Ph.D. from University of Basel, Switzerland
Postdoctoral experience- Department of Cell Biology, Biocenter, University
of Basel
Current Title- Assistant Professor, Department of Pathology
Director, University of Vermont Cell Imaging Facility
Email: dtaatjes@salus.uvm.edu
One of the chief functions of the Golgi apparatus is glycosylation. Much current evidence suggests that there is "subcompartmentalization" of the Golgi apparatus, in which enzymes involved in the processing of glycoconjugates are housed in the Golgi apparatus in a sequential manner according to the order in which they act. One of the main interests in my laboratory is to further define the functional compartmentalization of the Golgi apparatus by studying glycosylation events in a variety of cell ty pes. The methodology employed consists of high resolution post-embedding immunocytochemistry using purified antibodies against glycosyltransferases, and colloidal gold techniques. Using highly purified well characterized polyclonal and monoclonal antibod ies, we are currently investigating the Golgi apparatus distribution of a terminally-acting galactosyltransferase which adds galactose residues on to penultimate galactose in an à1,3 linkage. Since we also have antibodies recognizing the galactosyltransfe rase which adds the penultimate galactose on to the growing oligosaccharide chain, we are now poised to examine the distribution within the Golgi apparatus of two sequentially acting glycosyltransferases. These studies should help to determine the extent of Golgi apparatus functional subcompartmentation with respect to glycosylation. In conjunction with these studies, we are also preparing serial thin sections through an entire Golgi apparatus cisternal stack to determine the precise distribution of a gly cosyltransferase within an entire Golgi apparatus. This work will address a current model developed to explain how endogenous Golgi apparatus proteins (such as glycosyltransferases) maintain their compartmental distribution within the Golgi apparatus. The model suggests that endogenous Golgi apparatus proteins must be sequestered away from the dilated rims of the cisternae, which are thought to pinch off from one cisternae carrying secretory material and fuse with the adjacent cisternae. By using serial s ections to examine the distribution of a glycosyltransferase throughout an entire Golgi apparatus cisternal stack, we can assess the validity of this model.
In addition to their role in the modification of oligosaccharide chains as they transit the Golgi apparatus, some glycosyltransferases have also been detected at the cell surface in various cell types. In particular, galactosyltransferase has been pos tulated to play an important role in such processes as cell migration on the extracellular matrix and initiation of fertilization. However, the results of some of these studies have recently been called into question with the revelation that polyclonal an tibodies generated against galactosyltransferase contained a subpopulation of antibody moieties recognizing carbohydrate epitopes of the enzyme. We are now using a series of well defined monoclonal antibodies shown to recognize only protein epitopes of ga lactosyltransferase, in conjunction with immunoelectron microscopy to reexamine the purported presence of galactosyltransferase at the sperm plasma membrane.
A second research program concerns using immunoelectron microscopic techniques in surgical pathology. We are taking advantage of our close departmental clinical association to examine the ultrastructural distribution of clinically relevant antigens in neoplasms, with the aim of contributing information towards diagnosis or prognosis. We have now succeeded in providing ultrastructural information concerning the localization of antibodies used in the diagnosis of melanoma and Hodgkin's disease. At the s ame time, we are investigating ways to improve the structural preservation of human biopsy specimens, as well as means whereby immunoelectron microscopy can be considered a routine diagnostic adjunct for the surgical pathologist.
Selected publications:
1. Taatjes DJ, Roth J: Selective loss of sialic acid from rat small intestinal epithelial cells during postnatal development: Demonstration with lectin-gold techniques. Eur J Cell Biol 53:255-266, 1990.
2. Taatjes DJ, Roth J: Glycosylation in intestinal epithelium. Int Rev Cytol 126:135-194, 1991.
3. Russo RN, Shaper NL, Taatjes DJ, Shaper JH: þ1,4-Galactosyltransferase: A short NH2-terminal fragment that includes the cytoplasmic and transmembrane domain is sufficient for Golgi retention. J Biol Chem 267:9241-9247, 1992.
4. Taatjes DJ, Roth J, Shaper NL, Shaper JH: Immunocytochemical localization of þ1,4 galactosyltransferase in epithelial cells from bovine tissues using monoclonal antibodies. Glycobiology 2:579-589, 1992.
5. Taatjes DJ, Arendash-Durand B, von Turkovich M, Trainer TD: HMB-45 antibody demonstrates melanosome-specificity by immunoelectron microscopy. Arch Pathol Lab Med, 117:264-268, 1993.