New Insights into the Evolution of Metazoan Tyrosinase Gene Family

Tyrosinases, widely distributed among animals, plants and fungi, are involved in the biosynthesis of melanin, a pigment that has been exploited, in the course of evolution, to serve different functions. We conducted a deep evolutionary analysis of tyrosinase family amongst metazoa, thanks to the availability of new sequenced genomes, assessing that tyrosinases (tyr) represent a distinctive feature of all the organisms included in our study and, interestingly, they show an independent expansion in most of the analyzed phyla. Tyrosinase-related proteins (tyrp), which derive from tyr but show distinct key residues in the catalytic domain, constitute an invention of chordate lineage. In addition we here reported a detailed study of the expression territories of the ascidian Ciona intestinalis tyr and tyrps. Furthermore, we put efforts in the identification of the regulatory sequences responsible for their expression in pigment cell lineage. Collectively, the results reported here enlarge our knowledge about the tyrosinase gene family as valuable resource for understanding the genetic components involved in pigment cells evolution and development

Origine des membranes de la paroi chez

L’origine et l’évolution des membranes constituant la paroi de Toxoplasrna ont pu être suivies au cours de l’endogenèse par l’étude de coupes fines et de répliques de cryofracture. Le complexe membranaire interne provient de la différenciation de vésicules ergastoplasmiques au contact des microtubules du cytosquelette en formation ; il possède aussitôt sa structure définitive. Il peut aussi dériver du complexe homologue de la cellule-mère. Lors de l’émergence hors de la cellule-mère, les individus-fils acquièrent leur plasmalemme aux dépens de celui de cette cellule. Le plasmalemme montre une constante continuité. A la fin de l’endogenèse, la croissance du complexe membranaire interne des parasites-fils s’interrompt, créant un espace circulaire qui subsistera comme une « cicatrice » à la partie postérieure du Toxoplasme « adulte ». A cet endroit une jonction rend solidaires le complexe membranaire interne et le plasmalemme, jonction traduite après cryofracture du plasmalemme par un anneau de particules intramembranaires

Monoclonal antibodies against Nereis virens brain homogenates as probes for isolation and in situ detection of new neurosecretions

International audienceThe brain of Nereis contains 26 ganglionic nuclei which produce numerous neurosecretions. Only a few of them have been characterized. The production of monoclonal antibodies was adopted as an approach to discover unknown neurosecretions. Monoclonal antibodies produced against Nereis virens brain homogenates were selected using stepwise ELISA tests first with brain homogenates, then with brain neurosecretions. Eight antibodies specific for Nereis neurosecretions were selected. The results are illustrated with one of these monoclonal antibodies which was directed against a major peak after HPLC purification of brain neurosecretions. This antibody was subsequently used for the in situ detection of recognized epitope(s) in the brain and ventral nerve cord cells