sox9b functions in otic specification. (A,B) The splice-blocking morpholino against sox9b (sox9bMO) significantly reduces the size of the otic vesicle (B, n=40 embryos), compared with that of wild-type control embryos (A). (C,D) In jellyfish (jef) mutants that harbor a retroviral insertion in the sox9a gene (jef^hil134) (Amsterdam et al., 1999; Yan et al., 2002), injecting sox9b-MOs results in the loss of a morphologically recognizable otic vesicle (n=9 embryos), although a few dispersed pax2a-positive cells persist (D). In uninjected jef (sox9a) mutants (C, n=6 embryos), otic vesicles are slightly smaller than in wild-type control embryos (A). (E,F) Injecting sox9b-MO blocks formation of the residual otic cells of Df^b380 (4/6 Df^b380 embryos had residual pax2a-expressing cells, only 2/12 Df^b380 embryos had residual otic cells after injection with sox9b-MO). (A,B,E,F) prim-12 (28 h); (D,F) prim 25 (36 h). Side views, anterior towards the left, dorsal towards the top. Scale bar: 25 μm.

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