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Molecular mechanisms of classical Ehlers-Danlos syndrome (EDS).

ABSTRACT: Classical Ehlers-Danlos syndrome (EDS) is a heritable disorder characterized by joint hypermobility, skin hyperextensibility, and abnormal wound healing. The majority of affected individuals have alterations in 1 of the 2 type V collagen genes, COL5A1 and COL5A2. The most common mechanism is COL5A1 haploinsufficiency due to instability of the transcript of one allele. In dermal fibroblasts from our population of 76 individuals with clinical features of classical EDS, there were 21 (29.5%) with decreased expression of one COL5A1 allele, consistent with published estimates of the frequency of null alleles. We identified the causative mutation in nine of these cell strains (mutations for seven others had been previously described), and found two nonsense mutations, five splice mutations, and two insertion/deletions. The same type of genomic change at splice sites can have different effects at the RNA level and the outcome could not be predicted from the primary genomic DNA alteration.

SUBMITTER: Mitchell AL

PROVIDER: S-EPMC3827857 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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Molecular mechanisms of classical Ehlers-Danlos syndrome (EDS).

Mitchell Anna L AL Schwarze Ulrike U Jennings Jessica F JF Byers Peter H PH

Human mutation 20090601 6

Classical Ehlers-Danlos syndrome (EDS) is a heritable disorder characterized by joint hypermobility, skin hyperextensibility, and abnormal wound healing. The majority of affected individuals have alterations in 1 of the 2 type V collagen genes, COL5A1 and COL5A2. The most common mechanism is COL5A1 haploinsufficiency due to instability of the transcript of one allele. In dermal fibroblasts from our population of 76 individuals with clinical features of classical EDS, there were 21 (29.5%) with d ...[more]

PMID: 19370768

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Project description:Ehlers-Danlos syndromes (EDS) represent a group of rare genetic disorders affecting connective tissues. Globally, approximately 1.5 million individuals suffer from EDS, with 10,000 reported cases in Canada alone. Understanding the histological properties of collagen in EDS has been challenging, but advanced techniques like atomic force microscopy (AFM) have opened up new possibilities for label-free skin imaging. This approach, which explores Type I collagen fibrils at the nanoscale, could potentially enhance EDS diagnosis and our knowledge of collagen type I-related connective tissue disorders. In the current study, we have employed AFM to examine ex-vivo skin biopsies from four individuals: one with classical EDS (cEDS), one with hypermobile EDS (hEDS), one with hEDS and Scleroderma (hEDS-Scleroderma), and one healthy control. Picrosirius red (PS) staining was used to highlight collagen differences in the samples. For each case, 14 images and 1400 force curves were obtained, with seven images and 700 force curves representing healthy collagen (PS-induced red staining) and the rest showcasing disrupted collagen (yellow staining). The results showed that PS staining was uniform throughout the control section, while cEDS and hEDS displayed localized areas of yellow staining. In the case of hEDS-Scleroderma, the yellow staining was widespread throughout the section. AFM images revealed irregular collagen fibrils in the disrupted, yellow-stained areas, contrasting with aligned and well-registered collagen fibrils in healthy, red-stained regions. Additionally, the study assessed the ability of non-AFM specialists to differentiate between healthy and disrupted collagen in AFM images, yielding substantial agreement among raters according to Fleiss's and Cohen's kappa scores (0.96 and 0.79±0.1, respectively). Biomechanical analysis revealed that normal healthy collagen exhibited a predominant population at 2.5 GPa. In contrast, EDS-affected collagen displayed subpopulations with lower compressive elastic modulus, indicating weaker collagen fibrils in EDS patients. Although these findings pertain to a limited number of cases, they offer valuable insights into the nanoscale collagen structure and biomechanics in individuals with EDS. Over time, these insights could be developed into specific biomarkers for the condition, improving diagnosis and treatment for EDS and related connective tissue disorders.

Project description:The Ehlers-Danlos Syndromes (EDS), a group of hereditary connective tissue disorders, were classified into 13 subtypes in the 2017 International Classification. Recently, a new subtype of EDS called classical-like EDS type 2 (clEDS2), which is caused by biallelic variants in the adipocyte enhancer binding protein 1 (AEBP1) gene, was identified. We describe the 11th patient (9th family) with clEDS2, who was complicated by a critical vascular event (superior mesenteric artery aneurysm and rupture). A next-generation sequencing panel-based analysis revealed compound heterozygous variants in AEBP1: NM_001129.5:c.[2296G>T]; [2383dup], p.[(Glu766*)]; [(Glu795Glyfs*3)]. Light microscopic analyses showed increased interfibrillar spaces in the reticular dermis, a disorganized arrangement of collagen fibers, and decreased collagen content. An electron microscopic analysis showed the presence of collagen fibrils with irregular contours (flower-like appearance) and small collagen fibrils. A biochemical analysis showed reduced secretion of type I and type III procollagen. Clinical and molecular features of the current patient and all previously reported patients were reviewed comprehensively. Manifestations noted in most cases (>80%) included skin features (hyperextensibility, atrophic scars, easy bruising, excessive skin/skin folding, delayed wound healing, translucency, piezogenic papules), skeletal features (generalized joint hypermobility, dislocations/subluxations, pes planus), dental abnormalities, and neuromuscular abnormalities. Critical complications, each occurring in a single case, included superior mesenteric artery multiple aneurysm and rupture, aortic root dilation requiring surgery, and bowel rupture. Most AEBP1 variants were predicted or experimentally confirmed to lead to nonsense-mediated mRNA decay, whereas one variant resulted in a protein that was retained intracellularly and not secreted. Clinical, molecular, pathological, and biochemical features of the current patient, as well as a review of all previously reported patients, suggest the importance of the aortic carboxypeptidase-like protein encoded by AEBP1 in collagen fibrillogenesis.

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Molecular mechanisms of classical Ehlers-Danlos syndrome (EDS).

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Molecular mechanisms of classical Ehlers-Danlos syndrome (EDS).

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