To identify genes involved in embryonic cell-cell signaling and tissue patterning, Sharon Amacher's Lab in the Department of Molecular and Cell Biology screens for mutations that disrupt mesodermal segmentation in zebrafish. On the left is a wild-type zebrafish embryo at about 14 hours post-fertilization; this embryo has about 9 mesodermal segments (somites). At the same stage, the fused somites mutant embryo on the right has no visible somites.