Martin Psenicka (University of South Bohemia in České Budějovice, Faculty of Fisheries and Protection of Waters) and Radek Sindelka (Laboratory of Gene Expression) got funded their application submitted to Czech Science Foundation (GA20-23836S). Together, they will try to improve our current understanding of mechanims regulating early cleavages in cell divisions and their impact on development.
Sturgeon as a unique model for evolutionary transition from holoblastic to meroblastic cleavage pattern, and for endoderm development in vertebrates.
The first cell divisions after egg fertilization are crucial steps of newly formed organism. Unfortunately understanding about early cleavages and their impact on development is poor. Vertebrate embryo cleavage pattern is either holoblastic (complete) or meroblastic (partial). The holoblastic cleavage is ancestral for vertebrates and the meroblastic cleavage has evolved in a few groups including teleosts. Great model of a typical holoblastic cleavage pattern are Xenopus embryos, where blastomeres derived from vegetal hemisphere give rise to endoderm forming primitive gut. The endodermal cells contain yolk platelets, which are digested intracellularly. Sturgeon embryos (basal Actinopterygii) have been incorrectly equated with Xenopus until now. However, from our preliminary observations, sturgeon embryos represent a unique transition link between cleavage patterns and endoderm formation among vertebrates. Its endoderm origins from equatorial position and forms gastrointestinal tract, which encompasses and completely digests the yolky cells arising from the vegetal part of embryo.
1) description of development of endoderm and cells derived from vegetal part of sturgeon embryo (primordial germ cells and yolky cells); 2) establishment of a novel method for partial embryo cleavage inhibition; 3) elucidation of mechanisms of transition from holoblastic to meroblastic cleavage.
Fig. 1 shows sturgeon embryo (A. ruthenus) at 128-cell stage. Control is on the left side and the embryo with inhibited cleavage at vegetal hemisphere is on the right side.