This allele is derived from Samd8tm2Kwi or Samd8tm2.1Kwi by Cre recombinase-mediated excision of the loxP-flanked segment that contained the endogenous exon 5 through the 3' untranslated region. It contains a single loxP site upstream of a second copy of exon 5, which is followed in-frame by the EGFP coding sequence. Processing of the primary transcript results in splicing of exon 4 to the downstream copy of exon 5, leading to production of a SAMD8/EGFP fusion protein lacking the catalytic domain encoded by exon 6.