Homeobox genes in embryogenesis and pathogenesis.

The homeobox, a 60-amino acid-encoding DNA sequence, originally discovered in the genome of the fruit fly Drosophila, was subsequently identified throughout the three kingdoms of multicellular organisms. Homeobox-containing genes encode DNA-binding proteins that regulate gene expression and control various aspects of morphogenesis and cell differentiation. In particular, the Hox family of clustered homeobox genes plays a fundamental role in the morphogenesis of the vertebrate embryo, providing cells with regional information along the main body axis. The nonclustered or divergent homeobox genes include a large number of genes scattered throughout the genome that, nevertheless, can be organized in distinct families based on their homologies and functional similarities. This review will provide the reader with a brief overview on some recent studies aimed at understanding the functional role of homeobox genes in normal mammalian development as well as their involvement in congenital malformations and oncogenesis.