Clinical and molecular delineation of classical-like Ehlers-Danlos syndrome through a comprehensive next-generation sequencing-based screening system.

Classical-like Ehlers-Danlos syndrome (clEDS) is an autosomal recessive disorder caused by complete absence of tenascin-X resulting from biallelic variation in TNXB. Thus far, 50 patients from 43 families with biallelic TNXB variants have been identified. Accurate detection of TNXB variants is challenging because of the presence of the pseudogene TNXA, which can undergo non-allelic homologous recombination. Therefore, we designed a genetic screening system that is performed using similar operations to other next-generation sequencing (NGS) panel analyses and can be applied to accurately detect TNXB variants and the recombination of TNXA-derived sequences into TNXB. Using this system, we identified biallelic TNXB variants in nine unrelated clEDS patients. TNXA-derived variations were found in >75% of the current cohort, comparable to previous reports. The current cohort generally exhibited similar clinical features to patients in previous reports, but had a higher frequency of gastrointestinal complications (e.g., perforation, diverticulitis, gastrointestinal bleeding, intestinal obstruction, rectal/anal prolapse, and gallstones). This report is the first to apply an NGS-based screening for TNXB variants and represents the third largest cohort of clEDS, highlighting the importance of increasing awareness of the risk of gastrointestinal complications.

Case report: further delineation of AEBP1-related Ehlers-Danlos Syndrome (classical-like EDS type 2) in an additional patient and comprehensive clinical and molecular review of the literature.

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.

Comprehensive genetic screening for vascular Ehlers-Danlos syndrome through an amplification-based next-generation sequencing system.

Vascular Ehlers-Danlos syndrome (vEDS) is a hereditary connective tissue disorder (HCTD) characterized by arterial dissection/aneurysm/rupture, sigmoid colon rupture, or uterine rupture. Diagnosis is confirmed by detecting heterozygous variants in COL3A1. This is the largest Asian case series and the first to apply an amplification-based next-generation sequencing through custom panels of causative genes for HCTDs, including a specific method of evaluating copy number variations. Among 429 patients with suspected HCTDs analyzed, 101 were suspected to have vEDS, and 33 of them (32.4%) were found to have COL3A1 variants. Two patients with a clinical diagnosis of Loeys-Dietz syndrome and/or familial thoracic aortic aneurysm and dissection were also found to have COL3A1 variants. Twenty cases (57.1%) had missense variants leading to glycine (Gly) substitutions in the triple helical domain, one (2.9%) had a missense variant leading to non-Gly substitution in this domain, eight (22.9%) had splice site alterations, three (8.6%) had nonsense variants, two (5.7%) had in-frame deletions, and one (2.9%) had a multi-exon deletion, including two deceased patients analyzed with formalin-fixed and paraffin-embedded samples. This is a clinically useful system to detect a wide spectrum of variants from various types of samples.

Detection of DNA Damage-Induced DSBs by the Contour-Clamped Homogeneous Electric Field (CHEF) System in Mammalian Cells.

Double-strand breaks (DSBs) and their repair mechanisms are essential for normal cell life. However, quantitative analysis of DSBs on mammalian whole chromosomes remains difficult. The method described here enables the quantitative detection of mammalian chromosomal DSBs by pulsed-field gel electrophoresis (PFGE) using a contour-clamped homogeneous electric field (CHEF). We illustrate this method by measuring DNA damage-induced DSBs in mammalian cells. The electrophoresis conditions presented here enabled the visualization of fragmented DNA (several mega-base pairs down to 500 kbp) as a single band. Using this protocol, about 10-45 samples can be analyzed on a single gel, depending on the direction of electrophoresis.