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Fig. 4
Sequential activation of hoxa13a, evx1 and pthlha expression in the presumptive joint cells. Double FISH and DAPI counterstains on longitudinal cryosections of 4 dpa fin regenerates illustrate three distinct patterns of expression. (A-C′) Patterns I and II are observed in rays with presumptive joint cells (arrowheads). (A″-C″) Pattern III is observed in rays without presumptive joint cells. (A-C″) In joint-forming cells (yellow arrows), the three markers are co-expressed in the joint-forming cells. (A,A′,C,C′) In the presumptive joint cells (green or yellow arrowheads), hoxa13a is expressed alone (Pattern I, A,C) or co-expressed with evx1 (Pattern II, A′) or pthlha (Pattern II, C′). (B′,C′) pthlha is also co-expressed with evx1 (B′). (B,B′) evx1 is either expressed alone (B) or co-expressed with pthlha (B′). Numbers in each panel represent the number of sections with the expression pattern over the total number of sections analyzed. Scale bar: 50 μm (in A for A-C″).