NEXT GENERATION SEQUENCING AND EXPERIMENTAL MYOLOGY: P.380The complexity of splicing pattern in human adult skeletal muscles: a key to understanding genotype-phenotype correlations

Abstract

Most multi-exonic genes undergo tissue specific alternative splicing events (ASEs). Similarly, ASEs are often dependent on developmental stage. The splicing regulation of specific transcripts seems to be part of a large and complex process causing multiple physical and functional consequences. For example, differential splicing can modulate protein-protein interactions and, similarly, can affect the protein length modifying its structural and functional properties. We performed a RNA-Sequencing experiment on 42 human biopsies collected from 12 anatomically different skeletal muscles of 11 individuals without any muscle disorders in order to map ASEs in adult human skeletal muscles. Some of the largest human genes have a high expression level in skeletal muscles. One example is the 364-exon TTN gene encoding titin, a giant protein with multiple functions in skeletal and cardiac muscles. Because of alternative splicing, several titin isoforms are expressed. With over 1 million potential splicing variants, TTN is virtually the most alternatively spliced human gene. We have identified a large number of these ASEs, providing the first RNA-Seq-based picture of TTN splicing pattern in adult human skeletal muscle. Moreover, by using PAC-BIO, a long-read sequencing technology, we mapped several ASEs along the some molecule. The same approach shows similar complex splicing patterns for other muscle transcripts and also reveals previously unreported exons in well-known muscle disease genes. A refinement of the expression profiling in different muscular tissues (heart and skeletal muscles) and/or different pathological and physiological states (e.g., fetal versus adult) would further improve our understanding of genotype-phenotype correlations.