Effect of spermine on the kinetics of estradiol hydroxylation by rat liver microsomes

Résumé L'addition de spermine au microsomes du foie de rats femelles modifie leK _m du système enzymatique qui transforme 1'estradiol en 2-hydroxyestradiol et aussi en des produits aqueux. La nouvelle valeur resemble à celle qu'ont trouve avec des rats mâles, mais leV _max de la réaction reste inchangé. L'action de la spermine dans ce système est discutée.     

Lung cancer: intragenic ERBB2 kinase mutations in tumours

The protein-kinase family is the most frequently mutated gene family found in human cancer and faulty kinase enzymes are being investigated as promising targets for the design of antitumour therapies. We have sequenced the gene encoding the transmembrane protein tyrosine kinase ERBB2 (also known as HER2 or Neu) from 120 primary lung tumours and identified 4% that have mutations within the kinase domain; in the adenocarcinoma subtype of lung cancer, 10% of cases had mutations. ERBB2 inhibitors, which have so far proved to be ineffective in treating lung cancer, should now be clinically re-evaluated in the specific subset of patients with lung cancer whose tumours carry ERBB2 mutations.     

Monoamine oxidase activities in human brain microvessels

Summary Microvessels can be easily isolated from human brain samples obtained at autopsy. Human frontal cortex MAO type A and B activities are similar in microvessel and microvessel-free preparations. In microvessels, enzyme activities and the ratio of MAO type A to type B vary among the areas studied and could selectively regulate the passage of certain amines through the blood vessel wall.Acknowledgment. The technical assistance of N. Gentile and the financial support by NIMH grant MH31156 is gratefully acknowledged.     

Production of a mutation in mouse En-2 gene by homologous recombination in embryonic stem cells

A full understanding of the function of genes that control developmental events can be obtained only by a combination of molecular and mutational analysis. One putative developmental gene is the mouse engrailed-like gene En-2, which was isolated by virtue of its extensive homology to Drosophila engrailed, which contributes to the control of segmentation in the developing insect. Our hybridization analysis in situ has revealed that expression of En-2 is restricted to a specific domain of the developing central nervous system from 8 days of development on, indicating a role for the gene in establishing spatial domains in the brain. Unfortunately no En-2 mutations are available to elucidate further its function in development. To this end, we report here the isolation of three pluripotent embryonic stem cell lines in which one copy of the homoeobox-containing gene, En-2, has been altered by homologous recombination.     

The SH2 tyrosine phosphatase shp2 is required for mammalian limb development

The tyrosine phosphatase Shp2 is recruited into tyrosine-kinase signalling pathways through binding of its two amino-terminal SH2 domains to specific phosphotyrosine motifs, concurrent with its re-localization and stimulation of phosphatase activity. Shp2 can potentiate signalling through the MAP-kinase pathway and is required during early mouse development for gastrulation. Chimaeric analysis can identify, by study of phenotypically normal embryos, tissues that tolerate mutant cells (and therefore do not require the mutated gene) or lack mutant cells (and presumably require the mutated gene during their developmental history). We therefore generated chimaeric mouse embryos to explore the cellular requirements for Shp2. This analysis revealed an obligatory role for Shp2 during outgrowth of the limb. Shp2 is specifically required in mesenchyme cells of the progress zone (PZ), directly beneath the distal ectoderm of the limb bud. Comparison of Ptpn11 (encoding Shp2)-mutant and Fgfr1 (encoding fibroblast growth factor receptor-1)-mutant chimaeric limbs indicated that in both cases mutant cells fail to contribute to the PZ of phenotypically normal chimaeras, leading to the hypothesis that a signal transduction pathway, initiated by Fgfr1 and acting through Shp2, is essential within PZ cells. Rather than integrating proliferative signals, Shp2 probably exerts its effects on limb development by influencing cell shape, movement or adhesion. Furthermore, the branchial arches, which also use Fgfs during bud outgrowth, similarly require Shp2. Thus, Shp2 regulates phosphotyrosine-signalling events during the complex ectodermal-mesenchymal interactions that regulate mammalian budding morphogenesis.     

The organizer factors Chordin and Noggin are required for mouse forebrain development

In mice, there is evidence suggesting that the development of head and trunk structures is organized by distinctly separated cell populations. The head organizer is located in the anterior visceral endoderm (AVE) and the trunk organizer in the node and anterior primitive streak. In amphibians, Spemann's organizer, which is homologous to the node, partially overlaps with anterior endoderm cells expressing homologues of the AVE markers cerberus, Hex and Hesx1. For mice, this raises the question of whether the AVE and node are independent of each other, as suggested by their anatomical separation, or functionally interdependent as is the case in amphibians. Chordin and Noggin are secreted bone morphogenetic protein (BMP) antagonists expressed in the mouse node, but not in the AVE. Here we show that mice double-homozygous mutants that are for chordin and noggin display severe defects in the development of the prosencephalon. The results show that BMP antagonists in the node and its derivatives are required for head development.     

A transmembrane protein required for acetylcholine receptor clustering in Caenorhabditis elegans

Clustering neurotransmitter receptors at the synapse is crucial for efficient neurotransmission. Here we identify a Caenorhabditis elegans locus, lev-10, required for postsynaptic aggregation of ionotropic acetylcholine receptors (AChRs). lev-10 mutants were identified on the basis of weak resistance to the anthelminthic drug levamisole, a nematode-specific cholinergic agonist that activates AChRs present at neuromuscular junctions (NMJs) resulting in muscle hypercontraction and death at high concentrations. In lev-10 mutants, the density of levamisole-sensitive AChRs at NMJs is markedly reduced, yet the number of functional AChRs present at the muscle cell surface remains unchanged. LEV-10 is a transmembrane protein localized to cholinergic NMJs and required in body-wall muscles for AChR clustering. We also show that the LEV-10 extracellular region, containing five predicted CUB domains and one LDLa domain, is sufficient to rescue AChR aggregation in lev-10 mutants. This suggests a mechanism for AChR clustering that relies on extracellular protein-protein interactions. Such a mechanism is likely to be evolutionarily conserved because CUB/LDL transmembrane proteins similar to LEV-10, but lacking any assigned function, are expressed in the mammalian nervous system and might be used to cluster ionotropic receptors in vertebrates.