Expression of ihha and col10a1 during fin ray regeneration. In situ hybridization with probes corresponding to ihha (A-D), both ihha and shh (E) and col10a1 (F) on section of zebrafish caudal fin regenerates at 2- and 4-days post amputation (dpa). A,B, D-F: Longitudinal sections; C: transverse section. A: ihha expression is first detected in two faint domains in the blastema compartment (b) at the tip of each amputated hemiray (L), which may correspond to differentiating bone matrix-secreting cells, or scleroblasts. B-D: At 4dpa, during the regenerative outgrowth, ihha-expressing cells are found in two rows of cells adjacent to the basal layer of the epidermis (bel, in D). C: Transverse section of the regenerate at the level of the arrowhead indicated on B. Each hemiray region (L) contains two discrete ihha expression domains (arrows), which signal an imminent bifurcation event and labels the presumptive sister rays (*). Closer view of the epidermis-mesenchyme interface (D) confirms that ihha-expressing cells correspond to scleroblasts (arrow). E: Double in situ with shh and ihha shows that the shh domain (red arrow), which is restricted to the basal epidermal layer, is facing ihha-positive cells (black arrow). F: col10a1 is strongly expressed in both epithelial cells (red arrow) and scleroblasts, from the patterning zone to the proximal part of the regenerate. All longitudinal sections are oriented distal part to the top. bel, basal epidermal layer; e, epidermis; ec, epidermal cap; l, lepidotrichia; m, blastema mesenchyme; pz, patterning zone; *, presumptive sister rays.
|
