Developmental Effects of Kenpaullone, a member of the family of benzazepinones, on Sea Urchin Embryos

In a search for compounds able to inhibit epithelial mesenchymal transition in sea urchin embryos, we tested the in vivo activity of Kenpaullone (9-bromopaullone), described as a potent inhibitor of glycogen synthase kinase 3b and ATP-competitive inhibitor of Cdk1/cyclinB (1). GSK3a and b isoforms are phylogenetically closely related to the cyclin dependent protein kinases Cdk1 and Cdk2 (2). In the field of cancer, protein kinases have become the most important class of drug target for the pharmaceutical industry and it is increasingly evident that Cdks, cyclins and their inhibitors play key roles in transcription, epigenetic regulation and other important cellular processes in mammals (3). Nevertheless, careful analysis and comparisons of the effects of inhibitors on growing cells (4) and animal models should be exploited. Among other molecules, Kenpaullone (Kp), has drawn our attention. In preliminary screenings, treatment of Paracentrotus lividus embryos at different drug concentrations from fertilization up to 16-20 h, led to the development of empty living blastulae, suggesting that Kp does not inhibit cleavage. Pre-hatching treated embryos were drug sensitive showing developmental defects after few hours, while hatched embryos were more robust. In order to define time sensitivity windows linked to specific developmental effects, Kp was added at early developmental stages and different interval times, then removed. Embryos were allowed to develop for morphological analysis and immunological staining. Results indicate that even very short treatments at early cleavage stages inhibit primary mesenchyme cells ingression and/or specification.