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Selection for contextual fear conditioning affects anxiety-like behaviors and gene expression (palme-affy-mouse-84746)

ABSTRACT: These data are from the brains (amygdala and hippocampus) of mice originally derived from a cross between C57BL/6J and DBA/2J inbred strains. We used short-term selection to produce outbred mouse lines with differences in contextual fear conditioning, which is a measure of fear learning. We selected for a total of 4 generations. Fear learning differed in the selected lines and this difference was stronger with each successive generation of selection. These mice also showed differences for measures of anxiety-like behavior, but were not different for tests of non-fear motivated learning, suggesting that selection altered alleles that are specifically involved in emotional behaviors. We identified several QTLs for the selection response. We used Affymetrix microarrays to identify differentially expressed genes in the amygdala and hippocampus of mice from the final generation of selection. Amygdala and hippocampus samples were rapidly dissected out of experimentally naïve mice f rom each selected line. Three samples were pooled and hybridized to each array. Experimentally naïve mice were used because the behavior of the mice can be reliably anticipated due to their lineage. Thus, these gene expression differences are not due to the response to human handling, foot shock or fear-inducing conditioned stimuli. We have a second similar study that focuses on a different selected population that was based on C57BL/6J and A/J mice (see GES4034).

ORGANISM(S): Mus musculus

PROVIDER: GSE4035 | GEO | 2006/01/13

SECONDARY ACCESSION(S): PRJNA95161

REPOSITORIES: GEO

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Project description:Fear conditioning (FC) is a behavioral paradigm that measures an animalâs ability to learn fear related information. FC is measured by pairing a mild foot-shock with the surroundings in which the shock was received. Upon being placed back in the context, mice exhibit freezing behavior, which is a species-specific response to fear. We have used selective breeding to produce lines of mice with high or low levels of freezing behavior. We are able to identify alleles that govern the genetic variability for FC by using chromosomal markers in these lines. Using microarrays, we will identify differences in gene expression in two key brain regions: amygdala and hippocampus. Gene expression differences and data regarding chromosomal regions involved in the behavior will be compared to identify particular genes that are both differentially expressed and whose expression is governed by alleles that fall into critical chromosomal regions.,We will compare gene expression in the amygdala and hippocampus (brain regions known to be relevant to fear behavior) from the two lines of mice and use Bayesian statistics in an effort to identify gene expression that affects fear behavior.,We hypothesize that selection has acted in part by changing the frequency of alleles that cause differential expression of key genes in the amygdala and hippocampus of our selected lines. Selective breeding changes the frequency of trait relevant (FC) alleles. A relevant allele is expected to increase in one selected line and decrease in the oppositely selected line. Some trait relevant alleles are expected cause changes in the level of expression at particular genes.,Amygdala and hippocampus will be rapidly dissected out of experimentally naÃ¯ve mice from each line. NaÃ¯ve mice will be used for expression studies since the behavior of the mice in the FC test can be reliably anticipated due to their lineage. We have practiced these procedures, and can accurately and reproducibly remove these regions in less than 5 minutes. Different mice will be used to collect each brain region, since the dissection of hippocampus disrupts the removal of amygdala. We will collect enough samples from each region to accommodate a total of 6 microarrays per brain region, per line, thus we will use a total of 24 microarrays. We anticipate that a single brain region will be sufficient to for a microarray. However, we propose to utilize three samples per microarray, because this will reduce variability due to environmental factors and due to slight variability in our dissection procedures. Once this tissue is removed, we will isolate RNA for shipment to the Microarray consortium. We will also collect spleens from each subject as a source of genomic DNA, in order to permit direct comparison of genotype and expression phenotypes. Once we have the results of the microarray analysis, we use WebQTL.org to identify the chromosomal locations of alleles that are know to influence the expression of genes for which we have found differential expression. We will then superimpose this information on trait relevant chromosomal regions identified from our selected lines. This will allow us to rapidly identify genes which may account for genetic variability in FC due to differential expression. Such genes will then be subjected to further study.

Project description:Fear conditioning (FC) is a behavioral paradigm that measures an animal's ability to learn fear related information. FC is measured by pairing a mild foot-shock with the surroundings in which the shock was recieved. Upon being placed back in the context, mice exhibit freezing behavior, which is a species-specific response to fear. We have previously used selective breeding to produce lines of mice with high or low levels of freezing behavior. This experiment is a replication of a previous experiment that produced lines of mice with high or low levels of freezing behavior. These lines derive from different progenitor mouse strains. We are able to identify alleles that govern the genetic variability for FC by using chromosomal markers in these selected lines. Using microarrays, we will identify differences in gene expression in two key brain regions: amygdala and hippocampus. Gene expression differences and data regarding chromosomal regions involved in the behavior will be compared to identify particular genes that are both differentially expressed and whose expression is governed by alleles that fall into critical chromosomal regions.,We will compare gene expresion in the amygdala and hippocampus (brain regions known to be relevant to fear behavior) from the these two lines of mice and to the those in the previous experiment. Bayesian statistics will be used in an effort to identify gene expression that affects fear behavior.,We hypothesize that selection has acted in part by changing the frequency of alleles that cause differential expression of key genes in the amygdala and hippocampus of our selected lines. Slective breeding changes the frequency of trait relevand (FC) alleles. A relevant allele is expected to increas in one selected line and decrease in the oppositely selected line. Some trait relevant alleles are expected to cause changes in the level of expression at particular genes.,Amygdala and hippocampus will be rapidly dissected out of experimentally naÃ¯ve mice from each line. NaÃ¯ve mice will be used for expression studies since the behavior of the mice in the FC test can be reliably anticipated due to their lineage. We have practiced these procedures, and can accurately and reproducibly remove these regions in less than 5 minutes. Different mice will be used to collect each brain region, since the dissection of hippocampus disrupts the removal of amygdala. We will collect enough samples from each region to accommodate a total of 6 microarrays per brain region, per line, thus we will use a total of 24 microarrays. We anticipate that a single brain region will be sufficient to for a microarray. However, we propose to utilize three samples per microarray, because this will reduce variability due to environmental factors and due to slight variability in our dissection procedures. Once this tissue is removed, we will isolate RNA for shipment to the Microarray consortium. We will also collect spleens from each subject as a source of genomic DNA, in order to permit direct comparison of genotype and expression phenotypes. Once we have the results of the microarray analysis, we use WebQTL.org to identify the chromosomal locations of alleles that are know to influence the expression of genes for which we have found differential expression. We will then superimpose this information on trait relevant chromosomal regions identified from our selected lines. This will allow us to rapidly identify genes which may account for genetic variability in FC due to differential expression. Such genes will then be subjected to further study.

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Selection for contextual fear conditioning affects anxiety-like behaviors and gene expression (palme-affy-mouse-84746)

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