(a,c) Whole-mount images of 3-day old PthCre;CAG-td-Tomato;Foxn1::EGPF mice; parathyroid (PT) is red, thoracic thymus (TT) is green. Large boxes show high magnification of CT in small boxes. (Scale bar, 200 μm). (a) CT of parathyroid origin (yellow arrow) next to parathyroid. (b) Section of CT, one with green only, and one with green and red. (Scale bar, 50 μm). (c) Whole-mount image of non-parathyroid origin CT (white arrow). (d) No expression of Pth and Gcm2 in cervical thymus regardless of origin. (N>3, error bars represent s.e.m.). (e) Epithelial (pankeratin positive) cells at the thymus-parathyroid interface at E12.5 that express neither FOXN1 nor PTH (white arrow). Foxn1::EGPF, green; Pth-Cre-activated CAG-td Tomato, red; pan-keratin, violet; 4′,6-diamidino-2-phenylindole (DAPI), blue (Scale bar, 50 μm).