Confocal projections of larvae labeled for ihha and sp7, RNA in situ hybridization. (A) ihha is expressed at high levels in the wild-type Op, but only minimally in the BR. (B) Expanded ihha mef2ca mutant expression is present at the location of the BR (B3, arrow). (C) Op ihha expression is expanded (C3, arrow), but not detected at the location of the BR (C2, asterisk). Scale bar 50 μm.