Smarcb1^tm2Sho

A loxP-flanked neomycin selection cassette was inserted into intron 1 and a single loxP site in the same orientation was inserted 0.8 kb upstream of exon 1. The neomycin selection cassette was removed by transient Cre expression in ES cells, leaving loxP sites flanking exon 1 in the final allele. Upon Cre-mediated recombination, exon 1 and flanking sequences are deleted. (J:80224)