More news this year about FGFs and their roles in vertebrate limb initiatio
n; Writ signalling is shown for the first time to be another component of t
he signalling cascade involved in early limb formation. Ectodermal compartm
ents that control apical ridge formation were previously described in chick
embryos and are now shown to exist in mouse embryos; Engrailed1 is express
ed in the ventral ectodermal compartment but experiments in both chick and
mouse show that it is not responsible for compartment specification.