Congenic dissection of a major QTL for methamphetamine sensitivity implicates epistasis
ABSTRACT: We identified a congenic mouse with an introgressed region from the A/J donor inbred strain on an inbred C57BL/6J background that showed a reduced locomotor stimulant response to methamphetamine. We conducted microarray analysis of the striatum from drug-naive female and male mice that were 6-9 weeks old. The congenic region is on chromosome 11 and spans approximately 84-96 Mb. There were two groups of mice used in the analysis: B6 control mice versus congenic mice. Congenic mice were collapsed across heterozygous and homozygous genotypes. All mice are on a C57BL/6J background. Congenic mice differ only on chromosome 11 where they contain the introgressed A/J alleles from 84-96 Mb. 14 C57BL/6J wildtype mice and 14 B6.A/J congenic mice (84-96 Mb region from A/J strain) were examined for gene expression differences using striatal tissue (left and right punches pooled). All mice were drug-naïve and were 6-9 weeks old at the time of sacrifice.
Project description:Differential gene expression between mouse distal chromsome 1 congenic and background and reciprocal congenic and background Genetic factors significantly affect vulnerability to alcohol dependence (alcoholism). We previously identified a quantitative trait locus on chromosome 1 (Adw1) with a large effect on predisposition to alcohol physiological dependence and associated withdrawal following both chronic and acute alcohol exposure in mice. We fine-mapped these loci to a 1.1-1.7 Mb interval syntenic with human 1q23.2-23.3. Adw1 interval genes show remarkable genetic variation among mice derived from the C57BL/6J and DBA/2J strains, the two most widely studied genetic animal models for alcohol-related traits. Here, we report the creation of a novel recombinant Adw1 congenic model (R2) in which the Adw1 interval from a donor C57BL/6J strain is introgressed onto a uniform, inbred DBA/2J genetic background. As expected, R2 mice demonstrate significantly less severe alcohol withdrawal compared to wild-type littermates. Additionally, comparing R2 and background strain animals, as well as reciprocal congenic (R8) and appropriate background strain animals, we assessed Adw1 dependent brain gene expression using microarray and quantitative PCR analyses. To our knowledge this includes the first Weighted Gene Co-expression Network Analysis using reciprocal congenic models. Importantly, this allows detection of co-expression patterns limited to one or common to both genetic backgrounds with high and low predisposition to alcohol withdrawal severity. The gene expression patterns (modules) in common contain genes related to oxidative phosphorylation, building upon human and animal model studies that implicate involvement of oxidative phosphorylation in alcohol use disorders. Finally, we demonstrate that administration of N-acetylcysteine, an FDA-approved antioxidant, significantly reduces symptoms of alcohol withdrawal (convulsions) in mice, thus validating a phenotypic role for this network. Taken together, these studies support the importance of mitochondrial oxidative homeostasis in alcohol withdrawal and identify this network as a valuable therapeutic target in human alcohol use disorders. Overall design: Whole brain, naïve, males. n=10 inbred C57BL/6J (B6), n=10 R8 small interval Chr 1 congenic (1.1 Mb D2 interval on B6 background), n=6 inbred DBA/2J (D2), n=6 R2 small interval Chr 1 congenic (10.2 Mb B6 interval on D2 background)
Project description:Inbred congenic strain B6.C6.132.54/Vad was created using C57BL/6ByJ background and BALB/cJ donor strains. Flanking background markers at chr. 6: 75.9 Mb (rs4226008, NCBI Mouse Build 36 / dbSNP Build 126) and 122.3 Mb (rs3023093), and limiting donor markers at 81.9 Mb (rs4226024) and at 91.8 Mb (rs3712161) defined the introgressed region. We concluded the segment size must be between 9.9 Mb and 46.4 Mb. In a Quantitative Trait Gene identification study we compared brain (without cerebellum) gene expression between progenitors and congenics. Such comparisons can facilitate identification of cis-regulated genes and to establish genetic control of a complex phenotype whose expression is associated with the introgressed chromosome segment. We used microarrays to detail the global programme of gene expression underlying cellularisation and identified distinct classes of up-regulated genes during this process. Experiment Overall Design: Experiments were carried out in three batches. In each batch 10 animals per strain were used. After processing each hemisphere separately, 10 hemispheres were pooled for one high-density oligonucleotide microarray (Mouse Genome 430 2.0, Affymetrix, Santa Clara, CA). For each strain 3 oligonucleotide microarrays were used (n=3). We used adult, untreated, male mice (n=30, 90 mice in toto).
Project description:Genetically engineered mice (GEM) are essential tools for understanding gene function and disease modeling. Due to historical reasons, gene targeting was at first done in embryonic stem cells (ESC) derived from the 129 family of inbred strains, leading to mixed background or congenic mice when crossed with C57BL/6 mice. Depending on the number of backcrosses and breeding strategies genomic segments from 129-derived ESC can be introgressed into the C57BL/6 genome at different levels, establishing a unique genetic makeup that needs characterization in order to obtain valid conclusions of experiments using GEM models. We sequence wild-type (WT), heterozygous (Het) and knockout (KO) mouse embryonic fibroblasts (MEFs) from a knockout model of Sall2 (Sato A. et al, Zinc finger protein sall2 is not essential for embryonic and kidney development. Mol Cell Biol 2003, 23:62-69) maintained in a mixed background between C57BL/6J and 129P2OlaHsd mice. We also treated or not these cells with doxorubicin, as a global perturbation of the gene expression. With this schema, we aimed to detect genetic introgression of 129 mice onto C57BL/6J, KO-ligated variants (the so-called congenic footprint) and potential modifier genes. Overall design: Sall2 wild-type (WT), heterozygous (Het) and knockout (KO) MEFs treated or not with doxorubicin 1 µM for 16 hours
Project description:We previously constructed a congenic mouse, B6.S-D2Mit194-D2Mit311 (B6.S-2) with SPRET/Ei donor DNA on distal chromosome 2 in a C57BL/6J background that captured an obesity quantitative trait locus (QTL). Mice homozygous for SPRET/Ei alleles at the donor region had decreased body weight and obesity related phenotypes. The B6.S-2 congenic donor region spanned a minimum of 26 Mb. In this study, we constructed five overlapping subcongenics with smaller SPRET/Ei donor regions to fine map the underlying gene(s). One of the five subcongenic lines derived from the B6.S-2 founding congenic, B6.S-2A, captures most of the body weight and adiposity phenotypes in a donor region with a maximum size of 7.4 Mb. Homozygous SPRET/Ei donor alleles in both the founding congenic and the derived B6.S-2A subcongenic exhibit significant decreases in body weight, multiple fat pad weights with the greatest decrease in mesenteric fat pad weight, and Adiposity Index (total fat pad weight divided by body weight). Interval specific microarray analysis in four tissues for donor region genes from the founding B6.S-2 congenic identified several differentially expressed genes mapping to the B6.S-2A subcongenic donor region, including prohormone convertase 2 (PC2). Quantitative real-time PCR confirmed a modest decrease of PC2 expression in whole brains of mice homozygous for SPRET/Ei donor alleles. Analysis of the relative levels of mRNA for B6 and SPRET/Ei in heterozygous congenic mice showed differentially higher expression of the C57BL/6J allele over the SPRET/Ei allele indicating a cis regulation of differential expression. Using subcongenic mapping, we have successfully narrowed a body weight and obesity QTL interval and identified PC2 as a positional candidate gene. Keywords: Two strain comparison for gene discovery Overall design: Two genotypes of B6.S-2 background and congenic strains- for each strain four tissues (whole brain, liver, adipose, muscle) were collected with 3 biological replicates.
Project description:Expression analysis was carried out in Goto-Kakizaki (GK), Brown Norway (BN) and 24 derived congenic strains using the Illumina RatRef-12 microarray. Each congenic line contains an introgression of a single fragment of the GK strain in the background of the BN recipient strain or vice versa. The resulting lines were fixed by imbreeding. The sizes of the introgressed fragments vary from almost a complete chromosome (consomic) to smaller fragments and some of the fragments overlap. To investigate genetic control of gene expression by the introgressed fragments, we performed transcriptional profiling of liver, soleus muscle and white adipose tissue in 6 months old rats.
Project description:To study the effect of Prnp genetic ablation on different aspects of RNA metabolism, we performed RNA sequencing of the hippocampus of wild-type C57BL/6J, congenic B6.129-PrnpZH1/ZH1 and coisogenic C57BL/6J-PrnpZH3/ZH3 mice. We analyzed differential gene expression, exon usage and RNA editing. RNA sequencing on hippocampus of wild-type C57BL/6 mice, congenic B6.129-PrnpZH1/ZH1 and coisogenic C57BL/6-PrnpZH3/ZH3 mice (3 month-old males, n=4 per genotype).
Project description:To study the effect of Prnp genetic ablation on different aspects of RNA metabolism, we performed RNA sequencing of the hippocampus of wild-type C57BL/6J, congenic B6.129-PrnpZH1/ZH1 and coisogenic C57BL/6J-PrnpZH3/ZH3 mice. We analyzed differential gene expression, exon usage and RNA editing. Overall design: RNA sequencing on hippocampus of wild-type C57BL/6 mice, congenic B6.129-PrnpZH1/ZH1 and coisogenic C57BL/6-PrnpZH3/ZH3 mice (3 month-old males, n=4 per genotype).
Project description:We previously utilized interval-specific congenic lines derived from C57BL/6J (B6) and DBA/2J (D2) alleles to fine map a quantitative trait locus (QTL) influencing methamphetamine (MA)- induced locomotor activity. We identified a 0.23 MB critical interval on chromosome 11 containing only two protein coding genes, Rufy1 and Hnrnph1. Notably, Rufy1 contains three missense SNPs and Hnrnph1 contains 1 SNP near the 5’ UTR. In an effort to identify the molecular mechanisms that bridge genetic variation with behavior, we conducted transcriptome analysis via mRNA sequencing (RNA-seq) in a B6.D2 congenic line (chr.11: 50-60 Mb) that captures the QTL. There was an overrepresentation of cis-regulated, differentially expressed genes within the congenic interval (4 out of 92 differentially expressed genes; FDR < 0.05) and widespread genomic regulation on all autosomes. For this study, 3mm punches from both striatal hemispheres were collected and pooled from 16 mice (8 controls and 8 B6.D2 congenics), and RNA was extracted and prepared for cDNA library preparation using the Illumina TruSeq (oligo-dT; 50bp single-end reads). Samples 1-16, consisting of alternating B6 and B6.D2 congenics were run in four lanes total, with samples 1-8 run in duplicate across lanes 5 and 6 and samples 9-16 acorss lanes 7 and 8, respectively. Raw samples provided are labeled with the "CB-" prefix, followed by the sample number and the lane that it was run in is described at the tail end as "_L00#" with # being either lane 5, 6, 7 or 8. In this study, all odd samples (e.g. CB-1,3,5 etc.) are C57BL/6J littermate controls, while all even samples are B6.D2 congenics. Note that the lane 7 replicate for Sample CB-13 (CB-13_L007.fastq.gz) was not processed due to technical difficulties with the file.
Project description:Evidence from multiple linkage and genome-wide association studies suggest that human chromosome 2 (HSA2) contains alleles that influence blood pressure (BP). Homologous to a large segment of HSA2 is rat chromosome 9 (RNO9), to which a BP quantitative trait locus (QTL) was previously mapped. The objective of the current study was to further resolve this BP QTL. Eleven congenic strains with introgressed segments spanning <81.8kb to <1.33Mb were developed by introgressing genomic segments of RNO9 from the Dahl salt-resistant (R) rat onto the genome of the Dahl salt-sensitive (S) rat and tested for BP. The congenic strain with the shortest introgressed segment spanning <81.8kb significantly lowered BP of the hypertensive S rat by 25 mm Hg and significantly increased its mean survival by 45 days. In contrast, two other congenic strains had increased BP compared with the S. We focused on the <81.8kb congenic strain which represents the shortest genomic segment to which a BP QTL has been definitively mapped to date in any species. Sequencing of this entire region in both S and R rats detected 563 variants. The region did not contain any known or predicted rat protein coding genes. Further, a whole genome renal transcriptome analysis between S and the <81.8kb S.R congenic strain revealed alterations in several critical genes implicated in renal homeostasis. Taken together, our results provide the basis for future studies to examine the relationship between the candidate variants within the QTL region and the renal differentially expressed genes as potential causal mechanisms for BP regulation. Overall design: Six male S control and 6 male congenic S.R(9)x3x2Bx1x8 rats born on the same day were selected, weaned at 30 days of age, and caged with 1 congenic and 1 S rat per cage. They were raised on a High-salt (2%) diet (Harlan Teklad diet TD 7034; Harlan–Sprague-Dawley) and sacrificed at 53 days of age and total RNAs were isolated from the kidney. The isolated RNA from two animals were pooled together and considered as one biological sample. Three such RNA samples from S and congenic rats were used for the cRNA preparation. cRNA was prepared and fragmented as suggested by Affymetrix technical manual, and simultaneously hybridized (15 µg adjusted cRNA for each chip) to Rat Expression Array 230 2.0 (3' IVT Expression Analysis). Statistical analyses of the microarray data were performed using R statistical package (version 2.8.1).
Project description:The Gvh1 gene loci was identified by linkage analysis in a segregating mouse backcross. Congenic mapping has refined the linked loci to a 1.3 Mb interval on mouse Chr16 (39.41 - 40.71Mb) that constitutes the congenic interval in the B10.BALB-16.C2A mouse line. Gene expression microarray was performed to characterize downstream transcripitional regulation by risk variants in the congenic interval;. Each individual sample was pooled from 3 mice and performed in triplicate for each experimental group (TBI 900 cGy versus 0 cGy) for statistical analysis.