The question of trans-differentiation or how a committed cell can change its identity has important implications ranging from organ regeneration to cancer. The lineage of the nematode C. elegans has identified a few cells that change their fates as the worm develops (1), and appear to be examples of trans-differentiation in vivo during wild type development. One such trans-differentiation event appears to be the transformation of Y from an epithelial cell into a motor neuron called PDA. Y is an epithelial cell that is part of the rectum in young larvae; it has the hallmarks of a polarised epithelial cell, including the presence of tight junctions (2, 3). It subsequently detaches from the rectum, moves anteriorly and becomes PDA, a motor-neuron which has a characteristic axonal projection (4, 5). Accordingly, we have determined that expression of epithelial genes - such as
ajm-1, a component of the Ce junction - is fading or lost in Y during its migration and is definitely lost in PDA. We have been characterising the steps involved in the Y-to-PDA trans-differentiation with respect to the development of the somatic gonad, and we have examined the expression of cell fate markers in both cells. We also will analyse the changes involved for these cells at the ultra-structural level, in collaboration with Dave Hall. In addition, we are determining the importance of cell to cell interactions for the Y to PDA transformation by cell ablation studies. Finally, as we are interested in understanding the molecular events underlying the Y-to-PDA cell fate transformation, we are developing a set of useful molecular markers for forward and reverse genetic screens. We will report on our progress at the meeting. 1. J. E. Sulston, H. R. Horvitz, Dev Biol 56, 110-56 (Mar, 1977). 2.
http://www.wormatlas.org. 3. J. G. White, in The Nematode Caenorhabditis elegans W. B. Wood, Ed. (Cold Spring Harbor Laboratory Press, 1988) pp. 81-122. 4. J. G. White, E. Southgate, J. N. Thomson, S. Brenner, Phil. Trans. Royal Soc. London Series B, Biol Scien. 314, 1-340 (1986). 5. D. H. Hall, R. L. Russell, Journal of Neuroscience 11, 1-22 (1991).