Meeting Abstract

40.2  Jan. 6  Patterning domains in the vertebrate mesoderm and the generation of morphological variation. BURKE, A.C.*; DURLAND, J.L.; SFERLAZZO, M; Wesleyan University, Middletown, CT; Wesleyan University, Middletown, CT; Wesleyan University, Middletown, CT acburke@wesleyan.edu

The body plan of vertebrates comprises an axial system of a cranium and segmental vertebrae and ribs. In jawed vertebrates the axial system is integrated with an appendicular system, the paired fins or limbs and their girdles. In a developmental sense, this body plan is conserved throughout the lineage. The appendicular skeletal elements arise from the lateral plate mesoderm (LP) and the axial skeleton arises from the paraxial somites. All of the striated muscles for both systems arise from the somitic myotomes. Despite the conservation of this embryological pattern, the final morphological outcome is extremely diverse, as exemplified by the different adult morphology of frogs, snakes, turtles, humans, etc. Morphological evolution occurs primarily through changes in the actions of regulatory genes that affect patterning. We have explored the integration of the somitic and lateral plate mesoderm in a variety of tetrapods and define distinct primaxial and abaxial domains in the developing body wall. The dynamic interface between these domains we call the Lateral Somitic Frontier. Experimental evidence from chick and mouse suggests that patterning information changes when somitic cells cross the frontier. I will present a hypothesis whereby primaxial and abaxial domains behave as independently patterned modules, thus facilitating morphological evolution within the vertebrate body plan.