(A, A?) At 2 dpf jaw joint progenitor cells express both GFP and mCherry. (B, B?) By 3 dpf cells start to differentiate and nkx3.2(JRS1):mCherry activity is restricted to jaw joint-forming interzone, overlapping with sox10:egfp. Single-labelled mCherry-expressing cells are surrounding the joint-forming region. (C, C?) At 5 dpf mCherry-expressing cells are restricted to the articulation forming area between Meckel?s cartilage (m) and the palatoquadrate (pq). Double mCherry/GFP-expressing cells are restricted to posterior Meckel?s cartilage and anterior palatoquadrate. (D, D?) At 14 dpf a clear joint cavity is visible. nkx3.2(JRS1):mCherry activity is restricted to the joint cavity and to both lateral and medial palatoquadrate. Dashed box in (A?D) is magnified in (A??D?). (A?D) Represents maximum projection of confocal Z-stack, and (A??D?) represents a single confocal image. In nkx3.2?/? mutants nkx3.2(JRS1):mCherry marks the cells outside of the fused jaw joint at 3 dpf (E, E?) and 5 dpf (F, F?). Dashed boxes in (E, F) are magnified in (E?, F?). (E, F) and (E?, F?) represent maximum projection of confocal Z-stack. Asterisks indicate the approximate location of the fusion site. Scale bars: 100 ?m (A?F) and 25 ?m (A??F?).
