The Tc1/mariner Transposon Family

In many animals the main cause of mutations is transposon insertion. This is true, e.g., for strains of the nematode species C. elegans. It is not true for humans, where only relatively few cases have been reported of germline mutations caused by new transposon insertions, and where base-pair substitutions, frame-shifts, and errors in replication of nucleotide repeats are more common (Dombroski et al. 1991, 1993; Caskey et al. 1992). Caenorhabditis elegans is a free-living nematode that can be found in the soil anywhere in the world. All C. elegans strains analyzed to date contain several copies of the transposable element Tc1 (Transposon C. elegans number 1) (Emmons et al. 1980, 1983; Liao et al. 1983). Insertion of Tc1 is the main cause of gene inactivation in the strain Bergerac (Moerman and Waterston 1984; Eide and Anderson 1985). Since discovery of the Tc1 element, related elements have been found in the same species, and elements discovered in other species were also found to be homologous to Tc1. The best-described example is the mariner element, discovered in Drosophila mauritiana (Jacobson et al. 1986; Hartl 1989). At present it seems that members of the Tc1/mariner transposon family are found in virtually all animal phyla: vertebrates (Henikoff 1992; Heierhorst et al. 1992; Goodier and Davidson 1994; Radice et al. 1994), nematodes (Collins et al. 1989; Abad et al. 1991; Prasad et al. 1991; Sedensky et al. 1994), arthropods (Robertson 1993, 1994; Harris et al. 1988; Henikoff and Plasterk 1988; Brierley and Potter 1985; Hartl 1989; Harris et al. 1990; Garcia-Fernandez et al. 1993; Robertson et al. 1992; Caizzi et al. 1993; Franz and Savakis 1991; Bigot et al. 1994; Franz et al. 1994; Brezinsky et al. 1990), planarians (Capy et al. 1994), ciliates (Tausta and Klobutcher 1989; Williams et al. 1993), and even fungi (Daboussi et al. 1992). A recent alignment of the elements is in Robertson (1995).