307-bp fragment in HOXA7 upstream sequence is sufficient for anterior boundary formation

The HOX genes are expressed in a positionally and temporally restricted manner involving anteroposterior axial pattern formation during early embryogenesis. Previously, we studied the sequence and function of an upstream regulatory region of the human HOXA7 gene. To identify a critical cis-acting element, a deletion analysis was performed along the human control region (HCR) (about 1.1 kb), which was sufficient for setting the anterior boundary of expression in transgenic mice. We demonstrated that a 307-bp control region contains a cis-acting element(s) specifying an anterior boundary as well as a dorsal-ventral restriction in the neural tube at day 12.5 postconception (p.c.). The distinct anterior limit of expression was noted at the level of C7/T1 in the neural tube and spinal ganglia. In addition, our deletion experiments revealed that the HCR consisted of several cis-acting elements which were individually capable of driving regionally restricted expression patterns in the neural tube and limb buds.