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Papers by Béatrice Levacher

Pediatric Research, 2001

Endothelin-converting-enzyme (ECE-1) catalyzes the proteolytic activation of big endothelin-1 to ... more Endothelin-converting-enzyme (ECE-1) catalyzes the proteolytic activation of big endothelin-1 to mature endothelin-1. Most homozygous ECE-1Ϫ/Ϫ embryos die in utero and show severe craniofacial, enteric, and cardiac malformations precluding ventilatory function assessment. In contrast, heterozygous ECE-1ϩ/Ϫ embryos develop normally. Their respiratory function at birth has not been studied. Taking into account previous respiratory investigations in mice with endothelin-1 gene disruption, we hypothesized that ECE-1-deficient mice may have impaired ventilatory control. We analyzed ventilatory responses to hypercapnia (8% CO 2 ) and hypoxia (10% O 2 ) in newborn and adult mice heterozygous for ECE-1 deficiency (ECE-1ϩ/Ϫ) and in their wild-type littermates (ECE-1ϩ/ϩ). Ventilation, breath duration, and tidal volume were measured using whole-body plethysmography. Ventilatory responses to hypoxia were significantly weaker in ECE-1ϩ/Ϫ than in ECE-1ϩ/ϩ newborn mice (percentage ventilation increase: 1 Ϯ 25% versus 33 Ϯ 29%, p ϭ 0.010). Baseline breathing variables and ventilatory responses to hypercapnia were normal in the ECE-1ϩ/Ϫ newborn mice. No differences were observed between adult ECE-1ϩ/Ϫ and ECE-1ϩ/ϩ mice. We conclude that ECE-1 is required for normal ventilatory response to hypoxia at birth. (Pediatr Res 49: 705-712, 2001) Abbreviations CCHS, congenital central hypoventilation syndrome ECE-1, endothelin-converting-enzyme-1 ET-1, endothelin-1 ABSTRACT 705

Pediatric Research, 2004

Wolters Kluwer Health may email you for journal alerts and information, but is committed to maint... more Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining your privacy and will not share your personal information without your express consent. For more information, please refer to our Privacy Policy. ... Skip Navigation Links Home > May ...

Genomics, 2000

We isolated a novel mouse gene, RP42, in a systematic search for genes expressed in proliferating... more We isolated a novel mouse gene, RP42, in a systematic search for genes expressed in proliferating neuroblasts whose human orthologs map to susceptibility loci for autism. This gene is intronless and encodes a putative 259-amino-acid protein that exhibits 30-36% overall sequence identity to a fission yeast and a nematode protein (GenPept Accession Nos. CAA17006 and CAB54261). Nevertheless, no homology to any known gene was found. RP42 has developmentally regulated expression, particularly in proliferating neuroblasts from which neocortical neurons originate. Its human ortholog is located in a cluster of embryonic neuronally expressed genes on the 6q16 chromosome, making it a positional candidate susceptibility gene for autism.

Gene Expression Patterns, 2005

Neocortical neurons are generated predominantly from the cells that proliferate in the ventricula... more Neocortical neurons are generated predominantly from the cells that proliferate in the ventricular zone of the telencephalon. In order to understand the nature of these expanding cortical neuronal progenitor cells, we selected by differential display some transcripts that were enriched in the telencephalon as compared to the more caudal regions (diencephalon/mesencephalon). This systematic screening revealed one of the differentially expressed transcripts, namely the Fkbp25 mRNA that encodes a member of the FK506 binding proteins (FKBPs). Northern blot analysis showed that the expression of the single 1.4kb Fkbp25 transcript reached a maximum level on embryonic day 11.5 at the start of cortical neurogenesis in the mouse and was followed by a weak basal expression in the adult brain. In the embryo, Fkbp25 gene was strongly expressed in the telencephalon ventricular zone but also in areas active in myogenesis (walls of the ventricle and the atrium) and chondrogenesis (the cartilage of the rib and the hindlimb). An increase in the transcript levels of the Fkbp25 gene was also observed during the two successive proliferation waves of the cerebellum development. Immunostaining on primary cultures of embryonic day 10.5 telencephalon stem cells showed that the Fkbp25 protein was present in the cytoplasm and nuclei of cells cultured for 6h but exclusively in the nuclei of the Tuj-1 immunoreactive neurons obtained after 3 days of culture (The sequence data reported here have been submitted to GenBank under accession no. AF135595.).

FEBS Letters, 2002

Spatially and temporally regulated somatic mutations can be achieved by using the Cre/loxP recomb... more Spatially and temporally regulated somatic mutations can be achieved by using the Cre/loxP recombination system of bacteriophage P1. To develop a cell type-speci¢c system of gene targeting in the peripheral nervous system, we generated the transgenic mouse lines expressing Cre recombinase under the control of the mouse peripherin gene promoter. The activity of the Cre recombinase during embryonic development was examined by mating the peripherin-Cre transgenic mice to the knock-in Cre-mediated recombination reporter strain, R26R. Analysis of F1 embryos from this cross showed speci¢c excision of loxP-£anked sequences in the dorsal root ganglia, trigeminal ganglia, and olfactory epithelium, in a pattern very similar to the expression of the endogenous mouse peripherin gene, and the previously reported peripherin-lacZ transgenic mice. Thus, the peripherin-Cre mouse described here will provide a valuable tool for Cre-loxP-mediated conditional expression in the peripheral nervous system. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

Experimental Neurology, 1993

Most, if not all, nociceptor sensory neurons are dependent on nerve growth factor (NGF) during ea... more Most, if not all, nociceptor sensory neurons are dependent on nerve growth factor (NGF) during early embryonic development. A large subpopulation of these sensory neurons loses NGF dependency between embryonic day 16 and postnatal day 14 and become responsive to glial cell line-derived growth factor (GDNF), a member of the transforming growth factor ␤ (TGF-␤) family. To examine the survival and phenotypic effects of GDNF on sensory neurons in vivo, we generated transgenic mice that overexpress GDNF in the skin. GDNF-overexpresser mice had increased numbers of small unmyelinated sensory neurons that express the tyrosine kinase receptor Ret and bind the plant isolectin B4 (IB4). Surprisingly, in wild-type and trans-genic mice, few (ϳ2%) IB4-positive neurons expressed the vanilloid receptor VR1, a heat-sensitive receptor expressed by many IB4-positive neurons of the rat. Thus, in mouse, GDNFdependent IB4-positive neurons must use a non-VR1 heat receptor. In addition, the behavior of GDNF-overexpresser animals to noxious heat or mechanical stimuli was indistinguishable from wild-type animals, indicating that, on a behavioral level, peripherally applied GDNF does not alter the sensitivity of the somatosensory system.

European Journal of Human Genetics, 2004

Spinal muscular atrophy (SMA) is a recessive disorder involving the loss of motor neurons from th... more Spinal muscular atrophy (SMA) is a recessive disorder involving the loss of motor neurons from the spinal cord. Homozygous absence of the survival of motor neuron 1 gene (SMN1) is the main cause of SMA, but disease severity depends primarily on the number of SMN2 gene copies. SMN protein levels are high in normal spinal cord and much lower in the spinal cord of SMA patients, suggesting neuron-specific regulation for this ubiquitously expressed gene. We isolated genomic DNA from individuals with SMN1 or SMN2 deletions and sequenced 4.6 kb of the 5 0 upstream regions of the these. We found that these upstream regions, one of which is telomeric and the other centromeric, were identical. We investigated the early regulation of SMN expression by transiently transfecting mouse embryonic spinal cord and fibroblast primary cultures with three transgenes containing 1.8, 3.2 and 4.6, respectively, of the SMN promoter driving b-galactosidase gene expression. The 4.6 kb construct gave reporter gene expression levels five times higher in neurons than in fibroblasts, due to the combined effects of a general enhancer and a non-neuronal cell silencer. The differential expression observed in neurons and fibroblasts suggests that the SMN genes play a neuron-specific role during development. An understanding of the mechanisms regulating SMN promoter activity may provide new avenues for the treatment of SMA.

Cytogenetic and Genome Research, 2001

We identified new transcribed sequences, using a differential display paradigm to select genes ex... more We identified new transcribed sequences, using a differential display paradigm to select genes expressed in proliferating neuroblasts from mouse telencephalon at 10 days of embryonic development. In this systematic search, we isolated a 361-bp partial 3&amp;#39; untranslated region (3&amp;#39; UTR) homologous to the 3&amp;#39; UTR of the human gene encoding a putative intracellular kinase regulator, glia maturation factor beta (GMFB). We cloned a full-length, 4,311-bp mouse cDNA containing a 270-bp 5&amp;#39; UTR, a 3,615-bp 3&amp;#39; UTR, and an open reading frame of 426 nucleotides encoding a putative 142 amino-acid protein, identical to human GMFB, with the exception of two amino acids. This 4.3-kb transcript is present in a variety of adult tissues and is developmentally regulated as shown by Northern blot analysis. Differential expression in telencephalon was demonstrated by quantification of radioactive relative RT-PCR and confirmed by in situ hybridization. The isolation of this full-length clone of mouse Gmfb should facilitate investigation of the intracellular mechanisms involved in the development of telencephalon.

Human gene therapy methods, 2014

Numerous strategies targeting early and late steps of the HIV life cycle have been proposed for g... more Numerous strategies targeting early and late steps of the HIV life cycle have been proposed for gene therapy. However, targeting viral and host determinants of HIV entry is the only strategy that would prevent viral DNA-mediated CD4(+) cell death while diminishing the possibility for the virus to escape. To this end, we devised a bicistronic lentiviral vector expressing the membrane-bound form of the T20 fusion inhibitor, referred to as the C46 peptide, and a CCR5 superagonist, modified to sequester CCR5 away from the cell surface, referred to as the P2-CCL5 intrakine. We tested the effects of the vector on HIV infection and replication, using the human CEMR5 cell line expressing CD4 and CCR5, and primary human T cells. Transduced cells expressed the C46 peptide, detected with the 2F5 monoclonal antibody by flow cytometry. Expression of the P2-CCL5 intrakine correlates with lower levels of cell surface CCR5. Complete protection against HIV infection could be observed in cells expres...