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Presenting Author(s) Petr Valasek
Abstract Title A dual fate of hindlimb muscle blastema: cloacal/perineal muscles develop from leg muscle cells.
Full author List Petr Valasek, Darrell D. J. Evans, Flavio Maina, Milos Grim, Ketan Patel
Text of abstract

Cloaca serves as a common opening to the urinary and digestive systems. In most mammals cloaca is present only during embryogenesis before further septation. It is encompassed by striated cloacal sphincter muscles. The origin and the developmental mechanism of these muscles have not been determined so far. Here we show that the cloacal muscles originate from somites 30-34, which corresponds to the domain that gives rise to leg muscles (somites 26-33). Using in-situ hybridisation, we have determined the aetiology of cloacal muscles and found that their myoblasts initially migrate into the developing leg bud and then extend out of the ventral muscle blastema towards the cloacal tubercle. Using experimental embryological procedures and a genetic model we show that the development of the avian cloacal musculature is dependent on the proximal leg field formation. The development of homologous cloacal/perineal muscles was also examined in the mouse. Consistently, we found that perineal muscles also develop from the ventral muscle blastema of the hind limbs. In addition we provide genetic evidence that the perineal muscles are migratory like limb muscles by showing that they are absent in metd/d mutants.

Thus we discovered a novel muscle developmental mechanism in vertebrates, whereby muscle cells first migrate into the pelvic limb, then extend to the midline and finally differentiate into the single cloacal/perineal muscles.
Which session is your work most relevant to: Limb patterning