Identification of a novel downstream midline regulatory element in .

Development of the central nervous system midline depends on the gene ( ). Although regulation has been studied extensively, the fact that an enhancer mediating late embryonic transcription has not been identified suggests that additional regulatory sequences remain unknown. We tested several evolutionarily conserved sequences in the downstream region and isolated , whose midline activity in a reporter gene assay begins later than previously characterized enhancers. Its activity shares several key similarities with the _ enhancer, though is sufficiently different to warrant further investigation into how functions in its native context.