Extended Data Fig. 7: LPM origin of PAFF mesenchyme is conserved in medaka, paddlefish and Xenopus.

a–c, In situ hybridisation of medaka hand2 at Stage 39 (a) and Stage 40 (b–c) showing exclusive expression in pre-anal fin mesenchyme (yellow arrowhead, b), but not in the caudal fin mesenchyme (cyan outline). Ventral caudal fin imaged in (a). d–e, Lateral confocal images of PAFF of Stage 36 transgenic Tg(-6.35drl:EGFP) medaka embryo. Fluorescent confocal images of eGFP (d) are overlayed on Nomarski image (e). Faint eGFP perdurance is seen in nascent PAFF mesenchymal cells (yellow arrowheads and inset). f–i, Ventral (f,h) and lateral (g,i) confocal images of medaka embryo injected with DiI in the posterior LPM at Stage 20 (f,h) and traced to PAFF at Stage 40 (g,i). DiI within the mesenchyme indicated by yellow arrowheads, with higher magnification example shown in inset (g,i). DiI signal (f,g) is overlayed with Nomarski (h,i). Location of paraxial mesoderm (PM), Kupffer’s vesicle (KV) and region of posterior LPM are indicated in green, red, and white respectively in (h). j–l, In situ hybridisation of hand2 in Stage 38 (j) and Stage 39 (k–l) paddlefish embryos imaged laterally (j,k) or in transverse section (l). hand2-positive PAFF fin mesenchyme indicated by yellow arrowheads is located distally. Expression of hand2 is also seen in the nascent pelvic fins at Stage 39 (green arrowheads k,l). m–o, Confocal images of a region of Xenopus laevis PAFF at NF Stage 42 injected with -6.35drl:EGFP. Lateral x-y view (n) is shown with orthogonal sections in the x-z plane (m) and y-z plane (o). Transient mosaic expression in the interstitial mesenchyme is highlighted with yellow arrowheads (m–n). Scale Bars: 20 µm (a,d), 100 µm (b,i), 50 µm (b – inset, l,o), 200 µm (h,j,k).