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. 2014 Jun 15;390(2):231–246. doi: 10.1016/j.ydbio.2014.03.003

Fig. 10.

Fig. 10

Behaviour of non-migratory muscle precursors grafted to the occipital region. Lateral views of chick embryos at HH18-19, 36 hours after surgery; Lbx1 expression shown in blue, quail cells in brown; rostral is to the top, lateral to the right. Migratory muscle precursors expressing Lbx1 and entering the lateral mesoderm are marked with green arrows; white arrows indicate cells entering the lateral mesoderm without expressing Lbx1, open arrowheads mark cells that neither express Lbx1 nor trespass into the lateral mesoderm. (A) Control grafting of quail occipital somites in place of chick occipital somites. The quail cells express Lbx1 and leave the somites, contributing to the hypoglossal cord and eventually forming hypobranchial/hypoglossal muscle (green arrow). (B, C) Grafting of quail flank level somites (B) or quail head mesoderm (C) in place of chick occipital somites. The quail cells do not have characteristics of migratory muscle precursors as they lack expression of Lbx1. However, they enter the lateral mesoderm along the route normally taken by TMP (white arrow). (D) Control grafting of quail occipital and upper cervical somites in place of chick somites at forelimb levels. The quail cells express Lbx1 and migrate into the limb (green arrow), mimicking limb muscle precursors. (E) Grafting of quail flank somites in place of chicken somites at the forelimb–flank boundary. Cells under the influence of the forelimb become reprogrammed, expressing Lbx1 and contributing to the limb musculature (green arrow). Cells exposed to flank cues do not express Lbx1 or emigrate (open arrowhead). (F) Grafting of quail head mesoderm in place of chicken forelimb somites as shown in (Mootoosamy and Dietrich, 2002). The cells neither express Lbx1 nor migrate into the limb, indicating that they are not converted into migratory muscle precursors (open arrowhead). These findings suggest that in the occipital region, non-migratory cells may undertake movements similar to HMP. Abbreviations: cerv, cervical somites; fl, forelimb; hm, head mesoderm; hy, hyoid arch; and occ, occipital somites.