Smn1^tm1.1Cdid

A targeting vector was used to insert a 3 nucleotide mutation (gga-TTT) in exon 7 of Smn1, within an important splice enhancer element, and a floxed Neo cassette (in the opposite orientation to transcription) in intron 7. The mutation changes the exon splice enhancer into an exon splice silencer, thus greatly reducing the inclusion of exon 7 in transcripts, which results in producing Smn2-like transcripts. Cre mediated recombination deleted the neo cassette, which disrupted efficient transcription of Smn1. (J:176267, J:183080)