REGENERATION OF VERTEBRATE SENSORY RECEPTOR-CELLS - FINAL GENERAL DISCUSSION

Final general discussion Future directions Rubel: What I want to do first in this final discussion is to ask the cell biologists here to suggest where this field should go. Watt: I am working on epidermal stem cells and I am therefore particularly interested in the progenitor cell question. If I were working in this field I would be going in the direction that Anne Calof has chosen, trying to develop cell culture models. It's not realistic to attempt to produce a whole sensory organ in culture, but it might be possible to grow cells that retain some useful characteristics, such as the ability to generate differentiated progeny. So firstly I would like to see some more cell culture work. Secondly, the question of cell type-specific markers has come up frequently in the symposium. Many antibodies to potential markers are available and can be obtained either as gifts from the labs that developed then, or from commercial suppliers. There are monospecific antibodies to individual keratins, for example, and the tissue distributions of most keratins are quite well understood. I am struck by the importance of cellular interactions with basement membrane in these sensory organs. The last three years have seen a huge increase in our knowledge of integrin receptors for extracellular matrix molecules (reviewed by Hynes 1987. Ruoslahti & Pierschbacher 1987, Hemler 1990) and their functions. Again, monoclonal antibodies specific for individual subunits are available. In my field, people were using lectins to look for different cell subpopulations about 10 years ago (Watt 1983). This approach is not so popular these days, partly because identifying the molecular markers detected by lectins can be a problem: one lectin may bind to several different glycoproteins on the cell surface. Nevertheless, lectins provide a well-established way of picking out different subpopulations of cells. So there are two approaches, cell culture models and well-defined cell markers, that one would be looking for in sensory epithelium research during the next 2- 3 years. Potten: I can't add very much to that, other than to emphasize the value of the use of various cell markers, particularly at an individual cell level within the various sensory organs. Papers presented here have shown that cells in the various structures studied generally show keratin 19; but does every single cell within the structure show it? And, if there are some cells that don't, what other markers might they possess? I would also reiterate the value of the use of cell culture .techniques. I would also suggest that it will be advantageous to develop and use a much broader range of markers.