Early r1 rescue in fgf8-/-; OtxH embryos is independent of gbx2. Dorsal views, anterior towards the left showing efnb2a expression in wild-type (A, n=5/5), OtxH (B, n=8/9), wild type+SU5402 (C, n=12/15) or OtxH+SU5402 (D, n=18/23) embryos. The anteroposterior extent of r1 territory (arrows) is the same in OtxH with or without SU5402. Conversely, SU5402 treatment affects r5-7 development as previously reported (Maves et al., 2002). (E,F) Lateral views, anterior towards the left, of wild-type (E) and fgf8-/- (F) 8-somite stage embryos, showing double expression of otx2 (blue) and her5pac:egfp (red). (G-J) Lateral views, anterior towards the left, showing gbx2 expression in wild type (G), OtxH (H), fgf8-/- (I) or fgf8-/-; OtxH (J). gbx2 CNS expression is lost in fgf8-/- (arrows) and is not rescued in fgf8-/-; OtxH (out of 21 fgf8-/-; OtxH embryos, only five show a very faint rescue of Gbx2 expression in the very ventral metencephalic area). Asterisks indicate gbx2 expression in the epibranchial placode precursors.
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