A cluster of Drosophila homeobox genes involved in mesoderm differentiation programs

Although genes involved in common developmental programs are usually scatte red throughout the metazoan genome, there are some important examples of fu nctionally interconnected regulatory genes that display close physical link age, In particular the homeotic genes, which determine the identities of bo dy parts, are clustered in the Hox complexes and clustering is thought to b e crucial for the proper execution of their developmental programs, Here we describe the organization and functional properties of a more recently ide ntified cluster of six homeobox genes at 93DE on the third chromosome of Dr osophila, These genes, which include tinman, bagpipe, ladybird early, ladyb ird late, C15, and slouch, all participate in mesodermal patterning and dif ferentiation programs and show multiple regulatory interactions among each other. We propose that their clustering, through unknown mechanisms, is fun ctionally significant and discuss the similarities and differences between the 93DE homeobox gene cluster and the Hox complexes. (C) 2001 John Wiley & Sons, Inc.