Papers by Yannick Le Parco
HAL (Le Centre pour la Communication Scientifique Directe), 2003
Because calcareous sponges are triggering renewed interest with respect to basal metazoan evoluti... more Because calcareous sponges are triggering renewed interest with respect to basal metazoan evolution, a phylogenetic framework of their internal relationships is needed to clarify the evolutionary history of key morphological characters. Morphological variation was scored at the suprageneric level within Calcispongia, but little phylogenetic information could be retrieved from morphological characters. For the main subdivision of Calcispongia, the analysis of morphological data weakly supports a classification based upon cytological and embryological characters (Calcinea/Calcaronea) rather than the older classification scheme based upon the aquiferous system (Homocoela/Heterocoela). The 18S ribosomal RNA data were then analyzed, both alone and in combination with morphological characters. The monophyly of Calcispongia is highly supported, but the position of this group with respect to other sponge lineages and to eumetazoan taxa is not resolved. The monophyly of both Calcinea and Calcaronea is retrieved, and the data strongly rejected the competing Homocoela/Heterocoela hypothesis. The phylogeny implies that characters of the skeleton architecture are highly homoplastic, as are characters of the aquiferous system. However, axial symmetry seems to be primitive for all Calcispongia, a conclusion that has potentially far-reaching implications for hypotheses of early body plan evolution in Metazoa.
Cell differentiation and development, May 1, 1990
We have developed and characterized a battery of specific polyclonal antibodies directed against ... more We have developed and characterized a battery of specific polyclonal antibodies directed against specific portions of the alpha-chain of collagen type IV synthesized in Drosophila by the gene DCg1. Here, we describe the use of these antibodies together with in situ hybridization experiments in an attempt to study the expression and localization of collagen type IV during Drosophila oogenesis and early embryogenesis. The results clearly demonstrate that DCg1 is maternally expressed by follicle cells and that the collagen type IV chain produced is stockpiled in the growing oocyte. During the gastrulation stages, this component of Drosophila basement membranes concentrated on cells involved in the gradual invaginations leading to morphogenetic furrows. The presence of collagen type IV, which is an RGD-bearing molecule, during early stages of Drosophila development is discussed in comparison with the crucial, active role its vertebrate counterpart is supposed to play in morphogenetic processes.
Journal of Evolutionary Biology, 2002
Systematic Biology, Jun 1, 2003
Because calcareous sponges are triggering renewed interest with respect to basal metazoan evoluti... more Because calcareous sponges are triggering renewed interest with respect to basal metazoan evolution, a phylogenetic framework of their internal relationships is needed to clarify the evolutionary history of key morphological characters. Morphological variation was scored at the suprageneric level within Calcispongia, but little phylogenetic information could be retrieved from morphological characters. For the main subdivision of Calcispongia, the analysis of morphological data weakly supports a classification based upon cytological and embryological characters (Calcinea/Calcaronea) rather than the older classification scheme based upon the aquiferous system (Homocoela/Heterocoela). The 18S ribosomal RNA data were then analyzed, both alone and in combination with morphological characters. The monophyly of Calcispongia is highly supported, but the position of this group with respect to other sponge lineages and to eumetazoan taxa is not resolved. The monophyly of both Calcinea and Calcaronea is retrieved, and the data strongly rejected the competing Homocoela/Heterocoela hypothesis. The phylogeny implies that characters of the skeleton architecture are highly homoplastic, as are characters of the aquiferous system. However, axial symmetry seems to be primitive for all Calcispongia, a conclusion that has potentially far-reaching implications for hypotheses of early body plan evolution in Metazoa.
Mechanisms of Development, Aug 1, 1996
Type IV collagen forms a network that provides the major structural support for basement membrane... more Type IV collagen forms a network that provides the major structural support for basement membranes. Basement membranes are specialized forms of extracellular matrix with important functions in development. One collagen gene (Dcgl) was characterized in Drosophila melunogaster and shown to encode a collagen chain related to vertebrate basement membrane type IV collagen chains. Therefore, to access the functional importance of type IV collagen during Drosophila myogenesis, we adopted two different approaches to decrease the Dcgl gene expression in Drosophila embryos. We describe, here, that the decrease in Dcgl gene expression causes, in particular, defective muscle attachments. These mutant phenotypes suggest that type IV collagen acts to stabilize cell-matrix interactions.
Journal of Evolutionary Biology, 2008
In order to allow critical evaluation of the interrelationships between the three sponge classes,... more In order to allow critical evaluation of the interrelationships between the three sponge classes, and to resolve the question of mono‐ or paraphyly of sponges (Porifera), we used the polymerase chain reaction (PCR) to amplify almost the entire nucleic acid sequence of the 18S rDNA from several hexactinellid, demosponge and calcareous sponge species. The amplification products were cloned, sequenced and then aligned with previously reported sequences from other sponges and nonsponge metazoans and variously distant outgroups, and trees were constructed using both neighbour‐joining and maximum parsimony methods. Our results suggest that sponges are paraphyletic, the Calcarea being more related to monophyletic Eumetazoa than to the siliceous sponges (Demospongiae, Hexactinellida). These results have important implications for our understanding of metazoan origins, because they suggest that the common ancestor of Metazoa was a sponge. They also have consequences for basal metazoan classi...
Mechanisms of Development, May 1, 1996
We report the cloning of a Distal-less-like gene (PwDlx-3) and its pattern of expression during e... more We report the cloning of a Distal-less-like gene (PwDlx-3) and its pattern of expression during embryonic development and adult tail regeneration in the urodele Pleurodeles waltl. Using RT-PCR and in situ hybridization experiments we determined that, during regeneration, PwDlx-3 is expressed in the epidermis, the cells associated with muscle masses and in the ventrolateral parts of the ependymal tube. PwDlx-3 localization in the muscle masses and in cells of the ependymal tube, which give rise during regeneration to the ventral roots and the spinal ganglia, suggests that this gene might be expressed in cells which have some neural crest cell potentialities. PwDlx-3 is the first homeobox gene shown to be expressed in the regenerating spinal cord but not in the adult one and could thus be involved in the regeneration of the nervous system.
Biology of the Cell, 1986
We have used a cloned chicken collagen cDNA sequence to help identify hypothetic members of the c... more We have used a cloned chicken collagen cDNA sequence to help identify hypothetic members of the collagen gene family from Drosophila melanogaster. Several experimental evidences have been obtained which indicate that the Drosophila genome contains numerous collagen-like sequences. We have characterized in more detail ten distinct DNA sequences that hybridized strongly to the heterologous collagen probe. By in situ hybridization we have shown that these sequences are dispersed throughout the Drosophila genome. Two of them are shown to originate from the previously described DCg 1 and DCg 2 collagen genes. In other respects, we show that in addition to DCg 1 and DCg 2, at least five putative collagen genes are expressed during the Drosophila lifetime. These genes are unique, and some of them are seen to be transcribed into different size classes of mRNAs. Additionally, the data presented so far demonstrate that the expression of these genes is regulated temporally and/or quantitatively during the Drosophila life cycle.
Roux's archives of developmental biology, Apr 1, 1987
We report a direct examination of the expression of one collagen gene (DCg1) during Drosophila me... more We report a direct examination of the expression of one collagen gene (DCg1) during Drosophila melanogaster metamorphosis, based on data from in situ hybridization. The transcripts of this gene, thought to encode a basement membrane type IV collagen, are mainly accumulated during ecdysis in wandering haemocytes. Our results demonstrate that haemocytes contribute to extracellular matrix deposition and seem to perform a fibroblastic function during Drosophila development.
Experimental Cell Research, Apr 1, 1986
Based on data from developmental RNA profiles and in situ hybridization, we report a direct exami... more Based on data from developmental RNA profiles and in situ hybridization, we report a direct examination of the expression of one collagen gene (Dcg1) during drosophila melanogaster life cycle. These studies show, for the first time, that the expression of a collagen gene is both differential and tissue-specific during the course of development. Moreover, they demonstrate that the connective tissues in Drosophila do contain a collagen type synthesized by mesodermal tissues. Indeed the accumulation of Dcg1 transcripts was located mainly within the second instar fat bodies, the third instar lymph glands, and over adepithelial cells associated with third instar imaginal discs. In addition, these results seem to confirm the interpretation that wandering hemocytes released by the lymph glands could contribute in extracellular matrix composition in some tissues in the larva.
Development Genes and Evolution, Mar 11, 2003
We present the isolation of six Hox genes in the chaetognath Spadella cephaloptera. We identified... more We present the isolation of six Hox genes in the chaetognath Spadella cephaloptera. We identified one member of the paralogy group 3, four median genes and a mosaic gene that shares features of both median and posterior classes (SceMedPost). Several hypotheses may account for the presence of a mosaic Hox gene in this animal. Here we propose that SceMedPost may represent an ancestral gene, which has not diverged totally into a posterior or a median one. This hypothesis has interesting implications for the reconstruction of the evolutionary history of Hox genes and suggests that Chaetognatha lineage divergence could predate the deuterostome/protostome split. Such a phylogenetic position is considered in the light of their embryological and morphological characters.
Current Biology, Aug 1, 2006
Molecular Biology and Evolution, Aug 11, 2004
Determining the phylogenetic position of enigmatic phyla such as Chaetognatha is a longstanding c... more Determining the phylogenetic position of enigmatic phyla such as Chaetognatha is a longstanding challenge for biologists. Chaetognaths (or arrow worms) are small, bilaterally symmetrical metazoans. In the past decades, their relationships within the metazoans have been strongly debated because of embryological and morphological features shared with the two main branches of Bilateria: the deuterostomes and protostomes. Despite recent attempts based on molecular data, the Chaetognatha affinities have not yet been convincingly defined. To answer this fundamental question, we determined the complete mitochondrial DNA genome of Spadella cephaloptera. We report three unique features: it is the smallest metazoan mitochondrial genome known and lacks both atp8 and atp6 and all tRNA genes. Furthermore phylogenetic reconstructions show that Chaetognatha belongs to protostomes. This implies that some embryological characters observed in chaetognaths, such as a gut with a mouth not arising from blastopore (deuterostomy) and a mesoderm derived from archenteron (enterocoely), could be ancestral features (plesiomorphies) of bilaterians.
Developmental Dynamics, 1996
The urodele amphibians are nearly the only adult vertebrates able to regenerate their missing or ... more The urodele amphibians are nearly the only adult vertebrates able to regenerate their missing or amputated tail. The most striking feature of this model lies in the ability of the spinal cord (SC) to differentiate, within the regenerating tail, a new ependymal tube from which the SC and the peripheral nervous system originate. A fundamental question is whether, in response to tail excision, the ependymoglia of the old SC stump behaves as an embryonic neuroepithelium. To evaluate this possibility, cell lines from primary cell cultures of adult SC were established for the first time in newts, and two cell clones, immunochemically characterized as ependymoglial cell populations, could be obtained. To analyze the potentialities of these clonal cells, after transplantation in tail regenerates, cell-marking experiments, using either in vitro transfection with lacZ gene or the lineage tracer lysinated rhodamine dextran (LRD), were performed. One to 2 weeks postimplantation, most of labeled derivatives were identified as melanocytes. Interestingly, labeled cells were also seen integrated in the ependymoglia of the regenerating SC. Two to 6 weeks after implantation in young regenerates, we also observed LRD-labeled elongated cells close to nerves or myofibers which were unambiguously identified as Schwann cells by galactocerebroside staining. Taken together, these findings showed that clonal cells derived from adult newt SC cultures could largely find, in regenerate mesenchyme, suitable environmental conditions to differentiate into melanocytes or Schwann cells. Because these two cells types arise from neural crest cells during embryo-genesis, this supports the interesting view that multipotent cells are still present in the SC of adult urodeles.
The International journal of developmental biology, 1991
During post-traumatic regeneration of the polychaete annelid Owenia fusiformis, the extracellular... more During post-traumatic regeneration of the polychaete annelid Owenia fusiformis, the extracellular matrix (ECM) formation was studied by light and electron microscopy and by histoautoradiography after incorporation of tritiated proline as marker for collagenic proteins. Three days after amputation, a new basement membrane was reformed in the blastema between the ectoderm and the mesoderm. At the same time, the cytoskeleton and the anchoring structures (hemidesmosomes) were differentiated in the basal part of the ectodermal cells. Four days after amputation, collagen fibers appeared in the extracellular matrix newly reformed between the ectodermal and mesodermal layers. The existence of a proximo-distal gradient in the organization of the new extracellular matrix and the accumulation of molecules labeled by 3H-proline was shown. This accumulation started at the level of the injured segment of the stump. Differences in labeling intensity were seen in the regenerate. Within specific org...
The indels are plotted onto the branches (green lines). Noticeably, some individuals display mixe... more The indels are plotted onto the branches (green lines). Noticeably, some individuals display mixed sequences from different haplotypes, which is explained by recombination events between alleles (purple star). The substitutions occurring between copies of the same allele in the head and body of individuals (blue branches) are assumed to be somatic mutations. These neighbor-joining trees were inferred assuming kimura 2 parameter distances from Additional data files 7-10. Boostrap proportions are indicated for selected nodes.<b>Copyright information:</b>Taken from "Chætognath transcriptome reveals ancestral and unique features among bilaterians"http://genomebiology.com/2008/9/6/R94Genome Biology 2008;9(6):R94-R94.Published online 4 Jun 2008PMCID:PMC2481426.
Dataset completeness was estimated for datasets composed of 78 RPs (red) or 115 other genes (gree... more Dataset completeness was estimated for datasets composed of 78 RPs (red) or 115 other genes (green) retrieved from EST collections of a large range of sizes.<b>Copyright information:</b>Taken from "Chætognath transcriptome reveals ancestral and unique features among bilaterians"http://genomebiology.com/2008/9/6/R94Genome Biology 2008;9(6):R94-R94.Published online 4 Jun 2008PMCID:PMC2481426.
The EMBO Journal, 1992
Variegation in Drosophila is a manifest illustration of the important role played by chromatin st... more Variegation in Drosophila is a manifest illustration of the important role played by chromatin structure in gene expression. We have isolated mutants of modulo (mod) and shown that this gene is a dominant suppressor of variegation. Null mutants are recessive lethal with a melanotic tumour phenotype. The mod protein directly binds DNA, which indicates that it may serve to anchor multimeric complexes promoting chromatin compaction and silencing. Using a specific monoclonal antibody we examined by immunocytochemistry the accumulation pattern of mod protein during embryogenesis. The protein is first detected before the blastoderm cellularization in all somatic nuclei, precisely when pericentromeric heterochromatin becomes visible. After the fist cell division, mod protein is expressed in lineages of specific embryonic primordia. Based on its dominant phenotype, expression pattern and DNA-binding activity of its product, we propose that mod regulates chromatin structure and activity in specific cell lineages.
The extent of within-species genetic variation across the diversity of animal life is a fundament... more The extent of within-species genetic variation across the diversity of animal life is a fundamental but largely unexplored problem in ecology and evolution. The neutral theory of molecular evolution predicts that genetic variation scales positively with population size. However, the genetic diversity of mitochondrial DNA, a prominent marker used in DNA barcoding studies, shows very little variation across animal species. Here, we report an unprecedented case of extreme mitochondrial variation within natural populations of two species of chaetognaths (arrow worms). We determined that this diversity is composed of deep intraspecific mitochondrial lineages within single populations that could be as divergent as human and newt. This mitochondrial diversity is the highest ever reported in animals without evidence of cryptic speciation or allopatric divergence as supported by nuclear evidence. We sequenced 54 complete mitogenomes revealing gene order rearrangements between these intraspec...
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Papers by Yannick Le Parco