Abstract
The identity of individual cell types in a multicellular organism appears to be continuously maintained through active processes but is not irreversible. Changes in the identity of individual cell types can be brought about through ectopic mis-expression of regulatory factors, but in a number of cases also occurs in normal development. I will review here these natural cellular reprogramming processes occurring in the invertebrate model organisms Caenorhabditis elegans and Drosophila melanogaster. Furthermore, I will discuss the issue of why only certain cell types can be converted during induced reprogramming processes evoked by ectopic expression of regulatory factors and how recent work in model systems have shown that this cellular context-dependency can be manipulated.
