A 275bp "enhancer 1" minimal fragment corresponding to -1171 to -897 relative to the transcription start site of the eya-RB isoform, a 319bp spacer fragment from eya intron 1 (coordinates -896 to -577) and a 586bp "enhancer 2" fragment (coordinates -576 to +10) are fused upstream of a minimal Hsp70 promoter followed by the lacZ coding region.