Rr468^tm1.1Df

A 710 bp sequence, containing an intronic enhancer downstream of Thrb B2 isoform (ENSMUST00000022304)-specific alternative exon 1, was deleted from intron 4 (B2 intron 1). Initially, for selection purposes, a self-excising ACN cassette (loxP site + testis-specific ACE promoter driven cre gene + neomycin resistance gene cassette + loxP site) was inserted into intron 4. Subsequently, this cassette was self-deleted during breeding of chimeras, leaving only a single loxP site remaining at the boundary upstream of the enhancer (J:335506)