To find out if the haematopoietic system is common feature of vertebrates, we decided to examine haematopoiesis in a sea lamprey (Petromyzon marinus). All blood cells arises from the haematopoietic stem cells in higher vertebrates. We assume that this is common for the higher vertebrates and a jawless vertebrates, but nobody was interested in the jawless haematopoiesis since 1970. Using a reverse genetic, we identify homologues of important hematopoietic of higher vertebrates in transcriptome of the sea lamprey with emphasis on important receptors or transcription factors, because they can be used as the specific markers of different blood cells and their progenitors. Then we use those sequences for cloning, expression measurements and other work. We picked up sea lamprey as model organism because its unique phylogenetic position, important foe evo-devo studies, but also because lack of elementary knowledge about sea lamprey haematopoiesis. Key words: Petromyzon marinus, haematopoiesis, HSC, evo-devo

(ENGLISH) Hematopoiesis is dependent on the actions of hematopoietic stem cells (HSCs). This process is tightly controlled through a complex array of extrinsic and intrinsic factors. Even though the hematopoiesis seems to be well conserved across the disparate vertebrate animals, erythroid and thrombocytic differentiation have changed during the evolution of mammals. Specifically, adult mammalian red blood cells have the unique feature of being enucleated, and mammalian thrombocytes are not individual cells, but fragments of megakaryocytes, instead. It is likely that these enhancements provided a survival advantage to early mammalian species; however, they also bring up the question of evolutionary origin of these cells that studied using zebrafish (Danio rerio) model. First, it was necessary to generate a toolbox of a recombinant cytokines and optimized culture media that allowed us to manipulate zebrafish hematopoietic cells ex vivo in liquid and clonal cultures. Interestingly, teleost species underwent an extra duplication event during their evolution and as a result, two copies (paralogs) of some of the genes are present in zebrafish. This was also the case for majority of the cytokines from our toolbox and here, we provide functional characterization of these paralogs. Strikingly, our results...