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Fig. 5
Wnt/β-catenin and Fgf signaling target genes are expressed in interneuromast cells during wild type intercalary neuromast formation.
To see when intercalary neuromasts first arise we alkaline phosphatase stained wild type zebrafish at 2, 3, 4, 5 and 6 dpf. Quantification of total neuromast number shows a steady increase from 2 to 6 dpf (A). Most of the increase comes from primII deposited neuromasts (B). There is one intercalary neuromast by 4 dpf and two by 6 dpf (C). (D–G) Alkaline phosphatase staining from 2–5 dpf. The images were taken so that the first primI deposited neuromast is always at the left (without a label). Asterisk labels primII-derived neuromasts, the arrowhead labels interneuromast cells and squares label intercalary neuromasts. (H–K) lef1 in situ hybridization from 2–5 dpf. lef1 is expressed in interneuromast cells at 2 dpf (H, arrowhead) and is maintained in clumps of interneuromast cells from 3–5 dpf (I–K, arrowheads) that will likely give rise to intercalary neuromasts. The strong cluster of lef1 expression at 3 dpf is the leading edge of primII (I, arrow). lef1 is not expressed in mature neuromasts. (L–O) beta-catenin2 (ctnnb2) expression from 2–5 dpf. Similar to lef1, ctnnb2 is expressed in interneuromast cells at 2 dpf (L, arrowhead) and is maintained in clumps of interneuromast cells from 3–5 dpf (M–O, arrowhead). Unlike lef1, ctnnb2 is expressed in primary neuromasts (M–O, asterisk). (P–S) pea3 expression from 2–5 dpf. (P) At 2 dpf pea3 shows strong expression in primary neuromasts but not in interneuromast cells. (Q–R) At 3 and 4 dpf pea3 shows expression in primII (arrow) and primII derived neuromasts (asterisk) but still no interneuromast cell expression. At 5 dpf pea3 can be seen in a few cells near somite boundaries (S, arrowhead).