The circadian clock generates daily rhythms in mammalian liver processes, such as glucose and lipid homeostasis, xenobiotic metabolism, and regeneration. The mechanisms governing these rhythms are not well understood, particularly the distinct contributions of the cell-autonomous clock and central pacemaker to rhythmic liver physiology. Through microarray expression profiling in MMH-D3 hepatocytes, we identified over 1,000 transcripts that exhibit circadian oscillations, demonstrating that many rhythms can be driven by the cell-autonomous clock and that MMH-D3 is a valid circadian model system. The genes represented by these circadian transcripts displayed both co-phasic and anti-phasic organization within a protein-protein interaction network, suggesting the existence of competition for binding sites or partners by genes of disparate transcriptional phases. Multiple pathways displayed enrichment in MMH-D3 circadian transcripts, including the polyamine synthesis module of the glutathione metabolic pathway. The polyamine synthesis module, which is highly associated with cell proliferation and whose products are required for initiation of liver regeneration, includes enzymes whose transcripts exhibit circadian oscillations, such as ornithine decarboxylase (Odc1) and spermidine synthase (Srm). Metabolic profiling revealed that the enzymatic product of SRM, spermidine, cycles as well. Thus, the cell-autonomous hepatocyte clock can drive a significant amount of transcriptional rhythms and orchestrate physiologically relevant modules such as polyamine synthesis.
Cell-autonomous circadian clock of hepatocytes drives rhythms in transcription and polyamine synthesis.
Specimen part, Cell line
View SamplesmiR-92 enhances c-Myc induced apoptosis. In the R26MER/MER mouse embryonic fibroblasts (MEFs), a switchable variant of Myc, MycERT2, was knocked into the genomic region downstream of the constitutive Rosa26 promoter, allowing acute activation of c-Myc by 4-OHT-induced nuclear translocation. This in vitro system nicely recapitulates c-Myc-induced apoptosis, as activated MycERT2 induces strong p53-dependent apoptosis in response to serum starvation. Enforced miR-92 expression in three independent R26MER/MER MEF lines significantly enhanced Myc-induced apoptosis.
A component of the mir-17-92 polycistronic oncomir promotes oncogene-dependent apoptosis.
Specimen part
View SamplesThe function of ID4 in CLL development was studied in vivo using TCL1 transgenic mouse model that develop leukemia similar to human CLL. TCL1 mice with ID4 single knockout gene have accelerated CLL progression.
Silencing of the inhibitor of DNA binding protein 4 (ID4) contributes to the pathogenesis of mouse and human CLL.
Specimen part
View SamplesNeurofibromatosis Type 1 (NF1) patients develop benign neurofibromas and malignant peripheral nerve sheath tumors (MPNST). These incurable peripheral nerve tumors result from loss of NF1 tumor suppressor gene function, causing hyperactive Ras signaling. Activated Ras controls numerous downstream effectors, but specific pathways mediating effects of hyperactive Ras in NF1 tumors are unknown. Cross-species transcriptome analyses of mouse and human neurofibromas and MPNSTs identified global negative feedback of genes that regulate Ras-Raf- MEK- extracellular signal-regulated protein kinase (ERK) signaling in both species. Nonetheless, activation of ERK was sustained in mouse and human neurofibromas and MPNST. PD0325901, a highly selective pharmacological inhibitor of MEK, was used to test whether sustained Ras-Raf-MEK-ERK signaling contributes to neurofibroma growth in the Nf1fl/fl;Dhh-cre mouse model or in NF1 patient MPNST cell xenografts. PD0325901 treatment reduced aberrantly proliferating cells in neurofibroma and MPNST, prolonged survival of mice implanted with human MPNST cells, and shrank neurofibromas in >80% of mice tested. PD0325901 also caused effects on tumor vasculature. Our data demonstrate that deregulated Ras/ERK signaling is critical for the growth of NF1 peripheral nerve tumors and provide strong rationale for testing MEK inhibitors in NF1 clinical trials.
MEK inhibition exhibits efficacy in human and mouse neurofibromatosis tumors.
Specimen part
View SamplesNeutrophils were isolated form peripheral blood of wildtype and Phd3 null mice, cultured for 4 hours in hypoxia (3% O2) and micro array analysis performed
Prolyl hydroxylase 3 (PHD3) is essential for hypoxic regulation of neutrophilic inflammation in humans and mice.
Specimen part, Treatment
View Samples