Construction of the Ghrl^LCA acceptor and Ghrl:Cre-eGFP exchange alleles.

<p>(a) Schematic of the Ghrl:Cre-eGFP knock-in allele generated using recombinase mediated cassette exchange (RMCE). First, a floxed Ghrelin (Ghrl^LCA) allele was created by inserting a positive/negative selection cassette flanked by the Lox71 and Lox2272 modified lox sites into the ghrelin locus by homologous recombination. The Lox71 and Lox2272 sites allow for directional and irreversible Cre mediated recombination while suppressing intramolecular recombination. An exchange cassette vector containing the complimentary Lox66 and Lox2272 sites and a Cre-eGFP coding sequence spanning exons 2 and 3 (Ghrl:Cre-eGFP) was then created and inserted into the genome using RMCE. (b) Insertion of the Ghrl^LCA allele was confirmed by Southern blot using either ScaI digested (5′ recombination) or NdeI digested (3′ recombination) genomic DNA. (c) Correct exchange of the Ghrl:Cre-eGFP allele in clones that survived both positive and negative selection was confirmed by PCR analysis. All seven tested clones had correct allele exchange.