A 7.5kb genomic fragment containing the Gremlin cis regulatory region was digested from BAC RP23-113H17 and a loxP site was inserted upstream and an FRT site flanked neomycin resistance gene cassette and a second loxP cassette downstream of the enhancer (chr2:113640843-113641280, Build 38). After homologous recombination, cre-mediated recombination removed the enhancer/silencer and selection cassette. The enhancer regulates Grem1 but is located in intron 13 of Fmn1. (J:207959)