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Small Perturbation Approach Reveals Transcriptomic Steady State

ABSTRACT: The ‘small perturbation’ approach is critical in studying the ‘steady state’ of a biological system. In our experiments, small perturbations were generated by applying a series of repeating intermittent small doses of ultraviolet radiation to a human keratinocyte cell line, HaCaT. The biological response was assessed by monitoring the gene expression profiles using a high reliability and high resolution cDNA microarray system. Following intermittent 10 J/m2 UVB small perturbations, two opposite classes of genes, down-regulated and up-regulated, exhibited an immediate response followed by relaxation between each small perturbation, but were prolonged down- or up-regulated without relaxation while larger doses (233 or 582.5 J/m2) of UVB were applied. A repeated cycle pattern of gene expression following small perturbations is an indication of the existence of steady states. This cycle pattern is suppressed when large perturbations are applied. We believe that this is a universal phenomenon. In our experiments, the functions of up-regulated genes were mainly associated with anti-proliferation, anti-mitogenesis, and apoptosis. On the other hand, down-regulated genes were mainly related to proliferation, mitogenesis, and anti-apoptosis. In conclusion, this study experimentally proves the concept of steady state at the transcription level and demonstrates the feasibility of using small perturbation approaches for investigating steady states. This study could also set a foundation of computational systems biology, which has implicitly used the concept of steady state. Keywords: time course

ORGANISM(S): Homo sapiens

PROVIDER: GSE7060 | GEO | 2009/01/30

SECONDARY ACCESSION(S): PRJNA98461

REPOSITORIES: GEO

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Project description:The â??small perturbationâ?? approach is critical in studying the â??steady stateâ?? of a biological system. In our experiments, small perturbations were generated by applying a series of repeating intermittent small doses of ultraviolet radiation to a human keratinocyte cell line, HaCaT. The biological response was assessed by monitoring the gene expression profiles using a high reliability and high resolution cDNA microarray system. Following intermittent 10 J/m2 UVB small perturbations, two opposite classes of genes, down-regulated and up-regulated, exhibited an immediate response followed by relaxation between each small perturbation, but were prolonged down- or up-regulated without relaxation while larger doses (233 or 582.5 J/m2) of UVB were applied. A repeated cycle pattern of gene expression following small perturbations is an indication of the existence of steady states. This cycle pattern is suppressed when large perturbations are applied. We believe that this is a universal phenomenon. In our experiments, the functions of up-regulated genes were mainly associated with anti-proliferation, anti-mitogenesis, and apoptosis. On the other hand, down-regulated genes were mainly related to proliferation, mitogenesis, and anti-apoptosis. In conclusion, this study experimentally proves the concept of steady state at the transcription level and demonstrates the feasibility of using small perturbation approaches for investigating steady states. This study could also set a foundation of computational systems biology, which has implicitly used the concept of steady state. Keywords: time course Three UVB exposures are indicated by UV at time points of 0, 8 and 16 hours. T1, T2, T3, T4, T5, and T6 denote the sampling time points. T1, T3 and T5 are allocated 30 minutes after the corresponding UVB irradiation. T2, T4 and T6 are allocated 8 hours after each UVB irradiation. At each sampling time point, two samples (control and UV-irradiated) are collected. See supplementary file Loop_design.pdf for further explanation.

Project description:Dr. Liu's research group is interested in studying the expression and functions of galectin-3, -7 and -12, in particular the roles of these proteins in inflammation and neoplasm. Members of the galectin family are known to participate in cellular homeostasis by modulating cell growth, controlling cell cycle progression, and inducing or inhibiting apoptosis. It is known that some galectins have similar functions. However, it is not fully understood whether they work cooperatively or not. As the outermost barrier of the body, skin is directly and frequently exposed to a prooxidative environment, including solar ultraviolet A (UVA), ultraviolet B (UVB) radiation, and air pollution. Several reports have shown that exposure of cells to UV increase or decrease the levels of galectins. For example, the amounts of galectin-7 mRNA and protein are increased rapidly after UVB irradiation of keratinocytes (Proc. Natl. Acad. Sci. USA 1999; 96:11329-34). Heat shock and subculturing decrease, while alkylating agents and UV-light increase galectin-3 (Cell Physiol Biochem 2000; 10:149-58). To analyze the change of all galectin gene expression profiles after UVB irradiation and to determine the presence or absence of coordinate regulation, we analyzed the gene expression profiles of keratinocytes exposed to UVB. Normal human epidermal keratinocytes (NHEK) were irradiated with 200 J/m2 of UVB. Total RNA will be extracted at 0, 6, 12 and 24 h after irradiation (duplicate) for analysis on the Glyco gene chip. Several reports have shown that exposure to UV light can regulate levels of galectin in skin. This study seeks to analyze the changes in all galectin gene expression profiles post-UVB irradiation to determine the presence or absence of coordinate regulation. In this study, normal human keratinocytes were irradiated with 200J/m2 of UVB. Total RNA was extracted at 0, 6, 12, and 24-hour post irradiation time points, in duplicate. Samples were hybridized and analyzed using the GLYCOv2 array.

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Small Perturbation Approach Reveals Transcriptomic Steady State

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