Figure 7.
Hematopoietic cells do not contribute to the lymphatic vasculature. (A) Transverse section (10 μm) of an E12.0 wild-type embryo showing a Lyve-1+ jugular lymph sac (LS) beside the anterior cardinal vein (CV). (B) Transverse section of a Runx1−/− littermate showing no obvious difference in the appearance of the jugular lymph sac, but the sac is blood-filled (arrow). Runx1-MER-Cre-MER;R26R embryos exposed to TM at E9.5 were analyzed at E11.5 (C), E13.5 (D,E), and E16.5 (F). (C) An X-gal-stained E11.5 embryo was sectioned and immunostained for Prox1 (brown). No blue cells (descendents of Runx1+ cells) are observed in the field. (D,E) Lower- and higher-magnification pictures of a section from an E13.5 embryo coimmunostained for β-gal (brown) and Lyve-1 (purple). β-gal+ cells (red arrows) can be seen around the lymph sacs (LS) but do not colocalize with Lyve-1 staining. (F) E16.5 embryo coimmunostained for β-gal (brown) and Lyve-1 (purple). β-Gal+ cells are seen in the thymus (T) but not in the lymphatic vessel (arrow). Bar, 100 μm.