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Fig. 2. Developmental expression of Sox9 by whole-mount in situ hybridization. (A) Sox9 expression at the gastrula stage is found in a superficial ring around the blastopore (white arrows); lateral view. (B) Sox9 RNA is detected at the lateral edges of the neural plate (arrows) in a stage 12 embryo. Dorsal view, anterior towards the top. (C,D) Sox9 expression at stage 14 is in the neural crest (red arrow and arrowhead) and in the presumptive otic placode (yellow arrow). (E,F) Slug expression is shown for comparison. (C,E) are dorsal views, anterior towards the top; (D,F) are lateral views, anterior towards the right. (G) Transverse section of a stage 14 embryo. Sox9 expression is restricted to the medial (red arrowheads) and lateral (red arrows) neural crest. (H) Stage 16 embryo, dorsal view, anterior towards right. As the neural tube closes, Sox9 remains strongly expressed in both components of the neural crest (red arrow/arrowhead) and in the otic placode (yellow arrow) (I,J) Stage 23 embryos, (I) lateral view and (J) dorsal view. Genital ridge (green arrows), optic vesicle (blue arrows), otic placode (yellow arrow). (K,L) Stage 25 embryo. (K) In this frontal view, Sox9 is found in the nasal pits (purple arrows) and the prospective pineal gland (orange arrow). (L) Lateral view, anterior towards right. Sox9 is detected in the four streams of cranial neural crest (red arrows), otic placode (yellow arrows), genital ridge (green arrows) and the developing eye (blue arrows in K,L). (M-O) Transverse sections of a stage 25 embryo. (M) In this section, at the level of the forebrain, Sox9 is detected in the developing eye (blue arrow), dorsally in migrating neural crest cells (red arrow) and in discrete domains in the brain. (N) More posteriorly, Sox9 is strongly expressed in the developing otic placode (yellow arrow). (O) In the trunk region Sox9 is restricted to the genital ridge (green arrow) and the notochord (black arrow). (P) At stage 32, Sox9 expression is in the pharyngeal arches (red arrows), the otic vesicle (yellow arrow) and in restricted regions of the brain. |
