Modeling stomach curvature: in vivo and in silico

Project Summary Left-right (LR) differences in size, shape and/or anatomical position exist in almost every organ system. Consequently, abnormal LR asymmetry (known as heterotaxy, HTX) leads to a catastrophic syndrome of often-fatal birth defects. While the early embryonic events that establish global LR asymmetry have been well studied, it is the later-stage, organ-specific LR asymmetric morphogenesis events that determine normal anatomy; yet, for most organs, the molecular and cellular processes that sculpt their individual LR asymmetries have not been elucidated. This application addresses the asymmetric morphogenesis of the stomach, an organ whose familiar leftward curvature is an archetypical laterality among vertebrates. Our previous work has shown that the curvature of the stomach depends on LR asymmetric endoderm cell rearrangements, which cause preferential thinning and expansion of the left stomach wall. However, preliminary data suggest that this process alone is insufficient for proper curvature, and that events in the right stomach wall, as well as asymmetries in other tissue layers, including mesoderm and extracellular matrix (ECM), are also required for correct laterality. We hypothesize that stomach curvature is generated by interdependent LR asymmetries in endoderm rearrangement, mesoderm differentiation, and ECM composition. In the proposed project, we will integrate two powerful and complementary approaches to determine the individual and combined roles of different types of asymmetries in stomach curvature. First, we will use the exceptionally amenable frog embryo to execute tissue- and side-specific assays of gene function in vivo, along with innovative tests of tissue-mechanical properties. Second, we will use computational models of stomach morphogenesis to simulate multiple cell- and tissue-level asymmetries in silico, making testable predictions and revealing non-obvious, abiogenic effects on organ topology. In Aim 1, we will identify the LR asymmetries within each tissue layer that are required for stomach curvature in vivo. In Aim 2, we will employ computational modeling to determine the combinations of cell- and tissue-level LR asymmetries that are sufficient to reproduce realistic curvatures in silico. Aim 3 will utilize both in vivo and in silico modeling to ascertain the cell and tissue-level mechanisms underlying abnormal curvatures in HTX. Rigorously comparing computational simulations with anatomical data from nano-CT scans will ensure cross-validation and full integration of in vivo and in silico results throughout the project. Our findings will yield multilevel insights into the pathogenesis of LR defects in the stomach, with implications for the cell- and tissue-level events that underlie the emergence of more complex lateralities in other organs. This project will also highlight the value of in silico paradigms for morphogenesis research.