Four copies of a mutated 15bp region derived from the midline enhancer of Tl, containing a CNS midline enhancer element (ACGTG) are fused upstream of EGFP tagged with a nuclear localization signal (Tag:NLS(tra)). This construct differs from Avic\GFP4Toll.pH-Stinger by 5 nucleotides. The CCACAGA found downstream of the CNS midline enhancer element is changed to a T-rich sequence (CTTTTTA).