Roles for Msx and Dlx homeoproteins in vertebrate development

This review provides a comparative analysis of the expression patterns, fun ctions, and biochemical properties of Msx and Dix homeobox genes. These com prise multi-gene families that are closely related with respect to sequence features as well as expression patterns during vertebrate development. Thu s, members of the Msx and Dir families are expressed in overlapping, but di stinct, patterns and display complementary or antagonistic functions, depen ding upon the context. A common theme shared among Msx and Dir genes is tha t they are required during early, middle, and late phases of development wh ere their differential expression mediates patterning, morphogenesis, and h istogenesis of tissues in which they are expressed. With respect to their b iochemical properties, Msx proteins function as transcriptional repressors, while Dir proteins are transcriptional activators. Moreover, their ability to oppose each other's transcriptional actions implies a mechanism underly ing their complementary or antagonistic functions during development. (C) 2 000 Elsevier Science B.V. All rights reserved.