Fig. 5. (A) Morphology of the embryonic dorsal aorta isolated from E9.5 mouse embryos after pancreatin digestion. Note the absence of remnants of adjacent embryonic structures. (B) RT-PCR revealed that endothelial and hematopoietic markers (VE-Cad, Flk1 and CD34), but not myogenic markers (Myf5 and MyoD), were expressed in dissected aorta (A). Total embryo extract was used as a positive control (+). Negative control (no RNA) is shown in the first lane (–). (C) Phase contrast morphology of a clone from embryonic aorta growing on an STO feeder layer. (D) Phase contrast morphology of one typical clone (A4) from embryonic aorta after five passages in vitro. (E) RT-PCR of the messages expressed by several cell lines (A4, A6, A14 and B13) from the dorsal aorta after 5 passages in vitro. Note expression of hemo-angioblastic but not of tissue specific markers such as Myf5 or Nkx2.5.