A cDNA sequence encoding the full mouse Ighmbp2 was placed under the control of a modified 5.87 kb mouse genomic fragment containing the Ttn promoter, non-coding Ttn exon 1, intron 1, and 30 base pairs of Ttn exon 2 lacking the start codon. Transgene expression was limited to the heart and skeletal muscles as confirmed by RT-PCR expression using Ighmbp2 exon 1.