The movement and redistribution of lipids among cells and tissues are essential for normal growth and development. However, little information exists regarding lipid transport during mammalian embryogenesis where dynamic remodeling of tissues and systems occurs. Post-birth, lipoproteins, abundant in interstitial fluid, blood, lymph and cerebrospinal fluid, transport water-insoluble lipids throughout the body for utilization and storage. Apolipoproteins, the protein components of lipoproteins, are suited uniquely to the reorganization and transport of lipids. Expression of several apolipoproteins, including apolipoprotein (apo) AI and apoE, has been observed during isolated stages of development. However, their function(s) in embryogenesis have not been investigated. Dr. de Silva will undertake two complementary approaches to investigate the role of apoE and apoAI in lipid transport and redistribution in the developing embryo. A mouse model will be used because of well-characterized developmental stages and readily available apolipoprotein null mutants. First, Dr. de Silva will describe and quantitate the apoE and apoAI mRNA expression by in-situ hybridization in staged embryos and compare these results to the protein distribution pattern obtained by immunocytochemistry. She will also examine and quantitate the lipid-protein complexes secreted by staged mouse embryos. The second approach is to evaluate the compensatory mechanisms that occur in double-knockout mice generated by homologous recombination that lack functional apoE and apoAI genes. Dr. de Silva will quantitate the lipids and proteins present in lipid-protein complexes in these null mutants to understand the role of other apolipoproteins (and proteins) in early lipid transport.
