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Finding gene clusters for a replicated time course study.

ABSTRACT: Finding genes that share similar expression patterns across samples is an important question that is frequently asked in high-throughput microarray studies. Traditional clustering algorithms such as K-means clustering and hierarchical clustering base gene clustering directly on the observed measurements and do not take into account the specific experimental design under which the microarray data were collected. A new model-based clustering method, the clustering of regression models method, takes into account the specific design of the microarray study and bases the clustering on how genes are related to sample covariates. It can find useful gene clusters for studies from complicated study designs such as replicated time course studies.In this paper, we applied the clustering of regression models method to data from a time course study of yeast on two genotypes, wild type and YOX1 mutant, each with two technical replicates, and compared the clustering results with K-means clustering. We identified gene clusters that have similar expression patterns in wild type yeast, two of which were missed by K-means clustering. We further identified gene clusters whose expression patterns were changed in YOX1 mutant yeast compared to wild type yeast.The clustering of regression models method can be a valuable tool for identifying genes that are coordinately transcribed by a common mechanism.

SUBMITTER: Qin LX

PROVIDER: S-EPMC3906880 | biostudies-other | 2014 Jan

REPOSITORIES: biostudies-other

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Finding gene clusters for a replicated time course study.

Qin Li-Xuan LX Breeden Linda L Self Steven G SG

BMC research notes 20140124

<h4>Background</h4>Finding genes that share similar expression patterns across samples is an important question that is frequently asked in high-throughput microarray studies. Traditional clustering algorithms such as K-means clustering and hierarchical clustering base gene clustering directly on the observed measurements and do not take into account the specific experimental design under which the microarray data were collected. A new model-based clustering method, the clustering of regression ...[more]

PMID: 24460656

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Project description:TNF time course series of HelA tet off cells cultured in presence or absence of Dox TNF is a pro-inflammatory cytokine that controls expression of inflammatory genetic networks. Although the Nuclear Factor-kB (NF-kB) pathway is crucial for mediating cellular TNF responses, the complete spectrum of NF-kB dependent genes is unknown. In this study, we used a tetracycline-regulated cell line expressing an NF-kB inhibitor to systematically identify NF-kB dependent genes. A microarray data set generated from a time course of TNF stimulation in the presence or absence of NF-kB signaling was analyzed. Methods: Cell culture, treatment and transfection-The human cervical epithelioid carcinoma cell line HeLa expressing tTA (HeLa Tet-Off) pBI-EGFP- IkBa Mut was constructed earlier (23). HeLa Tet-Off were grown in medium containing 90 % Dulbecco’s Modified Eagle’s Medium (DMEM), 10 % heat-inactivated fetal bovine serum (FBS), 4mM L-glutamine, 0.1 mM non-essential amino acids, 1 mM sodium pyruvate, 100 mg/ml G418, 100 units /ml penicillin G sodium, and 100 mg/ml streptomycin sulfate in a humidified atmosphere of 5 % CO2. For TNF stimulation, freshly isolated cells were split into two cultures, one group maintained in Dox, the other without for 7 d, a time at which IkBa Mut expression was maximal. Thereafter, recombinant human (rh) TNFa (25 ng/ml, final concentration) was added directly to the culture medium for indicated times prior to harvest. Oligonucleotide probe based microarray-Hu95Av2 GeneChip (Affymetrix Inc, Santa Clara, CA) containing 12,626 sequenced human genes were hybridized according to the manufacturer’s recommendations and washed using both non-stringent (1 M NaCl, 25 °C) and stringent (1 M NaCl, 50 °C) conditions prior to staining with phycoerythrin streptavidin (10 mg/ml final). Arrays were scanned using a Gene Array Scanner (Hewlett Packard) and analyzed using the Gene Chip Analysis Suite 5 software (Affymetrix Inc). For each gene, 16-20 probe pairs are immobilized as ~25-mer oligonucleotides that hybridize throughout the mRNA; each probe pair is represented as a perfect match (PM) oligonucleotide and a mismatch (MM) oligonucleotide as hybridization control. The the Absolute Call [e.g., the gene is detected (“present”) or not (“absent”)] and the Signal Intensity (measure of mRNA abundance) is determined. Four independent experiments were performed identically including control (0 h ), 1, 3 and 6 h TNF stimulation (25 ng/ml) in the presence or absence of Doxycyline (2 mg/ml) in growth medium. These are indicated as 180, 181, 220 and 266 series, and are considered replicates of each other. Keywords: time-course

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Finding gene clusters for a replicated time course study.

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Finding gene clusters for a replicated time course study.

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