Temporal changes of gene expression in rat kidney and lung, and the effect of prior growth inhibition on these changes
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ABSTRACT: Temporal changes of gene expression from 1-wk- to 5-wk-old rat in kidney and lung, and the effect of prior growth inhibition on these genetic changes. In mammals, body growth is rapid in early life but decelerates with age. Somatic growth deceleration is caused by a gradual decline in cell proliferation that occurs simultaneously in many different organs, but is not caused by a hormonal mechanism. We hypothesize that growth deceleration is driven by a postnatal genetic program that occurs coordinately in multiple organs. Using microarrays, we investigated the changes of gene expression that occur with age in kidney and lung as growth slows down, and also investigated whether these changes were growth-driven, by asking whether prior delay of postnatal growth caused by malnutrition (tryptophan deficiency) would also delay these genetic changes.
Project description:Temporal changes of gene expression from 1-wk- to 5-wk-old rat in kidney and lung, and the effect of prior growth inhibition on these genetic changes. In mammals, body growth is rapid in early life but decelerates with age. Somatic growth deceleration is caused by a gradual decline in cell proliferation that occurs simultaneously in many different organs, but is not caused by a hormonal mechanism. We hypothesize that growth deceleration is driven by a postnatal genetic program that occurs coordinately in multiple organs. Using microarrays, we investigated the changes of gene expression that occur with age in kidney and lung as growth slows down, and also investigated whether these changes were growth-driven, by asking whether prior delay of postnatal growth caused by malnutrition (tryptophan deficiency) would also delay these genetic changes. To compare gene expression between fast-growing animals and more slowly growing animals, we extracted total mRNA from kidney and lung in 1-wk-old and 5-wk-old mice (5 animals each). Then, to investigate the effect of prior growth on these genetic changes, we also extracted total mRNA from kidney and lung in 5-wk-old mice that received a tryptophan-deficient diet from birth to 4wk of age.
Project description:Temporal changes of gene expression from 1-wk- to 4-wk and 8-wk-old mouse in heart, kidney and lung. Mammalian somatic growth is rapid in early postnatal life but then slows and eventually ceases in multiple tissues. We hypothesized that there exists a postnatal gene expression program that is common to multiple tissues and is responsible for this coordinate growth deceleration. Consistent with this hypothesis, microarray analysis identified >1600 genes that were regulated with age coordinately in kidney, lung, and heart of juvenile mice, including many genes that regulate proliferation. As examples, we focused on three growth-promoting genes, Igf2, Mest, and Peg3, that were markedly downregulated with age. We conclude that there exists an extensive genetic program occurring during postnatal life. Many of the involved genes are regulated coordinately in multiple organs, including many genes that regulate cell proliferation. At least some of these are themselves apparently regulated by growth, suggesting that, in the embryo, a gene expression pattern is established that allows for rapid somatic growth of multiple tissues but then, during postnatal life, this growth leads to negative-feedback changes in gene expression that in turn slow and eventually halt somatic growth, thus imposing a fundamental limit on adult body size. To compare gene expression between fast-growing animals and more slowly growing animals, we extracted total mRNA from kidney and lung in 1-wk, 4-wk, and 8-wk-old mice (5 animals each).
Project description:Temporal changes of gene expression from 1-wk- to 4-wk and 8-wk-old mouse in heart, kidney and lung. Mammalian somatic growth is rapid in early postnatal life but then slows and eventually ceases in multiple tissues. We hypothesized that there exists a postnatal gene expression program that is common to multiple tissues and is responsible for this coordinate growth deceleration. Consistent with this hypothesis, microarray analysis identified >1600 genes that were regulated with age coordinately in kidney, lung, and heart of juvenile mice, including many genes that regulate proliferation. As examples, we focused on three growth-promoting genes, Igf2, Mest, and Peg3, that were markedly downregulated with age. We conclude that there exists an extensive genetic program occurring during postnatal life. Many of the involved genes are regulated coordinately in multiple organs, including many genes that regulate cell proliferation. At least some of these are themselves apparently regulated by growth, suggesting that, in the embryo, a gene expression pattern is established that allows for rapid somatic growth of multiple tissues but then, during postnatal life, this growth leads to negative-feedback changes in gene expression that in turn slow and eventually halt somatic growth, thus imposing a fundamental limit on adult body size.
Project description:During early postnatal life, extensive changes in gene expression occur concomitantly in multiple major organs, indicating the existence of a common core developmental genetic program. This program includes hundreds of growth-promoting genes that are downregulated with age in liver, kidney, lung, and heart, and there is evidence that this component of the program drives the widespread decline in cell proliferation that occurs in juvenile life, as organs approach adult sizes. To investigate epigenetic changes that might orchestrate this program, we performed chromatin immunoprecipitation-promoter tiling array to assess temporal changes in histone H3K4 and H3K27 trimethylation (me3) at promoter regions throughout the genome in kidney and lung, comparing 1- to 4-wk-old mice. We found extensive genome-wide shifts in H3K4me3 and H3K27me3 occurring with age in both kidney and lung. The number of genes with concordant changes in the two organs was far greater than expected by chance. Temporal changes in H3K4me3 showed a strong, positive association with changes in gene expression, assessed by microarray, whereas changes in H3K27me3 showed a negative association. Gene ontology analysis indicated that shifts in specific histone methylation marks were associated with specific developmental functions. Of particular interest, genes with decreases in H3K4me3 with age in both organs were strongly implicated in cell cycle and cell proliferation functions. Taken together, the findings suggest that the common core developmental program of gene expression which occurs in multiple organs during juvenile life is associated with a common core developmental program of histone methylation. In particular, declining H3K4me3 is strongly associated with gene downregulation and occurs in the promoter regions of many growth-regulating genes, suggesting that this change in histone methylation may contribute to the component of the genetic program that drives juvenile body growth deceleration. Tissues samples were collect from Lung (1 and 4 week old) and Kindey (1 and 4 week old) respectively with four biological replications of mice that were collected, frozen in liquid nitrogen, and stored at -70 °C
Project description:During early postnatal life, extensive changes in gene expression occur concomitantly in multiple major organs, indicating the existence of a common core developmental genetic program. This program includes hundreds of growth-promoting genes that are downregulated with age in liver, kidney, lung, and heart, and there is evidence that this component of the program drives the widespread decline in cell proliferation that occurs in juvenile life, as organs approach adult sizes. To investigate epigenetic changes that might orchestrate this program, we performed chromatin immunoprecipitation-promoter tiling array to assess temporal changes in histone H3K4 and H3K27 trimethylation (me3) at promoter regions throughout the genome in kidney and lung, comparing 1- to 4-wk-old mice. We found extensive genome-wide shifts in H3K4me3 and H3K27me3 occurring with age in both kidney and lung. The number of genes with concordant changes in the two organs was far greater than expected by chance. Temporal changes in H3K4me3 showed a strong, positive association with changes in gene expression, assessed by microarray, whereas changes in H3K27me3 showed a negative association. Gene ontology analysis indicated that shifts in specific histone methylation marks were associated with specific developmental functions. Of particular interest, genes with decreases in H3K4me3 with age in both organs were strongly implicated in cell cycle and cell proliferation functions. Taken together, the findings suggest that the common core developmental program of gene expression which occurs in multiple organs during juvenile life is associated with a common core developmental program of histone methylation. In particular, declining H3K4me3 is strongly associated with gene downregulation and occurs in the promoter regions of many growth-regulating genes, suggesting that this change in histone methylation may contribute to the component of the genetic program that drives juvenile body growth deceleration.
Project description:Microarray analysis of male and female CD-1 mouse liver was carried out at 3, 4, and 8 wk of age to elucidate developmental changes in gene expression from the pre-pubertal period to young adulthood. A large number of sex-biased and sex-independent genes showed significant changes during this developmental period. Notably, sex-independent genes involved in cell cycle, chromosome condensation, and DNA replication were down regulated from 3 wk to 8 wk, while genes associated with metal ion binding, ion transport and kinase activity were up regulated. A majority of genes showing sex differential expression in adult liver did not display sex differences prior to puberty, at which time extensive changes in sex-specific gene expression were seen, primarily in males. Thus, in male liver, 76% of male-specific genes were up regulated and 47% of female-specific genes were down regulated from 3 to 8 wk of age, whereas in female liver 67% of sex-specific genes showed no significant change in expression. In both sexes, genes up regulated from 3 to 8 wk were significantly enriched (p < E-76) in the set of genes positively regulated by the liver transcription factor HNF4α, as determined in a liver-specific HNF4α knockout mouse model, while genes down regulated during this developmental period showed significant enrichment (p < E-65) for negative regulation by HNF4α. Significant enrichment of the developmentally regulated genes in genes subject to positive and negative regulation by pituitary hormone was also observed. Nine sex-specific transcription factors showed pubertal changes in expression and may contribute to the developmental changes that onset after 3-4 wk. Overall, the observed changes in gene expression during postnatal liver development reflect the deceleration of liver growth and the induction of specialized liver functions, with widespread changes in sex-specific gene expression primarily occurring in male liver.
Project description:Microarray analysis of male and female CD-1 mouse liver was carried out at 3, 4, and 8 wk of age to elucidate developmental changes in gene expression from the pre-pubertal period to young adulthood. A large number of sex-biased and sex-independent genes showed significant changes during this developmental period. Notably, sex-independent genes involved in cell cycle, chromosome condensation, and DNA replication were down regulated from 3 wk to 8 wk, while genes associated with metal ion binding, ion transport and kinase activity were up regulated. A majority of genes showing sex differential expression in adult liver did not display sex differences prior to puberty, at which time extensive changes in sex-specific gene expression were seen, primarily in males. Thus, in male liver, 76% of male-specific genes were up regulated and 47% of female-specific genes were down regulated from 3 to 8 wk of age, whereas in female liver 67% of sex-specific genes showed no significant change in expression. In both sexes, genes up regulated from 3 to 8 wk were significantly enriched (p < E-76) in the set of genes positively regulated by the liver transcription factor HNF4M-NM-1, as determined in a liver-specific HNF4M-NM-1 knockout mouse model, while genes down regulated during this developmental period showed significant enrichment (p < E-65) for negative regulation by HNF4M-NM-1. Significant enrichment of the developmentally regulated genes in genes subject to positive and negative regulation by pituitary hormone was also observed. Nine sex-specific transcription factors showed pubertal changes in expression and may contribute to the developmental changes that onset after 3-4 wk. Overall, the observed changes in gene expression during postnatal liver development reflect the deceleration of liver growth and the induction of specialized liver functions, with widespread changes in sex-specific gene expression primarily occurring in male liver. Liver RNA isolated from the following six groups of CD-1 mice was used in the present study: 3 wk old male (M) mice (n = 10; 5 per each pool) and female (F) mice (n = 10; 5 per each pool); 4 wk old male mice (n = 12; 6 per each pool) and female mice (n = 12; 6 per each pool); 8 wk old male mice (n = 12; 6 per each pool) and female mice (n = 12; 6 per each pool). These RNA pools were used in seven separate sets of competitive hybridization experiments: 1) 3 wk M vs. 3 wk F; 2) 4 wk M vs. 4 wk F; 3) 8 wk M vs. 8 wk F; 4) 3 wk M vs. 8 wk M; 5) 4 wk M vs. 8 wk M; 6) 3 wk F vs. 8 wk F; 7) 4 wk F vs. 8 wk F. Fluorescent labeling of RNA and hybridization of the Alexa 555-labeled (green) and Alexa 647-labeled (red) aRNA samples to Agilent Mouse Gene Expression 4x44k v2 microarrays (Agilent Technology, Palo Alto, CA; catalog # G4846A-026655) were carried out, with dye swapping for each of the seven hybridization experiments to eliminate dye bias. Two microarrays, one for each mixed cDNA sample, were hybridized for each of the seven fluorescent reverse pairs, giving a total of 14 microarrays.
Project description:To explore the mechanisms responsible for spatial and temporal regulation of the growth plate, we microdissected postnatal rat growth plates into their constituent zones and then used microarray analysis to characterize the changes in gene expression that occur as chondrocytes undergo spatially-associated differentiation and temporally-associated senescence. Microdissection was used to collect individual growth plate zones from proximal tibiae of 1-wk rats and the proliferative and early hypertrophic zones of growth plates from 3-, 6-, 9-, and 12-wk rats and gene expression was analyzed using microarray.
Project description:In order to characterize mRNA expression in the growth plate, we microdissected postnatal rat growth plates into their constituent zones and used microarray analysis to assess the abundences of individual transcripts. Expression patterns of PTHrP and Ihh-related genes were confirmed using real-time PCR. Using a gli1-lacZ mouse, Gli1 expression, presumably representing Ihh signaling, was visualized during pre- and postnatal development. Microdissection was used to collect individual growth plate zones from proximal tibiae of 1-wk rats and gene expression was analyzed using microarray.