Fig. 3.

Spatial expression of transcription factors Afi-alx1, Afi-ets1/2, Afi-foxB, Afi-tbr and Afi-gataC in the regenerating arm. Afi-tbr is not expressed at all in the regenerating arm. All four remaining genes are strongly upregulated directly beneath the undifferentiated distal cap. Proximal expression of Afi-alx1 is localized to the bases of the spines and podia and Afi-gataC only to the base of the spines, both at the 50% and 95% differentiation stages. Afi-ets1/2 shows a repetitive pattern of expression restricted to the site of developing vertebrae in the proximal regions of the regenerating arm. Expression of Afi-foxB is localized to the non-skeletogenic structures (around the base of the podia). Scale bar: 100 μm. P – proximal, D – distal. Arrowheads – site of developing spines, arrows – site of developing podia, asterisks – intervertebral muscles.