The relationships between the increase in blood ketone-body concentrations and several parameters that can potentially influence the rate of hepatic fatty acid oxidation were studied during progressive starvation (up to 24 h) in the rat in order to discover whether the sensitivity of mitochondrial overt carnitine palmitoyltransferase (CPT I) to malonyl-CoA plays an important part in determining the intrahepatic potential for fatty acid oxidation during the onset of ketogenic conditions. A rapid increase in blood ketone-body concentration occurred between 12 and 16 h of starvation, several hours after the marked fall in hepatic malonyl-CoA and in serum insulin concentrations and doubling of plasma non-esterfied fatty acid (NEFA) concentration. Consequently, both the changes in hepatic malonyl-CoA and serum NEFA preceded the increase in blood ketone-body concentration by several hours. The maximal activity of CPT I increased gradually throughout the 24 h period of starvation, but the increases did not become significant before 18 h of starvation. By contrast, the sensitivity of CPT I to malonyl-CoA and the increase in blood ketone-body concentration followed an identical time course, demonstrating the central importance of this parameter in determining the ketogenic response of the liver to the onset of the starved state.
The LMO2 gene encodes a LIM-only protein and is a target of chromosomal translocations in human T-cell leukemia. Recently, two X-SCID patients treated by gene therapy to rescue T-cell lymphopoiesis developed T-cell leukemias with retroviral insertion into the LMO2 gene causing clonal T-cell proliferation. In view of the specificity of LMO2 in T-cell tumorigenesis, we investigated a possible role for Lmo2 in T-lymphopoiesis, using conditional knockout of mouse Lmo2 with loxP-flanked Lmo2 and Cre recombinase alleles driven by the promoters of the lymphoid-specific genes Rag1, CD19, and Lck. While efficient deletion of Lmo2 was observed, even in the earliest detectable lymphoid cell progenitors of the bone marrow, there was no disturbance of lymphopoiesis in either T- or B-cell lineages, and in contrast to Lmo2 transgenic mice, there were normal distributions of CD4− CD8− thymocytes. We conclude that there is no mandatory role for LMO2 in lymphoid development, implying that its specific role in T-cell tumorigenesis results from a reprogramming of gene expression after enforced expression in T-cell precursors.
A pathological pathway leading from soluble monomeric to insoluble filamentous Tau is characteristic of many human neurodegenerative diseases, which also exhibit dysfunction and death of brain cells. However, it is unknown how the assembly of Tau into filaments relates to cell loss. To study this, we first used a mouse line transgenic for full-length human mutant P301S Tau to investigate the temporal relationship between Tau assembly into filaments, assessed using anti-Tau antibody AT100, and motor neuron numbers, in the lumbar spinal cord. AT100 immunoreactivity preceded nerve cell loss. Murine Tau did not contribute significantly to either Tau aggregation or neurodegeneration. To further study the relevance of filament formation for neurodegeneration, we deleted hexapeptides 275VQIINK280 and 306VQIVYK311, either singly or in combination, from human 0N4R Tau with the P301S mutation. These hexapeptides are essential for the assembly of Tau into filaments. Homozygous mice transgenic for P301S Tau with the hexapeptide deletions, which expressed Tau at a similar level to the heterozygous line transgenic for P301S Tau, had a normal lifespan, unlike mice from the P301S Tau line. The latter had significant levels of sarkosyl-insoluble Tau in brain and spinal cord, and exhibited neurodegeneration. Mice transgenic for P301S Tau with the hexapeptide deletions failed to show significant levels of sarkosyl-insoluble Tau or neurodegeneration. Recombinant P301S Tau with the hexapeptide deletions failed to form β-sheet structure and filaments following incubation with heparin. Taken together, we conclude that β-sheet assembly of human P301S Tau is necessary for neurodegeneration in transgenic mice.
Type-2 immunity is characterised by interleukin (IL)-4, IL-5 and IL-13, eosinophilia, mucus production, IgE, and alternatively activated macrophages (AAM). However, despite the lack of neutrophil chemoattractants such as CXCL1, neutrophils, a feature of type-1 immunity, are observed in type-2 responses. Consequently, alternative mechanisms must exist to ensure that neutrophils can contribute to type-2 immune reactions without escalation of deleterious inflammation. We now demonstrate that type-2 immune-associated neutrophil infiltration is regulated by the mouse RNase A homologue, eosinophil-associated ribonuclease 11 (Ear11), which is secreted by AAM downstream of IL-25-stimulated ILC2. Transgenic overexpression of Ear11 resulted in tissue neutrophilia, whereas Ear11-deficient mice have fewer resting tissue neutrophils, whilst other type-2 immune responses are not impaired. Notably, administration of recombinant mouse Ear11 increases neutrophil motility and recruitment. Thus, Ear11 helps maintain tissue neutrophils at homoeostasis and during type-2 reactions when chemokine-producing classically activated macrophages are infrequently elicited.
The EWS-ERG fusion protein is found in human sarcomas with the chromosomal translocation t(21;22)(q22;q12), where the translocation is considered to be an initiating event in sarcoma formation within uncommitted mesenchymal cells, probably long-lived progenitors capable of self renewal. The fusion protein may not therefore have an oncogenic capability beyond these progenitors. To assess whether EWS-ERG can be a tumour initiator in cells other than mesenchymal cells, we have analysed Ews-ERG fusion protein function in a cellular environment not typical of that found in human cancers, namely, committed lymphoid cells. We have used Ews-ERG invertor mice having an inverted ERG cDNA cassette flanked by loxP sites knocked in the Ews intron 8, crossed with mice expressing Cre recombinase under the control of the Rag1 gene to give conditional, lymphoid-specific expression of the fusion protein. Clonal T cell neoplasias arose in these mice. This conditional Ews gene fusion model of tumourigenesis shows that Ews-ERG can cause haematopoietic tumours and the precursor cells are committed cells. Thus, Ews-ERG can function in cells that do not have to be pluripotent progenitors or mesenchymal cells.
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