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Fig. 1. Sox9 whole-mount in situ hybridization. (A) Sox9 expression at early neurula stage (stage 3), dorsolateral view, anterior towards the right. Sox9 is detected in two major domains, the neural crest-forming regions (green arrows) and the prospective otic placode (red arrows). (B) Sox9 expression is greatly increased in the neural crest (green arrows) and in the prospective otic placode (red arrows) at stage 14. Lateral view, anterior towards right. (C) For comparison, Pax8 expression at the neurula stage is shown. Pax8 is detected in the prospective pronephros (green arrow) and the otic placode (red arrow). Lateral view, anterior towards the right. (D) Cross-section through the prospective otic placode of a stage 14 embryo, Sox9 is detected in the sensory layer of the ectoderm (op, red arrowheads) before any sign of thickening of the ectoderm. (E) At the tailbud stage, Sox9 persists in the invaginating otic placode (red arrow). Lateral view, anterior towards the right. (F) Serial cross-sections of a tailbud stage embryo; Sox9 is expressed throughout the invaginating otic cup. (G) Stage 30 embryo, lateral view, anterior towards the right; (H) corresponding section. Sox9 expression is detected in the dorsal region of the otic vesicle (ov, red arrows). (I-M) In stage-matched embryos, Sox9 is first detected in the presumptive otic ectoderm (red arrows) lateral to the prospective neural crest (green arrows) at stage 12.5 (J,K). (K) Higher magnification view of the embryo in J. Sox9 expression appears prior to that of Pax8 (L,M), which is initiated in the presumptive otic ectoderm (red arrow) and pronephros (green arrow) at stage 13 (N). Dorsal views, anterior towards the top (I,L). Lateral views, anterior towards the right (J,M,N). |
