Bernadette Holdener, Ph.D.
Department of Biochemistry and Cell Biology
346 Centers for Molecular Medicine
Stony Brook University
Stony Brook, NY 11794-5215
Office telephone: 631-632-8292
Lab telephone: 631-632-8442
My laboratory is interested in how interactions between early embryonic tissues control the growth and differentiation of the mouse epiblast. My current research focuses on the role two endoplasmic reticulum proteins, MESD (mesoderm development) and POFUT2 (Protein O-fucosyltransferase 2), that likely modulate activities of cell surface receptors and extra-cellular matrix composition during Epithelial to Mesenchymal Transition (EMT) in the gastrulating mouse embryo.
Role of Low-density lipoprotein receptor-Related Proteins (LRP) in progression of stem cell beyond a pluripotent state.
MESDis a novel endoplasmic reticulum chaperone whose function is specialized for maturation and trafficking of the beta-propeller/EGF motif that characterizes the LRP family of receptors. LRPs are known to modulate a number of cell-signaling pathways and also facilitate endocytosis of a wide variety of substrates. Loss of Mesd in the mouse embryo blocks gastrulation in the epiblast and disrupts endocytosis in the visceral endoderm. Mesd mutant embryos continue to express stem cell markers Oct4, Sox2, andNanog long after their littermates have undergone organogenesis, and mutant stem cells fail to differentiate in chimeras or teratomas. Since MESD is essential for maturation of the LRP receptors, these results suggest that LRP function is essential for progression of the early epiblast to a differentiation competent state. Current studies in my laboratory utilize tissue specific disruption of Mesd to determine how loss of LRPs blocks epiblast differentiation.
Role of Thrombospondin repeat O-fucosylation in limiting epithelial to mesenchymal transition.
Protein O-fucosyltransferase-2 (POFUT2) adds a fucose to thrombospondin repeats (TSRs) containing the enzyme consensus sequence. TSRs are found in a limited number of matricellular proteins known to modulate diverse processes ranging from bioavailability of signaling molecules to cell migration. In contrast to Mesd mutations that block epithelial to mesenchymal transition (EMT) and epiblast differentiation, mutations in Pofut2 result loss of epiblast pluripotency, excessive EMT, and biased differentiation of mesoderm into vascular endothelial cells. These results suggest that targets of POFUT2 normally limit EMT and influence mesoderm patterning. Current studies utilize tissue specific disruption of Pofut2 to address the mechanism by which O-fucosylation of TSRs restricts EMT to a narrow region of the primitive streak and examine the effects of the Pofut2 mutation on cell signaling and extra-cellular matrix composition during development.
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