Ten copies of the UAS regulatory sequence drive expression of a deleted robo2 coding sequence (lacks amino acid residues 84-1022, numbering according to GenBank AAF51375) which is tagged at the N-terminal end with three copies of the Tag:HA tag. 5'UTR and signal sequences from the wg gene are also present.
Expression of robo2ΔC.10xScer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4elav.PLu in embryos results in ectopic crossing of the midline by Fas2-positive axons in 100% of segments. All three Fas2-positive pathways collapse at the midline in nearly every segment.
Expression of robo2ΔC.10xScer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4ap.PU in embryos results in low levels of ectopic crossing of the midline by ap-expressing neurons.
Expression of robo2ΔC.10xScer\UAS.T:Ivir\HA1,T:SS-wg under the control of Scer\GAL4sli.PS in embryos results in ectopic crossing of the midline by Fas2-positive axons in almost all segments. Fused commissures are seen in approximately 80% of segments.