Biallelic mutations in Tenascin-X cause classical-like Ehlers-Danlos syndrome with slowly progressive muscular weakness

Post-traumatic stress and joint hypermobility in children and adolescents of Nepal after exposure to an earthquake

A substantial body of literature has traditionally addressed the connection between the exposure to catastrophic events and the development of Post-Traumatic Stress disorder (PTSD), especially in the vulnerable stratum of children and adolescents. However, little is known about their biological predisposing factors, and further research is needed, especially in the context of the recent earthquakes in Turkey and Syria. The data of this study was collected 4 months after the 2015 earthquakes in Nepal, with the objective of providing new evidence to the field and documenting the role of a new potential predisposing factor: the Joint Hypermobility Syndrome (JHS). 941 subjects from three different regions of the country, aged 8-18 years, were assessed in a school-based cross-sectional investigation. PTSD, as the main response variable, was assessed using the Child PTSD Symptom Scale (CPSS) questionnaire and analysed considering three sub-dimensions: the severity of symptoms, the severity of impairment, and both taken together. JHS was assessed using the Screening Questionnaire to detect Hypermobility (SQ-CH) questionnaire. The severity of symptoms was strongly predicted by the distance to the epicentre. Females showed more severe symptomatology, but a lower perturbation in the daily functioning. Younger children reported a greater functional impairment. JHS group showed more severe PTSD than non-JHS group. We observed variability in the severity of PTSD according to previously known risk factors such as the distance to the epicentre, sex, and age. We also found an association between PTSD and JHS, which is discussed in reference to the neuroconnective endophenotype. It might be useful to consider the role of each variable when planning a mass intervention after a disaster.

Tenascin-X Deficiency Causing Classical-Like Ehlers-Danlos Syndrome Type 1 in Humans is a Significant Risk Factor of Gastrointestinal and Tracheal Ruptures

INTRODUCTION

Classical-like Ehlers-Danlos syndrome type 1 (clEDS1) is a very rare form of Ehlers-Danlos syndrome caused by tenascin-X deficiency, with only 56 individuals reported in medical literature. Tenascin-X is an extracellular matrix protein needed for collagen stability. Previous publications propose that individuals with clEDS1 might be at risk of gastrointestinal (GI) tract perforations and/or tracheal ruptures. The aim of this study was to characterize complications resulting from perforations of the GI tract and/or tracheal rupture in an international case series of individuals with clEDS1 due to disease-related tissue fragility.

METHODS

This case series includes individuals with confirmed clEDS1 and GI perforations and/or tracheal ruptures from participating centers. Researchers who previously reported such individuals were contacted for additional information. A retrospective assessment of clinical features was performed.

RESULTS

Fifteen individuals were included. Ten had spontaneous GI perforations, 7 of whom had multiple GI perforations. Almost all had severe diverticulosis. Three individuals experienced iatrogenic tracheal ruptures.

DISCUSSION

Severe GI complications, such as perforation, and tracheal rupture were observed in a substantial number of individuals with clEDS1. As these features seem significantly more common in clEDS1 than in the average population, we advise vigilance during intubation and GI endoscopic interventions of individuals with clEDS1. Routine referrals to clinical geneticists are recommended for patients with symptoms indicative of clEDS1, especially with unexplained GI perforations and connective tissue symptoms. Our findings offer valuable insights for the clinical management of clEDS1 and underscore the importance of specialized care, providing a foundation for improved clinical guidelines and preventive strategies.

The coordinated activities of collagen VI and XII in maintenance of tissue structure, function and repair: evidence for a physical interaction

Collagen VI and collagen XII are structurally complex collagens of the extracellular matrix (ECM). Like all collagens, type VI and XII both possess triple-helical components that facilitate participation in the ECM network, but collagen VI and XII are distinct from the more abundant fibrillar collagens in that they also possess arrays of structurally globular modules with the capacity to propagate signaling to attached cells. Cell attachment to collagen VI and XII is known to regulate protective, proliferative or developmental processes through a variety of mechanisms, but a growing body of genetic and biochemical evidence suggests that at least some of these phenomena may be potentiated through mechanisms that require coordinated interaction between the two collagens. For example, genetic studies in humans have identified forms of myopathic Ehlers-Danlos syndrome with overlapping phenotypes that result from mutations in either collagen VI or XII, and biochemical and cell-based studies have identified accessory molecules that could form bridging interactions between the two collagens. However, the demonstration of a direct or ternary structural interaction between collagen VI or XII has not yet been reported. This Hypothesis and Theory review article examines the evidence that supports the existence of a functional complex between type VI and XII collagen in the ECM and discusses potential biological implications.

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.

Genetic architecture and polygenic risk score prediction of degenerative suspensory ligament desmitis (DSLD) in the Peruvian Horse

Introduction: Spontaneous rupture of tendons and ligaments is common in several species including humans. In horses, degenerative suspensory ligament desmitis (DSLD) is an important acquired idiopathic disease of a major energy-storing tendon-like structure. DSLD risk is increased in several breeds, including the Peruvian Horse. Affected horses have often been used for breeding before the disease is apparent. Breed predisposition suggests a substantial genetic contribution, but heritability and genetic architecture of DSLD have not been determined. Methods: To identify genomic regions associated with DSLD, we recruited a reference population of 183 Peruvian Horses, phenotyped as DSLD cases or controls, and undertook a genome-wide association study (GWAS), a regional window variance analysis using local genomic partitioning, a signatures of selection (SOS) analysis, and polygenic risk score (PRS) prediction of DSLD risk. We also estimated trait heritability from pedigrees. Results: Heritability was estimated in a population of 1,927 Peruvian horses at 0.22 ± 0.08. After establishing a permutation-based threshold for genome-wide significance, 151 DSLD risk single nucleotide polymorphisms (SNPs) were identified by GWAS. Multiple regions of enriched local heritability were identified across the genome, with strong enrichment signals on chromosomes 1, 2, 6, 10, 13, 16, 18, 22, and the X chromosome. With SOS analysis, there were 66 genes with a selection signature in DSLD cases that was not present in the control group that included the TGFB3 gene. Pathways enriched in DSLD cases included proteoglycan metabolism, extracellular matrix homeostasis, and signal transduction pathways that included the hedgehog signaling pathway. The best PRS predictive performance was obtained when we fitted 1% of top SNPs using a Bayesian Ridge Regression model which achieved the highest mean of R2 on both the probit and logit liability scales, indicating a strong predictive performance. Discussion: We conclude that within-breed GWAS of DSLD in the Peruvian Horse has further confirmed that moderate heritability and a polygenic architecture underlies the trait and identified multiple DSLD SNP associations in novel tendinopathy candidate genes influencing disease risk. Pathways enriched with DSLD risk variants include ones that influence glycosaminoglycan metabolism, extracellular matrix homeostasis, signal transduction pathways.