Fig. 4. K19 identifies embryonic multipotent mTEC progenitors (mmTECp).

a K19^Cre was induced in Krt19^CreERTtdTom embryos at E15.5 via the administration of tamoxifen to pregnant mice, and fate-mapped thymi were harvested at PNd0 (n = 14, from 3 independent experiments). Fate-mapped cells were detected within EpCAM1⁺ cells by flow cytometry and quantitated. b Representative FACS plots and quantitation of K19-tdTom fate-mapped cells within EpCAM1⁺UEA1⁺ and EpCAM1⁺Ly51⁺ TEC. c Expression of Ly51 and UEA1 by total EpCAM1⁺ cells, K19-tdTom^- EpCAM1⁺ cells (non-fate-mapped) and K19-tdTom⁺EpCAM1⁺ cells (fate-mapped). d Bar charts show proportions of Ly51⁺UEA1^- and Ly51^-UEA1⁺ cells, and mTEC:cTEC ratio within non-fate-mapped and fate-mapped TEC. e Bar chart shows fold change in Ly51⁺UEA1^- and Ly51^-UEA1⁺ cells within non-fate-mapped and fate-mapped TEC. f Immunofluorescence of PNd0 thymi following K19-fate-mapping at E15.5. K19-tdTom (red) and K5 (turquoise). ‘C’, and ‘M’ indicate cortex and medullary areas respectively. Scale bar denotes 20 μm. Image representative of 4 thymi. g Expression of MHCII by EpCAM1⁺Ly51⁺ fate-mapped (FM) or non-fate-mapped (Non-FM) TEC. h Representative FACS plots illustrating the phenotype of fate-mapped mTEC subsets. mTEC^hi (MHCII^hiCD80^hi, n = 14), mTEC^lo (MHCII^loCD80^lo, n = 14), Aire⁺ (MHCII^hiCD80^hiAire⁺, n = 14), CCL21⁺ (n = 6), tuft cells (MHCII^loCD80^loDCLK1⁺, n = 8), and corresponding quantitation. i, j Immunofluorescence of PNd0 thymi where K19^Cre was induced at E15.5. Scale bar denotes 10 μm. Image representative of 4 thymi, from 3 independent experiments. K19-tdTom (red), EpCAM1 (blue), f Aire (turquoise), g DCLK1 (turquoise). Data analysed using a Student’s t test. The data are shown as mean ± SEM.