Region-specific enhancers near two mammalian homeo box genes define adjacent rostrocaudal domains in the central nervous system.

To gain insight to the mechanisms underlying region-specific gene expression in mammalian development, we investigated the regulatory DNA associated with the proximal promoter of two homeo box genes, murine Hox-1.3 and human Hox-5.1. Using lacZ gene fusions intransgenic mice, we identified regulatory elements in the 5'-flanking sequences of the Hox-1.3 and the Hox-5.1 genes that specifically direct β-galactosidase expression to the brachial and the upper cervical regions (respectively) of the central nervous system (CNS). The findings represent the first demonstration of region-specific mammalian enhancers and raise the possibility that the mammalian CNS may be subdivided into a series of rostrocaudal domains on the basis of the activity of enhancers near homeo box genes