Differentiation of nkx2.2-expressing duct cells into insulin-expressing cells occurs in the intrapancreatic duct during larval stages. (A–D) Projections of confocal stack images at different larval stages of Tg(-3.5nkx2.2a:GFP)ia3/Tg(-1.2ins:dsRed) fish. Single focal plans of channels red, green and their overlay are represented at the bottom of each panel. In panel B the small arrow indicates the budding of an insulin-expressing cell from the duct. (C) Budding of two new insulin-expressing cells (arrows) occurring with a concomitant division of an insulin-expressing cell (arrowheads). (D) Pairs of insulin-expressing cells lie among nkx2.2a-expressing duct cells (arrowheads).