Organization of early development by calcium patterns

This survey focuses on early or primitive developmental phenomena for which the location of a steady high calcium region or the direction of a calcium wave is critical and calcium is more than a trigger. It starts with the lo ng studied roles of calcium in fucoid eggs and in Dictyostelium and progres ses to newer work on high calcium regions in medaka fish, zebrafish, and Dr osophila eggs. It then proposes that propagated, ultraslow developmental wa ves in six diverse systems indicate a new and important class of calcium wa ves. These include the morphogenetic furrow in Drosophila eye discs, floret formation in sunflowers, DNA replication waves in protozoan macronuclei, g rowth-cone like waves in hippocampal neurons, and two others. It then consi ders the possible organizing roles of slow calcium waves. Here, it emphasiz es surface contractile waves during primary neural induction and elsewhere as well as the possibility of cellular peristalsis. Finally, it reviews the organizing roles of fast calcium waves in ascidian eggs. BioEssays 21.657- 667, 1999. (C) 1999 John Wiley & Sons, Inc.