Quantitative trait locus analysis identifies Gabra3 as a regulator of behavioral despair in mice

The Tail Suspension Test (TST), which measures behavioral despair, is widely used as an animal model of human depressive disorders and antidepressant efficacy. In order to identify novel genes involved in the regulation of TST performance, we crossed an inbred strain exhibiting low immobility in the TST (RIIIS/J) with two high-immobility strains (C57BL/6J and NZB/BlNJ) to create two distinct F2 hybrid populations. All F2 offspring (n = 655) were genotyped at high density with a panel of SNP markers. Whole-genome interval mapping of the F2 populations identified statistically significant quantitative trait loci (QTLs) on mouse chromosomes (MMU) 4, 6, and X. Microarray analysis of hippocampal gene expression in the three parental strains was used to identify potential candidate genes within the MMUX QTLs identified in the NZB/BlNJ × RIIIS/J cross. Expression of Gabra3, which encodes the GABA_A receptor α3 subunit, was robust in the hippocampus of B6 and RIIIS mice but absent from NZB hippocampal tissue. To verify the role of Gabra3 in regulating TST behavior in vivo, mice were treated with SB-205384, a positive modulator of the α3 subunit. SB-205384 significantly reduced TST immobility in B6 mice without affecting general activity, but it had no effect on behavior in NZB mice. This work suggests that GABRA3 regulates a behavioral endophenotype of depression and establishes this gene as a viable new target for the study and treatment of human depression.     

The regular and light-dark Suok tests of anxiety and sensorimotor integration: utility for behavioral characterization in laboratory rodents

Animal behavioral models are crucial for neurobiological research, allowing for the thorough investigation of brain pathogenesis to be performed. In both animals and humans, anxiety has long been linked to vestibular disorders. However, although there are many tests of anxiety and vestibular deficits, there are few protocols that address the interplay between these two domains. The Suok test and its light-dark modification presented here appear to be suitable for testing this pathogenetic link in laboratory rodents. This protocol adds a new dimension to previously used tests by assessing animal anxiety and balancing simultaneously, resulting in efficient, high-throughput screens for testing psychotropic drugs, phenotyping genetically modified animals, and modeling clusters of human disorders related to stress/anxiety and balancing.     

Biphasic survival analysis of trypanotolerance QTL in mice

A marker-assisted introgression (MAI) experiment was conducted to transfer trypanotolerance quantitative trait loci (QTL) from a donor mouse strain, C57BL/6, into a recipient mouse strain, A/J. The objective was to assess the effect of three previously identified chromosomal regions on mouse chromosomes 1 (MMU1), 5 (MMU5) and 17 (MMU17) in different genetic backgrounds on the survival pattern following infection with Trypanosoma congolense. An exploratory data analysis revealed a biphasic pattern of time to death, with highly distinct early and late mortality phases. In this paper, we present survival analysis methods that account for the biphasic mortality pattern and results of reanalyzing the data from the MAI experiment. The analysis with a Weibull mixture model confirmed the biphasic pattern of time to death. Mortality phase, an unobserved variable, appears to be an important factor influencing survival time and is modeled as a binary outcome variable using logistic regression analysis. Accounting for this biphasic pattern in the analysis reveals that a previously observed sex effect on average survival is rather an effect on proportion of mice in the two mortality phases. The C57BL/6 (donor) QTL alleles on MMU1 and MMU17 act dominantly in the late mortality phase while the A/J (recipient) QTL allele on MMU17 acts dominantly in the early mortality phase. From this study, we found clear evidence for a biphasic survival pattern and provided models for its analysis. These models can also be used when studying defense mechanisms against other pathogens. Finally, these approaches provide further information on the nature of gene actions.     

Intersection tests for single marker QTL analysis can be more powerful than two marker QTL analysis

Background

It has been reported in the quantitative trait locus (QTL) literature that when testing for QTL location and effect, the statistical power supporting methodologies based on two markers and their estimated genetic map is higher than for the genetic map independent methodologies known as single marker analyses. Close examination of these reports reveals that the two marker approaches are more powerful than single marker analyses only in certain cases.Simulation studies are a commonly used tool to determine the behavior of test statistics under known conditions. We conducted a simulation study to assess the general behavior of an intersection test and a two marker test under a variety of conditions. The study was designed to reveal whether two marker tests are always more powerful than intersection tests, or whether there are cases when an intersection test may outperform the two marker approach.We present a reanalysis of a data set from a QTL study of ovariole number in Drosophila melanogaster.

Results

Our simulation study results show that there are situations where the single marker intersection test equals or outperforms the two marker test. The intersection test and the two marker test identify overlapping regions in the reanalysis of the Drosophila melanogaster data. The region identified is consistent with a regression based interval mapping analysis.

Conclusion

We find that the intersection test is appropriate for analysis of QTL data. This approach has the advantage of simplicity and for certain situations supplies equivalent or more powerful results than a comparable two marker test.

     

不同行为学测试方法在家族性肌萎缩侧索硬化小鼠模型的比较

目的比较目前常用的5种行为学检测方法在家族性肌萎缩侧索硬化鼠模型研究中的作用。方法分为模型组(SOD1-G93A转基因鼠)和阴性对照组(同窝阴性对照)。使用5种行为学评价方法(一般状况评分、体重测定、转棒试验、抓力测定和步长分析)评价其行为学变化。结果 (1)一般状况评分:在第89天,模型组的一般状况评分开始下降。在第101天时,与对照组相比开始有统计学差异(P=0.000)。(2)体重测定:15周(第105天)时,模型组的体重开始下降,且与阴性对照组相比(P=0.026),开始有统计学差异。(3)转棒试验:11周(第77天)时,模型组的转棒时间开始下降。第13周(第91天)时,与阴性对照组相比开始有统计学差异(P=0.047)。(4)抓力测定:10周(第70天)时,模型组的后肢抓力开始下降。第13周(第91天)时,与阴性对照组相比开始有统计学差异(P=0.000)。(5)步长分析:第14周(第98天)后模型组的步长开始变短。15周(第105天)时与阴性对照组相比开始有统计学意义(P=0.000)。结论抓力测定优于其他行为学检测方法。     

The ethological analysis of imitation

Theorists and experimental researchers have long debated whether animals are able to imitate. A variety of definitions of imitation have been proposed to describe this complex form of social learning. Experimental research on imitation has often been hampered by either a too loose 'anthropomorphic' approach or by too narrow 'behaviourist' definitions. At present neither associative nor cognitive theories are able to offer an exhaustive explanation of imitation in animals. An ethological approach to imitation offers a different perspective. By integrating questions on function, mechanism, development and evolution one can identify possible directions for future research. At present, however, we are still far from developing a comprehensive theory of imitation. A functional approach to imitation shows that, despite some evidence for imitative learning in food processing in apes, such learning has not been shown to be involved in the social transmission of either tool-use skills or communicative signals. Recently developed procedures offer possible ways of clarifying the role of imitation in tool use and visual communication. The role of imitation in explorative play in apes is also investigated and the available data suggest that copying during play might represent a behavioural homologue of human imitation. It is proposed that the ability to copy the behaviour of a companion is under a strong genetic influence in many social species. Many important factors have not been examined experimentally, e.g. the effect of the demonstrator, the influence of attention and memory and the ability to generalize. The potential importance of reinforcement raises the possibility that copying abilities serving divergent functions might be partly under the control of different mechanisms.     

Genome‐wide SNP analysis identifies major QTL for Salmonella colonization in the chicken

Salmonella‐infected poultry products are a major source of human Salmonella infection. The prophylactic use of antimicrobials in poultry production was recently banned in the EU, increasing the need for alternative methods to control Salmonella infections in poultry flocks. Genetic selection of chickens more resistant to Salmonella colonization provides an attractive means of sustainably controlling the pathogen in commercial poultry flocks and its subsequent entry into the food chain. Analysis of different inbred chickens has shown that individual lines are consistently either susceptible or resistant to the many serovars of Salmonella that have been tested. In this study, two inbred chicken lines with differential susceptibility to Salmonella colonization (6₁^(R) and N^(S)) were used in a backcross experimental design. Unlike previous studies that used a candidate gene approach or low‐density genome‐wide screens, we have exploited a high‐density marker set of 1255 SNPs covering the whole genome to identify quantitative trait loci (QTL). Analysis of log‐transformed caecal bacterial levels between the parental lines revealed a significant difference at 1, 2, 3 and 4 days post‐infection (P < 0.05). Analysis of the genotypes of the backcross (F₁ × N) population (n = 288) revealed four QTL on chromosomes 2, 3, 12 and 25 for the two traits examined in this study: log‐transformed bacterial counts in the caeca and presence of a hardened caseous caecal core. These included one genome‐wide significant QTL on chromosome 2 at 20 Mb and three additional QTL, on chromosomes 3, 12 and 25 at 96, 15 and 1 Mb, respectively, which were significant at the chromosome‐wide level (P < 0.05). The results generated in this study will inform future breeding strategies to control these pathogens in commercial poultry flocks.     

Provisional QTL for circadian period of wheel running in laboratory mice: quantitative genetics of period in RI mice.

Wheel running was monitored in B x D recombinant inbred (RI) mice under dark-dark (DD) conditions, and the mean circadian period was calculated for each strain. There were significant differences for this trait among B x D recombinant inbred strains (p < .0001) and a narrow-sense heritability of 21%. Analysis of strain means and variances indicates that at least four segregating loci contribute to the genetic variance for the free-running circadian period in this population. Correlation of the strain means for the circadian period of wheel running for each RI strain against the distribution of markers at over 1500 loci along the mouse genome identified a number of provisional quantitative trait loci (QTL). There were provisional QTL for wheel running at p < .001 on chromosome 11 and at p < .01 on chromosomes 1, 6, 9, 17, and 19. Most were in agreement with a second analysis done under similar conditions.     

Origin of double and multiple tests in benthic foraminifera: observations in laboratory cultures

Many juvenile and adult double and multiple tests of benthic foraminifera were observed on specimens grown in laboratory cultures or collected in various natural environments. Our observations bring to light three possible causes for such abnormalities, each one referring to characteristic morphological features. Double tests may result: (1) from an anomaly in the development of a single juvenile, building two or three second chambers or two third chambers, each one possibly developing in an individual whorl; (2) from the early fusion of two juveniles, which both develop after their fusion; (3) from the attachment of a juvenile on a parental test after the schizogony followed by the young's development.     

A factor analysis of behavioral organization in mice]

Laboratory mice with Robertsonian translocation Rb(8,17)1Iem, mice of CBA substrain with the same translocation as well as CBA normal karyotype mice were investigated in several behavioural tests, their results being analysed by means of factor analysis. The genetic differences were revealed in the patterns of factor loadings, in particular in factors "feeding behaviour structure" and "weight loss". The behaviour of mice during logic problem solving (the ability to extrapolate the direction of food stimulus movement was tested) proved to be genotype-dependent in respect to connections with exploratory behaviour indices. Tendencies towards stereotypic or variable (plastic) behaviour patterns were revealed in CBA mice and mice with Rb(8,17)1Iem mice respectively.     

An ethological analysis of open-field behaviour in chickens

Two salient but previously unacknowledged aspects of open-field testing involve contact with a potential predator, as a consequence of placement in the open field by a human, and separation from imprinted companions. As a result we propose that open-field behaviour in chickens (Gallus gallus) represents a compromise between opposing tendencies to reinstate contact with conspecifics and minimize detection in the face of possible predation. Five experiments were conducted to test various implications of this model. Manipulations designed to enhance the predatory overtones of open-field testing were found to postpone reinstatement behaviours (e.g. distress calling and escape attempts) and prolong behaviours that serve to minimize detection (e.g freezing). Unlike the more traditional view of open-field behaviour as an index of general emotionality, our model suggests that the principal reason for movement is based on attempts to reinstate social contact. In support of the model, birds tested in the presence of cagemates showed significantly longer durations of freezing than those tested individually. The same was true for birds maintained in social isolation for two days prior to testing. The applicability of this approach to conceptualizing the behaviour of chickens in the open field is discussed, and the supposed relationship between fear and distress calling is critically evaluated.     

Genotype-dependent participation of coat color gene loci in the behavioral traits of laboratory mice

To evaluate if loci responsible for coat color phenotypes contribute to behavioral characteristics, we specified novel gene loci associated with social exploratory behavior and examined the effects of the frequency of each allele at distinct loci on behavioral expression. We used the F2 generation, which arose from the mating of F1 mice obtained by interbreeding DBA/2 and ICR mice. Phenotypic analysis indicated that the agouti and albino loci affect behavioral traits. A genotype-based analysis revealed that novel exploratory activity was suppressed in a manner dependent on the frequency of the dominant wild-type allele at the agouti, but not albino, locus. The allele-dependent suppression was restricted to colored mice and was not seen in albino mice. The present results suggest that the agouti locus contributes to a particular behavioral trait in the presence of a wild-type allele at the albino locus, which encodes a structural gene for tyrosinase.     

Bayesian analyses of multiple epistatic QTL models for body weight and body composition in mice

To comprehensively investigate the genetic architecture of growth and obesity, we performed Bayesian analyses of multiple epistatic quantitative trait locus (QTL) models for body weights at five ages (12 days, 3, 6, 9 and 12 weeks) and body composition traits (weights of two fat pads and five organs) in mice produced from a cross of the F1 between M16i (selected for rapid growth rate) and CAST/Ei (wild-derived strain of small and lean mice) back to M16i. Bayesian model selection revealed a temporally regulated network of multiple QTL for body weight, involving both strong main effects and epistatic effects. No QTL had strong support for both early and late growth, although overlapping combinations of main and epistatic effects were observed at adjacent ages. Most main effects and epistatic interactions had an opposite effect on early and late growth. The contribution of epistasis was more pronounced for body weights at older ages. Body composition traits were also influenced by an interacting network of multiple QTLs. Several main and epistatic effects were shared by the body composition and body weight traits, suggesting that pleiotropy plays an important role in growth and obesity.     

Phenotypic characterization of a genetically diverse panel of mice for behavioral despair and anxiety

Background

Animal models of human behavioral endophenotypes, such as the Tail Suspension Test (TST) and the Open Field assay (OF), have proven to be essential tools in revealing the genetics and mechanisms of psychiatric diseases. As in the human disorders they model, the measurements generated in these behavioral assays are significantly impacted by the genetic background of the animals tested. In order to better understand the strain-dependent phenotypic variability endemic to this type of work, and better inform future studies that rely on the data generated by these models, we phenotyped 33 inbred mouse strains for immobility in the TST, a mouse model of behavioral despair, and for activity in the OF, a model of general anxiety and locomotor activity.

Results

We identified significant strain-dependent differences in TST immobility, and in thigmotaxis and distance traveled in the OF. These results were replicable over multiple testing sessions and exhibited high heritability. We exploited the heritability of these behavioral traits by using in silico haplotype-based association mapping to identify candidate genes for regulating TST behavior. Two significant loci (-logp >7.0, gFWER adjusted p value <0.05) of approximately 300 kb each on MMU9 and MMU10 were identified. The MMU10 locus is syntenic to a major human depressive disorder QTL on human chromosome 12 and contains several genes that are expressed in brain regions associated with behavioral despair.

Conclusions

We report the results of phenotyping a large panel of inbred mouse strains for depression and anxiety-associated behaviors. These results show significant, heritable strain-specific differences in behavior, and should prove to be a valuable resource for the behavioral and genetics communities. Additionally, we used haplotype mapping to identify several loci that may contain genes that regulate behavioral despair.     

The physiological and behavioral impact of sensory contact among unfamiliar adult mice in the laboratory

Housing mice in the laboratory in groups enables social interaction and is the way a laboratory should house mice. However, adult males show reciprocal aggression and are therefore frequently housed individually. Alternatively, a grid divider, which allows sensory contact by sight and smell but prevents fighting and injuries, can separate mice within 1 cage. This study examined the influence of this housing method on various physiological and behavioral parameters. Adult male mice housed for 10 days with sensory contact to an unfamiliar male displayed significant increases in heart rate (HR), body core temperature (BT), and motor activity (ACT). Furthermore, the mice suffered impaired nest-building behavior and significantly reduced body weight. Conversely, males housed in a similar manner with a female companion showed only a transient elevation of ACT, BT, and HR. Although no clear beneficial effect of housing males with sensory contact to females was evident, this study could not exclude it. On the other hand, housing of mature males in this way leads to sustained detrimental alterations of physiology and behavior, thus implying severe impairment of animal well-being.     

DeFries-Fulker multiple regression analysis of sibship QTL data: a SAS macro

A SAS macro package for performing multipoint QTL mapping using the DeFries-Fulker multiple regression method is presented.     

Evaluation of bedding and nesting materials for laboratory mice by preference tests.

Bedding and nesting materials can improve the health and environmental welfare of laboratory mice. This study was carried out to examine which items are actually preferred by mice. Two series of studies were performed on four types of floor-covering materials (Wood-shavings (Clean-chip), Cloth (Agrebe), Recycled-paper (Paper-clean), Paper (Care-feeaz), and on four types of nesting materials (Recycled-paper (Shepherd-shack), Cloth (Agrebe), Wood (Wood-cylinder), and Polycarbonate (Mouse-igloo). Preference of bedding materials was judged by the time length of staying in a cage. The results indicate that mice stayed in the cloth material (Agrebe) longer than in other bedding materials (light 51.1 +/- 5.3%, dark 51.5 +/- 2.6%). In the second experiment, the duration of stay in Agrebe was significantly longer than that in the other nesting materials in the light phase (70.9 +/- 2.4%). In the dark phase, staying time both in Agrebe and Shepherd-shack were significantly longer. These data suggest that cloth bedding and nesting is recommended for the environmental enrichment of laboratory mice.     

Large-scale neurochemical metabolomics analysis identifies multiple compounds associated with methamphetamine exposure

Methamphetamine (MA) is an illegal stimulant drug of abuse with serious negative health consequences. The neurochemical effects of MA have been partially characterized, with a traditional focus on classical neurotransmitter systems. However, these directions have not yet led to novel drug treatments for MA abuse or toxicity. As an alternative approach, we describe here the first application of metabolomics to investigate the neurochemical consequences of MA exposure in the rodent brain. We examined single exposures at 3 mg/kg and repeated exposures at 3 mg/kg over 5 days in eight common inbred mouse strains. Brain tissue samples were assayed using high-throughput gas and liquid chromatography mass spectrometry, yielding quantitative data on >300 unique metabolites. Association testing and false discovery rate control yielded several metabolome-wide significant associations with acute MA exposure, including compounds such as lactate (p = 4.4 × 10^?5, q = 0.013), tryptophan (p = 7.0 × 10^?4, q = 0.035) and 2-hydroxyglutarate (p = 1.1 × 10^?4, q = 0.022). Secondary analyses of MA-induced increase in locomotor activity showed associations with energy metabolites such as succinate (p = 3.8 × 10^?7). Associations specific to repeated (5 day) MA exposure included phosphocholine (p = 4.0 × 10^?4, q = 0.087) and ergothioneine (p = 3.0 × 10^?4, q = 0.087). Our data appear to confirm and extend existing models of MA action in the brain, whereby an initial increase in energy metabolism, coupled with an increase in behavioral locomotion, gives way to disruption of mitochondria and phospholipid pathways and increased endogenous antioxidant response. Our study demonstrates the power of comprehensive MS-based metabolomics to identify drug-induced changes to brain metabolism and to develop neurochemical models of drug effects.