@misc{oai:ir.soken.ac.jp:00001035, author = {高橋, 阿貴 and タカハシ, アキ and TAKAHASHI, Aki}, month = {2016-02-17, 2016-02-17}, note = {Emotionality, such as fear and anxiety, is an evolutionally conserved trait in many animals to prepare for and react against danger. However, excess level of emotionality interrupts their normal life, and it will be diagnosed as psychological disorder in human (e.g. anxiety disorder).
It is known that emotionality has genetic bases as well as environmental effect, and recently a number of genes contributing to anxiety have been progressively found. In the animal model, several behavioral tests and indices are developed and used to measure emotionality of animals.
However, it has been noticed that all of those emotionality-related indices do not have consistent correlation within individuals, even between measurements in the same test. That is, those indices are measuring several different aspects. In psychological studies, emotionality has been considered as a "complex of factors" rather than a single alternative construct. However, not many studies that aim to identify genes associated with emotionality have concerned this multifactorial architecture of emotionality. There are some attempts by combining genetic analysis and multivariate analysis of behavior to identify genetic loci related to the "complex of factors", but those are just a beginning. In this study, I examined the structure of those multiple factors of emotionality, validated those factors genetically, and tried to identify genetic loci related to those factors. I focused on the open-field test, which is the first model for measuring emotionality, and still common today.
　At the start point of this study, I examined genetic contribution to the open-field behavior by using conventional measurements, ambulation and defecation, and some ethological measurements in a variety of wild-derived mouse strains. By describing open-field behavior in detail and examining temporal changes, I was able to identify the prominent behavioral features of each strain of mice. Conventional simple measurements lose substantial information, such as the variety of behaviors that can be displayed, and the use of too few indices might easily lead to confusion in interpreting the genetic mechanisms underlying open-field behavior or "emotionality". Principal component analysis showed that the open-field behavior consisted of three dimensions of psychological trait: "locomotor activity", "thigmotaxis", and "anxious tension state".
　In order to perform genetic mapping of open-field behavior, I used consomic strains of mouse established from C57BL/6J and MSM/Ms (B6-Chr^MSMCSSs) in which one of each chromosome of C57BL/6J was substituted by a corresponding chromosome of MSM. By analyzing a series of CSSs, I was able to map the chromosomes associated with a certain phenotype. In addition to open-field test, two kinds of other emotionality-related tests, elevated plus-maze and social interaction test, were examined. By analyzing a panel of CSSs, I identified multiple chromosomes that have a QTL or QTLs related to conventional and ethological measurements of open-field behaviors, elevated-plus maze, and social interaction test. Many CSSs had substantially large effect QTLs due to the non-additive effect, and thus they were expected to be superior tool for the next step of QTL analysis: identifying the quantitative trait gene. By analyzing both males and females of CSSs, I found that there were many sex-dependent QTLs. Principal component analysis of a series of CSSs validated the three factors underlying open-field behavior as in wild-derived mouse strains. Because behaviors loaded on "anxious tension state "factor have rarely been analyzed in most behavior genetic analysis, I focused on this factor for the further analysis.
　One CSS, B6-17MSM, that has substituted chromosome 17 from MSM, showed increase of the "anxious tension state " factor. They also exhibited reduced novelty- induced activity and highly increased social interaction behavior, but no differences in their home-cage activity. Thus, it was expected that there is a genetic locus/loci related to some aspect of "emotionality" on the chromosome 17. For characterizing B6-17MSM in more detail, I conducted several behavioral tests and brain morphological analysis. Fear conditioning tests revealed B6-17MSM had an increased fear memory in the cue-fear conditioning but not in the context-fear conditioning.
Thus, it was expected there is a genetic locus/loci related to cue-specific fear learning on the chromosome 17. On the other hand, this strain had increased incidence of hydrocephalus.
Histological analysis revealed that externally-normal individuals of B6-17MSM had enlarged brain ventricle size than C57BL/6J. Despite the hydrocephalus phenotype, B6-17MSM showed normal sensorimotor gating and motor coordination as C57BL/6J.
　The analysis of reciprocal F1 intercross of B6-17MSM and C57BL/6J revealed that there are prominent maternal effects on their behavior. To identify genetic loci related to those behaviors and the hydrocephalus-like phenotype, I established a series of congenic mouse strains of B6-17MSM. By analyzing those congenic strains, I successfully revealed novel genetic loci associated with the brain ventricle size on the chromosome 17. Behavioral analysis also identified several genetic loci related to each behavior. Although social interaction behavior was prominently high in B6-17MSM, any congenic strains showed increased duration of social contact. It was supposed that there are interacting epistatic genes for inducing social interaction on this chromosome.
　So far, I conducted the factor analyses of open-field measurements in the wild-derived strains and consomic mouse strains, and confirmed that there are "locomotor activity", "thigmotaxis", and "anxious tension state" factors related to their behaviors. Behavioral analysis of congenic strains also revealed the existence and independence of those factors. The analysis of open-field behavior revealed two interesting congenic strains, C10 and C15; C10 has relation to "locomotor activity" factor, and C15 is associated with both "locomotor activity" and "anxious tension state" factors. Further behavioral characterization of these congenic strains showed differences of home-cage activity and fear conditioning between C10 and C15. This result suggested that the "locomotor activity" factor and "anxious tension state" factor are independent traits and have relation to different genetic and biological pathways.
　In addition to the above study, I conducted genetic analysis of other important emotion, aggression. Aggression has considerable importance for animal’s living and is evolutionally ancient behavior. Because the wild-derived strain MSM/Ms still retains considerable aggression, it was expected that B6-Chr^MSMCSSs would have advantages to identify genetic loci associated with the aggressive behavior. In this study, I focused on one CSS, B6-15MSM, which has substituted chromosome 15 from MSM, and examined their aggression in the resident-intruder paradigm. Resident-intruder test revealed that B6-15MSM shows elevated aggressive behavior toward the same genotype intruder compared to C57BL/6J. By analyzing both homogenous pairs and reciprocal, heterogenous pairs in the resident-intruder test, I found prominent effect of the opponent (intruder) in their aggressive behavior: aggressive behavior was increased when the intruder was B6-15MSM but not C57BL/6J. The analysis of reciprocal F1 progeny indicated there are dominance effect on the tail-rattling and submission behavior, and also maternal effect on attack behavior. Preliminary analysis of congenic strains showed the possibility to identify the genetic loci associated with the aggressive behavior of B6-15MSM, and suggested there are multiple genetic loci related to the aggressive behavior on chromosome 15.
, application/pdf, 総研大甲第1064号}, title = {Genetic analysis of emotionality using consomic mouse strains established from C57BL/6J and MSM/Ms}, year = {} }