Mutation frequency and type during ageing in mouse seminiferous tubules

Mutations arise in the germline by errors of replication, recombination and repair, and the movement of transposable elements. Transgenic mice bearing reporter genes such as lacZ have proven useful for measurements of spontan eous and induced mutation frequencies, as well as studies of the effects of ageing. In this study, testicular DNA from lacZ transgenic mice was examin ed for age-related effects on mutation frequency and type. The recovered tr ansgene was tested for simple substitutions and rearrangements including tr ansposition of endogenous mobile elements. There was no evidence for either an age-related accumulation of mutations, or for the insertion of retrotra nsposons into the lacZ reporter gene in the testis. We conclude that the fr equency of retrotransposition of several mouse mobile elements into the lac Z reporter gene is less than 3.73 x 10(-8). This is significantly less than the known frequency of similar to 7% of all spontaneous mutations in the m ouse being due to retrotransposition of these elements. (C) 2001 Elsevier S cience Ireland Ltd. All rights reserved.