Regulated splicing of the fibronectin EDA exon is essential for proper skin wound healing and normal lifespan

TLDR

Fibronectins are multifunctional glycoproteins whose primary transcript undergoes alternative splicing, producing up to 20 variants, yet the specific roles of these isoforms—particularly the extra domain A (EDA) exon regulated during development and aging—remain poorly understood. The authors aimed to determine the in vivo function of EDA exon splicing by generating mice lacking regulated splicing of this exon. They engineered constitutive inclusion by optimizing splice sites and achieved complete exclusion via CRE‑loxP–mediated deletion of the exon. Although both mutant strains were viable, mice lacking EDA exhibited impaired skin wound healing, mice with constitutive inclusion had markedly reduced fibronectin levels, and both groups had shortened lifespans, underscoring the necessity of EDA splicing for long‑term biological maintenance.

Abstract

Fibronectins (FNs) are multifunctional high molecular weight glycoproteins present in the blood plasma and in the ECMs of tissues. The FN primary transcript undergoes alternative splicing in three regions generating up to 20 main different variants in humans. However, the precise role of the FN isoforms is poorly understood. One of the alternatively spliced exons is the extra domain A (EDA) or extra type III homology that is regulated spatially and temporally during development and aging. To study its in vivo function, we generated mice devoid of EDA exon-regulated splicing. Constitutive exon inclusion was obtained by optimizing the splice sites, whereas complete exclusion was obtained after in vivo CRE-loxP-mediated deletion of the exon. Homozygous mouse strains with complete exclusion or inclusion of the EDA exon were viable and developed normally, indicating that the alternative splicing at the EDA exon is not necessary during embryonic development. Conversely, mice without the EDA exon in the FN protein displayed abnormal skin wound healing, whereas mice having constitutive inclusion of the EDA exon showed a major decrease in the FN levels in all tissues. Moreover, both mutant mouse strains have a significantly shorter lifespan than the control mice, suggesting that EDA splicing regulation is necessary for efficient long-term maintenance of biological functions.