"Génomique fonctionnelle de l’ovocyte de poisson"

With more than 30,000 species, teleost fish represent half of vertebrates on earth. In addition to the two rounds of whole genome duplications (VGD1 & VGD2) that occurred at the root of the vertebrate lineage, teleost fish also experienced an ancient additional whole genome duplication event (TGD, teleost-specific genome duplications) followed by more recent additional lineage-specific WGD that can also be found in tetrapods. Together, these WGD followed by reciprocal losses in tetrapod and teleosts, as well as lineage-specific gene losses and duplications frustrate the identification of orthologs between Humans and fish despite the extensive use of teleost fish for various biomedical purposes. In this context, the INRA Fish Physiology and Genomics laboratory has been involved in various international genome sequencing projects including the rainbow trout (a salmonid species with recent WGD) and the gar, an holostean species that did not experienced TGD and could thus help to connect tetrapods and teleost fish. In both salmonids and teleosts, we have observed that miRNA genes were more likely to be retained in 2 copies following WGD than protein coding genes 1, 2. RNA-seq analysis conducted in gar, zebrafish and medaka have also shed new light on the evolution of gene expression after WGD and revealed novel cases of neo-functionalization and sub-functionalization 2, 3, 4.

The Sex & Oogenesis group is also interested in gene predominantly expressed in the oocyte, which are known to have major roles in oogenesis (i.e. oocyte formation) as well as during early embryonic development (i.e. before the onset of zygotic genome). Among those genes some have been found to exhibit this so called “oocyte specific” pattern throughout evolution, not only in vertebrates, but also from drosophila to fish and Humans 5. Using a Crispr/CAS9-based genome editing strategy, we have studied the function of some evolutionary-conserved protein-coding genes and miRNA genes in model fish species. Our results have shown the importance of these genes to produced developmentally competent fish oocytes able to be fertilized and subsequently allow embryo development. Among the genes of interest are miR-202 6, otulina, and slc29a4 that are required for fertilization. In contrast, eggs originating from mutant fish for foxR1, npm2a, and npm2b 7-10 can be fertilized but result in heavy embryonic mortalities. Further studies are in progress to investigate the mechanisms behind these phenotypes.

Julien BOBE, Directeur du Laboratoire de Physiologie et Génomique des Poissons de l'INRA

invité par Gregory EOT-HOULIER

>> vendredi 15 mars 2019 à 11h00' - salle de conférence de l'IGDR, rez-de-chaussée, bâtiment 4/ Villejean Campus

Séminaire en anglais, entrée libre dans la limite des places disponibles

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