Live imaging of targeted cell ablation in Xenopus: a new model to study demyelination and repair.

Live imaging studies of the processes of demyelination and remyelination have so far been technically limited in mammals. We have thus generated a Xenopus laevis transgenic line allowing live imaging and conditional ablation of myelinating oligodendrocytes throughout the CNS. In these transgenic pMBP-eGFP-NTR tadpoles the myelin basic protein (MBP) regulatory sequences, specific to mature oligodendrocytes, are used to drive expression of an eGFP (enhanced green fluorescent protein) reporter fused to the Escherichia coli nitroreductase (NTR) selection enzyme.

Myogenic waves and myogenic programs during Xenopus embryonic myogenesis.

Unlabelled: Although Xenopus is a key model organism in developmental biology, little is known about the myotome formation in this species. Here, we assessed the expression of myogenic regulatory factors of the Myod family (MRFs) during embryonic development and revealed distinct MRF programs.

Results: The expression pattern of each MRF during embryonic development highlights three successive myogenic waves.

In vitro susceptibility of Plasmodium falciparum to monodesethylamodiaquine, quinine, mefloquine and halofantrine in Abidjan (Côte d'Ivoire).

Background: Malaria is the primary cause of hospitalization in Côte d'Ivoire. Early treatment is one of the strategies to control this illness. However, the spread of resistance of Plasmodium falciparum to antimalarial drugs can seriously compromise this strategy.

Reduced levels of survival motor neuron protein leads to aberrant motoneuron growth in a Xenopus model of muscular atrophy.

Spinal muscular atrophy (SMA) is a neurodegenerative disease characterized by motor neuron loss and skeletal muscle atrophy. The loss of function of the smn1 gene, the main supplier of survival motor neuron protein (SMN) protein in human, leads to reduced levels of SMN and eventually to SMA. Here, we ask if the amphibian Xenopus tropicalis can be a good model system to study SMA.

Insights from Xenopus genomes.

Amphibians have been used since the 19th century as vertebrate models for the experimentalist. Since 50 years or so, Xenopus laevis is the most widely used anuran amphibian research organism. However, because it is a pseudo-tetraploid species, its genetics has been lagging behind.

Early aspects of gonadal sex differentiation in Xenopus tropicalis with reference to an antero-posterior gradient.

In an effort to contribute to the development of Xenopus tropicalis as an amphibian model system, we carried out a detailed histological analysis of the process of gonadal sex differentiation and were able to find evidence that gonadal differentiation in X. tropicalis follows an antero-posterior gradient. Although the main reason for the presence of a gradient of sex differentiation is still unknown, this gradient enabled us to define the early events that signal ovarian and testicular differentiation and to identify the undifferentiated gonad structure.

Antifolate screening using yeast expressing Plasmodium vivax dihydrofolate reductase and in vitro drug susceptibility assay for Plasmodium falciparum.

The presence of homologous point mutations in the dhfr gene in Plasmodium vivax and Plasmodium falciparum is associated with resistance to antifolate drugs. The spread of antifolate resistance encouraged research for novel antifolate drugs active against both wild-type and dhfr-mutant strains of malaria parasites. Because P.

Regulation of XSnail2 expression by Rho GTPases.

We analyzed the effects of Rho GTPases on XSnail2 expression during neural crest (NC) ontogeny in Xenopus laevis embryos. The ectopic expression of both dominant-negative (N-) and constitutively active (V-) Rho GTPase mutants after RNA or DNA microinjection disrupted the endogenous expression of XSnail2, XFoxD3, and XSnail1. V14RhoA and N17Rac1 were inhibitory, whereas N19RhoA and V12Rac1 increased NC marker gene expression.

Exploring nervous system transcriptomes during embryogenesis and metamorphosis in Xenopus tropicalis using EST analysis.

Background: The western African clawed frog Xenopus tropicalis is an anuran amphibian species now used as model in vertebrate comparative genomics. It provides the same advantages as Xenopus laevis but is diploid and has a smaller genome of 1.7 Gbp.

Sulfadoxine-pyrimethamine susceptibilities and analysis of the dihydrofolate reductase and dihydropteroate synthase of Plasmodium falciparum isolates from Côte d'Ivoire.

Over a 2-year study period, three methods [a test of therapeutic efficacy, an in-vitro assay, and sequencing of the parasites' dihydrofolate-reductase (dhfr) and dihydropteroate-synthase (dhps) genes] were used to monitor sulfadoxine-pyrimethamine (SP) resistance in the Plasmodium falciparum strains infecting young children near Abidjan, the largest city in Côte d'Ivoire. Overall, 118 children aged<5 years and infected with P. falciparum were treated with SP.

tBid mediated activation of the mitochondrial death pathway leads to genetic ablation of the lens in Xenopus laevis.

Xenopus is a well proven model for a wide variety of developmental studies, including cell lineage. Cell lineage in Xenopus has largely been addressed by injection of tracer molecules or by micro-dissection elimination of blastomeres. Here we describe a genetic method for cell ablation based on the use of tBid, a direct activator of the mitochondrial apoptotic pathway.

Generation of trangenic Xenopus laevis using the Sleeping Beauty transposon system.

Using the Sleeping Beauty (SB) transposon system, we have developed a simple method for the generation of Xenopus laevis transgenic lines. The transgenesis protocol is based on the co-injection of the SB transposase mRNA and a GFP-reporter transposon into one-cell stage embryos. Transposase-dependent reporter gene expression was observed in cell clones and in hemi-transgenic animals.

Developmental cell death during Xenopus metamorphosis involves BID cleavage and caspase 2 and 8 activation.

Elimination of tadpole organs during Xenopus metamorphosis is largely achieved through apoptosis, and recent evidence suggest involvement of the mitochondrial death route and bax-initiated caspase-3 and -9 deployment. However, events upstream of the activation of Bax are unknown. In other models, proteins of the BH3-only group such as BID are known to assure this function.

Survivin increased vascular development during Xenopus ontogenesis.

Survivin is a member of the inhibitor of apoptosis proteins (IAP) family. These proteins contain one to three zinc-binding motifs termed bacculoviral IAP-binding repeats (BIRs). Survivin contains a single BIR motif.

Evi1 is specifically expressed in the distal tubule and duct of the Xenopus pronephros and plays a role in its formation.

The ecotropic viral integration site 1 (Evi1) and related MEL1 (MDS1/Evi1-like gene 1) genes are zinc finger oncogenic transcription factors involved in myeloid leukaemia. Here, we show that in Xenopus, Evi1 and MEL1 have partially overlapping restricted embryonic expression profiles. Within the pronephros, Evi1 and MEL1 are sequentially expressed within the distal tubule and duct compartments, Evi1 transcription being detected prior to any sign of pronephric morphogenesis.

Plasmodium vivax dihydrofolate reductase as a target of sulpha drugs.

Sulpha drugs act as competitive inhibitors of p-amino benzoic acid, an intermediate in the de novo folate pathway. Dihydropteroate synthase condenses sulpha drugs into sulpha-dihydropteroate (sulpha-DHP), which competes with dihydrofolate, the dihydrofolate reductase (DHFR) substrate. This designates DHFR as a possible target of sulpha-DHP.

The mariner transposons belonging to the irritans subfamily were maintained in chordate genomes by vertical transmission.

Mariner-like elements (MLEs) belong to the Tc1-mariner superfamily of DNA transposons, which is very widespread in animal genomes. We report here the first complete description of a MLE, Xtmar1, within the genome of a poikilotherm vertebrate, the amphibian Xenopus tropicalis. A close relative, XlMLE, is also characterized within the genome of a sibling species, Xenopus laevis.

Characterization of multiple lineages of Tc1-like elements within the genome of the amphibian Xenopus tropicalis.

We have used genomic sequencing data extracted from the first assembly of the Xenopus tropicalis genome combined with a degenerated PCR approach to identify multiple lineages of Tc1 related transposable elements. Full-length elements were isolated in each lineage and were characterized. Most of them exhibit the typical characteristics of Tc1-like elements (TLEs).

Phylogenomic analysis and expression patterns of large Maf genes in Xenopus tropicalis provide new insights into the functional evolution of the gene family in osteichthyans.

We have performed an exhaustive characterization of the large Maf family of basic leucine zipper transcription factors in vertebrates using the genome data available, and studied the embryonic expression patterns of the four paralogous genes thus identified in Xenopus tropicalis. Our phylogenetic analysis shows that, in osteichthyans, the large Maf family contains four orthology classes, MafA, MafB, c-Maf and Nrl, which have emerged in vertebrates prior to the split between actinopterygians and sarcopterygians. It leads to the unambiguous assignment of the Xenopus laevis XLmaf gene, previously considered a MafA orthologue, to the Nrl class, the identification of the amphibian MafA and c-Maf orthologues and the identification of the zebrafish Nrl gene.

[Monitoring the chemoresistance of Plasmodium falciparum malaria in Yopougon (Abidjan): in vivo study of chloroquine sensitivity and evaluation of pyrimethamine resistance following the analysis of point mutation in the dihydrofolate reductase gene].

A major endemic in Côte d'Ivoire, malaria is the first cause of hospital admissions and mortality in tropical Africa. The decrease of morbidity and mortality depends on early diagnosis and relevant treatment. This situation is hampered by an emerging resistance of P.

Deletion and dosage modulation of the eEF1A gene in Podospora anserina: effect on the life cycle.

eEF1A is encoded by a unique gene in the filamentous fungus Podospora anserina. We show here that (1) this gene is essential for vegetative growth, (2) readthrough at UGA stop codon level is positively correlated with eEF1A level, (3) eEF1A level is regulated in P. anserina.

Xenopus Bcl-X(L) selectively protects Rohon-Beard neurons from metamorphic degeneration.

Amphibian metamorphosis involves extensive, but selective, neuronal death and turnover, thus sharing many features with mammalian postnatal development. The antiapoptotic protein Bcl-X(L) plays an important role in postnatal mammalian neuronal survival. It is therefore of interest that accumulation of the mRNA encoding the Xenopus Bcl-X(L) homologue, termed xR11, increases abruptly in the nervous system, but not in other tissues, during metamorphosis in Xenopus tadpoles.

Kinetic properties of dihydrofolate reductase from wild-type and mutant Plasmodium vivax expressed in Escherichia coli.

Antifolate drugs inhibit malarial dihydrofolate reductase (DHFR). In Plasmodium falciparum, antifolate resistance has been associated with point mutations in the gene encoding DHFR. Recently, mutations at homologous positions have been observed in the P.

Informational suppressor alleles of the eEF1A gene, fertility and cell degeneration in Podospora anserina.

Mutations that increase readthrough at a UGA stop codon (informational suppressor mutations) were created in the gene (AS4) that encodes translation elongation factor eEF1A in the filamentous fungus Podospora amserina. The results strongly suggest that the net charge of the eEF1A protein controls the accuracy of translation. Physiological analysis of the mutant strains shows that some of the alleles dominantly increase life span, while only one drastically modifies fertility.