Doctor of Philosophy, Case Western Reserve University, 2011, Pathology

In mammals, fucose molecules are frequently present as a terminal modification of glycans. To elucidate the biological roles of fucose molecules, we previously characterized mice engineered to be conditionally deficient in all fucosylation. These mice yield phenotypes, including growth retardation, infertility, thymic hypoplasia and myeloproliferation. Functional analyses reveal that fucose-dependent thymic hypoplasia and myeloproliferation phenotypes are a result of defective Notch activity. Notch signaling is a conserved pathway that regulates cell fate determination. The extracellular domain of Notch is decorated with multiple O-fucose molecules, of which the additions are catalyzed by Protein O-fucosyltransferase-1 (Pofut1). These fucose-containing glycans have been demonstrated to be critical in modulating transactivation of Notch. To elucidate the role of O-fucose-dependent Notch activity in post-natal hematopoiesis, we studied mice with conditional inactivation of Pofut1. Adult animals bearing the homozygous Pofut1-deficient allele exhibits myeloproliferation, faulty marginal zone B-cell development and thymic hypoplasia in both cell-autonomous and non-autonomous fashions. Similarly, Pofut1-deficient bone marrow progenitors display robust myeloid development but fail to differentiate into T lymphocytes while co-culturing with Notch-ligand-expressing stromal cells in vitro. Both myeloproliferation and deficient mature T cell traits are reversed when Pofut1-deficient progenitors are reconstituted with constitutively active Notch1, which illustrates the critical role of Notch O-fucosylation in regulating hematopoietic homeostasis. Although O-glycans are essential for Notch function, it is unclear whether all O-fucose molecules are important. To address this issue, we used cell-based assays to assess the binding efficiency of the Notch ligands Delta-like-1, Delta-like-4, Jagged1 and Jagged2 to mouse Notch1 and the expression levels of surface Notch1 as a function (open full item for complete abstract)

Committee: John Lowe (Advisor); Robert Fairchild (Advisor); Clark Distelhorst (Committee Chair); Lan Zhou (Committee Member); Clive Hamlin (Committee Member) Subjects: Immunology