Fig. 6. Loss of Six1 function alters the expression of Fgf3, Fgf10, Bmp4, Nkx5.1 and Gata3 in the otic vesicle. (A-D,G-J) Transverse sections; (E,F) Horizontal sections. (A,B) Fgf3 begins to be expressed in the ventrolateral region of the otic vesicle (ov) at E9.5 and its expression was undetectable in Six1^-/- embryos. Note Fgf3 expression in the hindbrain (hb) is relatively normal in Six1^-/- embryos. (C,D) Fgf10 is normally expressed in a broad region of ventral otic vesicle and the gVIII in wild-type embryos at E10.5; however, residual expression of Fgf10 was only detected in the ventromedial otic vesicle in Six1^-/- embryos (arrow). (E,F) Bmp4 is normally observed in two specific spots, one dorsal and one ventrolateral in the otic vesicle of wild-type embryos at E10.5. In Six1^-/- embryos, the dorsal expression spot (arrowhead) was undetectable and the ventrolateral spot became very weak (arrow). (G,H) Nkx5.1 is expressed in the dorsolateral region of the otic vesicle in wild-type embryos at E10.5. In Six1^-/- embryos, however, Nkx5.1 expression is excluded from the dorsolateral region (arrow) and its expression domain shifted or expanded ventrally, including the ventral-most region. (I,J) Gata3 is expressed strongly dorsolaterally and weakly ventromedially in the wild-type embryos at E10.5. Similarly, in Six1^-/- embryos it is not expressed in the dorsolateral region (arrow) and its expression domain shifted ventrally. By contrast, its expression in the ventromedial region of the otic vesicle was unaffected in Six1^-/- embryos. Scale bars: 100 µm.