<i>Pax2-Cre</i>: <i>Gata3^f/f</i> ears have altered organ of Corti topology.

<p><b>A-D</b>) High magnification of organ of Corti showing immunohistochemistry for BDNF (red, hair cells), Sox2 (green, supporting cells), α-tubulin (cyan, neurons). In the mutant patch of sensory epithelia there is one row of inner hair cells and three rows of outer hair cells as in the control. However there are some ectopic BDNF positive cells which are always paired with a Sox2 positive cell (arrows <b>B</b>′). A major difference between the mutant and control is where the hair cells are located within the Sox2 expressing domain. In the control there are very few Sox2 expressing cells lateral to the hair cells and a larger portion medially. However, this setup is reversed in the mutant; indicating that there is a shift in the relative topology of hair cells and the Sox2 positive supporting cell domain. The neurons of the mutant are overshooting the hair cells into the ectopic Sox2 domain then looping. <b>E and E</b>′) <i>Fgf8</i> in situ hybridization in control and mutant cochlea. Even though BDNF staining indicated specification of inner versus outer hair cells, the inner hair cell marker <i>Fgf8</i> was absent. <b>F</b>) Low magnification SEM of the torus like vestibular structure. The saccular pouch is not shown. <b>G</b>) The utricular stereocilia lack connections between each other and are splayed out in a random fashion. Stereocilia from a single hair cell have been false-colored violet. <b>H</b>) Low magnification of cochlear duct. The sensory patch apical-basal extent is marked by the white bracket. The abnormal tectorial membrane can be seen as a web like structure that partially covers the sensory patch. There is no spiral limbus in which the tectorial membrane is attached. <b>I</b>) A single <i>Pax2-Cre</i>: <i>Gata3^f/f</i> hair cell in the location of an inner hair cell. The thickness of the stereocilia is different than in the wt (J) and does not tapper at the bottom. <b>K</b>) Hair cell in the location of an outer hair cell. There is no polarity with respect to the stereocilia, and no staircase pattern as in the control (L). All images are of E18.5 cochlea except J and L (P5).