The BAC clone RP23-288P18 was modified with recombineering techniques so that an icreERT2 is driven by the Amigo2 promotor. The Amigo2 ATG was replaced with the icre ATG preceded with a perfect KOZAK sequence. At the 3â end of the icreERT2 cassette, a synthetic bovine growth hormone (BGH) polyadenylation signal was added after the STOP codon. For the selection of recombined BACs, a flippase-site flanked neomycin resistance gene was incorporated into the targeting fragment following the icreERT2 cassette. Recombined BACs without the neo marker were linearized and purified and microinjected into pronuclei of B6SJLF1 mouse oocytes. Six independent founder mice resulted. Two lines showing adult expression of icreERT2 in CA2 were established. This is line 2 of two lines. This line showed expression of Cre in CA2 as well as sparse expression in the dentate gyrus, fasciola cinerea and hypothalamus.