Regulatory DNA required for vnd/NK-2 homeobox gene expression pattern in neuroblasts.

Vnd/NK-2 protein was detected in 11 neuroblasts per hemisegment in Drosophila embryos, 9 medial and 2 intermediate neuroblasts. Fragments of DNA from the 5'-flanking region of the vnd/NK-2 gene were inserted upstream of an enhancerless betagalactosidase gene in a P-element and used to generate transgenic fly lines. Antibodies directed against Vnd/NK-2 and beta-galactosidase proteins then were used in double-label experiments to correlate the expression of beta-galactosidase and Vnd/NK-2 proteins in identified neuroblasts. DNA region A, which corresponds to the -4.0 to -2.8-kb fragment of DNA from the 5'-flanking region of the vnd/NK-2 gene was shown to contain one or more strong enhancers required for expression of the vnd/NK-2 gene in ten neuroblasts. DNA region B (-5.3 to -4.0 kb) contains moderately strong enhancers for vnd/NK-2 gene expression in four neuroblasts. Hypothesized DNA region C, whose location was not identified, contains one or more enhancers that activate vnd/NK-2 gene expression only in one neuroblast. These results show that nucleotide sequences in at least three regions of DNA regulate the expression of the vnd/NK-2 gene, that the vnd/NK-2 gene can be activated in different ways in different neuroblasts, and that the pattern of vnd/NK-2 gene expression in neuroblasts of the ventral nerve cord is the sum of partial patterns.