Figure 4

The fndc3a^wue1/wue1 mutation results in structural defects in epidermal cells during fin development. Visualization of actinotrichia by either differential interference contrast microscopy (A) or immunofluorescence staining of Col2a (B) showed loss of mature actinotrichia in fndc3a^wue1/wue1 mutants 52 hpf (control n = 0/17; fndc3a^wue1/wue1 n = 19/26; white arrows indicate lost actinotrichia and Col2a accumulation in apical cells of the median fin fold). (C) Investigation of fndc3a^wue1/wue1 mutants showed reduced median fin fold width and reduced TP63 positive epidermal cell number in the ventral median fin. (D,E) Quantification of median fin fold width and TP63 positive cells in 24 and 48 hpf embryos (Mann-Whitney U test; p < 0.05; two-tailed, significant U value changes are indicated with asterisks). (F) Ultrastructural analysis of dorsal and ventral fins of control and fndc3a^wue1/wue1 mutants revealed breakdown of actinotrichia fibers and cellular malformations in cells of the basal epidermal layer in the ventral fin folds of 52 hpf old embryos (circles indicate misplaced fibers; dashed lines indicate the basal membrane; yellow brackets indicate outer epidermal cells and green brackets indicate basal epidermal cells; black asterisks indicate cavities). a: actinotrichia; bel: basal epidermal layer; epi: epidermis; mff: median fin fold; m: mesenchymal cell; N: nucleus; oel: outer epidermal layer.