Fig. 4.

Lineage tracing of a cohort of cells that expressed Tbx6-creERT2 between E6.75 and E8. Pregnant Cre-reporter females were injected with tamoxifen at E6.5 and embryos were dissected 2-4 days later as indicated on each panel and stained for lacZ. (A) Unturned whole-mount E8.5 embryo with lacZ-positive cells in the allantois, cardiac crescent and laterally along the length of the embryo. (B) A whole-mount E9.5 embryo of approximately 20-25 somites with lacZ-positive cells in the head (arrow), somites, with higher concentration in somites 4-15, lateral body wall, and in a posterior lateral stripe marking the mesonephros. (C-L) Transverse sections of embryos showing representative tissues with labeled cells, notably head mesenchyme (C), heart (C), differentiating somites (C-I), mesonephric ducts (F,K), mesenchyme surrounding the esophagus and bronchi (J), in the lateral body wall and limb (H,K,L), lining of the coelom and pericardio-peritoneal canal (E,H), and genital ridge (K,L). A minority of embryos had labeled cells in the neural tube (arrowheads) (I) and notochord (black arrows in G and H show labeled and unlabeled notochord, respectively). Dorsal is to the top of each panel. a, dorsal aorta; al, allantois; b, bronchus; c, coelom; cc, cardiac crescent; e, esophagus; fg, foregut; fl, forelimb; g, gut; gr, genital ridge; h, heart; hf, head folds; lbw, lateral body wall; m, mesonephric duct; nt, neural tube; ppc, pericardio-peritoneal canal; so, somatopleure; som, somite. Scale bars: 100 μm.