pHLEA-768 and pPitMut are identical with the exception that a putative Pitx1 site has been mutated from TAATCC to GACTAC in pPitMut. The following primers were used to introduce the mutation by PCR (mutated bases underlined):5′-AGCCCGTCGCCAGGGTAGTCGTGCCCGTCTGTTGGTGG-3′and 5′-ACTACCCTGGCGACGGGCTGGGGTGGCGTCTGGGAGTT-3′.