<i>Sox10</i> is required by bulb melanocytes postnatally.

Abstract

<p>(A–B) <i>Sox10^fl/fl</i> (<i>fl/fl; +/+</i>) and <i>Sox10^fl/fl; Tyr::CreERT2</i> (<i>fl/fl; Cre/+</i>) pups treated with TAM by IP injection to the lactating mother on P0–3 display variegated hypopigmentation on the belly and back and exhibit a white head spot upon the emergence of the morphogenetic coat (P10 shown here, n>5). (C) Number of PAX3⁺ melanocytes per hair bulb in skins harvested from these mice at P10 are significantly decreased in <i>Sox10^fl/fl; Tyr::CreERT2</i> animals compared to similarly-treated <i>Sox10^fl/fl</i> animals (*p = 0.002). (D–E) Adult <i>Sox10^fl/fl; Tyr::CreERT2</i> mice treated with TAM by IP injection on 0–3dpp exhibit white hairs within the plucked region upon hair regrowth that is not visible in similarly treated <i>Sox10^fl/fl</i> mice (brackets indicate plucked region, lower image is a magnification of plucked region). (F) Number of PAX3⁺ melanocytes per hair bulb in skins harvested from similarly-treated mice at 7dpp are significantly decreased in <i>Sox10^fl/fl; Tyr::CreERT2</i> animals compared to <i>Sox10^fl/fl</i> animals (*p = 0.001). (G–H) Fluorescent and corresponding brightfield images of hair bulbs from mice described in D–E. Arrows and arrowheads indicate PAX3⁺/SOX10⁺ and PAX3⁺/SOX10⁻ melanocytes, respectively. (I) Distribution of melanocytes double-labeled for PAX3 and SOX10 within pigmented (gray) and non-pigmented (white) hair bulbs in skins from <i>Sox10^fl/fl</i> (n = 3) and <i>Sox10^fl/fl; Tyr::CreERT2</i> (n = 4) harvested on 7dpp from mice treated with TAM on 0–3dpp (*p<0.006).</p