High-frequency excision of transposable element Tc1 in the nematode caenorhabditis elegans is limited to somatic cells

Tc1 transposable elements in the nematode Caenorhabditis elegans undergo excision at high frequency. We show here that this excision occurs primarily or entirely in the somatic tissues of the organism. Absence of germ-line excision is demonstrated by showing that Tc1 elements are genetically stable; elements at particular genomic sites, as well as the overall number of elements in the genome, were stably maintained during a year of continuous, nonselective propagation. Somatic excision is demonstrated by showing that empty Tc1 sites arise during a single generation of growth of a synchronous population and are not inherited by the next generation. These results suggest that excision of Tc1 elements is under the control of tissue-specific factors.