Fig. 1: Plexin-B1/Plexin-B2 suppress epidermal stem cell proliferation during embryonic development.

a Confocal images of immunostainings of murine skin at embryonic day 15.5 (E15.5), 16.5 (E16.5), 18.5 (E18.5) and at an adult stage using anti-phospho-histone H3 (pHH3; red) and anti-keratin 14 (K14; green) antibodies. Dashed lines indicate the basement membrane. Scale bar, 25 µm. b Quantification of pHH3-positive cells at different time points of embryonic (E) development and in the adult (mean ± s.e.m.; n = 3 mice per time point). c mRNA expression levels of genes encoding B-plexins (plxnb) in the murine skin at the indicated time points as determined by quantitative RT-PCR (mean ± s.e.m.; n = 3 mice per time point). d Confocal images of immunostainings of murine epidermis at embryonic day 16.5 (E16.5) using anti-Plexin-B1 (green) and anti-Plexin-B2 antibodies (red). Dashed lines indicate the basement membrane. Scale bar, 10 µm. e Confocal images of immunostainings of murine epidermis at E16.5 using anti-Plexin-B2 (red), and anti-keratin 14 (K14) or anti-keratin 10 (K10) antibodies (green). Scale bar, 10 µm. f Immunohistochemistry on murine embryonic epidermis using an anti-BrdU antibody (brown). “contr.”: control mice (genotype plxnb1^flox/flox;plxnb2^flox/flox), “PlexDKO”: epidermis-specific Plexin-B1/Plexin-B2 double-knockout mice (genotype K14-Cre;plxnb1^flox/flox;plxnb2^flox/flox). Blue: Hematoxylin. Scale bar, 50 µm. g Quantification of the data in f (mean ± s.e.m.; E15.5: n = 5 mice per genotype, E16.5: n = 4 mice per genotype; p = 0.0429 for E15.5, p = 0.0175 for E16.5; two-sided unpaired t-test). h H&E-stained histological sections of murine epidermis at the indicated time points of embryonic development. Brackets indicate epidermal thickness. Scale bar, 50 µm. i Quantification of the data in h (mean ± s.e.m.; E14.5: n = 6 mice per genotype, E15.5 and E16.5: n = 7 mice per genotype and time point; p = 0.625 for E14.5, p = 0.494 for E15.5, p = 0.005 for E16.5; two-sided unpaired t-test). j Confocal images of immunostainings of murine embryonic epidermis using anti-K14 (green) and anti-K10 (red) antibodies. Scale bar, 25 µm. k Quantification of K14-positive cells (mean ± s.e.m.; n = 7 mice per genotype and time point; p = 0.38 for E14.5, p = 0.0009 for E15.5, p = 0.0497 for E16.5; two-sided unpaired t-test).