Date Published: February 4, 2019
Publisher: Public Library of Science
Author(s): Nicola Chiarelli, Giulia Carini, Nicoletta Zoppi, Marco Ritelli, Marina Colombi, Robert W. Dettman.
Classical Ehlers-Danlos syndrome (cEDS) is a dominant inherited connective tissue disorder mainly caused by mutations in the COL5A1 and COL5A2 genes encoding type V collagen (COLLV), which is a fibrillar COLL widely distributed in a variety of connective tissues. cEDS patients suffer from skin hyperextensibility, abnormal wound healing/atrophic scars, and joint hypermobility. Most of the causative variants result in a non-functional COL5A1 allele and COLLV haploinsufficiency, whilst COL5A2 mutations affect its structural integrity. To shed light into disease mechanisms involved in cEDS, we performed gene expression profiling in skin fibroblasts from four patients harboring haploinsufficient and structural mutations in both disease genes. Transcriptome profiling revealed significant changes in the expression levels of different extracellular matrix (ECM)-related genes, such as SPP1, POSTN, EDIL3, IGFBP2, and C3, which encode both matricellular and soluble proteins that are mainly involved in cell proliferation and migration, and cutaneous wound healing. These gene expression changes are consistent with our previous protein findings on in vitro fibroblasts from other cEDS patients, which exhibited reduced migration and poor wound repair owing to COLLV disorganization, altered deposition of fibronectin into ECM, and an abnormal integrin pattern. Microarray analysis also indicated the decreased expression of DNAJB7, VIPAS39, CCPG1, ATG10, SVIP, which encode molecular chaperones facilitating protein folding, enzymes regulating post-Golgi COLLs processing, and proteins acting as cargo receptors required for endoplasmic reticulum (ER) proteostasis and implicated in the autophagy process. Patients’ cells also showed altered mRNA levels of many cell cycle regulating genes including CCNE2, KIF4A, MKI67, DTL, and DDIAS. Protein studies showed that aberrant COLLV expression causes the disassembly of itself and many structural ECM constituents including COLLI, COLLIII, fibronectin, and fibrillins. Our findings provide the first molecular evidence of significant gene expression changes in cEDS skin fibroblasts highlighting that defective ECM remodeling, ER homeostasis and autophagy might play a role in the pathogenesis of this connective tissue disorder.
Classical Ehlers-Danlos syndrome (cEDS) (MIM #130000) is an autosomal dominant connective tissue disorder with an estimated prevalence of 1:20,000 and is mainly characterized by abnormal skin texture and joint hypermobility (JHM). According to the 2017 EDS nosology , skin hyperextensibility plus atrophic scarring (criterion 1) and generalized JHM (criterion 2) are major criteria for cEDS, whereas easy bruising, soft and doughy skin, skin fragility, molluscoid pseudotumors, subcutaneous spheroids, hernia, epicanthal folds, and JHM complications, such as sprains, luxation/subluxation, pain, and family history of a first-degree relative are minor criteria. Minimal criteria suggestive for cEDS are major criterion 1 plus either major criterion 2 and/or at least three minor criteria. Confirmatory molecular testing is mandatory to reach a final diagnosis [1–3].
The present study reports the first molecular evidence of significant gene expression changes in dermal fibroblasts from cEDS patients. Although the reduction in the amount of COLLV is central to the pathogenesis of cEDS [26,27], so far, the molecular mechanisms contributing to the pathophysiology of the disease have never been investigated in-depth. Even if we recognize the limited number of analyzed samples and that findings should be confirmed in a larger cohort of patients, our results provide intriguing insights into dysregulated gene expression pattern and related biological processes that likely contribute to the molecular pathology of cEDS. We specifically focused on different candidate genes mainly involved in ECM remodeling, wound healing/inflammation, ER homeostasis/autophagy, and associated with cell cycle regulation (Fig 5).