Canal Cristae Growth and Fiber Extension to the Outer Hair Cells of the Mouse Ear Require Prox1 Activity
Figure 9
Immunolabeling and dye tracing reveals Type II fiber disorganization in the organ of Corti of Prox1 flox/flox; Tg(Nes-Cre) conditional mutant embryos.
(A, A′,A″) This 1 day old basal turn shows that the Prox1 protein is present in the supporting cells (A′, A″) and that neuron processes extend beyond the first row of Deiter's cells to form a bundle of intertwined fibers near the second and third row of Prox1 positive Deiter's cells. Inserts in A, A′ and A″ show tubulin immunostaining in spiral ganglion cells (SPG) but show no immunoreaction for Prox1. The disorganization of nerve fibers becomes particularly obvious in a side by side comparison with the regular pattern of cells (shown with Hoechst stain) Type II process in wildtype (B,C). In the apex, Type II fibers extend in a random way towards base and apex between Prox1 positive supporting cells (D). Epoxy section of Prox1 (red) and tubulin immunostained (green) and Hoechst counterstained (blue) organ of Corti shows the normal organization of the greater epithelial ridge (GER) with Prox1 being restricted to 5 rows of supporting cells. Point applications of lipophilic dyes allows imaging the growth cones and their regular turns toward the base in wildtype (F,G) but shows a disorganized outgrowth and growth cones (GC) in Prox1 flox/flox; Nes-Cre conditional mutant mice. D1–3, Deiter's cells row 1–3; IP, inner pillar; OP, outer pillar; SPG, spiral ganglion. Bar, 100 µm (A–D), 50 µm (E–H; inserts in A,A′, A″).