Meeting Abstract

P2.69  Wednesday, Jan. 5  The cellular basis of growth and shape change in frog cranial cartilage ROSE, C.S.*; EDMONDS, W.R.; VERGARA, M.F.; NASHIMOTO, K.; James Madison University rosecs@jmu.edu

Our research addresses the role of cell behaviors in the growth and metamorphic remodeling of cranial cartilages in the frog Xenopus laevis. Amphibians are distinguished from most vertebrates by having pharyngeal arch cartilages grow isometrically and then undergo different kinds of change shape at metamorphosis. How the isometric growth and shape changes occur at the level of cell behaviors is unclear. Cell behaviors that might contribute to growth and shape change in cartilage include cell division, cell growth, change in cell shape, cell death, cell apposition, and matrix secretion. The cell behaviors underlying shape change might be either regionalized or interspersed within cartilages. This study focuses on two cartilages, Meckels cartilage of the lower jaw and the ceratohyal, that are not replaced by bone and lack any evidence of regionalized cell behaviors at larval stages. We produce spatial maps of cell behaviors to test hypotheses about how specific cell behaviors contribute to growth and shape change. Specimens at early, mid and late larval and metamorphic stages are BrdU-treated, wax-embedded and sectioned frontally and transversely. Photographs through specific regions of each cartilage are analyzed using CellProfiler to measure cell size, shape and orientation, and the variation within cartilages and between stages is analyzed using MANOVA and ANOVA. The spatial distribution of dividing cells and orientation of cleavage planes are also compared among stages. This data is used to describe how cell division, cell growth, and cell apposition contribute to isometric growth, how metamorphic cell behaviors are patterned inside larval cartilages, and how cell behaviors change in the two transitions between growth and shape change.