Fig. 7. Expression profile of developmental control genes in the otocysts of wild-type and Hmx2^lacZnull embryos. The Hmx2 genotype is indicated on the top of each column. The molecular markers examined are listed on the lower right corner of each panel. The embryonic stages are indicated on the upper right corner of each panel. Arrows in K,L indicate the position of the developing sensory patches in the otic vesicle. Arrowheads indicate the presumptive fusion plate. (A,B) No discernible difference in Hmx3 expression can be seen between wild-type and Hmx2^lacZnull backgrounds. (C,D) Altered Dlx5 expression in the Hmx2^lacZ–/– inner ear is demonstrated by the loss of its expression in the discrete epithelial patches and ectopic Dlx5 expression in the presumptive fusion plate. (E,F) Down regulation of Pax2 expression in the lateral aspect of the Hmx2^lacZnull otocyst can be clearly seen at this stage. (G-J) Although both genes play a critical role in inner ear development, no discernible alteration of either BF1 or netrin 1 expression was observed in the developing inner ears in the Hmx2^lacZnull embryos. At early embryonic stages, Bmp4 mRNA is restricted to the sensory epithelial cells in the developing otic vesicle. K-N show the Bmp4 expression in the otic vesicles in the wild-type and Hmx2^lacZ–/– embryos by whole mount in situ hybridization. (K,L) At E10.5, Bmp4 is expressed in a correct spatial fashion in the Hmx2^lacZ–/– otocyst. No differences in Bmp4 expression are seen at this stage of development. However, from E11.5, the sensory patches fail to express Bmp4 (M,N). Instead, preferential expression of Bmp4 in discrete regions of the lateral portion of the wild-type otic vesicle is replaced by a homogenous expression in the corresponding region in the Hmx2^lacZnull mutants (O,V). P, R, T and V show the expression pattern of Bmp4 in the wild-type and Hmx2^lacZ–/– otic vesicles examined by in situ hybridization on paraffin sections of embryos of E11.5 and E12.0. O, Q, S and U are the corresponding bright-field views of P, R, T and V. C, caudal; L, lateral; M, medial; R, rostral.

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