Biology and MB&B

Graduate Student Career Retreat 2008

Name:  Frank Tulenko   

   Lab:  Ann C. Burke [Biology]

 Abstract

Topic: Vertebrate Evolution

We use 3D modeling to visualize changes in the lateral somitic frontier (LSF) during chick and mouse development. The LSF marks the interface between two distinct embryonic domains. The primaxial domain contains somitic cells that differentiate in a somitic environment, whereas the abaxial domain contains somitic migratory cells that differentiate in a lateral plate (LP) environment. The initial boundary between somitic and LP mesoderm is uniform along the post-cranial anteroposterior (AP) axis of the embryo. As development proceeds, the topography of the frontier varies because of differential growth of primaxial and abaxial tissues along the AP axis. Interestingly, the smooth profile of the frontier is interrupted by specific muscles, nerves, and skeletal elements. We visualize the LSF in transgenic mice with a LP-specific Cre recombinase driving alkaline phosphatase, and in avian embryos by transplanting quail presomitic mesoderm into chick hosts. We use 3D models generated with AmiraTM to track the dynamics of the frontier during morphogenesis at different anatomical resolutions (e.g., whole embryos, specific musculoskeletal elements, and spinal nerves). Specifically, we have reconstructed primaxial and abaxial components of the mouse pectoral girdle, and are modeling this boundary in the avian shoulder. We are generating a developmental series of whole-body reconstructions of the LSF in mice, including spinal nerve patterning. Preliminary data suggest that discontinuities along the frontier arise from structures that bridge the axial and appendicular systems, and that major changes in the trajectory of spinal nerves are coincident with the frontier.  We report a somitic contribution in the mouse scapula and track changes in the relationship between somitic chondrocytes and lateral plate connective tissue during morphogenesis and growth.  Visualizing morphological data in 3D will help clarify patterns of cell differentiation in the context of the embryonic environment, and facilitate comparative studies across taxa.