Reply to Shoji and Katsuma.

Our paper reports a novel strategy for the artificial introduction of DNA methylation in mouse gonocytes. The manuscript presents data showing that the concomitant expression of sense and anti-sense of EGFP transgenes in embryonic male germ cells induces gene silencing via the piRNA pathway and that the expression of an antisense Dnmt3L transgene induces silencing of the endogenous Dnmt3L gene.