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A number of studies have suggested that retinoic acid (RA) is an important signal for patterning the hindbrain, the branchial arches and the limb bud. Retinoic acid is thought to act on the posterior hindbrain and the limb buds at somitogenesis stages in chick and mouse embryos. Here we report a much earlier requirement for RA signalling during(More)
We applied independent species concepts to clarify the phylogeographic structure of the ascidian Ciona intestinalis, a powerful model system in chordate biology and for comparative genomic studies. Intensive research with this marine invertebrate is based on the assumption that natural populations globally belong to a single species. Therefore,(More)
Hox genes are essential for growth and patterning of the tetrapod limb skeleton. Mice mutant for the Hoxd-13 gene have an important delay in morphogenesis owing to reduced proliferation. Based on the appearance of atavisms in such mice, we suggested that modifications of Hox gene regulation may have been a source of morphological variation during the(More)
In tetrapods, Hox genes are essential for the proper organization and development of axial structures. Experiments involving Hox gene inactivations have revealed their particularly important functions in the establishment of morphological transitions within metameric series such as the vertebral column. Teleost fish show a much simpler range of axial (trunk(More)
Vertebrate Hox genes are required for the establishment of regional identities along body axes. This gene family is strongly conserved among vertebrates, even in bony fish which display less complex ranges of axial morphologies. We have analysed the structural organization and expression of Abd-B related zebrafish HoxA cluster genes (Hoxa-9, Hoxa-10,(More)
Molecular phylogenies using mitochondrial DNA and nuclear alleles of the lactate dehydrogenase B locus were found to be concordant for populations of Fundulus heteroclitus ranging from Canada to Florida. Both mitochondrial DNA and lactate dehydrogenase alleles show a clear separation between the northern individuals (from Nova Scotia and Maine) and the(More)
Individual mitochondrial genes or genomic features are commonly used as phylogenetic markers at many taxonomic levels. We used a mitogenomics approach to demonstrate the existence of two cryptic species in the ascidian Ciona intestinalis, a model chordate whose status as a single species has recently been questioned. Comprehensive comparative analysis of(More)
The distribution of FMRFamide-like immunoreactive (ir) neurons and fibers was investigated in the central nervous system of developing zebrafish and juvenile sturgeon (sterlet). Adult zebrafish was also studied. In zebrafish embryos FMRFamide-ir elements first appeared 30 h post-fertilization (PF). Ir somata were located in the olfactory placode and in the(More)
Somite formation involves the establishment of a segmental prepattern in the presomitic mesoderm, anteroposterior patterning of each segmental primordium and formation of boundaries between adjacent segments. How these events are co-ordinated remains uncertain. In this study, analysis of expression of zebrafish mesp-a reveals that each segment acquires(More)
The vertebrate Vox/Vent family of transcription factors plays a crucial role in the establishment of the dorsoventral (DV) axis, by repressing organizer genes such as bozozok/dharma, goosecoid, and chordino. In Danio rerio (zebrafish), members of the vox/vent gene family (vox/vega1, vent/vega2, and ved) are thought to share expression patterns and(More)