Two recent large-scale genetic screens in zebrafish have identified ma
ny mutations that affect differentiation in a variety oi organ systems
, particularly the notochord, the neural crest and the blood. The comb
ination of these newly identified mutations and well established embry
ological methods makes zebrafish uniquely suited among vertebrate expe
rimental systems to simultaneously address the roles of specific genes
and specific cell-cell interactions during differentiation.