Roles for Msx and Dlx homeoproteins in vertebrate development

This review provides a comparative analysis of the expression patterns, functions, and biochemical properties of Msx and Dix homeobox genes. These comprise multi-gene families that are closely related with respect to sequence features as well as expression patterns during vertebrate development. Thus, members of the Msx and Dir families are expressed in overlapping, but distinct, patterns and display complementary or antagonistic functions, depending upon the context. A common theme shared among Msx and Dir genes is that they are required during early, middle, and late phases of development where their differential expression mediates patterning, morphogenesis, and histogenesis of tissues in which they are expressed. With respect to their biochemical 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 underlying their complementary or antagonistic functions during development. (C) 2000 Elsevier Science B.V. All rights reserved.