A retrotransposon highly homologous to murine early transposon (ETn) endogenous retrovirus (ERV) 3 (ETnERV3) inserted 12 kb upstream of Ptf1a resulting in over-expression. The transposon insertion also results in the over-expression of Gm13344 and Gm13336. (J:195133, J:195196, J:195197)