Fig. 2. Expression of GFP in the chick inner ear after electroporation of control IRES-GFP plasmid DNA. (A) Low magnification view of the cochlear duct of an E9 chick embryo electroporated at stage HH 17 (E2.5). In the basilar papilla and the lagenar macula, each red dot corresponds to the stereociliary bundle of one hair cell. (B) High magnification view of a more proximal region of the BP of the same specimen. Scattered GFP-positive cells (green) include both hair cells (with rounded GFP-positive cell body and HCA-positive apical surface, arrowheads) and supporting cells (elongated cell bodies and absence of HCA staining). (C,D) Utricular macula of an E8 chick embryo electroporated at stage HH 13 (E2). Several groups of GFP-positive cells are present within this sensory patch. (D) Transverse view of this epithelium at higher magnification. Some of the GFP-positive cells are hair cells (asterisk), with HCA-positive hair bundles and HCS-1-positive cytoplasm; others are supporting cells (arrows), with elongated cell bodies extending below the hair cell layer. All images other than (D) are projections of confocal optical sections of immunostained whole mounts; (D) is a single optical section. Counterstain for actin (blue) in B and C, combined with the red HCA fluorescence, makes hair bundles appear purple. BP, basilar papilla; L, lagenar macula.