Figure 8. Loss of Eda signaling decreases Merkel cell (MC) density in trunk, but not facial skin.

(A–F) Representative confocal images of MCs in the trunk of animals of the indicated genotypes at the indicated stages. Dotted yellow lines indicate posterior scale boundaries. nm, neuromasts of the posterior lateral line. (G) Quantification of MC density in the trunk skin relative to standard length (SL). Gray shading indicates a 95% CI around the linear regression lines. The difference between genotypes was significant above 12.5 mm SL (p<0.05, Johnson-Neyman Technique). Each dot represents an individual fish (N=16–18 fish/genotype). (H) Histograms of the distribution of trunk MCs along a rectangular segment encompassing three scales in a sibling and an identically sized region in an eda mutant (18–19 mm SL). (I) Boxplots of MC densities in the epidermis above the cornea or operculum in animals of the indicated genotypes. ns, not significant (cornea, p=0.21; operculum, p=0.14; Mann-Whitney test). Scale bars: 50 μm (A–F).

Figure 8—figure supplement 1. eda mutants exhibit significantly decreased MC addition.

(A) Schematic of experimental approach. Following whole animal photoconversion, densities of converted and non-converted MCs were quantified at 4 dpc. (B-C’’) Representative lateral confocal micrographs of MCs at 4 dpc in adults of the indicated genotypes. Numbers label newly added cells, distinguishable by the absence of photoconverted nls-Eos (magenta). (D) Boxplots of MC addition at 4 dpc in the indicated genotypes. eda mutants show a significantly lower rate of MC cell addition (Mann-Whitney test). (E) Boxplots of photoconverted MC density in animals of the indicated genotypes at 0 and 4 dpc. p-values from a Mann-Whitney test are listed above the boxplots for each genotype. For D and E, 1–3 independent regions were analyzed from N=4–5 fish/genotype. Scale bars: 20 μm (B, C).