For example, it is unclear how cell migration is regulated during gastrulation, when mesodermal and endodermal germ layers form.

We conducted extensive genomic inventories on signaling pathway components and genes known to be critical to neural and mesodermal cell types, among others.

S, serosa; A, amnion; E, ectoderm; N, rudiment of nerve-cord; M, mesodermal pouches.