The present study was designed to test the hypothesis that limited growth of the fetal liver in the model of maternal fasting is independent of well-characterized signaling mechanisms that are known to regulate somatic growth in adult animals.
Regulation of fetal liver growth in a model of diet restriction in the pregnant rat.
Specimen part, Treatment
View SamplesOur strategy was to manipulate mTOR signaling in vivo, then characterize the transcriptome and translating mRNA in liver tissue. In adult rats, we used the non-proliferative growth model of refeeding after a period of fasting, and the proliferative model of liver regeneration following partial hepatectomy. We also studied livers from pre-term fetal rats (embryonic day 19-20) in which fetal hepatocytes are asynchronously proliferating. All three models employed rapamycin to inhibit mTOR signaling.
Profiling of the fetal and adult rat liver transcriptome and translatome reveals discordant regulation by the mechanistic target of rapamycin (mTOR).
Specimen part, Time
View SamplesTo assess the potential of PP6 as a therapeutic target in liver disorders, we attenuated expression of the PP6 catalytic subunit in HepG2 cells using lentiviral-transduced shRNA. Two PP6 knock-down (PP6KD) cell lines 18.5 and 19.5, (90% reduction of PP6-C protein content) were studied in depth.
Adaptation of HepG2 cells to a steady-state reduction in the content of protein phosphatase 6 (PP6) catalytic subunit.
Specimen part, Cell line, Treatment
View SamplesLiver transplantation is the only therapeutic option for patients with end-stage liver disease. The shortage of donor organs has led to the search for alternative therapies to restore liver function and bridge patients to transplantation. Our previous work has shown that the proliferation of late gestation E19 fetal hepatocytes is mitogen-independent. This is manifested as differences in the control of ribosome biogenesis, global translation, cell cycle progression and gene expression. In the present study, we investigated whether E19 fetal hepatocytes would engraft and repopulate an injured adult liver.
Engraftment and Repopulation Potential of Late Gestation Fetal Rat Hepatocytes.
Specimen part
View SamplesDNA methylation is an important epigenetic control mechanism that has been shown to be associated with gene silencing through the course of development, maturation and aging. However, only limited data are available regarding the relationship between methylation and gene expression in human development. We analyzed the methylomes and transcriptomes of three human fetal liver samples (gestational age 20-22 weeks) and three adult human liver samples. Genes whose expression differed between fetal and adult numbered 7,673. Adult overexpression was associated with metabolic pathways and, in particular, cytochrome P450 enzymes, while fetal overexpression reflected enrichment for DNA replication and repair. Analysis for DNA methylation using the Illumina Infinium 450K HumanMethylation BeadChip showed that 42% of the quality filtered 426,154 methylation sites differed significantly between adult and fetal tissue (q0.05). Differences were small; 69% of the significant sites differed in their mean methylation beta value by 0.2. There was a trend among all sites toward higher methylation in the adult samples with the most frequent difference in beta being 0.1. Characterization of the relationship between methylation and expression revealed a clear difference between fetus and adult. Methylation of genes overexpressed in fetal liver showed the same pattern as seen for genes that were similarly expressed in fetal and adult liver. In contrast, adult overexpressed genes showed fetal hypermethylation that differed from the similarly expressed genes. An examination of gene region-specific methylation showed that sites proximal to the transcription start site or within the first exon with a significant fetal-adult difference in beta (>0.2) showed an inverse relationship with gene expression. Nearly half of the CpGs in human liver show a significant difference in methylation comparing fetal and adult samples. Sites proximal to the transcription start site or within the first exon that show a transition from hypermethylation in the fetus to hypomethylation or intermediate methylation in the adult are associated with inverse changes in gene expression. In contrast, increases in methylation going from fetal to adult are not associated with fetal-to-adult decreased expression. These findings indicate fundamentally different roles for and/or regulation of DNA methylation in human fetal and adult liver.
Patterns of gene expression and DNA methylation in human fetal and adult liver.
Sex, Age, Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Rapamycin response in tumorigenic and non-tumorigenic hepatic cell lines.
No sample metadata fields
View SamplesWe previously identified the mTOR pathway as critical to progenitor cell proliferation in a model of liver injury, we investigated the temporal activation of mTOR signaling in a rat model of hepatic carcinogenesis. The model employed chemical carcinogens and partial hepatectomy to induce progenitor marker-positive HCC. Rats were administered the mTOR inhibitor rapamycin for a three week period and liver harvested one month following cessation of rapamycin treatment. Short-term rapamycin treatment resulted in a significant reduction of focal lesion burden. Microarray analysis was performed to characterize the gene expression signature of persistent focal lesions in the rapamcyin and placebo treated animals. This analysis revealed a persistent effect of short-term mTORC1 inhibition on gene expression that resulted in a genetic signature reminiscent of normal liver.
Persistent effect of mTOR inhibition on preneoplastic foci progression and gene expression in a rat model of hepatocellular carcinoma.
Sex, Specimen part, Treatment
View SamplesTwo rat hepatic cell lines, WB-F344 and WB311, were characterized for the effect of rapamycin on gene expression. The WB311 cell line, which is tumorigenic and resistant to the growth inhibitory effects of rapamycin, was originally derived from the WB-F344 parental hepatic epithelial cell line. The goal of this experiment was to identify genes that responded to rapamycin in the sensitive cells but not the resistant cells, thereby providing insight into the mechanism of rapamycin resistance.
Rapamycin response in tumorigenic and non-tumorigenic hepatic cell lines.
No sample metadata fields
View SamplesRecent work using mouse models has revealed that mTORC2, which unlike mTORC1 is not acutely sensitive to rapamycin, plays a key role in the regulation of organismal physiology. The substrates and pathways regulated by mTORC2 are at present relatively unknown
Hepatic signaling by the mechanistic target of rapamycin complex 2 (mTORC2).
Sex, Specimen part, Treatment
View SamplesWe used microarrays to compare gene expression profile of spleen CD8 T cells from IL-17RA KO and WT mice at different time-point after T. cruzi infection.
IL-17RA-Signaling Modulates CD8+ T Cell Survival and Exhaustion During <i>Trypanosoma cruzi</i> Infection.
Specimen part, Time
View Samples