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Figure 1. Raldh2 shows dynamic expression in the mesenchyme during limb development. Roman numerals I–V indicate forming digits of the autopod, and lowercase “h” following st. indicates hindlimb whereas “f” indicates a forelimb. Limbs are proximal to the left and posterior uppermost and viewed from the dorsal side, except in B where both hindlimbs are viewed from the ventral side of the tadpole. A, B: In very early hindlimb buds, expression is proximal (black arrow). C: By st. 51, expression is limited to proximal-most cells (black arrow) with lower levels of expression distally (white asterisk). D: Additional expression domains appear in the anterior at st. 52, one either side of the hindlimb (white arrows) and one posteriorly (yellow arrow). Distal expression is resolving into interdigital staining (black arrowheads). E: Interdigital expression is in four domains at st. 53 (black arrowheads). A small area begins to express Raldh2 in the anterior zeugopod region (yellow arrow). F: In st.54 hindlimbs, expression is interdigital (black arrowheads), and is still seen in proximal (black arrow), proximal/anterior (white arrow), and anterior and posterior zeugopod patches (yellow arrows). G: As the hindlimb digits form, Raldh2 is limited to cells surrounding cartilage and proximal expression disappears. H, I: In early stage forelimbs, expression is also only proximal (black arrow). J: Forelimb expression at st. 53. Proximal (black arrow), proximal/anterior (white arrow), and interdigital domains (arrowhead). K: As the forelimb digits form, Raldh2 is limited to cells surrounding cartilage and proximal expression disappears. |
