Unknown,Transcriptomics,Genomics,Proteomics

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The Genetic Regulation of the Terminating Phase of Liver Regeneration

ABSTRACT: The liver regeneration process terminates when the normal liver-mass/body-weight ratio of 2.5 % has been re-established. We aimed to generate and analyse global expression profiles to study the genetic interactions in relation to liver regeneration, to illuminate the genetic interactions between genes regulating the cell cycle and apoptosis, and to clarify the role of TGF-M-CM-^_ signalling in the terminating phase of liver regeneration. Twelve pigs were randomised to either 60% liver resection (n=4), sham operation (n=4) or control animals (n=4). Liver biopsies were taken at time of resection, after three weeks and upon termination the sixth week. Global gene expression profiles in the biopsies were obtained using porcine oligonucleotide microarrays, representing approximately 20000 porcine genes. Microarray analysis revealed a clear dominance of genes regulating apoptosis towards the end of regeneration, compared to the sham and control groups. Caspase Recruitment Domain-Containing Protein 11 (CARD11) was upregulated six weeks after liver resection, suggesting the involvement of the caspase system at this time. Zinc Finger Protein (ZNF490) gene, with a potential negative effect on cell cycle progression and promotion of apoptosis, was only up regulated at three and six weeks after liver resection indicating a central role at this time. TGF-M-CM-^_ was not found to be significantly affected. CARD11 and ZNF490 appear to play a central role in the termination of liver regeneration in the present study. The lack of TGF-M-CM-^_ could indicate that signaling by TGF-M-CM-^_ is not required for termination of liver regeneration. time course, treatment comparison

ORGANISM(S): Sus scrofa

SUBMITTER: Jakob Hedegaard

PROVIDER: E-GEOD-14396 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Following parenchymal loss, the liver regenerates restoring normal mass and metabolic function. Prevailing theories on triggering events leading to regeneration include humoral, metabolic and flow-mediated mechanisms, the latter emphasizing the importance of shear stress mediated nitric oxide (NO) regulation. We aimed to investigate whether the grade of resection and hence the portal venous pressure and sinusoidal shear stress increase, would be reflected in the gene expression profiles in the liver remnant by employing a global porcine cDNA microarray chip with approximately 23 000 genes represented. Six pig livers were resected with 62% (Low Portal Pressure Resection, LPPR) and 75% (High Portal Pressure Resection) resulting in a portal venous pressure increase from a baseline of 6.1 mmHg to 8.2 and 12 mmHg respectively. By sampling consecutive biopsies from the liver remnants we found differentially expressed genes in the HPPR group to have functions related primarily to apoptosis, nitric oxide metabolism and oxidative stress, whereas differentially expressed genes in the LPPR group potentially regulate the cell cycle. Common to both groups was the upregulation of genes regulating inflammation, transport, cell proliferation and development and protein metabolism. Also common to both groups was both up- and downregulation of genes regulating cell-cell signaling, signal transduction, cell adhesion and translation. Genes regulating the metabolism of lipids, hormones, amines, and alcohol were downregulated in both groups. Conclusions: The genetic regenerative response in the liver remnant to varies according to the level of resection. Keywords: time course, treatment comparison Three pigs underwent a 62% liver resection (low-pressure resection, LPR) and three underwent a 75% resection (high-pressure resection, HPR). Biopsies from the liver remnant were taken from all animals at time points 1, 30, 90, minutes and 3, 4 and 6 hours after resection. Expression profiling was conducted by hybridising each sample against a common reference, consisting of liver RNA from an unrelated animal.

Project description:ABSTRACT: BACKGROUND: Boar taint is the unpleasant odour and flavour of the meat of uncastrated male pigs that is primarily caused by high levels of androstenone and skatole in adipose tissue. Androstenone is a steroid and its levels are mainly genetically determined. Studies on androstenone metabolism have, however, focused on a limited number of genes. Identification of additional genes influencing levels of androstenone may facilitate implementation of marker assisted breeding practices. In this study, microarrays were used to identify differentially expressed genes and pathways related to androstenone metabolism in the liver from boars with extreme levels of androstenone in adipose tissue. RESULTS: Liver tissue samples from 58 boars of the two breeds Duroc and Norwegian Landrace, 29 with extreme high and 29 with extreme low levels of androstenone, were selected from more than 2500 individuals. The samples were hybridised to porcine cDNA microarrays and the 1 % most significant differentially expressed genes were considered significant. Among the differentially expressed genes were metabolic phase I related genes belonging to the cytochrome P450 family and the flavin-containing monooxygenase FMO1. Additionally, phase II conjugation genes including UDP-glucuronosyltransferases UGT1A5, UGT2A1 and UGT2B15, sulfotransferase STE, N-acetyltransferase NAT12 and glutathione S-transferase were identified. Phase I and phase II metabolic reactions increase the water solubility of steroids and play a key role in their elimination. Differential expression was also found for genes encoding 17beta-hydroxysteroid dehydrogenases (HSD17B2, HSD17B4, HSD17B11 and HSD17B13) and plasma proteins alpha-1-acid glycoprotein (AGP) and orosomucoid (ORM1). 17beta-hydroxysteroid dehydrogenases and plasma proteins regulate the availability of steroids by controlling the amount of active steroids accessible to receptors and available for metabolism. Differences in the expression of FMO1, NAT12, HSD17B2 and HSD17B13 were verified by quantitative real competitive PCR. CONCLUSIONS: A number of genes and pathways related to metabolism of androstenone in liver were identified, including new candidate genes involved in phase I oxidation metabolism, phase II conjugation metabolism, and regulation of steroid availability. The study is a first step towards a deeper understanding of enzymes and regulators involved in pathways of androstenone metabolism and may ultimately lead to the discovery of markers to reduce boar taint. Liver samples from 116 animals with extreme androstenone values, 29 high and 29 low from each of the two breeds Norwegian Landrace and Duroc, were used for this experiment. Each sample was hybridised together with a common refrence resulting in a total of 116 microarrays.

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The Genetic Regulation of the Terminating Phase of Liver Regeneration

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