Fig. 10. Lmx1a maintains specified domains.

The globes represent the developing otocyst in wildtype and dr^J/dr^J mutants. The ventral neurogenic region is shaded gray. The ventro-lateral putative vestibular neurogenic region (blue stripes) is Lmx1a-negative, Fgf3-positive, and Gata3-negative. The ventro-medial, presumably auditory neurogenic region (red stripes) is Lmx1a-positive, Fgf3-negative, and Gata3-positive. In the developing otocysts of wildtype mice there is a distinct border between the Fgf3 and Lmx1a expression domains. However, in dr^J/dr^J, non-functional Lmx1a cannot maintain the proper Fgf3–positive region and the Fgf3 expression domain expands medially (blue-red gradient). Lmx1a expression domain does not change, but the ventro-medial neurogenic region (gray shading in dr^J/dr^J) is expanded posteriorly in the mutant otocyst. Because Gata3 is normally expressed at low levels in the medial otic epithelium, it is unclear whether the Gata3 domain is expanded in that region of dr^J/dr^J otocyst (red question mark).