6%) and females (65.7% and 51.4%) from the residential and agricultural farm habitats, respectively. The findings of the study showed that the sex ratio of the mice found in different habitats did not influence the level of ectoparasite infestation (P > 0.05). Therefore, we combined only sex-wise samples for each habitat and isolated habitats treated separately for our subsequent analyses. A total of 514 ectoparasites individuals belong to four species were recovered from the mice, which included 339 of flea (Xenopsylla cheopis Rothschild, 1903), 39 of sucking lice (Polyplax spinulosa Burmeister, 1835), 37 of sucking lice Polyplax serrata Burmeister, 1839), and 99 of mite species (Laelaps echidninus Berlese, 1887).

The presence of zoonotic parasites indicates that Mus musculus as a reservoir, might represent a danger to the public health particularly in the two sampled areas. Results also suggest an increasingly need for further studies to assess the role of the ectoparasites of house mice and their possible involvment in transmission of diseases among these areas.

A circuit from hippocampal CA2 to lateral septum disinhibits social aggression

Although the hippocampus is known to be important for declarative memory, how hippocampal output regulates motivated behaviors, such as social aggression, is less well understood. Here we report that hippocampal CA2 pyramidal neurons, which are important for social memory, promote social aggression. This action depends on CA2 output to the lateral septum that is selectively enhanced immediately prior to attack. Activation of lateral septum by CA2 recruits a circuit that disinhibits a subnucleus of the ventro-medial hypothalamus known to trigger attack. The social hormone arginine-vasopressin enhances social aggression by acting on arginine-vasopressin 1b receptors on CA2 presynaptic terminals in lateral septum to facilitate excitatory synaptic transmission. In this manner, release of vasopressin in lateral septum, driven by an animal’s internal state, may serve as a modulatory control that determines whether CA2 activity leads to declarative memory of a social encounter or proceeds to promote motivated social aggression.

Attenuated Chemosensory Responsiveness of the Grueneberg Ganglion in Mouse Pups at Warm Temperatures

Neurons of the Grueneberg ganglion (GG) in the anterior nasal region of mice respond to a small set of odorous compounds, including given dimethylpyrazines present in mouse urine. Consequently, mouse pups living in murine colonies are presumably commonly exposed to such GG-activating substances. Since stimulation of the GG elicits alarm and stress reactions in mice, the question arises whether such a GG activation potentially inducing stress could be reduced when pups might rather feel secure in the presence of their mother. Being together with their warmth-giving dam, mouse pups experience a nest temperature of ∼35 °C. Therefore, we hypothesized that such a warm temperature may attenuate the responses of GG neurons to dimethylpyrazines. Monitoring the expression of the activity marker c-Fos, GG responses to dimethylpyrazines were significantly lower in pups exposed to these substances at 35 °C compared to exposure at 30 °C. By contrast, dimethylpyrazine-induced responses of neurons in the main olfactory epithelium were not diminished at 35 °C in comparison to 30 °C. The attenuated chemosensory responses of GG neurons at 35 °C coincided with a reduced dimethylpyrazine-evoked activation of the glomeruli in the olfactory bulb innervated by GG neurons. The reduction in dimethylpyrazine-evoked GG responses by warm temperatures was positively correlated with exposure time, suggesting that warm temperatures might enhance desensitization processes in GG neurons. In summary, the findings indicate that warm temperatures similar to those in mouse nests in the presence of the dam attenuate GG activation by colony-derived odorants.

Gancidin W, a potential low-toxicity antimalarial agent isolated from an endophytic Streptomyces SUK10

Endophytic Streptomyces strains are potential sources for novel bioactive molecules. In this study, the diketopiperazine gancidin W (GW) was isolated from the endophytic actinobacterial genus Streptomyces, SUK10, obtained from the bark of Shorea ovalis tree, and it was tested in vivo against Plasmodium berghei PZZ1/100. GW exhibited an inhibition rate of nearly 80% at 6.25 and 3.125 μg kg-1 body weight on day four using the 4-day suppression test method on male ICR strain mice. Comparing GW at both concentrations with quinine hydrochloride and normal saline as positive and negative controls, respectively, 50% of the mice treated with 3.125 μg kg-1 body weight managed to survive for more than 11 months after infection, which almost reached the life span of normal mice. Biochemical tests of selected enzymes and proteins in blood samples of mice treated with GW were also within normal levels; in addition, no abnormalities or injuries were found on internal vital organs. These findings indicated that this isolated bioactive compound from Streptomyces SUK10 exhibits very low toxicity and is a good candidate for potential use as an antimalarial agent in an animal model.

Lifetime development of behavioural phenotype in the house mouse (Mus musculus)

With each trajectory taken during the ontogeny of an individual, the number of optional behavioural phenotypes that can be expressed across its life span is reduced. The initial range of phenotypic plasticity is largely determined by the genetic material/composition of the gametes whereas interacting with the given environment shapes individuals to adapt to/cope with specific demands. In mammalian species, the phenotype is shaped as the foetus grows, depending on the environment in the uterus, which in turn depends on the outer environment the mother experiences during pregnancy. After birth, a complex interaction between innate constitution and environmental conditions shapes individual lifetime trajectories, bringing about a wide range of diversity among individual subjects.

In laboratory mice inbreeding has been systematically induced in order to reduce the genetic variability between experimental subjects. In addition, within most laboratories conducting behavioural phenotyping with mice, breeding and housing conditions are highly standardised. Despite such standardisation efforts a considerable amount of variability persists in the behaviour of mice. There is good evidence that phenotypic variation is not merely random but might involve individual specific behavioural patterns consistent over time. In order to understand the mechanisms and the possible adaptive value of the maintenance of individuality we review the emergence of behavioural phenotypes over the course of the life of (laboratory) mice. We present a literature review summarizing developmental stages of behavioural development of mice along with three illustrative case studies. We conclude that the accumulation of environmental differences and experiences lead to a “mouse individuality” that becomes increasingly stable over the lifetime.

Smells familiar: group-joining decisions of predatory mites are mediated by olfactory cues of social familiarity

Group-living animals frequently have to trade off the costs and benefits of leaving an established group and joining another group. Owing to their high fitness relevance, group-joining decisions are commonly nonrandom and may be based on traits of both individual members and the group such as life stage, body size, social status and group density or size, respectively. Many group-living animals are able to recognize and to associate preferentially with familiar individuals, i.e. those encountered before. Hence, after dispersing from established groups, animals commonly have to decide whether to join a new familiar or unfamiliar group. Using binary choice situations we assessed the effects of social familiarity on group-joining behaviour of the plant-inhabiting predatory mite Phytoseiulus persimilis. Group living in P. persimilis is brought about by the patchy distribution of its spider mite prey and mutual conspecific attraction. In the first experiment, gravid predator females given a choice between spider mite patches occupied by unfamiliar and familiar groups of females strongly preferred to join familiar groups and to deposit their eggs in these patches. Preference for socially familiar groups was robust across biases of spider mite prey densities between choice options. The second experiment revealed that the predatory mite females can smell social familiarity from a distance. Females subjected to odour choice situations in artificial cages were more strongly attracted to the odour of familiar than unfamiliar groups. We argue that P. persimilis females preferentially join socially familiar groups because a familiar social environment relaxes competition and optimizes foraging and reproduction.

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Group-joining decisions should be based on cues indicating fitness prospects.

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Group-living predatory mites preferentially join socially familiar groups.

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Attraction to familiar groups from the distance is mediated by olfactory cues.

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Previous work showed that familiar individuals reproduce more than unfamiliar ones.

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Thus we argue that preferentially joining socially familiar groups is adaptive.