The effects of lithium chloride on pattern formation in Tetrahymena thermophila

Lithium ions have long been known to exert dramatic effects on the specification of cell fates in multicellular systems. We have analyzed the effects of Li+ on intracellular patterning in a complex unicellular organism, the ciliate Tetrahymena thermophila. LiCl does not affect the locations of major structural landmarks in the cortical region of wild-type cells and does not modify the phenotype of pattern-mutant cells. However, in all strains studied LiCl differentially affects early stages of oral development. It initially triggers a slow regression of oral primordia, which is followed by an excessive proliferation of basal bodies that leads to a hypertrophy of the ciliature of the cell's feeding organelle. This hypertrophy mimics the effects of the membranellar-pattern-D mutation, the phenotype of which is enhanced in the presence of LiCl. These effects were partially reversed by myo-inositol; however, neomycin failed to mimic the effects of LiCl. Thus, although lithium ions have major cellular effects on Tetrahymena, they do not influence the specification of the body plan in a manner analogous to that observed in multicellular organisms and may work in part through mechanisms other than the now-classical inositol-phosphate cycle.