A 5' segment of the mouse Zic1 gene contains a region specific enhancer for dorsal hindbrain and spinal cord.
Zic1 encodes a zinc finger protein, which is required for the development of the dorsal neural tissue. The gene is a mammalian homologue of the Drosophila odd-paired. We examined the regulatory elements in the 5' flanking region of the Zic1 gene as an initial step to understanding how the Zic1 expression is restricted to the dorsal neural tissue. When a 2.9-kb fragment of the 5' flanking segment of the mouse Zic1 gene was linked to the E. coli beta-galactosidase gene, the enzyme was consistently expressed in the dorsal half of the embryonic spinal cord and in the vestibulocochlear nucleus in all four transgenic mouse lines. The transgene expression mimics the Zic1 expression with respect to the region where it occurs. But this is not so for the neuronal cell types. This suggests that the segment contains a region-specific enhancer. In vivo and in vitro deletion analyses indicated that there are essential regions between -2.0 and -0.9 kb and within the proximal 0.9 kb. The distal element is necessary for the transgene expression in the embryonic dorsal spinal cord whereas the adult vestibulocochlear nucleus expression is regulated by both elements. In these regions, there are sequences similar to the binding sequences for potential regulatory proteins.