Development of the head and trunk mesoderm in the dogfish, Scyliorhinus torazame: II. Comparison of gene expression between the head mesoderm and somites with reference to the origin of the vertebrate head.

摘要: SUMMARY The vertebrate mesoderm differs distinctly between the head and trunk, evolutionary origin of remains enigmatic. Although presence somite-like segmentation in model animals is generally denied at molecular developmental levels, appearance cavities elasmobranch embryos has not been explained, possibility that they may represent vestigial somites once present an amphioxus-like ancestor ruled out entirely. To examine whether shark embryo exhibit any signatures reminiscent trunk somites, we isolated several developmentally key genes, including Pax1, Pax3, Pax7, Pax9, Myf5, Sonic hedgehog, Patched2, which are involved myogenic chondrogenic differentiation Pitx2, Tbx1, Engrailed2, related to patterning mesoderm, from species, Scyliorhinus torazame. Observation expression patterns these genes revealed most were expressed resembled those found amniote embryos. In addition, did overt similarity somites; is, was no greater than unsegmented other vertebrates. Moreover, showed amniote-like somatic/visceral distinction according Engrailed2. We conclude do a manifestation ancestral rather, more likely derived trait obtained lineage gnathostomes.