GOOSECOID MISEXPRESSION ALTERS THE MORPHOLOGY AND HOX GENE-EXPRESSIONOF THE DEVELOPING CHICK LIMB BUD

The homeobox-containing gene goosecoid (gsc) has been implicated in a variety of embryonic processes from gastrulation to rib patterning. We have analyzed the role it plays during chick limb development. Expres sion is initially observed at stage 20 in a proximal-anterior-ventral domain of the early limb bud which expands during subsequent stages. L ater in limb development a second domain of expression appears distall y which resolves to regions which surround the condensing cartilage. I n order to understand the function of gsc in limb development, we have examined the effect of misexpressing gsc throughout the limb. Two str iking phenotypes are observed. The first, evident at stage 24, is an a lteration in the angle of femur outgrowth from the main body axis. The second, which can be detected at day 10 of development, is an overall decrease in the size of the limb with bones that are small, misshapen and bent. These phenotypes correlate with a decrease in levels of Hox gene expression in gsc-infected limb buds. From these results we sugg est that gsc may normally function to regulate growth and patterning o f the limb, perhaps through regulation of Hox gene expression. (C) 199 7 Elsevier Science Ireland Ltd.