Interactions between foreign DNA and SECs (scavenger endothelial cells) in vitro and in vivo

Nucleic acid (NA) molecules (DNA and RNA) in food/feed are taken up from the intestines and circulate in the bloodstream of mammals. Isogenic NA shed from apoptotic and necrotic cells are also released into the blood circulation. DNA is usually very rapid ly cleared from the bloodstream, and degraded to undetectable levels, in a short time. Lining the mammalian liver sinusoids, scavenger endothelial cells (SECs) are important for the endocytic uptake and degradation of blood-born soluble waste macromolecul es, thus maintaining homeostasis. SECs have specific receptors that mediate endocytosis of circulating waste molecules. Recognition and degradation of NAs may occur when these molecules are complexed to other macromolecules (e.g. proteins or carbohydrates ) under physiological and pathological conditions. Some of these complexing macromolecules may provide additional binding sites for receptor-mediated uptake of the NA-complexes. The major goal of the present project proposal is to find out whether and t o what extent SECs are responsible for the recognition and degradation of NAs. Recent data indicate that the general DNA clearance mechanisms may occasionally fail. Such elimination failure may be caused by specific sequences or structural features of the DNA that somehow permit the macromolecules to elude lysosomal degradation after endocytosis in SEC. To understand these sequences and features is a crucial point in the context of understanding the potential for health effects associated with transgeneti c engineering enterprises. It is essential to ascertain whether specific DNA sequences, structures or complexing macromolecules may result in a less efficient lysosomal degradation, followed by nuclear transport and chromosomal integration of foreign DNA. We will study the general biological consequences of SEC/NA interactions and also investigate the possibilities of transgene expression from an episomal or integrated state.