I study the morphogenesis of vertebrate embryoes in Ray Keller's lab. Our model organism is the frog Xenopus laevis , in which the embryonic body axis is shaped by stereotyped cellular behaviors by which cells intercalate along one axis and drive extension of the cellular array in another, perpendicular direction. These movements, termed convergent extension, shape the early embryos of many animals and are driven in part by mediolateral intercalation of cells within the prospective dorsal axis. Recently it has been shown in flies and frogs that mediolateral intercalation depends upon correct antero-posterior (A-P) patterning, and that intercalation may be cued by disparities in A-P position between apposed cells.

I am working to describe a phenomenon of reorientation of cells within dorsal axial tissues explanted from Xenopus neurulae experimentally apposed to dorsal axial tissues of opposite A-P polarity. At mis-matched levels, cells do not intercalate across the notochords, but reorient by up to 90 degrees from original mediolateral. The deviation from mediolateral to anteroposterior orientation increases with increasing A-P disparity between the apposed tissues. I hypothesize that this phenomenon depends on cells recognizing the relative magnitude of A-P disparity between themselves and their neighbors, possibly by the same mechanism that initially orients mediolateral intercalation in the gastrula. Elucidation of the cell behaviors involved in reorientation may suggest underlying molecular mechanisms of original cellular orientation within the embryo, which is necessary for productive convergent extension movements and the elongation of the body axis.