Mutations in two of the predicted furin cleavage sites: amino acid replacement R325A within the "Main" high probability site and amino acid replacement R126A within the "Pro" predicted site.
gbbR126A.R325A.Tag:FLAG fails to rescue gbbD20/Df(2R)bw-S46
gbbR126A.R325A.T:Zzzz\FLAG partially rescues the loss of posterior crossvein seen in gbb4/Dp(2;2)DTD48 gbb4 flies.