Splicing Isoforms Associated to TGFb-Induced Myofibroblast Activation

Myofibroblast differentiation is a key process in developmental biology and involved in numerous physiopathology. The gene expression program orchestrating fibroblast to myofibroblast differentiation, as well as its recapitulation by TGF{beta} stimulation in vitro, is relatively well characterized. Intriguingly, it is known that the splicing isoform EDA+FN1 is a marker and driver of myofibroblast differentiation, but the alternative splicing landscape of myofibroblast is unknown. Here, we performed a high-throughput transcriptomic approach by RNA-Seq in a primary skin fibroblast line and uncover more than 250 splicing isoforms associated with TGF{beta}-induced myofibroblasts using two different bioinformatic pipelines. This splicing profile highlights a distinct layer of regulation when compared to the global gene expression profile of myofibroblasts. A 5 alternative splicing event (ASE) signature [ACTN1-19A/19B; COL5A1-64A/64B; COL6A3 exon 4; FLNA exon 30 and TPM1-6a/6b] was further validated by ddPCR and AS-PCR and retrieved in publicly available RNA-Seq datasets describing other TGF{beta}-stimulated lung and skin fibroblasts. Surprisingly, TGF{beta} does not induce an EDA+FN1 splicing shift, although it stimulates global fibronectin expression. Thus, we conclude that the 5 ASEs signature may be used as putative universal myofibroblast markers and be of functional significance to myofibroblast formation and biology.