Differential regulation of Dlx gene expression by a BMP morphogenetic gradient

Three members of the vertebrate Distal-less gene family, DIx3, 5 and 6, are transcribed in early gastrula embryos of Xenopus laevis. This expression i s confined to ectoderm and is excluded from the presumptive neural plate re gion. Expression of all three genes is dependent upon BMP signaling, with s ignificant differences in how the three genes respond to the BMP antagonist chordin. This correlates with the different expression domain boundaries i n vivo for DIx3 compared to DIx5 and 6, suggesting that BMP signal attenuat ion could be the primary factor in determining these different patterns in the gastrula ectoderm.