COMPARATIVE-STUDY OF MSX-1 EXPRESSION IN EARLY NORMAL AND VITAMIN-A-DEFICIENT AVIAN EMBRYOS

Homeobox-containing genes may play an important role in establishing e mbryonic patterns during development of vertebrates. Retinoic acid is able to induce expression of Hox genes in cells in culture and to alte r expression patterns in the developing vertebrate embryos. Using whol emount in situ hybridization, we have examined and compared the expres sion patterns of a homeobox-containing gene, Msx-1, in early normal an d vitamin A-deficient quail embryos. At gastrulation stage, Msx-1 is p rimarily expressed in the posterior half of both normal and vitamin A- deficient embryos. However, the gene is expressed wider and stronger i n the vitamin A-deficient embryos. At neurulation stages, Msx-1 is con tinuously expressed in the posterior region up to Hensen's node and in the edge of the neural fold in both normal and vitamin A-deficient em bryos. Notably, in the vitamin A-deficient embryos, Msx-1 is expressed more strongly and is also expressed ectopically in the anterior and p recardiac regions. These results provide evidence that endogenous reti noids are involved in the normal expression of Msx-1 in avian embryo a nd that the expression of Msx-1 is downregulated by endogenous and phy siological retinoids in vivo during early avian embryogenesis. (C) 199 5 Wiley-Liss, Inc.