Fig. 1. Specific expression of Tbx3 in hepatoblasts isolated from the developing mouse liver. (A) Of the 17 mouse T-box genes, Eomes, Tbx3, Tbx6, Tbx10, Tbx12, Tbx15 and Tbx20 were expressed in the E13.5 mouse liver, as assessed by RT-PCR. The upper band in the Tbx3 lane represents a transcript variant of this gene (Bamshad et al., 1999). (B) Flow-cytometric fractionation of E13.5 liver cells into CD45⁺, Ter119⁺, c-Kit⁺, c-Kit^- CD45^- Ter119^-, c-Met^- c-Kit^- CD45^- Ter119^-, and c-Met⁺ c-Kit^- CD45^- Ter119^- cell populations. Cells in each fraction were sorted and analyzed. (C,D) RT-PCR analyses of T-box gene expression in cells sorted from each fraction shown in B. Erythroid cell-specific glycophorin A was recognized by anti-Ter119 antibody. (E,F) Hnf4 (E) and Tbx3 (F) immunofluorescent images of E13.5 liver sections. Insets denote individual cells as labeled with DAPI (blue). (G-I) Co-immunofluorescence staining of Hnf4 and Tbx3 showed that a subpopulation of Hnf4⁺ cells was marked by either strong or weak staining of Tbx3. (J) All Tbx3⁺ cells expressed E-cadherin. (K,L) Tbx3 was expressed in Alb^-/low primitive hepatic cells (arrowheads) and in a subpopulation of Alb⁺ differentiating hepatocytes (K), and in a few CK7⁺ cholangiocytes (L). Scale bars: 100 µm in E,F; 50 µm in I; 25 µm in J-L.