Figure 1.

Expression of PRTG protein in the mouse embryo. A, Expression of rat prtg in the nervous system at different stages of development as analyzed by the Northern blot. Ad, Adult; Br, brain; Nt, neural tube. B, Specificity of PRTG antibodies. Cell lysates of HEK293T cells transfected with the control vector, prPRTGf (rat full-length PRTG), prPRTGΔc (rat PRTG without cytoplasmic domain), or prPRTGc (rat cytoplasmic tail), and rat E10.5 neural tube lysate (Embryo) were subjected to Western blot using α-PRTG1 and α-PRTG2 mAbs. Addition of peptide E (E; ectodomain) or peptide C (C; cytoplasmic tail) competes out the bands recognized by the monoclonal antibodies. C, Schematic structure of PRTG. Peptide E or C for generating antibodies is marked in blue. D–H, Transverse sections through the mid-body level of mouse at E7 (D), E7.75 (E), E8.25 (F), E9.5 (G), and E10.5 (H) were stained using α-PRTG2 mAb (red). The dorsal is up in all panels. D, At E7, PRTG labeling is weakly detected in the mesoderm (me), whereas Oct4 is restricted to the ectoderm (ec; green). E, At E7.75, PRTG is detected in neuroepithelium, mesoderm, endoderm, and posterior epiblasts (arrows). The yolk sac (ys) surrounding the embryo is nonspecifically stained by the secondary antibodies. F, G, PRTG protein is present in almost all cells between E8.25 and E9.5 (red) but not in the notochord (n), differentiating cardiac cells, and some mesenchymal cells. The endocardium is labeled with anti-endoglin antibody (green). ac, Atrial chamber; dm, dermomyotome; vc, ventricular chamber; sc, spinal cord. H, PRTG is not detectable at E10.5. I, Expression of PRTG (red) and SSEA1 (green) in a transverse section of E7 and E8.25 mouse embryos. J–N, Expression of PRTG (red) and nestin (J), Ascl1 (K), TuJ1 (L), MAP2 (M), and NeuN (N) (green) in adjacent transverse sections through the thoracic level of E9.5 (top) and E10.5 (bottom) mouse embryos.