Project description:Despite recent advances in genomics, the identification of genes underlying complex diseases remains challenging. Inbred rat strains offer well-established experimental models to support the identification of susceptibility genes for diseases such as kidney damage associated with elevated blood pressure or hypertension. Here, we combined quantitative trait locus (QTL) mapping in two contrasting inbred rat strains with targeted next generation sequencing (NGS), compartment-specific transcriptome sequencing (RNA-Seq), and phenotype directed follow-up translational analysis.
Project description:Although the evidence for a genetic predisposition to human essential hypertension is compelling, the genetic control of blood pressure (BP) is poorly understood. The Dahl salt-sensitive (S) rat is a model for studying the genetic component of BP. Using this model we previously reported the identification of 16 different genomic regions that contain one or more BP quantitative trait loci (QTLs). The proximal region of rat chromosome 1 contains multiple BP QTLs. Of these, we have localized the BP QTL1b region to a 13.5cM (20Mb) region. Interestingly, five additional independent studies in rats and four independent studies in humans have reported genetic linkage for BP control by regions homologous to QTL1b. To view the overall renal transcriptional topography of the positional candidate genes for this QTL, we sought a comparative gene expression profiling between a congenic strain containing QTL1b and control S rats by employing: (1) a saturated QTL1b interval specific oligonucleotide array, and (2) a whole genome cDNA microarray representing 20,465 unique genes that are positioned outside the QTL. Results indicated that 19 out of the 231 positional candidate genes for this QTL are differentially expressed between the two strains tested. Surprisingly, over 1,500 genes outside of QTL1b were differentially expressed between the two rat strains. Integrating the results from the two approaches revealed at least one complex network of transcriptional control initiated by the positional candidate Nr2f2. This network appears to account for the majority of gene expression differences occurring outside of the QTL interval. Further substitution mapping is currently underway to test the validity of each of these differentially expressed positional candidate genes. These results demonstrate the importance of using a saturated oligonucleotide array for identifying and prioritizing differentially expressed positional candidate genes of a BP QTL. Keywords: : rat, hypertension, genetics, polygenic trait, microarray, gene expression
Project description:Although the evidence for a genetic predisposition to human essential hypertension is compelling, the genetic control of blood pressure (BP) is poorly understood. The Dahl salt-sensitive (S) rat is a model for studying the genetic component of BP. Using this model we previously reported the identification of 16 different genomic regions that contain one or more BP quantitative trait loci (QTLs). The proximal region of rat chromosome 1 contains multiple BP QTLs. Of these, we have localized the BP QTL1b region to a 13.5cM (20Mb) region. Interestingly, five additional independent studies in rats and four independent studies in humans have reported genetic linkage for BP control by regions homologous to QTL1b. To view the overall renal transcriptional topography of the positional candidate genes for this QTL, we sought a comparative gene expression profiling between a congenic strain containing QTL1b and control S rats by employing: (1) a saturated QTL1b interval specific oligonucleotide array, and (2) a whole genome cDNA microarray representing 20,465 unique genes that are positioned outside the QTL. Results indicated that 19 out of the 231 positional candidate genes for this QTL are differentially expressed between the two strains tested. Surprisingly, over 1,500 genes outside of QTL1b were differentially expressed between the two rat strains. Integrating the results from the two approaches revealed at least one complex network of transcriptional control initiated by the positional candidate Nr2f2. This network appears to account for the majority of gene expression differences occurring outside of the QTL interval. Further substitution mapping is currently underway to test the validity of each of these differentially expressed positional candidate genes. These results demonstrate the importance of using a saturated oligonucleotide array for identifying and prioritizing differentially expressed positional candidate genes of a BP QTL. Pairs of Cy5 and Cy3 labeled targets were co-hybridized onto either the oligonucleotide microarray or a custom TIGR rat cDNA array consisting of 26,401 probe elements representing 20,465 unique non-QTL1b genes. A âflip-dyeâ design was used as the experimental method of choice to account for potential dye-bias labeling effects. Seven âflip dyeâ normalized files are submitted for the oligonucleotide array and twelve individual hybridizations are submitted for the cDNA array.
Project description:A highly significant quantitative trait locus (QTL) that influenced alcohol preference was identified in the iP/iNP rats on chromosome 4. Congenic strains in which the iP chromosome 4 QTL interval was transferred to the iNP (NP.P) exhibited the expected increase in alcohol consumption compared to the iNP background strain. This study was undertaken to identify genes in the chromosome 4 QTL interval that might contribute to the differences in alcohol consumption between the alcohol-naïve congenic and background strains. RNA from five brain regions from each of 6 NP.P and 6 iNP rats was labeled and analyzed separately on an Affymetrix Rat Genome 230 2.0 microarray. Expression levels were normalized using robust multi-chip average (RMA). Differential gene expression was validated using quantitative real-time PCR. An analysis combining five brain regions, including nucleus accumbens, frontal cortex, amygdala, hippocampus, and striatum, identified twenty three transcripts and nine ESTs that were differentially expressed between the NP.P and iNP. Of the twenty three observed transcripts, thirteen were known genes, 9 were predicted genes and all but one were located in the chromosome 4 QTL interval. Very interesting cis-regulated candidate genes for alcohol consumption were identified using microarray profiling of gene expression differences in congenic animals carrying a QTL for alcohol preference. Keywords: alcohol, congenic, rat, gene expression, brain, nucleus accumbens, amygdala, frontal cortex, hippocampus, striatum
Project description:The BcA86 strain is a unique recombinant congenic strain created from parental strains A/J and C57BL/6J. Naive mice from the BcA86 strain have a lung responsiveness phenotype resembling mice from airway hyperresponsive strain A/J. However, majority of the BcA86 genome is from the hyporesponsive strain C57BL/6J. Our goal was to identify the genomic regions that are associated with this BcA86 phenotype. Using F2 mice generated from BcA86 backcrossed to C57BL/6J, we identified a QTL for airway hyperresponsiveness on mouse chromosome 12. We validated the importance of mouse chromosome 12 in airway responsiveness using a chromosome 12 substitution strain (CSS12) which contains A/J chromosome 12 on a C57BL/6J background. The CSS12 strain also had a lung responsiveness phenotype similar to A/J. We selected genes within our QTL as candidates for airway hyperresponsiveness if they contained a deleterious coding variant (based on PROVEAN analysis) or if they were differently expressed between hyperresponsive (A/J, BcA86, CSS12) and hyporesponsive (C57BL/6J) strains.
Project description:Febrile seizures (FS) are the most common type of seizures in young children. Complex FS are a risk factor for mesial temporal lobe epilepsy (mTLE). Twin studies and mutations in families with complex epilepsy syndromes including FS, indicate a genetic contribution to FS susceptibility. By employing a phenotype driven genetic strategy using consomics we mapped a quantitative trait locus (QTL) for hyperthermia-induced FS susceptibility on mouse chromosome 1. Signal Recognition Particle 9 (Srp9) in the QTL was differentially expressed between parental strains, and its binding partner Srp14 was co-identified as a strong candidate gene in another FS susceptibility QTL. The SRP complex plays a key role in the synthesis of membrane proteins, such as glutamate receptors. In vivo knock-down of brain Srp9 or inhibition of protein synthesis reduced FS susceptibility. The mouse strain (CSS1) with reduced Srp9 expression and FS susceptibility, exhibited reduced hippocampal AMPA and NMDA currents. Down-regulation of Srp9 in hippocampal neurons reduced surface expression of AMPA receptor subunit GluA1. Consistent with a role of SRP9 in human FS, we detected increased hippocampal SRP9 expression in mTLE patients with antecedent FS. Comparing mTLE patients and healthy controls we found an association of a SRP9 promoter SNP (rs12403575 G/A) with FS and mTLE, which was replicated in FS patients. Our findings identify SRP9 as a novel FS susceptibility gene and implicate ER-dependent protein synthesis and glutamate receptor expression in the mechanism.
Project description:Seasonal influenza outbreaks and recurrent influenza pandemics present major challenges to public health. By studying immunological responses to influenza in different host species, it may be possible to discover common mechanisms of susceptibility in response to various influenza strains. This could lead to novel therapeutic targets with wide clinical application. Using a mouse-adapted strain of influenza (A/HK/1/68-MA20 [H3N2]), we produced a mouse model of severe influenza (p-flu) that reproduces the hallmark high viral load and overexpression of cytokines associated with susceptibility to p-flu in humans. We mapped genetic determinants of the host response using a panel of 29 closely related mouse strains (AcB/BcA panel of recombinant congenic strains) created from influenza-susceptible A/J and influenza-resistant C57BL/6J (B6) mice. Combined clinical quantitative trait loci (cQTL) and lung expression QTL (eQTL) mapping identified candidate genes for two sex-specific QTLs on chromosomes 2 and 17. The former includes the previously described Hc gene, a deficit of which is associated with the susceptibility phenotype in females. The latter includes the phospholipase gene Pla2g7 and Tnfrsf21, a member of the tumor necrosis factor receptor superfamily. Confirmation of the gene underlying the chromosome 17 QTL may reveal new strategies for influenza treatment.
Project description:A QTL intercross was performed bewteen C57BL/6J and KK/HIL for albuminurea, asthma and cardiovascular related phenotypes. Several QTL were identified for most phenotypes. We performed microarray analysis from liver samples to identify genes differentially expressed between the parental strains. The results helped us narrow down the QTL and identify the candidate genes based on differential expression between the parental strains.
Project description:We have combined large-scale mRNA expression and gene mapping methods to identify genes and loci that control hematopoietic stem cell (HSC) functioning. mRNA expression levels were measured in purified HSC isolated from a panel of densely genotyped recombinant inbred mouse strains. Quantitative trait loci (QTLs) associated with variation in expression of thousands of transcripts were mapped. Comparison of the physical transcript position with the location of the controlling QTL identified polymorphic cis-acting stem cell genes. In addition, multiple trans-acting control loci were highlighted that modify expression of large numbers of genes. These groups of co-regulated transcripts identify pathways that specify variation in stem cells. We illustrate this concept with the identification of strong candidate genes involved with HSC turnover. We compared expression QTLs in HSC and brain from the same animals, and document both shared and tissue-specific QTLs. Our data are accessible through WebQTL, a web-based interface that allows custom genetic linkage analysis and identification of co-regulated transcripts. Keywords: other