Background:

In muscle sarcomeres the giant protein titin is a crucial element indispensable for proper myofibril assembly and function. Titin is the largest known protein in human and encoded by the TTN gene spanning 363 exons. Mutations in this giant protein are linked to cardiomyopathies; however, the enormous size of titin has so far limited mechanistic insight. Whereas loss-of-function studies in cell culture are commonly used in mechanistic studies, such approaches are difficult to realize with titin.

Aim:

We assumed that antisense-induced exon-skipping is an elegant way to study the function of titin domains in myocytes. In a first attempt, we aimed to switch the cardiac-specific splicing of titin exon 49 to a skeletal muscle-specific skipping of exon 49.

Methods:

We adapted the method of antisense-mediated exon skipping for the titin pre-mRNA message. We used a 6-fluorescein amidite (6-FAM) labeled 2'-O-methyl-modified phosphorothioate antisense oligonucleotide (AON) targeting the cardiac-only titin exon 49 in the cardiac cell line, HL-1.

Results:

One day after transfection the 6-FAM labeled AON targeting exon 49 could be visualized in the cytoplasm and nucleus of HL-1 cells. Analyses on the mRNA level 48 hours post transfection demonstrated that we were able to induce the skipping of titin exon 49, thereby promoting a skeletal muscle-specific splicing in this TTN region.

Conclusion:

Antisense-mediated exon skipping is a suitable method for altering titin splicing. We now have a tool at hand to skip certain domains in titin and pursue loss-of-function studies to mimic human titin mutations linked to heart disease.