The use of lectins as markers for differentiated secretory cells in planarians

Freshwater planarians have reemerged as excellent models to investigate mechanisms underlying regeneration. The introduction of molecular tools has facilitated the study of planarians, but cell- and tissue-specific markers are still needed to examine differentiation of most cell types. Here we report the utility of fluorescent lectin-conjugates to label tissues in the planarian Schmidtea mediterranea. We show that 16 lectin-conjugates stain planarian cells or tissues; 13 primarily label the secretory cells, their cytoplasmic projections, and terminal pores. Thus, we examined regeneration of the secretory system using lectin markers and functionally characterized two genes expressed in the secretory cells: marginal adhesive gland-1 (mag-1) and Smed-reticulocalbin1 (Smed-rcn1). RNAi knockdown of these genes caused a dramatic reduction of secretory cell lectin staining, suggesting a role for mag-1 and Smed-rcn1 in secretory cell differentiation. Our results provide new insights into planarian secretory system regeneration and add new markers for labeling several planarian tissues.