Figure 6

Hypaxial SEM grafted to the epaxial domain generates chondrocytes. A) Schematic illustration of the grafting procedure. Quail hypaxial SEM (blue) at the level of somite 20/21 was transplanted to the epaxial domain of chick embryo (red). m, myotome; n, neural tube; sc, sclerotome; sem, sub-ectodermal mesenchyme. B and C) In situ hybridization with qPax1 after two days of re-incubation. B) Control side shows normal Pax1 expression pattern in scapula anlagen (region between white arrows). C) Abnormal expression of Pax1 in epaxial domain (red arrowhead) in a central, operated region of the chick Pax1-positive scapula anlagen (between white arrows). D and E) Skeletal staining after five days of re-incubation. D) Control side shows normal scapula (s) and humerus (h). E) Operated side shows an ectopic cartilaginous element besides the normal scapula (white arrowhead). F and G) Immunohistochemistry on transverse sections through the operated region. F) Control side shows normal skeletal elements. n, neural tube; r, rib; vb, vertebral body. G) Operated side shows an ectopic cartilaginous element (black asterisk) of quail origin in epaxial position. Insert in G) shows higher magnification of QCPN-positive cells in the ectopic cartilage.