Loss of Isl1 eliminates the dorsal pyloric outer longitudinal muscle Gata3 expression. (A) Double immunostaining for Isl1 and Gata3 in the dorsal pylorus at E14.5. The region of mesodermal cells (asterisks) expressing Gata3 was smaller in the Isl1MCM/Del pylorus than Isl1Fl+. (B) Double immunostaining for Isl1 and Gata3 in the dorsal pylorus at E18.5. Inducible Isl1 knockout effectively eliminated Isl1 expression, with concomitant loss of Gata3 expression in the dorsal OLM cells (asterisks). Yellow dotted lines mark the epithelial basement membrane and white dotted lines indicate the ICM and OLM boundary. White arrowhead indicates non-specific stain. Red staining is Isl1, green staining is Gata3, and DAPI nuclear counterstaining (DNA) is blue. Scale bars: 50 μm. ICM, inner circular muscle; OLM, outer longitudinal muscle.