Fig. 1

mmp9+ Cells in Fin Ray Joints Migrate to Contribute to Tissue Regeneration (A) Labeling of mmp9+ joint cells by Cre-loxP recombination. Treatment of Tg(mmp9:CreERt2; Olactb:loxP-dsred2-loxP-egfp) with TAM induced the expression of EGFP in cells of the joints (arrows). Scale bar, 500 μm. (B) Tracking of EGFP-labeled cells during regeneration. The marked cells migrated distally to become cells within the regenerated tissue including cells in the regenerating joint (arrowheads). Dashed lines, amputation sites. Scale bar, 10 μm. (C) Zns5 and Sp7 antibody staining of a cross-section through the joint of Cre-labeled Tg. mmp9-expressing joint cells have a characteristic cell shape with dendritic projections and are positive for Zns5 (cell-surface labeling), but not Sp7. The absence of sp7 expression in the mmp9+ joint cells is also seen in the Tg(sp7:mcherry) (Figure 3F). Nuclei, TO-RPO-3. Arrowheads, representative cells that are positive for EGFP and Zns5, but not Sp7. Scale bar, 10 μm.