An active Ac-like transposable element in teleost fish

The i(4)/i(4) genotype of the medakafish, Oryzias latipes, exhibits a quasi albino phenotype due to insertion of a novel transposable element, Tol2, i nto the tyrosinase gene. Tol2 is 4681 bp in length, has short inverted term inal repeats, and contains four ORFs with the potential to encode a transpo sase protein. Excision activity of the element has been detected by PCR ana lysis. Genomic Southern of the Tol2 element revealed that about 20 copies a re present in the diploid genome. Dot-matrix comparisons of amino acid sequ ences of ORFs show relatively high similarity with transposases from Ac of maize, hobo of Drosophila, and Tam3 of snapdragon. which are all active tra nsposable elements. Tol2 is thus concluded to be an active Ac-like transpos able element probably encoding a transposase protein. It should therefore f ind application as a unique material for establishing a gene tagging system in fish.