UAS regulatory sequences drive expression of gbb with mutations in the three predicted furin cleavage sites: amino acid replacement R325A within the "Main" high probability site, amino acid replacement K334N within the "Shadow" low probability site and amino acid replacement R126A within the "Pro" predicted site.
Expression of gbbR126A.R325A.K334N.Scer\UAS under the control of Scer\GAL4Act5C.PU results in either partial or complete loss of the posterior crossvein.
Expression of gbbScer\UAS.cKa under the control of Scer\GAL4en.PU from the onset of pupal development (the temperature sensitive allele Scer\GAL80ts.αTub84B is used to restrict the stage during which expression occurs) results in variable crossvein defects.