BAC clone RP23-131B16 containing a mouse Chromosome 17 piRNA cluster was modified to express FRT-PGK-gb2-neo-FRT and EGFP (inserted antisense) from the 3' end of the cluster downstream of a central bi-directional promoter. Lines 13 and 37 were generated. Line 37 was generated and does not exhibit EGFP expression. (J:189061)