Modulation of cell adhesion is essential to the cell rearrangements that characterize Xenopus gastrulation. The spatial and temporal regulation of cell movement requires a highly coordinated cross-talk between cadherin and integrin adhesion receptors. Beta-parvin is an integrin associated scaffolding protein consisting of two calponin homology (CH) domains. Xenopus beta-parvin is highly conserved being ~95% similar to mammalian orthologs. Beta-parvin is expressed in the blastocoel roof and dorsal marginal zone of the embryo during gastrulation, suggesting a potential role in morphogenesis. Over-expression of full-length beta-parvin has no effect on embryogenesis, however, over-expression of either CH domain causes a failure in gastrulation. When over-expressed the CH1 domain causes a failure in fibronectin (FN) matrix assembly, epiboly and convergent extension in vivo. CH1 domain over-expression also inhibits tissue separation (TS) and Brachet’s cleft formation. The CH1 domain of beta-parvin localizes to sites of cell-cell adhesion, and down-regulates C-cadherin adhesion through activation of Rac1, independent of receptor expression. Significantly, the CH1 domain can rescue convergent extension downstream of integrin ex vivo suggesting a role for beta-parvin in the integrin mediated control of cell intercalation. Over-expression of the CH2 domain also inhibits morphogenesis in a similar fashion as CH1. However, the CH2 domain localizes to sites of integrin adhesion and inhibits integrin function resulting in a loss of FN assembly. The CH2 domain binds ILK and inhibits integrin function. When over-expressed the CH2 domain promotes TS in the pre-involution mesoderm through the activation of Rho. While the CH1 domain inhibits TS through Rac and the CH2 domain promotes TS through Rho, full-length beta-parvin over-expression has no embryonic phenotype and its signaling properties appear to be intermediate between expression of either isolated CH domain. At the dorsal lip full-length beta-parvin shuttles between integrin in the pre-involution mesoderm and cell-cell adhesion sites in the post-involution mesoderm indicating it plays significant roles in the previously characterized integrin-cadherin cross talk. My research has defined novel roles for beta-parvin as a key player in the regulation of integrin-cadherin cross-talk during tissue morphogenesis.

Color theory was first formalized in the seventeenth century by Isaac Newton just a couple of decades after the first microscope was built. But it was not until the twentieth century that technological advances led to the integration of color theory, optical spectroscopy and light microscopy through spectral image processing. However, while the focus of image processing often concerns modeling of how images are perceived by humans, the goal of image processing in natural sciences and medicine is the objective analysis. This thesis is focused on color theory that promotes quantitative analysis rather than modeling how images are perceived by humans. Color and fluorescent dyes are routinely added to biological specimens visualizing features of interest. By applying spectral image processing to histopathology, subjectivity in diagnosis can be minimized, leading to a more objective basis for a course of treatment planning. Also, mathematical models for spectral image processing can be used in biotechnology research increasing accuracy and throughput, and decreasing bias. This thesis presents a model for spectral image formation that applies to both fluorescence and transmission light microscopy. The inverse model provides estimates of the relative concentration of each individual component in the observed mixture of dyes. Parameter estimation for the model is based on decoupling light intensity and spectral information. This novel spectral decomposition method consists of three steps: (1) photon and semiconductor noise modeling providing smoothing parameters, (2) image data transformation to a chromaticity plane removing  intensity variation while maintaining chromaticity differences, and (3) a piecewise linear decomposition combining advantages of spectral angle mapping and linear decomposition yielding relative dye concentrations. The methods described herein were used for evaluation of molecular biology techniques as well as for quantification and interpretation of image-based measurements. Examples of successful applications comprise quantification of colocalization, autofluorescence removal, classification of multicolor rolling circle products, and color decomposition of histological images.