Fig. 5: Evolutionary trajectory of mimetic cells.
From: Developmental trajectory and evolutionary origin of thymic mimetic cells
a, Macroscopic view of the gill basket of a juvenile S. canicula specimen; gc, gill chamber; sc, spinal chord; H&E, haematoxylin and eosin. b, Higher magnification of the thymus region in a, showing the cortical (c) and medullary (m) structures of the thymus. Images in a,b are representative of n = 3 animals. c, Micrographs of the shark thymus after RNA ISH with FOXN1 (blue). d,e, Micrographs of the shark thymus after RNA ISH with TTR (d) and FOXI1 (e). Images on the right show the medullary regions at higher magnification. c–e, Images are representative of n = 2 animals. f, Signature enrichment analysis of mouse Foxn1−/− mutants expressing ancient Foxn1 and Foxn4 genes under the control of the mouse Foxn1 promoter compared against corresponding wild-type controls. tgFoxn4Cm, Foxn4 gene from the cartilaginous fish C. milii (n = 4); tgFoxn1Cm, Foxn1 gene from C. milii (n = 3); tgFoxn1Cm;tgFoxn4Cm (double-transgenic mice, n = 5); wild type, n = 3. The last column represents a comparison of TECs from the two single-transgenic strains. g, Signature enrichment analysis in bulk RNA-seq of whole thymi from foxn1−/− zebrafish (n = 3) compared with foxn1+/+ wild types (n = 3). h, Signature enrichment analysis of mouse Foxn1−/− mutants expressing the Foxn4 gene from the cephalochordate B. lanceolatum (n = 4); wild type, n = 3. i, Left, micrograph depicting a gill filament of Lampetra planeri (H&E staining). thy, thymoid; sl, secondary lamellae. Right, further magnified view of the thymoid, indicating the tissue heterogeneity (H&E staining); the blood vessel is filled with nucleated erythrocytes. Image representative of n = 20 animals. j–l, Micrographs of thymoids after RNA ISH with probes specific for CDA1 (j), TTR (k) and MYHC1 (l). Rows depict consecutive sections; images are representative of n = 3 animals. Scale bars: 0.1 mm (a); 0.2 mm (b–e); 0.1 mm (i–l).
