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The development of limb muscle has been well studied in most land dwelling vertebrates such as humans and modern research models. In these species, muscle precursors, or cells that will form limb muscle, travel to the limb bud, a location in the developing embryo where they multiply and form muscle tissue under the control of genes that coordinate limb-muscle formation, such as Lbx1. It has been shown that this mechanism of development is shared with bony but not with cartilaginous fish.
The study, "Migratory Appendicular muscles precursor cells in the common ancestor to all vertebrates", published in Nature Ecology & Evolution, was a collaboration between several centers in Japan and Spain, namely the Tokyo Tech, RIKEN Center for Life Science Technologies, the University of Tokyo as well as the Center for Genomic Regulation and Universitat Pompeu Fabra. Using catshark embryos as their research model, the investigators confirmed that Lbx1-positive cells are found in cartilaginous fish fin as well as in hypobranchial (pertaining to the segment below the gills) muscles, and that these are formed via the mechanism that has been established in land dwelling...
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