Conceptual and methodological issues in the genetics of mouse agonistic behavior

Targeted Tshz3 deletion in corticostriatal circuit components segregates core autistic behaviors

We previously linked TSHZ3 haploinsufficiency to autism spectrum disorder (ASD) and showed that embryonic or postnatal Tshz3 deletion in mice results in behavioral traits relevant to the two core domains of ASD, namely social interaction deficits and repetitive behaviors. Here, we provide evidence that cortical projection neurons (CPNs) and striatal cholinergic interneurons (SCINs) are two main and complementary players in the TSHZ3-linked ASD syndrome. In the cerebral cortex, TSHZ3 is expressed in CPNs and in a proportion of GABAergic interneurons, but not in cholinergic interneurons or glial cells. In the striatum, TSHZ3 is expressed in all SCINs, while its expression is absent or partial in the other main brain cholinergic systems. We then characterized two new conditional knockout (cKO) models generated by crossing Tshz3^flox/flox with Emx1-Cre (Emx1-cKO) or Chat-Cre (Chat-cKO) mice to decipher the respective role of CPNs and SCINs. Emx1-cKO mice show altered excitatory synaptic transmission onto CPNs and impaired plasticity at corticostriatal synapses, with neither cortical neuron loss nor abnormal layer distribution. These animals present social interaction deficits but no repetitive patterns of behavior. Chat-cKO mice exhibit no loss of SCINs but changes in the electrophysiological properties of these interneurons, associated with repetitive patterns of behavior without social interaction deficits. Therefore, dysfunction in either CPNs or SCINs segregates with a distinct ASD behavioral trait. These findings provide novel insights onto the implication of the corticostriatal circuitry in ASD by revealing an unexpected neuronal dichotomy in the biological background of the two core behavioral domains of this disorder.

Evolution of stress responses refine mechanisms of social rank

Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.

Why are Women More Religious than Men? Do Risk Preferences and Genetic Risk Predispositions Explain the Gender Gap?

Risk preference theory argues that the gender gap in religiosity is caused by greater female risk aversion. Although widely debated, risk preference theory has been inadequately tested. Our study tests the theory directly with phenotypic and genetic risk preferences in three dimensions-general, impulsive, and sensation-seeking risk. Moreover, we examine whether the effect of different dimension of risk preference on the gender gap varies across different dimensions of religiosity. We find that general and impulsive risk preferences do not explain gender differences in religiosity, whereas sensation-seeking risk preference makes the gender gap in self-assessed religiousness and church attendance insignificant, but not belief in God, prayer, or importance of religion. Genetic risk preferences do not remove any of the gender gaps in religiosity, suggesting that the causal order is not from risk preference to religiosity. Evidence suggests that risk preferences are not a strong predictor for gender differences in religiosity.

Correlation between GRIK2 rs6922753, rs2227283 polymorphism and aggressive behaviors with Bipolar Mania in the Chinese Han population

OBJECTIVES

Animal studies have shown that glutamate receptor ionotropic kainate 2 (GRIK2) gene knockout mice are more impulsive and aggressive. This study aims to verify whether the rs6922753 and rs2227283 polymorphisms of the GRIK2 gene are associated with both aggressive behavior and bipolar mania in the Chinese Han population.

METHODS

Polymerase chain reaction (PCR) was applied in the genotype rs6922753 and rs2227283 polymorphisms of the GRIK2 gene in 201 bipolar manic patients with aggressive behaviors, 198 bipolar manic patients without aggressive behaviors, and 132 healthy controls. The Modified Overt Aggression Scale (MOAS) was used to evaluate aggressive behavior in patients with bipolar mania.

RESULTS

No correlation was found between aggressive behavior and the rs6922753 polymorphism in the three groups. The A/A genotype and A allele of the rs2227283 polymorphism were found significantly more frequently in patients with aggressive behavior than in healthy controls (p = .004 and p = .013, respectively) and in patients with nonaggressive behavior (p = .002 and p = .018, respectively). The A/A genotype and A allele were associated with an increased risk of aggressive behavior.

CONCLUSION

This study suggests that the rs2227283 polymorphism of the GRIK2 gene is related to aggressive behaviors in bipolar manic patients and that the A/A genotype and A allele may increase the risk of the aggressive behavior in bipolar manic patients.

Construct Validity and Cross Validity of a Test Battery Modeling Autism Spectrum Disorder (ASD) in Mice

Modeling in other organism species is one of the crucial stages in ascertaining the association between gene and psychiatric disorder. Testing Autism Spectrum Disorder (ASD) in mice is very popular but construct validity of the batteries is not available. We presented here the first factor analysis of a behavioral model of ASD-like in mice coupled with empirical validation. We defined fourteen measures aligning mouse-behavior measures with the criteria defined by DSM-5 for the diagnostic of ASD. Sixty-five mice belonging to a heterogeneous pool of genotypes were tested. Reliability coefficients vary from .68 to .81. The factor analysis resulted in a three- factor solution in line with DSM criteria: social behavior, stereotypy and narrowness of the field of interest. The empirical validation with mice sharing a haplo-insufficiency of the zinc-finger transcription factor TSHZ3/Tshz3 associated with ASD shows the discriminant power of the highly loaded items.

Differential Brain, Cognitive and Motor Profiles Associated with Partial Trisomy. Modeling Down Syndrome in Mice

We hypothesize that the trisomy 21 (Down syndrome) is the additive and interactive outcome of the triple copy of different regions of HSA21. Because of the small number of patients with partial trisomy 21, we addressed the question in the Mouse in which three chromosomal regions located on MMU10, MMU17 and MMU16 carries almost all the HSA21 homologs. Male mice from four segmental trisomic strains covering the D21S17-ETS2 (syntenic to MMU16) were examined with an exhaustive battery of cognitive tests, motor tasks and MRI and compared with TS65Dn that encompasses D21S17-ETS2. None of the four strains gather all the impairments (measured by the effect size) of TS65Dn strain. The 152F7 strain was close to TS65Dn for motor behavior and reference memory and the three other strains 230E8, 141G6 and 285E6 for working memory. Episodic memory was impaired only in strain 285E6. The hippocampus and cerebellum reduced sizes that were seen in all the strains indicate that trisomy 21 is not only a hippocampus syndrome but that it results from abnormal interactions between the two structures.

Peer Influence, Genetic Propensity, and Binge Drinking: A Natural Experiment and a Replication

The authors draw data from the College Roommate Study (ROOM) and the National Longitudinal Study of Adolescent Health to investigate gene-environment interaction effects on youth binge drinking. In ROOM, the environmental influence was measured by the precollege drinking behavior of randomly assigned roommates. Random assignment safeguards against friend selection and removes the threat of gene-environment correlation that makes gene-environment interaction effects difficult to interpret. On average, being randomly assigned a drinking peer as opposed to a nondrinking peer increased college binge drinking by 0.5-1.0 episodes per month, or 20%-40% the average amount of binge drinking. However, this peer influence was found only among youths with a medium level of genetic propensity for alcohol use; those with either a low or high genetic propensity were not influenced by peer drinking. A replication of the findings is provided in data drawn from Add Health. The study shows that gene-environment interaction analysis can uncover social-contextual effects likely to be missed by traditional sociological approaches.

Mapping of Genetic Factors That Elicit Intermale Aggressive Behavior on Mouse Chromosome 15: Intruder Effects and the Complex Genetic Basis

Despite high estimates of the heritability of aggressiveness, the genetic basis for individual differences in aggression remains unclear. Previously, we showed that the wild-derived mouse strain MSM/Ms (MSM) exhibits highly aggressive behaviors, and identified chromosome 15 (Chr 15) as the location of one of the genetic factors behind this escalated aggression by using a panel of consomic strains of MSM in a C57BL/6J (B6) background. To understand the genetic effect of Chr 15 derived from MSM in detail, this study examined the aggressive behavior of a Chr 15 consomic strain towards different types of opponent. Our results showed that both resident and intruder animals had to have the same MSM Chr 15 genotype in order for attack bites to increase and attack latency to be reduced, whereas there was an intruder effect of MSM Chr 15 on tail rattle behavior. To narrow down the region that contains the genetic loci involved in the aggression-eliciting effects on Chr 15, we established a panel of subconsomic strains of MSM Chr 15. Analysis of these strains suggested the existence of multiple genes that enhance and suppress aggressive behavior on Chr 15, and these loci interact in a complex way. Regression analysis successfully identified four genetic loci on Chr 15 that influence attack latency, and one genetic locus that partially elicits aggressive behaviors was narrowed down to a 4.1-Mbp region (from 68.40 Mb to 72.50 Mb) on Chr 15.

Gene by Social-Environment Interaction for Youth Delinquency and Violence: Thirty-Nine Aggression-related Genes

Complex human traits are likely to be affected by many environmental and genetic factors, and the interactions among them. However, previous gene-environment interaction (G×E) studies have typically focused on one or only a few genetic variants at a time. To provide a broader view of G×E, this study examines the relationship between 403 genetic variants from 39 genes and youth delinquency and violence. We find evidence that low social control is associated with greater genetic risk for delinquency and violence and high/moderate social control with smaller genetic risk for delinquency and violence. Our findings are consistent with prior G×E studies based on a small number of genetic variants, and, more importantly, we show that these findings still hold when a large number of genetic variants are considered simultaneously. A key implication of these findings is that the expression of multiple genes related to delinquency depends on the social environment: gene expression is likely to be amplified in low-social-control environments but, tends to be suppressed in high/moderate-social-control environments. This study not only deepens our understanding of how the social environment shapes individual behavior, but also provides important conceptual and methodological insights for future G×E research on complex human traits.

Androgen-mediated nurturing and aggressive behaviors during paternal care in bluegill sunfish (Lepomis macrochirus)

Male parental care in vertebrates often involves both defensive and nurturing behaviors. Whether androgens differentially mediate these two types of behaviors, or a trade-off exists between them, has been studied by behavioral endocrinologists for years but predominantly in species with biparental care. In such systems, potential detrimental effects of elevated androgens on parental care behaviors are often compensated for by changes in behavior of the unmanipulated parent. In contrast, for species where only one parent provides care, manipulation of androgen levels may more clearly determine if there are differential effects of androgens on these two types of behaviors and whether the proposed trade-off between defensive and nurturing behavior exists. Here, we manipulated androgen levels in two ways in bluegill sunfish (Lepomis macrochirus), a species where males provide sole parental care for the young. At the onset of the care period, males were implanted with 11-ketotestosterone, a major teleost androgen, the androgen receptor antagonist flutamide, or a blank implant. A separate control group experienced no manipulation. Males were then observed over several days and tested for their aggressiveness towards an experimentally-presented brood predator and for nurturing behavior (fanning of the eggs, removal of dead or fungal-infected eggs). Males implanted with 11-ketotestosterone displayed 64% more aggressive behaviors and 71% fewer nurturing behaviors than control groups. In contrast, males implanted with flutamide displayed 7% fewer aggressive behaviors and 126% more nurturing behaviors than control males. Taken together, these results show that aggression and nurturing behaviors are mediated by androgens and suggest that there is a trade-off between the two behaviors during parental care in this species.

Analysis of male aggressive and sexual behavior in mice

Pheromone and odor signals play a pivotal role in male mouse reproductive behaviors, such as sexual and aggressive behavior. There are several methods used to assess male behaviors, each of which examines a unique aspect of the biological function of mice. There are two major ways of assessing male aggressive behavior in mice, one is using isolation-induced aggression, and the other is territorial aggression in pair-housed males. To analyze male sexual behavior, a female mouse that is hormone-primed with estradiol and progesterone is usually introduced into a male home range, and mounting, intromission, and ejaculation behaviors are observed for 1 h. Here, we summarize the detailed protocols for assessing male behaviors.

Brain pathways mediating the pro-aggressive effect of the steroid sulfatase (Sts) gene

STS is the single enzyme that converts all steroid sulfates into their free steroid forms. Initiation of attack behavior against conspecific male mice appeared to be linked to Sts. Here we have confirmed the role of Sts through an association study with attack behavior. Previous studies indicated a positive correlation between the initiation of attack behavior and liver STS concentration levels in male mice, but this finding was not compatible with established knowledge of STS mechanisms. High STS concentrations induce low concentrations of sulfated steroids. Sulfated and un-sulfated steroids are GABA(A) receptor agonists and NMDA receptor positive allosteric modulators. This synaptic pattern of functioning can generate attack behavior and we have confirmed here that an injection of the sulfated steroid dehydroepiandrosterone sulfate (DHEA-S) increases attack behavior. To solve the paradox, we measured the transcription activity of the genes underlying the pathways involved in the hydrolysis of sulfated steroids and leading to the formation of un-conjugated steroids in the mouse brain. We observed that the genes monitoring the steroid biosynthesis pathways exhibited a transcription pattern resulting in an increased sulfotransferase activity in the attacking males that could counterbalance the de-sulfating activity of Sts in the attacking mice.

The vicious cycle towards violence: focus on the negative feedback mechanisms of brain serotonin neurotransmission

Violence can be defined as a form of escalated aggressive behavior that is expressed out of context and out of inhibitory control, and apparently has lost its adaptive function in social communication. Little is known about the social and environmental factors as well as the underlying neurobiological mechanisms involved in the shift of normal adaptive aggression into violence. In an effort to model the harmful acts of aggression and violence in humans, we recently (re)developed an animal model that is focused on engendering uncontrolled forms of maladaptive aggressive behavior in laboratory-bred feral rats and mice. We show that certain (8-12%) constitutionally aggressive individuals gradually develop, over the course of repetitive exposures to victorious social conflicts, escalated (short-latency, high-frequency and ferocious attacks), persistent (lack of attack inhibition by defeat/submission signals and perseverance of the aggressive attack-biting bout), indiscriminating (attacking female and anesthetized male intruders) and injurious (enhanced vulnerable-body region attacks and inflicted wounding) forms of offensive aggression. Based on the neurobiological results obtained using this model, a revised view is presented on the key role of central serotonergic (auto)regulatory mechanisms in this transition of normal aggression into violence.

Genetic mapping of social interaction behavior in B6/MSM consomic mouse strains

Genetic studies are indispensable for understanding the mechanisms by which individuals develop differences in social behavior. We report genetic mapping of social interaction behavior using inter-subspecific consomic strains established from MSM/Ms (MSM) and C57BL/6J (B6) mice. Two animals of the same strain and sex, aged 10 weeks, were introduced into a novel open-field for 10 min. Social contact was detected by an automated system when the distance between the centers of the two animals became less than ~12 cm. In addition, detailed behavioral observations were made of the males. The wild-derived mouse strain MSM showed significantly longer social contact as compared to B6. Analysis of the consomic panel identified two chromosomes (Chr 6 and Chr 17) with quantitative trait loci (QTL) responsible for lengthened social contact in MSM mice and two chromosomes (Chr 9 and Chr X) with QTL that inhibited social contact. Detailed behavioral analysis of males identified four additional chromosomes associated with social interaction behavior. B6 mice that contained Chr 13 from MSM showed more genital grooming and following than the parental B6 strain, whereas the presence of Chr 8 and Chr 12 from MSM resulted in a reduction of those behaviors. Longer social sniffing was observed in Chr 4 consomic strain than in B6 mice. Although the frequency was low, aggressive behavior was observed in a few pairs from consomic strains for Chrs 4, 13, 15 and 17, as well as from MSM. The social interaction test has been used as a model to measure anxiety, but genetic correlation analysis suggested that social interaction involves different aspects of anxiety than are measured by open-field test.

Genetic influences on aggressive behaviors and arousability in animals

In a variety of species, strain differences in aggressive behaviors strongly indicate genetic influences. In people, as suggested, for example, by the work of Kagan, Rothbart, Cloninger, and their collaborators, long-lasting differences in temperament argue for genetic as well as environmental effects. After well-controlled experimentation in mice, we have learned five lessons about gene/behavior causal relations bearing on sociosexual and aggressive behaviors. The effect of a given gene on a given behavior depends upon: (1) exactly when and where that gene is expressed in the brain; (2) the gender of the animal in which it is expressed; (3) the age of the animal; (4) the nature of the opponent; and (5) the form of aggression (e.g., testosterone-facilitated aggression vs. maternal aggression). Moreover, in female mice, better social recognition is correlated with lower levels of aggression. We have gathered evidence for a four-gene micronet involving estrogen receptors alpha and beta, oxytocin, and the oxytocin receptor as expressed in the hypothalamus and amygdala. Normal performance of this micronet is required for social recognition and thus for control over aggression. Underlying certain genetic influences on sociosexual behaviors and aggression may be alterations in generalized brain arousal.

Aggressive and mating behaviors in two types of sex reversed mice: XY females and XX males

Aggressive and mating behaviors were assessed in XX females, XY females, and XY males of the C57BL/6/J/Ei ("C57BL/6" or "B6") strain of mouse. The Y chromosome of the XY females derives from Mus domesticus poschiavinus and the Y chromosome of the XY males derives from Mus musculus. The poschiavinus Y in the C57BL/6 background results in XY mice with either ovaries or ovotestes. Only those with ovaries were tested. These XY females appear to be endocrinologically identical to XX females. Aggressive and mating behaviors were also tested in XX males and XY males of the FVB/NtacfBR Odsex ("FVB") strain of mouse. The XX males have a transgene inserted 1 Mb upstream of the SOX9 gene, resulting in gonadal differentiation as a testis in the absence of a Y chromosome. C57BL/6 mice were tested for aggression in an instigated resident intruder paradigm and FVB/NtacfBR Odsex mice were tested for aggression in a neutral cage paradigm. Mice of both strains were tested with opponents of the same sex chromosome complement and gonadal sex. On the C57BL/6 background, the XY males were more aggressive than the XY and XX females, but there was no significant difference between the XX and XY females in aggression. On the FVB background, the XY and XX males were equally aggressive. Mice from both C57BL/6 and FVB backgrounds were tested for mating behaviors with females in hormonal estrus. On the C57BL/6 background, the XY males mounted more than the XY females, but there was no significant difference between the XY and XX females in mounting. On the FVB background, mounting, intromissions, and ejaculations were the same in XY and XX males. The implications of these findings for the effect of sex chromosome complement on sex differences in aggression and mating in mice are discussed.

Mouse behavioral assays relevant to the symptoms of autism

While the cause of autism remains unknown, the high concordance between monozygotic twins supports a strong genetic component. The importance of genetic factors in autism encourages the development of mutant mouse models, to advance our understanding of biological mechanisms underlying autistic behaviors. Mouse models of human neuropsychiatric diseases are designed to optimize (i) face validity (resemblance to the human symptoms) (ii) construct validity (similarity to the underlying causes of the disease) and (iii) predictive validity (expected responses to treatments that are effective in the human disease). There is a growing need for mouse behavioral tasks with all three types of validity, to define robust phenotypes in mouse models of autism. Ideal mouse models will incorporate analogies to the three diagnostic symptoms of autism: abnormal social interactions, deficits in communication and high levels of repetitive behaviors. Social approach is tested in an automated three chambered apparatus that offers the subject a choice between spending time with another mouse, with a novel object, or remaining in an empty familiar environment. Reciprocal social interaction is scored from videotapes of interactions between pairs of unfamiliar mice. Communication is evaluated by measuring emission and responses to vocalizations and olfactory cues. Repetitive behaviors are scored for measures of grooming, jumping, or stereotyped sniffing of one location or object. Insistence on sameness is modeled by scoring a change in habit, for example, reversal of the spatial location of a reinforcer in the Morris water maze or T-maze. Associated features of autism, for example, mouse phenotypes relevant to anxiety, seizures, sleep disturbances and sensory hypersensitivity, may be useful to include in a mouse model that meets some of the core diagnostic criteria. Applications of these assays include (i) behavioral phenotyping of transgenic and knockout mice with mutations in genes relevant to autism; (ii) characterization of inbred strains of mice; (iii) evaluation of environmental toxins; (iv) comparison of behavioral phenotypes with genetic factors, such as unusual expression patterns of genes or unusual single nucleotide polymorphisms; and (v) evaluation of proposed therapeutics for the treatment of autism.

Social approach behaviors in oxytocin knockout mice: comparison of two independent lines tested in different laboratory environments

Oxytocin mediates social affiliation behaviors and social memory in rodents. It has been suggested that disruptions in oxytocin contribute to the deficits in reciprocal social interactions that characterize autism. The present experiments employed a new social approach task for mice which is designed to detect low levels of sociability, representing the first diagnostic criterion for autism. Two lines of oxytocin knockout mice were tested, the National Institute of Mental Health line in Bethesda, and the Baylor/Emory line at the University of North Carolina in Chapel Hill. Similar methods were used for each line to evaluate tendencies to spend time with a stranger mouse versus with an inanimate novel object with no social valence. Adult C57BL/6J males were tested identically, as controls to confirm the robustness of the methods used in the social task. Comprehensive phenotyping of general health, neurological reflexes, olfactory and other sensory abilities, and motor functions was employed to assess both lines. No genotype differences were detected in any of the control measures for either line. Normal sociability, measured as time spent with a novel stranger mouse as compared to time spent with a novel object, was seen in both the NIMH and the Baylor/Emory lines of oxytocin null mutants, heterozygotes, and wild-type littermate controls. Normal preference for social novelty, measured as time spent with a second novel stranger as compared to time spent with a more familiar mouse, was seen in both the NIMH and the Baylor/Emory lines of oxytocin null mutants, heterozygotes, and wild-type littermate controls, with minor exceptions. Similar behavioral results from two independent targeted gene mutations, generated with different targeting vectors, bred on different genetic backgrounds, and tested in different laboratory environments, corroborates the negative findings on sociability in oxytocin mutant mice. Intact tendencies to spend time with another mouse versus with a novel object, in both lines of oxytocin knockouts, supports an interpretation that oxytocin plays a highly specific role in social memory, but is not essential for general spontaneous social approach in mice.

A mouse model system for genetic analysis of sociability: C57BL/6J versus BALB/cJ inbred mouse strains

BACKGROUND

Impairments in social behaviors are highly disabling symptoms of autism, schizophrenia, and other psychiatric disorders. Mouse model systems are useful for identifying the many genes and environmental factors likely to affect complex behaviors, such as sociability (the tendency to seek social interaction). To progress toward developing such a model system, we tested the hypothesis that C57BL/6J inbred mice show higher levels of sociability than BALB/cJ inbred mice.

METHODS

Mice tested for sociability were 4- and 9-week-old, male and female C57BL/6J and BALB/cJ mice. On 2 consecutive days, the sociability of each test mouse toward an unfamiliar 4-week-old DBA/2J stimulus mouse was assessed with a social choice paradigm conducted in a three-chambered apparatus. Measures of sociability included the time that the test mouse spent near versus far from the stimulus mouse, the time spent directly sniffing the stimulus mouse, and the time spent in contact between test and stimulus mice in a free interaction.

RESULTS

C57BL/6J mice showed higher levels of sociability than BALB/cJ mice overall in each of these measures.

CONCLUSIONS

We propose that C57BL/6J and BALB/cJ mice will be a useful mouse model system for future genetic and neurobiological studies of sociability.

Normal and abnormal aggression: human disorders and novel laboratory models

We review here aggression-related human psychopathologies and propose that human aggressiveness is mainly due to three major factors: (i) brain dysfunction affecting aggression-controlling brain centers (e.g. in certain types of brain lesions, epilepsy, Alzheimer disease, etc.); (ii) hypoarousal associated with chronically low plasma glucocorticoids, which foster violence by diminishing emotional barriers that limit such behaviors (e.g. in conduct disorder and antisocial personality disorder); (iii) hyperarousal which leads to irritability and outbursts (e.g. in depression, intermittent explosive disorder, chronic fatigue, etc.). Different disorders are associated with different types of aggressiveness; e.g. hypoarousal is often associated with instrumental aggression, whereas hyperarousal is associated with uncontrollable outbursts. Many psychological disorders have been simulated in laboratory models, which were used to assess aggressiveness. Little effort was invested, however, in assessing the abnormal dimension of such aggressiveness. We present here three models that appear especially suitable to assess abnormal aspects of rodent aggression: (i) abnormal attack targeting (head, throat, and belly) that is induced by hypoarousal in rats and models violence in hypoarousal-driven human aggression (ii) 'escalated' aggression (increased aggressive response due to frustration or instigation), which models irritability and hyperarousal-driven aggressiveness; and (iii) context-independent attacks induced by hypothalamic stimulation or genetic manipulations. These three models address different aspects of abnormal aggressiveness, and can become extremely useful in three areas: in evaluating and assessing models of human psychopathologies, in studying transgenic animals, and in developing new treatment strategies. Research based on these or similar models do not address aggressiveness in quantitative terms, but follows the development of abnormal aspects, and the possibilities of their specific treatment.

A review of the methods of studies on infant ultrasound production and maternal retrieval in small rodents

Ultrasonic vocalizations or calls produced by young rodents have been associated with aspects of maternal behavior, in particular retrieving. We reviewed the methods of study used by investigators on each topic, focusing on intrinsic or subject variables and extrinsic or experimental variables. Intrinsic variables included the species studied, genotypes employed, number and sex composition of the litters, and the ages of mothers and pups. Extrinsic variables for studies on ultrasonic calling included: eliciting stimuli, test surroundings, and the length of observation. Extrinsic variables in studies of maternal retrieval included the testing procedure and the length of observation. The methods used in studies within each topic vary greatly. In an effort to facilitate progress in the areas, especially with respect to isolating individual genes with a contribution to ultrasonic call production or studying the effects of pharmaceutical agents on either behavior, we propose some standardization of nomenclature and/or procedure in four areas: (1) the stimuli or situations used to elicit ultrasonic calls, (2) the length of observation in ultrasonic call studies, (3) the number of pups per litter and the sex composition of litters in both ultrasonic call and maternal retrieval studies and finally, (4) the apparatus or testing situation used in studies of pup retrieval.

Designing mouse behavioral tasks relevant to autistic-like behaviors

The importance of genetic factors in autism has prompted the development of mutant mouse models to advance our understanding of biological mechanisms underlying autistic behaviors. Mouse models of human neuropsychiatric diseases are designed to optimize (1) face validity, i.e., resemblance to the human symptoms; (2) construct validity, i.e., similarity to the underlying causes of the disease; and (3) predictive validity, i.e., expected responses to treatments that are effective in the human disease. There is a growing need for mouse behavioral tasks with all three types of validity for modeling the symptoms of autism. We are in the process of designing a set of tasks with face validity for the defining features of autism: deficits in appropriate reciprocal social interactions, deficits in verbal social communication, and high levels of ritualistic repetitive behaviors. Social approach is tested in an automated three-chambered apparatus that offers the subject a choice between a familiar environment, a novel environment, and a novel environment containing a stranger mouse. Preference for social novelty is tested in the same apparatus, with a choice between the start chamber, the chamber containing a familiar mouse, and the chamber containing a stranger mouse. Social communication is evaluated by measuring the ultrasonic distress vocalizations emitted by infant mouse pups and the parental response of retrieving the pup to the nest. Resistance to change in ritualistic repetitive behaviors is modeled by forcing a change in habit, including reversal of the spatial location of a reinforcer in a T-maze task and in the Morris water maze. Mouse behavioral tasks that may model additional features of autism are discussed, including tasks relevant to anxiety, seizures, sleep disturbances, and sensory hypersensitivity. Applications of these tests include (1) behavioral phenotyping of transgenic and knockout mice with mutations in genes relevant to autism, (2) characterization of mutant mice derived from random chemical mutagenesis, (3) DNA microarray analyses of genes in inbred strains of mice that differ in social interaction, social communication and resistance to change in habit, and (4) evaluation of proposed therapeutics for the treatment of autism.

Genetic modules and networks for behavior: lessons fromDrosophila

Behaviors are quantitative traits determined through actions of multiple genes and subject to genome-environment interactions. Early studies concentrated on analyzing the effects of single genes on behaviors, often generating views of simplified linear genetic pathways. The genome era has generated a profound paradigm shift enabling us to identify all the genes that contribute to expression of a behavioral phenotype, to investigate how they are organized as functional ensembles and to begin to identify polymorphisms that contribute to phenotypic variation and are targets for natural selection. Recent studies show that the genetic architecture of behavior is determined by dynamic and plastic modular networks of pleiotropic genes and that the behavioral phenotype manifests itself as an emergent property of such networks. Such networks are exquisitely sensitive to genetic background and sex effects. This review describes how Drosophila can serve as a model for uncovering fundamental principles of the genetic architecture of behavior.