Chitin oligosaccharides as candidate patterning agents in zebrafish embryogenesis.

In this work we investigate the possible function of N-acetyl-chitooligosaccharides (NACOs) produced during zebrafish (Danio rerio) development. First, we show that NACOs are synthesized in vivo during early embryogenesis in the zebrafish. Second, we demonstrate that injection of a pure bacterial chitinase into one-cell stage embryos elicits developmental defects in which the posterior trunk and tail of developing embryo are severely affected. In addition, an endogenous chitinase activity detected both intra- and extracellularly is described, suggesting that cells may secrete it into the extracellular space. Moreover, this compartmentalization appears to be functionally relevant as inhibition of the extracellular, but not the intracellular, endogenous chitinase activity causes morphological defects similar to those seen in embryos injected with chitinase 63. Finally, analysis of the expression of the zebrafish ZDG42 gene, which has been suggested to be involved in synthesis of NACOs, is described. Transcripts are detected from late blastula stage, during gastrulation, and move as an anterior-posterior wave of expression in adaxial mesoderm during somitogenesis.