Importing genetically altered animals: ensuring quality

The reproducibility of research using laboratory animals requires reliable management of their quality, in particular of their genetics, health and environment, all of which contribute to their phenotypes. The point at which these biological materials are transferred between researchers is particularly sensitive, as it may result in a loss of integrity of the animals and/or their documentation. Here, we describe the various aspects of laboratory animal quality that should be confirmed when sharing rodent research models. We also discuss how repositories of biological materials support the scientific community to ensure the continuity of the quality of laboratory animals. Both the concept of quality and the role of repositories themselves extend to all exchanges of biological materials and all networks that support the sharing of these reagents.

[p27Kip1 independently promotes neuronal differentiation and migration in the cerebral cortex]

The generation of glutamatergic neurons by stem and progenitor cells is a complex process involving the tight coordination of multiple cellular activities, including cell cycle exit, initiation of neuronal differentiation and cell migration. The mechanisms that integrate these different events into a coherent program are not well understood. Here we show that the cyclin-dependent kinase inhibitor p27Kip1 plays an important role in neurogenesis in the mouse cerebral cortex, by promoting the differentiation and radial migration of cortical projection neurons. Importantly, p27Kip1 promotes neuronal differentiation and neuronal migration via two distinct mechanisms, which are themselves independent of the cell cycle regulatory function of p27Kip1. p27Kip1 inactivation by gene targeting or RNA interference results in neuronal differentiation and radial migration defects, demonstrating that p27Kip1 regulates cell migration in vivo. The differentiation defect, but not the migration defect, is rescued by overexpression of the proneural gene Neurogenin 2. p27Kip1 acts by stabilizing Neurogenin 2 protein, an activity carried by the N-terminal half of the protein. The migration defect resulting from p27Kp1 inactivation is rescued by blocking RhoA signalling, an activity that resides in the c-terminal half of p27Kip1. Thus, p27Kip1 plays a key role in cortical development, acting as a modular protein that independently regulates and couples multiple cellular pathways contributing to neurogenesis.

Structural and functional characterization of the mouse fatty acid translocase promoter: activation during adipose differentiation

Fatty acid translocase (FAT/CD36) is a cell-surface glycoprotein that functions as a receptor/transporter for long-chain fatty acids (LCFAs), and interacts with other protein and lipid ligands. FAT/CD36 is expressed by various cell types, including platelets, monocytes/macrophages and endothelial cells, and tissues with an active LCFA metabolism, such as adipose, small intestine and heart. FAT/CD36 expression is induced during adipose cell differentiation and is transcriptionally up-regulated by LCFAs and thiazolidinediones in pre-adipocytes via a peroxisome-proliferator-activated receptor (PPAR)-mediated process. We isolated and analysed the murine FAT/CD36 promoter employing C(2)C(12)N cells directed to differentiate to either adipose or muscle. Transient transfection studies revealed that the 309 bp upstream from the start of exon 1 confer adipose specific activity. Sequence analysis of this DNA fragment revealed the presence of two imperfect direct repeat-1 elements. Electrophoretic mobility-shift assay demonstrated that these elements were peroxisome-proliferator-responsive elements (PPREs). Mutagenesis and transfection experiments indicated that both PPREs co-operate to drive strong promoter activity in adipose cells. We conclude that murine FAT/CD36 expression in adipose tissue is dependent upon transcriptional activation via PPARs through binding to two PPREs located at -245 to -233 bp and -120 to -108 bp from the transcription start site.

Long chain fatty acids as modulators of gene transcription in preadipose cells

During the last years, it has been clearly established that long-chain fatty acids act as modulators of gene expression in various tissues, such as adipose tissue, intestine and liver. This transcriptional action of fatty acids explains in part adaptation mechanisms of tissues to nutritional changes and especially to high-fat diets by increasing expression of proteins involved in lipid catabolism in liver and fatty acid uptake and utilization in other tissues. It is now clearly demonstrated that some of these transcriptional effects of fatty acids are mediated by activation of specific nuclear hormone receptors, called peroxisome proliferator-activated receptors (PPARs). These findings will be discussed with a special reference to control of gene expression in preadipocytes and adipose tissue development.

Trans-differentiation of myoblasts to adipoblasts: triggering effects of fatty acids and thiazolidinediones

Long-chain fatty acids (LCFA) and thiazolidinediones are potent activators of differentiation of preadipose cells. These adipogenic effects are, at least in part, mediated by nuclear receptors of the peroxisome proliferator-activated receptor (PPAR) subfamily. This report describes the effects of these agents on the differentiation pathway of myoblasts. Exposure of C2C12 myoblasts to LCFA or thiazolidinediones prevents the formation of multinucleated myotubes and the expression of specific muscle markers, leading in parallel to the expression of a typical adipose differentiation program. Similar transdifferentiation also occurs in mouse muscle satellite cells maintained in primary cell culture. These observations indicate that PPAR activators, such as LCFA or thiazolidinediones, convert the differentiation pathway of myoblasts into that of adipoblasts. This phenomenon could explain the appearance of adipocytes into muscle which occurs in some pathological states characterized by an increase of fatty acid disposal, such as obesity or mitochondrial myopathy.

Fatty acids regulate the expression of lipoprotein lipase gene and activity in preadipose and adipose cells

During fasting, a reduction in lipoprotein lipase (LPL) activity has been observed in rat fat pad with no change in enzyme mass, whereas LPL mRNA and synthesis are increased, suggesting that insulin and/or fatty acids (FA) regulate LPL activity post-translationaly [Doolittle, Ben-Zeev, Elovson, Martin and Kirchgessner (1990) J. Biol. Chem. 265, 4570-4577]. To examine the role of FA, either preadipose Ob1771 cells or Ob1771 and 3T3-F442A adipose cells were exposed to long-chain FA and to 2-bromopalmitate, a non-metabolized FA. A rapid (2-8 h) and dose-dependent increase (up to 6-fold) in LPL mRNA occurred, primarily due to increased transcription, which is accompanied by a decrease (down to 4-fold) in LPL cellular activity. Under these conditions, secretion of active LPL was nearly abolished. Removal of FA led to full recovery of LPL activity. LPL gene expression in 3T3-C2 fibroblasts was not affected by FA treatment. However fatty acid-activated receptor transfected-3T3-C2 cells, which show FA responsiveness, had increased LPL gene expression upon FA addition. LPL synthesis and cellular content appeared unaffected by FA treatment, whereas secretion of LPL was inhibited. These results indicate that FA regulate the post-translational processing of LPL. It is proposed that the regulation of LPL activity by FA is important with regard to the fine-tuning of FA entry into adipocytes during fasting/feeding periods.

Thiazolidinediones and fatty acids convert myogenic cells into adipose-like cells

Fatty acids and thiazolidinediones act as potent activators of the adipose differentiation program in established preadipose cell lines. In this report, the effects of these agents on the differentiation pathway of myoblasts have been investigated. Exposure of C2C12N myoblasts (a subclone of the C2C12 cell line) to thiazolidinediones or fatty acids prevents the expression of myogenin, alpha-actin, and creatine kinase, thus abolishing the formation of multinucleated myotubes. These treatments lead in parallel to the expression of a typical adipose differentiation program including acquisition of adipocyte morphology and activation of adipose-related genes. A similar transition toward the adipose differentiation pathway also occurs in mouse muscle satellite cells maintained in primary culture. Thiazolidinediones exert their adipogenic effects only in non-terminally differentiated myoblasts; myotubes are insensitive to the compounds. Continuous exposure to inducers after growth arrest is not required to maintain the adipose phenotype, but proliferation of adipose-like C2C12N cells leads to a complete reversion toward undifferentiated cells able to undergo either myogenic or adipogenic differentiation depending on the composition of culture medium. These results indicate that adipogenic inducers, such as thiazolidinediones or fatty acids, specifically convert the differentiation pathway of myoblasts into that of adipoblasts.

Evidence for a common mechanism of action for fatty acids and thiazolidinedione antidiabetic agents on gene expression in preadipose cells

In diabetic rodents, thiazolidinediones are able to improve insulin sensitivity of target tissues and to reverse, at least partially, the diabetic state. The effects of these drugs on phenotypic expression in various tissues, including adipose tissue, have been reported. We report here that a new thiazolidinedione compound, BRL 49653, exerts, in preadipose cells, potent effects on the expression of genes encoding proteins involved in fatty acid metabolism. These effects of BRL 49653 in Ob 1771 preadipose cells are similar, in terms of kinetics, reversibility, specificity of genes affected, and requirement for protein synthesis, to those already described for natural or nonmetabolizable fatty acids. Moreover, when used at submaximally effective concentrations, BRL49653 and 2-bromopalmitate act in an additive manner to induce gene expression in preadipose cells, but this additivity of effects is lost when one of the compounds is used at a maximally effective concentration. These observations, suggesting similar mechanisms of action for thiazolidinediones and fatty acids, are strongly supported by the demonstration that (i) both molecules activate, in a heterogolous trans-activation assay, the same nuclear receptor of the steroid/thyroid hormone nuclear receptor superfamily and (ii) transfection of 3T3-C2 fibroblasts with an expression vector for this nuclear receptor confers thiazolidinedione inducibility of adipocyte lipid-binding protein gene expression.

[Corticotherapy and stomatologic oncology]

Long-term use of corticoids had proved beneficial in the treatment of advanced stomatological cancers, the effective dose being 40 mg of prednisone per day. In so far as it is possible to distinguish any specific action on individual symptoms, its action on pain was obvious in 40% of cases, on inflammation and infection in 52% of cases on fever (independent of infection) in 14% of cases, on oedema in 34% of cases. It was almost invariably favourable on the general condition. The method of using it emphasize how easy it is to use corticoids by injection which is of particular value in our speciality in view of: dysphagia, administration of large doses, deficiencies in the general condition, sometimes a matter of urgency. The counter-indications usually recognized for corticoids need to be modified in the case of cancer patients. Incidents occur surprisingly rarely and are minor relative to the advantages of the therapy, provided the patient is kept under strict supervision.