Fig. 4

Alternative splicing of contractile protein gene tropomyosin. Tropomyosin undergoes cell type-specific alternative splicing and regulates muscle contraction. Exons 2 and 3 are mutually exclusive, and transcript with exon 3 is skeletal muscle specific. Also, the inclusion of SM exon is skeletal muscle specific, while NM exon is included in non-muscle cells. The inclusion of exons 9a and 9b of tropomyosin transcript is unique for isoforms of the skeletal muscle. Cell type-specific inclusion of exons alters the affinity with and polymerization of actin filaments, contributing to altered muscle contraction