Fig. 1

Bone matrix synthesis in the uninjured fin is controlled by RA production and degradation. (A) Overview of relevant structures and tissue types of a fin ray. (B) Mean hemiray thickness at different positions along the proximodistal axis in adult fish (red) and at an intermediate position in fins of different lengths (black) show that hemirays are thicker in older fish (longer fin) and at more proximal positions. (C) IHC for ZNS-5 and GFP in aldh1a2:gfp fish in the uninjured fin reveals aldh1a2 expression in fibroblasts (arrowhead) adjacent to osteoblasts (arrow). Asterisk indicates bone matrix. (D) RA and R115866 injections upregulate expression of bone matrix genes. Conversely, inhibition of RA signaling in hsp70I:cyp26a1 fish downregulates expression (qPCR analysis). (E) ISH demonstrates cyp26b1 expression in osteoblasts (arrowhead). Asterisk indicates bone matrix. (F) Model of bone matrix synthesis regulation by RA synthesis and degradation in the uninjured fin. Data are represented as mean±s.e.m. *P<0.05, **P<0.01, ***P<0.001. Scale bars: 10µm in C; 20µm in E. h, hours; hs, heat shock.