Truncation variants in the gene TTN encoding titin are the most common cause of familial dilated cardiomyopathy (DCM), with both haploinsufficiency and “poison peptide” implicated as contributory mechanisms of disease. In this issue of the JCI, Kim et al. identify a highly conserved enhancer element approximately 500 bp downstream of the transcriptional start site of TTN in intron 1, which they demonstrated to be critical in regulating TTN expression. This work helps to further clarify the relative role of haploinsufficiency in TTN-related DCM and provides a potential target for therapies aimed at treating TTN-related DCM.
