Proceedings of the 2003 Systems and Information Engineering Design Symposium Matthew H. Jones, Barbara E. Tawney, and K. Preston White, Jr., eds. 127 ABSTRACT Computer simulation of the interactions between numerous cells is a novel approach to analyzing and comprehending the spatial and temporal patterns that are formed in a large network of cells within a tissue. Coupled with experimen- tal observation, computational modeling at the cellular level is a powerful method that is capable of providing valuable information about the functions of quite complex biological systems. For this study, the biological system under examination is the Xenopus laevis embryo. In the blastocoel roof of the Xenopus laevis embryo, thinning of multiple cell layers into two cell layers is accomplished via radial intercalation of the deep layer cells. A cell-based simulation has been developed to analzye the process of blastocoel roof (BCR) thinning event. The cellular auto- mata model can predict important characteristics of the BCR thinning process including total thinning time and spatial fibronectin fibril densities. 1 INTRODUCTION In the blastocoel roof (BCR) of the Xenopus laevis embryo, thinning of multiple cell layers into two cell layers is ac- complished via radial intercalation of the deep layer cells. Experimental work involving the observation of individual cells during morphogenetic events in the Xenopus laevis have been previously described (Keller, 1978). That work involved the use of time-lapse cinemicrography to investi- gate the behavior of individual cells in the superficial layer of the BCR of Xenopus laevis embryos. Subsequently, Keller progressed to describing in detail the cellular behav- ior of deep cells of the BCR (Keller, 1980). Scanning elec- tron microscopy revealed the activities of individual cells in the deep layers of the BCR. Although the behavior of individual cells in the BCR was described, the cellular mechanisms causing such behavior were not revealed by this work. More recently, experiments investigating fi- bronectin matrix formation on the BCR have been con- ducted. For example, the mechanisms of fibronectin fibril growth on the BCR have been studied (Winklbauer and Stoltz, 1995), and the conditions necessary for fibronectin fibril formation have been explored (Winklbaeur, 1998). Furthermore, multiple scientific publications have sug- gested that the fibronectin matrix that forms on the BCR plays an important role in morphogenetic movements which occur subsequent to radial intercalation of cells in the BCR. For example, the importance of fibronectin in governing tissue separation during embryonic development has been described (Wacker, 2000). At the University of Virginia, Dr. Douglas DeSi- mone’s cell biology laboratory has been striving to acquire a greater comprehension of the cellular mechanisms re- sponsible for BCR thinning. In particular, Dr. DeSimone and the members of his laboratory are interested in explor- ing the possibility that there may be an interaction between the expression of integrins and the expression of cadherins which affects radial intercalation. Their lab is also inter- ested in examining the relationship between the formation of the fibronectin matrix on the BCR and radial intercala- tion in the BCR (DeSimone et al., 2002). In 2001, Mars- den and DeSimone described their examination of the im- portance of integrin and fibronectin during epiboly in Xenopus laevis (Marsden and DeSimone, 2001). Systems which are characterized by complex behav- iors that arise from the interactions of many components have been termed Complex Adaptive Systems (CAS) (Chan, 2001). The interacting agents in the Xenopus laevis embryo are cells. Cell-based simulations allow the nonlin- ear characteristics of a Complex Adaptive System (CAS) to be replicated. A programming tool called StarLogo was developed for purpose of building simulations of behaviors that emerge from the interactions of a large number of agents (Hayes, 1999). StarLogo has been used for simulat- COMPUTATIONAL AUTOMATA SIMULATION OF BLASTOCOEL ROOF THINNING IN THE XENOPU LAEVIS EMBRYO . Diane Longo Shayn Peirce Thomas Skalak Department of Biomedical Engineering University of Virginia Mungo Marsden Lance Davidson Bette Dzamba Douglas DeSimone Department of Cell Biology University of Virginia