CYTOSKELETAL PROTEIN EXPRESSION IN PLANARIANS

In freshwater planarians the existence of at least two major actin iso forms has been demonstrated. One isoform is expressed by differentiate d muscle cells and is different from vertebrate alpha-sarcomeric and a lpha-smooth actin. The other isoform is recognized by a specific anti warm-blooded vertebrate alpha-smooth muscle actin monoclonal antibody. This latter isoforms is expressed mainly in mesenchymal-like cells - generally called neoblasts - activated during regeneration and growth. To data planaria is the only invertebrate where the existence of an a ntigen related to alpha-smooth muscle actin has been demonstrated. Fur ther studies in this field may be important to define the phylogenetic position of Platyhelminthes.