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BackgroundMusculocontractural Ehlers−Danlos syndrome is caused by biallelic loss-of-function variants in CHST14 (mcEDS-CHST14) or DSE (mcEDS-DSE). Although 48 patients in 33 families with mcEDS-CHST14 have been reported, the spectrum of pathogenic variants, accurate prevalence of various manifestations and detailed natural history have not been systematically investigated.MethodsWe collected detailed and comprehensive clinical and molecular information regarding previously reported and newly identified patients with mcEDS-CHST14 through international collaborations.ResultsSixty-six patients in 48 families (33 males/females; 0–59 years), including 18 newly reported patients, were evaluated. Japanese was the predominant ethnicity (27 families), associated with three recurrent variants. No apparent genotype–phenotype correlation was noted. Specific craniofacial (large fontanelle with delayed closure, downslanting palpebral fissures and hypertelorism), skeletal (characteristic finger morphologies, joint hypermobility, multiple congenital contractures, progressive talipes deformities and recurrent joint dislocation), cutaneous (hyperextensibility, fine/acrogeria-like/wrinkling palmar creases and bruisability) and ocular (refractive errors) features were observed in most patients (>90%). Large subcutaneous haematomas, constipation, cryptorchidism, hypotonia and motor developmental delay were also common (>80%). Median ages at the initial episode of dislocation or large subcutaneous haematoma were both 6 years. Nine patients died; their median age was 12 years. Several features, including joint and skin characteristics (hypermobility/extensibility and fragility), were significantly more frequent in patients with mcEDS-CHST14 than in eight reported patients with mcEDS-DSE.ConclusionThis first international collaborative study of mcEDS-CHST14 demonstrated that the subtype represents a multisystem disorder with unique set of clinical phenotypes consisting of multiple malformations and progressive fragility-related manifestations; these require lifelong, multidisciplinary healthcare approaches.

Purpose Infantile Caffey disease is a rare disorder characterized by acute inflammation with subperiosteal new bone formation, associated with fever, pain, and swelling of the overlying soft tissue. Symptoms arise within the first weeks after birth and spontaneously resolve before the age of two years. Many, but not all, affected individuals carry the heterozygous pathogenic COL1A1 variant (c.3040C>T, p.(Arg1014Cys)). Methods We sequenced COL1A1 in 28 families with a suspicion of Caffey disease and performed ultrastructural, immunocytochemical, and biochemical collagen studies on patient skin biopsies. Results We identified the p.(Arg1014Cys) variant in 23 families and discovered a novel heterozygous pathogenic COL1A1 variant (c.2752C>T, p.(Arg918Cys)) in five. Both arginine to cysteine substitutions are located in the triple helical domain of the pro alpha 1(I) procollagen chain. Dermal fibroblasts (one patient with p.(Arg1014Cys) and one with p.(Arg918Cys)) produced molecules with disulfide-linked pro alpha 1(I) chains, which were secreted only with p.(Arg1014Cys). No intracellular accumulation of type I procollagen was detected. The dermis revealed mild ultrastructural abnormalities in collagen fibril diameter and packing. Conclusion The discovery of this novel pathogenic variant expands the limited spectrum of arginine to cysteine substitutions in type I procollagen. Furthermore, it confirms allelic heterogeneity in Caffey disease and impacts its molecular confirmation.

Classical Ehlers-Danlos syndrome (cEDS) is a heritable connective tissue disorder mainly caused by pathogenic variants in COL5A1 or COL5A2, encoding type V collagen. Its diagnosis, based on clinical criteria and molecular confirmation, can be challenging. We report the molecular and clinical characteristics of 168 probands (72 clinically evaluated at our center) and 65 relatives with a clinical presentation of cEDS. Type V collagen defects were found in 145 probands, 121 (83.5%) were located in COL5A1 and 24 (16.5%) in COL5A2. Although 85.6% of molecularly confirmed patients presented the two major clinical criteria (generalized joint hypermobility, hyperextensible skin with atrophic scarring), significant inter- and intrafamilial phenotypic variability was noted. COL5A2 variants often caused a more severe phenotype. Vascular complications were rare in individuals with type V collagen defects (1.4%). Among the 72 probands clinically evaluated in our center, the mutation detection rate was 82.0%. The majority (68.1%) harbored COL5A1/COL5A2 defects. Yet, 13.9% harbored a defect in another gene (COL1A1, PLOD1, TNXB, AEBP1) highlighting important clinical overlap and the need for molecular confirmation of the diagnosis as this has implications regarding follow-up and genetic counseling. Eighteen percent of the 72 probands remained molecularly unexplained and a COL5A1 variant of unknown significance was identified in 6.9%.

Classical Ehlers-Danlos syndrome (cEDS) is a connective tissue disorder caused by heterozygous mutations in one of the type V collagen-encoding genes, COL5A1 or COL5A2. cEDS is characterized by generalized joint hypermobility and instability, hyperextensible, fragile skin and delayed wound healing. Chronic pain is a major problem in cEDS patients, but the underlying mechanisms are largely unknown, and studies in animal models are lacking. Therefore, we assessed pain-related behaviors in haploinsufficient Col5a1(+/−) mice, which clinically mimic human cEDS. Compared to wild-type (WT) littermates, 15–20 week-old Col5a1(+/−) mice of both sexes showed significant hypersensitivity to mechanical stimuli in the hind paws and the abdominal area, but responses to thermal stimuli were unaltered. Spontaneous behaviors, including distance travelled and rearing, were grossly normal in male Col5a1(+/−) mice, while female Col5a1(+/−) mice showed altered climbing behavior. Finally, male and female Col5a1(+/−) mice vocalized more than WT littermates when scruffed. Decreased grip strength was also noted. In view of the observed pain phenotype Col5a1(+/−) mice were crossed with Na(V)1.8-tdTomato reporter mice, enabling visualization of nociceptors in the glabrous skin of the footpad. We observed a significant decrease in intra-epidermal nerve fiber density, with fewer nerves crossing the epidermis, and a decreased total nerve length of Col5a1(+/−) mice compared to WT. In summary, male and female Col5a1(+/−) mice show hypersensitivity to mechanical stimuli, indicative of generalized sensitization of the nervous system, in conjunction with an aberrant organization of cutaneous nociceptors. Therefore, Col5a1(+/−) mice will provide a useful tool to study mechanisms of pain associated with cEDS.

OBJECTIVE: Following destabilization of the medial meniscus (DMM), mice develop experimental osteoarthritis (OA) and associated pain behaviors that are dependent on the stage of disease. We aimed to describe changes in gene expression in knee-innervating dorsal root ganglia (DRG) after surgery, in order to identify molecular pathways associated with three pre-defined pain phenotypes: “post-surgical pain”, “early-stage OA pain”, and “persistent OA pain”. DESIGN: We performed DMM or sham surgery in 10-week old male C57BL/6 mice and harvested L3-L5 DRG 4, 8, and 16 weeks after surgery or from age-matched naïve mice (n=3/group). RNA was extracted and an Affymetrix Mouse Transcriptome Array 1.0 was performed. Three pain phenotypes were defined: “post-surgical pain” (sham and DMM 4-week vs. 14-week old naïve), “early OA pain” (DMM 4-week vs. sham 4-week), and “persistent OA pain” (DMM 8- and 16-week vs. naïve and sham 8- and 16-week). ‘Top hit’ genes were defined as p

Chronic pain is one of the most common, yet poorly studied, complaints in people suffering from Ehlers-Danlos syndromes (EDS). This heterogeneous group of heritable connective tissue disorders is typically characterized by skin hyperextensibility, joint hypermobility, and generalized connective tissue fragility. Most EDS types are caused by genetic defects that affect connective tissue biosynthesis, thereby compromising collagen biosynthesis or fibrillogenesis and resulting in a disorganized extracellular matrix. Even though chronic pain is a major source of disability, functional impairment, and psychosocial suffering in EDS, currently used analgesics and other treatment strategies provide inadequate pain relief and thus represents an important unmet medical need. An important contributor to this is the lack of knowledge about the underlying mechanisms. In this narrative review, we summarize the current understanding of pain and the associated mechanisms in EDS based on clinical studies focusing on questionnaires and experimental pain testing as well as studies in animal models of EDS. In addition, we highlight the challenges, gaps, and opportunities in EDS-pain research.

The Ehlers–Danlos Syndromes (EDS) comprise a clinically and genetically heterogeneous group of complex hereditary disorders of connective tissue, with common features including joint hypermobility, soft and hyperextensible skin, abnormal wound healing, easy bruising, and signs of generalized connective tissue friability. Initial ultrastructural studies suggested that the abnormalities underlying EDS affected the collagen “wickerwork” of the connective tissue, and early biochemical and genetic studies identified defects in fibrillar types I, III, and V collagen, and in enzymes involved in their posttranslational modification, lysyl hydroxylase 1 and the procollagen amino-proteinase ADAMTS2. More recent discoveries have implicated a range of other, diverse extracellular matrix (ECM) molecules in the physiopathology of EDS, including the glycoprotein tenascin X, the FACIT type XII collagen, the intracellular chaperone and peptidylprolyl isomerase FKBP22, enzymes involved in glycosaminoglycan biosynthesis (D4ST1, DS-epi1, galactosyltransferase I and II), an intracellular zinc transporter ZIP13, (putative) transcription factors ZNF469 and PRDM5, factors involved in the classical complement pathway (C1r and C1s), and most recently, the ECM molecule AEBP1 that is involved in collagen polymerization. In this chapter, we give an overview of the different types of EDS and describe how the identification of their molecular underpinnings, and the study of pathophysiologic consequences of these defects in humans and in cellular and mouse models have provided key insights into the complex pathways of collagen fibrillogenesis and supramolecular organization of the collagen fibrils in the ECM.

TANGO1 (transport and Golgi organization‐1 homolog) encodes a transmembrane protein, which is located at endoplasmic reticulum (ER) exit sites where it binds bulky cargo, such as collagens, in the lumen and recruits membranes from the ER‐Golgi intermediate compartment (ERGIC) to create an export route for cargo secretion. Mice lacking Mia3 (murine TANGO1 orthologue) show defective secretion of numerous procollagens and lead to neonatal lethality due to insufficient bone mineralization. Recently, aberrant expression of truncated TANGO1 in humans has been shown to cause a mild‐to‐moderate severe collagenopathy associated with dentinogenesis imperfecta, short stature, skeletal abnormalities, diabetes mellitus, and mild intellectual disability. We now show for the first time that complete loss of TANGO1 results in human embryonic lethality with near‐total bone loss and phenocopies the situation of Mia3 −/− mice. Whole‐exome sequencing on genomic DNA (gDNA) of an aborted fetus of Indian descent revealed a homozygous 4‐base pair (4‐bp) deletion in TANGO1 that is heterozygously present in both healthy parents. Parental fibroblast studies showed decreased TANGO1 mRNA expression and protein levels. Type I collagen secretion and extracellular matrix organization were normal, supporting a threshold model for clinical phenotype development. As such, our report broadens the phenotypic and mutational spectrum of TANGO1‐related collagenopathies, and underscores the crucial role of TANGO1 for normal bone development, of which deficiency results in a severe‐to‐lethal form of osteochondrodysplasia. © 2021 American Society for Bone and Mineral Research © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Brittle cornea syndrome (BCS) is a rare autosomal recessive disorder characterized by corneal thinning and fragility, leading to corneal rupture, the main hallmark of this disorder. Non-ocular symptoms include not only hearing loss but also signs of connective tissue fragility, placing it in the Ehlers-Danlos syndrome (EDS) spectrum. It is caused by biallelic pathogenic variants in ZNF469 or PRDM5, which presumably encode transcription factors for extracellular matrix components. We report the clinical and molecular features of nine novel BCS families, four of which harbor variants in ZNF469 and five in PRDM5. We also performed a genotype- and phenotype-oriented literature overview of all (n = 85) reported patients with ZNF469 (n = 53) and PRDM5 (n = 32) variants. Musculoskeletal findings may be the main reason for referral and often raise suspicion of another heritable connective tissue disorder, such as kyphoscoliotic EDS, osteogenesis imperfecta, or Marfan syndrome, especially when a corneal rupture has not yet occurred. Our findings highlight the multisystemic nature of BCS and validate its inclusion in the EDS classification. Importantly, gene panels for heritable connective tissue disorders should include ZNF469 and PRDM5 to allow for timely diagnosis and appropriate preventive measures for this rare condition., SCOPUS: ar.j, info:eu-repo/semantics/published

Background Musculocontractural Ehlers–Danlos Syndrome (mcEDS) is a rare connective tissue disorder caused by biallelic loss‐of‐function variants in CHST14 (mcEDS‐CHST14) or DSE (mcEDS‐DSE), both of which result in defective dermatan sulfate biosynthesis. Forty‐one patients with mcEDS‐CHST14 and three patients with mcEDS‐DSE have been described in the literature. Methods Clinical, molecular, and glycobiological findings in three additional patients with mcEDS‐DSE were investigated. Results Three patients from two families shared craniofacial characteristics (hypertelorism, blue sclera, midfacial hypoplasia), skeletal features (pectus and spinal deformities, characteristic finger shapes, progressive talipes deformities), skin features (fine or acrogeria‐like palmar creases), and ocular refractive errors. Homozygous pathogenic variants in DSE were found: c.960T>A/p.Tyr320* in patient 1 and c.996dupT/p.Val333Cysfs*4 in patients 2 and 3. No dermatan sulfate was detected in the urine sample from patient 1, suggesting a complete depletion of DS. Conclusion McEDS‐DSE is a congenital multisystem disorder with progressive symptoms involving craniofacial, skeletal, cutaneous, and cardiovascular systems, similar to the symptoms of mcEDS‐CHST14. However, the burden of symptoms seems lower in patients with mcEDS‐DSE., Clinical, molecular, and glycobiological findings in three additional patients from two families with musculocontractural Ehlers–Danlos syndrome (mcEDS‐DSE) are described. McEDS‐DSE is a congenital multisystem disorder with progressive symptoms involving craniofacial, skeletal, cutaneous, and cardiovascular systems, similar to the symptoms of mcEDS‐CHST14. However, the burden of symptoms seems lower in patients with mcEDS‐DSE.

Contains fulltext : 207011.pdf (Publisher’s version ) (Closed access) The Ehlers-Danlos syndromes (EDSs) are a clinically and molecularly diverse group of heritable connective tissue disorders caused by defects in a wide range of genes. Recently, bi-allelic loss-of-function mutations in the adipocyte enhancer-binding protein 1 (AEBP1) gene were reported in three families with an autosomal recessive EDS-like condition characterized by thin and hyperextensible skin, poor wound healing with prominent atrophic scarring, joint hypermobility and osteoporosis. Using whole exome sequencing, we identified novel bi-allelic AEBP1 variants in two unrelated adult patients, previously diagnosed with an undefined EDS type, which shows important clinical resemblance to several other EDS subtypes. Our patients present with similar cutaneous and musculoskeletal features as the previously reported patients. They also show unreported clinical features, including pectus deformity, premature aged appearance, sparse and frizzled hair, fatigue and pain. AEBP1 is ubiquitously expressed and encodes the secreted aortic carboxypeptidase-like protein (ACLP) that can bind fibrillar collagens and assist in collagen polymerization. Transmission electron microscopy studies on the patients' skin biopsies show ultrastructural alterations in collagen fibril diameter and appearance, underscoring an important role for ACLP in collagen fibril organization. This report further expands the clinical, molecular and ultrastructural spectrum associated with AEBP1 defects and highlights the complex and variable phenotype associated with this new EDS variant.

Type III collagen is a major fibrillar collagen consisting of three identical α1(III)-chains that is particularly present in tissues exhibiting elastic properties, such as the skin and the arterial wall. Heterozygous mutations in the COL3A1 gene result in vascular Ehlers-Danlos syndrome (vEDS), a severe, life-threatening disorder, characterized by thin, translucent skin and propensity to arterial, intestinal and uterine rupture. Most human vEDS cases result from a missense mutation substituting a crucial glycine residue in the triple helical domain of the α1(III)-chains. The mechanisms by which these mutant type III collagen molecules cause dermal and vascular fragility are not well understood. We generated a transgenic mouse line expressing mutant type III collagen, containing a typical helical glycine substitution (p.(Gly182Ser)). This Col3a1Tg-G182S mouse line displays a phenotype recapitulating characteristics of human vEDS patients with signs of dermal and vascular fragility. The Col3a1Tg-G182S mice develop severe transdermal skin wounds, resulting in early demise at 13-14weeks of age. We found that this phenotype was associated with a reduced total collagen content and an abnormal collagen III:I ratio, leading to the production of severely malformed collagen fibrils in the extracellular matrix of dermal and arterial tissues. These results indicate that expression of the glycine substitution in the α1(III)-chain disturbs formation of heterotypic type III:I collagen fibrils, and thereby demonstrate a key role for type III collagen in collagen fibrillogenesis in dermal and arterial tissues.

Genetic etiologies of chronic mucocutaneous candidiasis (CMC) disrupt human IL-17A/F-dependent immunity at mucosal surfaces, whereas those of connective tissue disorders (CTDs) often impair the TGF-β-dependent homeostasis of connective tissues. The signaling pathways involved are incompletely understood. We report a three-generation family with an autosomal dominant (AD) combination of CMC and a previously undescribed form of CTD that clinically overlaps with Ehlers-Danlos syndrome (EDS). The patients are heterozygous for a private splice-site variant of MAPK8, the gene encoding c-Jun N-terminal kinase 1 (JNK1), a component of the MAPK signaling pathway. This variant is loss-of-expression and loss-of-function in the patients' fibroblasts, which display AD JNK1 deficiency by haploinsufficiency. These cells have impaired, but not abolished, responses to IL-17A and IL-17F. Moreover, the development of the patients' TH17 cells was impaired ex vivo and in vitro, probably due to the involvement of JNK1 in the TGF-β-responsive pathway and further accounting for the patients' CMC. Consistently, the patients' fibroblasts displayed impaired JNK1- and c-Jun/ATF-2-dependent induction of key extracellular matrix (ECM) components and regulators, but not of EDS-causing gene products, in response to TGF-β. Furthermore, they displayed a transcriptional pattern in response to TGF-β different from that of fibroblasts from patients with Loeys-Dietz syndrome caused by mutations of TGFBR2 or SMAD3, further accounting for the patients' complex and unusual CTD phenotype. This experiment of nature indicates that the integrity of the human JNK1-dependent MAPK signaling pathway is essential for IL-17A- and IL-17F-dependent mucocutaneous immunity to Candida and for the TGF-β-dependent homeostasis of connective tissues.

β4GalT7 is a transmembrane Golgi enzyme, encoded by B4GALT7, that plays a pivotal role in the proteoglycan linker region formation during proteoglycan biosynthesis. Defects in this enzyme give rise to a rare autosomal recessive form of Ehlers-Danlos syndrome (EDS), currently known as ‘spondylodysplastic EDS (spEDS-B4GALT7)’. This EDS subtype is mainly characterized by short stature, hypotonia and skeletal abnormalities, thereby illustrating its pleiotropic importance during human development. Insights into the pathogenic mechanisms underlying this disabling disease are very limited, in part due to the lack of a relevant in vivo model. As the majority of mutations identified in patients with spEDS-B4GALT7 are hypomorphic, we generated zebrafish models with partial loss of B4galt7 function, including different knockdown (morphant) and mosaic knockout (crispant) b4galt7 zebrafish models and studied the morphologic, functional and molecular aspects in embryonic and larval stages. Morphant and crispant zebrafish show highly similar morphological abnormalities in early development including a small, round head, bowed pectoral fins, short body-axis and mild developmental delay. Several craniofacial cartilage and bone structures are absent or strongly misshapen. In addition, the total amount of sulfated glycosaminoglycans is significantly diminished and particularly heparan and chondroitin sulfate proteoglycan levels are greatly reduced. We also show impaired cartilage patterning and loss of chondrocyte organization in a cartilage-specific Tg(Col2a1aBAC:mcherry) zebrafish reporter line. The occurrence of the same abnormalities in the different models confirms these are specifically caused by B4galt7 deficiency. A disturbed actin pattern, along with a lack of muscle tone, was only noted in morphants in which translation of b4galt7 was blocked. In conclusion, we generated the first viable animal models for spEDS-B4GALT7, and show that in early development the human spEDS-B4GALT7 phenotype is faithfully mimicked in these zebrafish models. Our findings underscore a key role for β4GalT7 in early development of cartilage, bone and muscle. These models will lead to a better understanding of spEDS-B4GALT7 and can be used in future efforts focusing on therapeutic applications.

Background Proteoglycans are large and structurally complex macromolecules which can be found in abundancy in the extracellular matrix and on the surface of all animal cells. Mutations in the genes encoding the enzymes responsible for the formation of the tetrasaccharide linker region between the proteoglycan core protein and the glycosaminoglycan side chains lead to a spectrum of severe and overlapping autosomal recessive connective tissue disorders, collectively coined the ‘glycosaminoglycan linkeropathies’. Results We report the clinical findings of two novel patients with a complex linkeropathy due to biallelic mutations in B3GAT3, the gene that encodes glucuronosyltransferase I, which catalyzes the addition of the ultimate saccharide to the linker region. We identified a previously reported c.667G > A missense mutation and an unreported homozygous c.416C > T missense mutation. We also performed a genotype and phenotype-oriented literature overview of all hitherto reported patients harbouring B3GAT3 mutations. A total of 23 patients from 10 families harbouring bi-allelic mutations and one patient with a heterozygeous splice-site mutation in B3GAT3 have been reported. They all display a complex phenotype characterized by consistent presence of skeletal dysplasia (including short stature, kyphosis, scoliosis and deformity of the long bones), facial dysmorphology, and spatulate distal phalanges. More variably present are cardiac defects, joint hypermobility, joint dislocations/contractures and fractures. Seven different B3GAT3 mutations have been reported, and although the number of patients is still limited, some phenotype-genotype correlations start to emerge. The more severe phenotypes seem to have mutations located in the substrate acceptor subdomain of the catalytic domain of the glucuronosyltransferase I protein while more mildly affected phenotypes seem to have mutations in the NTP-sugar donor substrate binding subdomain. Conclusions Loss-of-function mutations in B3GAT3 are associated with a complex connective tissue phenotype characterized by disproportionate short stature, skeletal dysplasia, facial dysmorphism, spatulate distal phalanges and -to a lesser extent- joint contractures, joint hypermobility with dislocations, cardiac defects and bone fragility. Based on the limited number of reported patients, some genotype-phenotype correlations start to emerge.

To date, heterozygous or homozygous COL12A1 variants have been reported in 13 patients presenting with a clinical phenotype overlapping with collagen VI–related myopathies and Ehlers–Danlos syndrome (EDS). The small number of reported patients limits thorough investigation of this newly identified syndrome, currently coined as myopathic EDS. DNA from 78 genetically unresolved patients fulfilling the clinical criteria for myopathic EDS was sequenced using a next-generation panel of COL12A1, COL6A1, COL6A2, and COL6A3. Among this cohort, we identified four pathogenic heterozygous in-frame exon skipping (∆) defects in COL12A1, clustering to the thrombospondin N-terminal region and the adjacent collagenous domain (Δ52, Δ53, Δ54, and Δ56 respectively), one heterozygous COL12A1 arginine-to-cysteine substitution of unclear significance (p.(Arg1863Cys)), and compound heterozygous pathogenic COL6A1 variants (c.[98–6G>A];[301C>T]) in one proband. Variant-specific intracellular accumulation of collagen XII chains, extracellular overmodification of the long isoform and near-absence of the short isoform of collagen XII, and extracellular decrease of decorin and tenascin-X were observed for the COL12A1 variants. In contrast, the COL6A1 variants abolished collagen VI and V deposition and increased tenascin-X levels. Our data further support the significant clinical overlap between myopathic EDS and collagen VI–related myopathies, and emphasize the variant-specific consequences of collagen XII defects.

Biallelic defects in the RIN2 gene, encoding the Ras and Rab interactor 2 protein, are associated with a rare autosomal recessive connective tissue disorder, with only nine patients from four independent families reported to date. The condition was initially termed MACS syndrome (macrocephaly, alopecia, cutis laxa, and scoliosis), based on the clinical features of the first identified family; however, with the expansion of the clinical phenotype in additional families, it was subsequently coined RIN2 syndrome. Hallmark features of this condition include dysmorphic facial features with striking, progressive facial coarsening, sparse hair, normal to enlarged occipitofrontal circumference, soft redundant and/or hyperextensible skin, and scoliosis. Patients with RIN2 syndrome present phenotypic overlap with other conditions, including EDS (especially the dermatosparaxis and kyphoscoliosis subtypes). Here, we describe a 10th patient, the first patient of Caucasian origin and the oldest reported patient so far, who harbors the previously identified homozygous RIN2 mutation c.1878dupC (p. (Ile627Hisfs*7)). Besides the hallmark features, this patient also presents problems not previously associated with RIN2 syndrome, including cervical vertebral fusion, mild hearing loss, and colonic fibrosis. We provide an overview of the clinical findings in all reported patients with RIN2 mutations and summarize some of the possible pathogenic mechanisms that may underlie this condition. © 2016 Wiley Periodicals, Inc.

Sorsby fundus dystrophy (SFD) is a macular degeneration caused by mutations in TIMP3, the majority of which introduce a novel cysteine. However, the exact molecular mechanisms underlying SFD remain unknown. We aimed to provide novel insights into the functional consequences of a distinct N‐terminal mutation. Haplotype reconstruction in three SFD families revealed that the identified c.113C>G, p.(Ser38Cys) mutation is a founder in Belgian and northern French families with a late‐onset SFD phenotype. Functional consequences of the p.(Ser38Cys) mutation were investigated by high‐resolution Western blot analysis of wild type and mutant TIMP3 using patient fibroblasts and in vitro generated proteins, and by molecular modeling of TIMP3 and its interaction partners. We could not confirm a previous hypothesis on dimerization of mutant TIMP3 proteins. However, we identified aberrant intramolecular disulfide bonding. Our data provide evidence for disruption of the established Cys36‐Cys143 disulfide bond and formation of a novel Cys36‐Cys38 bond, possibly associated with increased glycosylation of the protein. In conclusion, we propose a novel pathogenetic mechanism underlying the p.(Ser38Cys) TIMP3 founder mutation involving intramolecular disulfide bonding. These results provide new insights into the pathogenesis of SFD and other retinopathies linked to mutations in TIMP3, such as age‐related macular degeneration.

International audience; Proteoglycans are among the most abundant and structurally complex biomacromolecules and play critical roles in connective tissues. They are composed of a core protein onto which glycosaminoglycan (GAG) side chains are attached via a linker region. Biallelic mutations in B3GALT6, encoding one of the linker region glycosyltransferases, are known to cause either spondyloepimetaphyseal dysplasia (SEMD) or a severe pleiotropic form of Ehlers-Danlos syndromes (EDS). This study provides clinical, molecular and biochemical data on 12 patients with biallelic B3GALT6 mutations. Notably, all patients have features of both EDS and SEMD. In addition, some patients have severe and potential life-threatening complications such as aortic dilatation and aneurysm, cervical spine instability and respiratory insufficiency. Whole-exome sequencing, next generation panel sequencing and direct sequencing identified biallelic B3GALT6 mutations in all patients. We show that these mutations reduce the amount of β3GalT6 protein and lead to a complete loss of galactosyltransferase activity. In turn, this leads to deficient GAG synthesis, and ultrastructural abnormalities in collagen fibril organization. In conclusion, this study redefines the phenotype associated with B3GALT6 mutations on the basis of clinical, molecular and biochemical data in 12 patients, and provides an in-depth assessment of β3GalT6 activity and GAG synthesis to better understand this rare condition.

The evolutionarily conserved transmembrane anterior posterior transformation 1 protein, encoded by TAPT1, is involved in murine axial skeletal patterning, but its cellular function remains unknown. Our study demonstrates that TAPT1 mutations underlie a complex congenital syndrome, showing clinical overlap between lethal skeletal dysplasias and ciliopathies. This syndrome is characterized by fetal lethality, severe hypomineralization of the entire skeleton and intra-uterine fractures, and multiple congenital developmental anomalies affecting the brain, lungs, and kidneys. We establish that wild-type TAPT1 localizes to the centrosome and/or ciliary basal body, whereas defective TAPT1 mislocalizes to the cytoplasm and disrupts Golgi morphology and trafficking and normal primary cilium formation. Knockdown of tapt1b in zebrafish induces severe craniofacial cartilage malformations and delayed ossification, which is shown to be associated with aberrant differentiation of cranial neural crest cells.

Whereas the vast majority of osteogenesis imperfecta (OI) is caused by autosomal dominant defects in the genes encoding type I procollagen, mutations in a myriad of genes affecting type I procollagen biosynthesis or bone formation and homeostasis have now been associated with rare autosomal recessive OI forms. Recently, homozygous or compound heterozygous mutations in BMP1, encoding the metalloproteases bone morphogenetic protein-1 (BMP1) and its longer isoform mammalian Tolloid (mTLD), were identified in 5 children with a severe autosomal recessive form of OI and in 4 individuals with mild to moderate bone fragility. BMP1/mTLD functions as the procollagen carboxy-(C)-proteinase for types I to III procollagen but was also suggested to participate in amino-(N)-propeptide cleavage of types V and XI procollagens and in proteolytic trimming of other extracellular matrix (ECM) substrates. We report the phenotypic characteristics and natural history of 4 adults with severe, progressive OI characterized by numerous fractures, short stature with rhizomelic shortening, and deformity of the limbs and variable kyphoscoliosis, in whom we identified novel biallelic missense and frameshift mutations in BMP1. We show that BMP1/mTLD-deficiency in humans not only results in delayed cleavage of the type I procollagen C-propeptide but also hampers the processing of the small leucine-rich proteoglycan prodecorin, a regulator of collagen fibrillogenesis. Immunofluorescent staining of types I and V collagen and transmission electron microscopy of the dermis show impaired assembly of heterotypic type I/V collagen fibrils in the ECM. Our study thus highlights the severe and progressive nature of BMP1-associated OI in adults and broadens insights into the functional consequences of BMP1/mTLD-deficiency on ECM organization.

Introduction: The Ehlers-Danlos syndrome (EDS) comprises a clinically and genetically diverse group of heritable connective tissue disorders, characterized by joint hypermobility, skin hyperextensibility and generalized connective tissue friability. Although the initially characterized subtypes were shown to result from defects in fibrillar collagens (types I, III, V) or their modifying enzymes, recent discoveries have implicated other molecules, such as tenascin X and glycosaminoglycan synthesis enzymes, in the pathogenesis of these disorders.Areas covered: This article summarizes the current knowledge on the biosynthesis of collagen fibrils and focuses on the molecules involved in this process, especially those relevant to the pathogenesis of EDS. It also provides an overview of the general clinical presentation of EDS and the genetic defects underlying its different subtypes.Expert opinion: The recent identification of several novel types of EDS has greatly expanded its clinical and genetic heterogenei...

PURPOSE OF REVIEW: Osteoarthritis (OA) is the most common form of arthritis and a major source of pain and disability worldwide. OA-associated pain is usually refractory to classically used analgesics, and disease-modifying therapies are still lacking. Therefore, a better understanding of mechanisms and mediators contributing to the generation and maintenance of OA pain is critical for the development of efficient and safe pain-relieving therapies. RECENT FINDINGS: Both peripheral and central mechanisms contribute to OA pain. Clinical evidence suggests that a strong peripheral nociceptive drive from the affected joint maintains pain and central sensitization associated with OA. Mediators present in the OA joint, including nerve growth factor, chemokines, cytokines, and inflammatory cells can contribute to sensitization. Furthermore, structural alterations in joint innervation and nerve damage occur in the course of OA. SUMMARY: Several interrelated pathological processes, including joint damage, structural reorganization of joint afferents, low-grade inflammation, neuroplasticity and nerve damage all contribute to the pain observed in OA. It can be anticipated that elucidating exactly how these mechanisms are operational in the course of progressive OA may lead to the identification of novel targets for intervention.

Item does not contain fulltext Complete deficiency of the extracellular matrix glycoprotein tenascin-X (TNX) leads to recessive forms of Ehlers-Danlos syndrome, clinically characterized by hyperextensible skin, easy bruising and joint hypermobility. Clinical and pathological studies, immunoassay, and molecular analyses were combined to study a patient suffering from progressive muscle weakness. Clinical features included axial and proximal limb muscle weakness, subclinical heart involvement, minimal skin hyperextensibility, no joint abnormalities, and a history of easy bruising. Skeletal muscle biopsy disclosed striking muscle consistency and the abnormal presence of myotendinous junctions in the muscle belly. TNX immunostaining was markedly reduced in muscle and skin, and serum TNX levels were undetectable. Compound heterozygous mutations were identified: a previously reported 30kb deletion and a non-synonymous novel missense mutation in the TNXB gene. This study identifies a TNX-deficient patient presenting with a primary muscle disorder, thus expanding the phenotypic spectrum of TNX-related abnormalities. Biopsy findings provide evidence that TNX deficiency leads to muscle softness and to mislocalization of myotendinous junctions.

Contains fulltext : 169752.pdf (Publisher’s version ) (Closed access) Defects of the V-type proton (H+) ATPase (V-ATPase) impair acidification and intracellular trafficking of membrane-enclosed compartments, including secretory granules, endosomes, and lysosomes. Whole-exome sequencing in five families affected by mild to severe cutis laxa, dysmorphic facial features, and cardiopulmonary involvement identified biallelic missense mutations in ATP6V1E1 and ATP6V1A, which encode the E1 and A subunits, respectively, of the V1 domain of the heteromultimeric V-ATPase complex. Structural modeling indicated that all substitutions affect critical residues and inter- or intrasubunit interactions. Furthermore, complexome profiling, a method combining blue-native gel electrophoresis and liquid chromatography tandem mass spectrometry, showed that they disturb either the assembly or the stability of the V-ATPase complex. Protein glycosylation was variably affected. Abnormal vesicular trafficking was evidenced by delayed retrograde transport after brefeldin A treatment and abnormal swelling and fragmentation of the Golgi apparatus. In addition to showing reduced and fragmented elastic fibers, the histopathological hallmark of cutis laxa, transmission electron microscopy of the dermis also showed pronounced changes in the structure and organization of the collagen fibers. Our findings expand the clinical and molecular spectrum of metabolic cutis laxa syndromes and further link defective extracellular matrix assembly to faulty protein processing and cellular trafficking caused by genetic defects in the V-ATPase complex.

Type V collagen mutations are associated with classic Ehlers-Danlos Syndrome (EDS), but it is unknown for which proportion they account and to what extent other genes are involved. We analyzed COL5A1 and COL5A2 in 126 patients with a diagnosis or suspicion of classic EDS. In 93 patients, a type V collagen defect was found, of which 73 were COL5A1 mutations, 13 were COL5A2 mutations and seven were COL5A1 null-alleles with mutation unknown. The majority of the 73 COL5A1 mutations generated a COL5A1 null-allele, whereas one-third were structural mutations, scattered throughout COL5A1. All COL5A2 mutations were structural mutations. Reduced availability of type V collagen appeared to be the major disease-causing mechanism, besides other intra- and extracellular contributing factors. All type V collagen defects were identified within a group of 102 patients fulfilling all major clinical Villefranche criteria, that is, skin hyperextensibility, dystrophic scarring and joint hypermobility. No COL5A1/COL5A2 mutation was detected in 24 patients who displayed skin and joint hyperextensibility but lacked dystrophic scarring. Overall, over 90% of patients fulfilling all major Villefranche criteria for classic EDS were shown to harbor a type V collagen defect, which indicates that this is the major--if not only--cause of classic EDS.

International audience; We present clinical and molecular findings of three patients with an EDS VIB phenotype from two consanguineous families. The clinical findings of EDS kyphoscoliotic type (EDS type VI A&B) comprise kyphoscoliosis, muscular hypotonia, hyperextensible, thin and bruisable skin, atrophic scarring, jointhypermobility and variable ocular involvement. Distinct craniofacial abnormalities, joint contractures, wrinkled palms, and normal urinary pyridinoline ratios distinguish EDS VIB from EDS VIA. A genome-wide SNP scan and sequence analyses identified a homozygous frameshift mutation (NM_130468.2:c.145delG, NP_569735.1:p.Val49*) in CHST14, encoding dermatan-4-sulfotransferase 1 (D4ST-1), in two Turkish siblings. Subsequent sequence analysis of CHST14 identified a homozygous 20-bp duplication (NM_130468.2:c.981_1000dup, NP_569735.1:p.Glu334Glyfs*107) in an Indian patient. Loss-of-function mutations in CHST14 were recently reported in adducted thumb-clubfoot syndrome (ATCS). Patients with ATCS present similar craniofacial and musculoskeletal features as the EDS VIB patients reported here, but lack the severe skin manifestations. By identifying an identical mutation in patients with EDS VIB and ATCS, we show that both conditions form a phenotypic continuum. Our findings confirm that the EDS-variant associated with CHST14 mutations (Miyake, et al., 2010) forms a clinical spectrum, which we propose to coin as "musculo-contractural EDS", and which results from a defect in dermatan sulfate biosynthesis, perturbing collagen assembly.

Defects leading to impaired intracellular trafficking have recently been shown to play an important role in the pathogenesis of genodermatoses, such as the Ehlers-Danlos and the cutis laxa syndromes. A new genodermatosis, termed macrocephaly, alopecia, cutis laxa and scoliosis (MACS) syndrome has been described, resulting from a homozygous 1-bp deletion in RIN2. RIN2 encodes the Ras and Rab interactor 2, involved in the regulation of Rab5-mediated early endocytosis. We performed a clinical, ultrastructural and molecular study in a consanguineous Algerian family with three siblings affected by a distinctive autosomal recessive genodermatosis, reported in 2005 by Verloes et al. The most striking clinical features include progressive facial coarsening, gingival hypertrophy, severe scoliosis, sparse hair and skin and joint hyperlaxity. Ultrastructural studies of the skin revealed important abnormalities in the collagen fibril morphology, and fibroblasts exhibited a dilated endoplasmic reticulum and an abnormal Golgi apparatus with rarefied and dilated cisternae. Molecular analysis of RIN2 revealed a novel homozygous 2-bp deletion in all affected individuals. The c.1914_1915delGC mutation introduces a frameshift and creates a premature termination codon, leading to nonsense-mediated mRNA decay. These findings confirm that RIN2 defects are associated with a distinct genodermatosis and underscore the involvement of RIN2 and its associated pathways in the pathogenesis of connective tissue disorders. The current family displays considerable phenotypic overlap with MACS syndrome. However, our family shows a dermatological and ultrastructural phenotype belonging to the Ehlers-Danlos rather than the cutis laxa spectrum. Therefore, the MACS acronym is not entirely appropriate for the current family.

PURPOSE: The Ehlers-Danlos syndrome (EDS), dermatosparaxis type, is a recessively inherited connective tissue disorder caused by deficient activity of ADAMTS-2, an enzyme that cleaves the aminoterminal propeptide domain of types I, II, and III procollagen. Only 10 EDS dermatosparaxis patients have been reported, all presenting a recognizable phenotype with characteristic facial gestalt, extreme skin fragility and laxity, excessive bruising, and sometimes major complications due to visceral and vascular fragility. METHODS: We report on five new EDS dermatosparaxis patients and provide a comprehensive overview of the current knowledge of the natural history of this condition. RESULTS: We identified three novel homozygous loss-of-function mutations (c.2927_2928delCT, p.(Pro976Argfs*42); c.669_670dupG, p.(Pro224Argfs*24); and c.2751-2A>T) and one compound heterozygous mutation (c.2T>C, p.? and c.884_887delTGAA, p.(Met295Thrfs26*)) in ADAMTS2 in five patients from four unrelated families. Three of these displayed a phenotype that was strikingly milder than that of previously reported patients. CONCLUSION: This study expands the clinical and molecular spectrum of the dermatosparaxis type of EDS to include a milder phenotypic variant and stresses the importance of good clinical criteria. To address this, we propose an updated set of criteria that accurately captures the multisystemic nature of the dermatosparaxis type of EDS.Genet Med advance online publication 14 January 2016Genetics in Medicine (2016); doi:10.1038/gim.2015.188.

Bi-allelic variants in CHST14, encoding dermatan 4-O-sulfotransferase-1 (D4ST1), cause musculocontractural Ehlers-Danlos syndrome (MC-EDS), a recessive disorder characterized by connective tissue fragility, craniofacial abnormalities, congenital contractures, and developmental anomalies. Recently, the identification of bi-allelic variants in DSE, encoding dermatan sulfate epimerase-1 (DS-epi1), in a child with MC-EDS features, suggested locus heterogeneity for this condition. DS-epi1 and D4ST1 are crucial for biosynthesis of dermatan sulfate (DS) moieties in the hybrid chondroitin sulfate (CS)/DS glycosaminoglycans (GAGs). Here, we report four novel families with severe MC-EDS caused by unique homozygous CHST14 variants and the second family with a homozygous DSE missense variant, presenting a somewhat milder MC-EDS phenotype. The glycanation of the dermal DS proteoglycan decorin is impaired in fibroblasts from D4ST1- as well as DS-epi1-deficient patients. However, in D4ST1-deficiency, the decorin GAG is completely replaced by CS, whereas in DS-epi1-deficiency, still some DS moieties are present. The multisystemic abnormalities observed in our patients support a tight spatiotemporal control of the balance between CS and DS, which is crucial for multiple processes including cell differentiation, organ development, cell migration, coagulation, and connective tissue integrity.

Joint hypermobility is a common, mostly benign, finding in the general population. In a subset of individuals, however, it causes a range of clinical problems, mainly affecting the musculoskeletal system. Joint hypermobility often appears as a familial trait and is shared by several heritable connective tissue disorders, including the hypermobility subtype of the Ehlers-Danlos syndrome (EDS-HT) or benign joint hypermobility syndrome (BJHS). These hereditary conditions provide unique models for the study of the genetic basis of joint hypermobility. Nevertheless, these studies are largely hampered by the great variability in clinical presentation and the often vague mode of inheritance in many families. Here, we performed a genome-wide linkage scan in a unique three-generation family with an autosomal dominant EDS-HT phenotype and identified a linkage interval on chromosome 8p22-8p21.1, with a maximum two-point LOD score of 4.73. Subsequent whole exome sequencing revealed the presence of a unique missense variant in theLZTS1gene, located within the candidate region. Subsequent analysis of 230 EDS-HT/BJHS patients resulted in the identification of three additional rare variants. This is the first reported genome-wide linkage analysis in an EDS-HT family, thereby providing an opportunity to identify a new disease gene for this condition.

We report on a series of 514 consecutive diagnoses of skeletal dysplasia made over an 8-year period at a tertiary hospital in Kerala, India. The most common diagnostic groups were dysostosis multiplex group (n = 73) followed by FGFR3 (n = 49) and osteogenesis imperfecta and decreased bone density group (n = 41). Molecular confirmation was obtained in 109 cases. Clinical and radiographic evaluation was obtained in close diagnostic collaboration with expert groups abroad through Internet communication for difficult cases. This has allowed for targeted biochemical and molecular studies leading to the correct identification of rare or novel conditions, which has not only helped affected families by allowing for improved genetic counseling and prenatal diagnosis but also resulted in several scientific contributions. We conclude that (1) the spectrum of genetic bone disease in Kerala, India, is similar to that of other parts of the world, but recessive entities may be more frequent because of widespread consanguinity; (2) prenatal detection of skeletal dysplasias remains relatively rare because of limited access to expert prenatal ultrasound facilities; (3) because of the low accessibility to molecular tests, precise clinical-radiographic phenotyping remains the mainstay of diagnosis and counseling and of gatekeeping to efficient laboratory testing; (4) good phenotyping allows, a significant contribution to the recognition and characterization of novel entities. We suggest that the tight collaboration between a local reference center with dedicated personnel and expert diagnostic networks may be a proficient model to bring current diagnostics to developing countries. © 2014 Wiley Periodicals, Inc.

International audience; Proteoglycans are important components of cell plasma membranes and extracellular matrices of connective tissues. They consist of glycosaminoglycan chains attached to a core protein via a tetrasaccharide linkage, whereby the addition of the third residue is catalyzed by galactosyltransferase II (β3GalT6), encoded by B3GALT6. Homozygosity mapping and candidate gene sequence analysis in three independent families, presenting a severe autosomal-recessive connective tissue disorder characterized by skin fragility, delayed wound healing, joint hyperlaxity and contractures, muscle hypotonia, intellectual disability, and a spondyloepimetaphyseal dysplasia with bone fragility and severe kyphoscoliosis, identified biallelic B3GALT6 mutations, including homozygous missense mutations in family 1 (c.619G>C [p.Asp207His]) and family 3 (c.649G>A [p.Gly217Ser]) and compound heterozygous mutations in family 2 (c.323_344del [p.Ala108Glyfs(∗)163], c.619G>C [p.Asp207His]). The phenotype overlaps with several recessive Ehlers-Danlos variants and spondyloepimetaphyseal dysplasia with joint hyperlaxity. Affected individuals' fibroblasts exhibited a large decrease in ability to prime glycosaminoglycan synthesis together with impaired glycanation of the small chondroitin/dermatan sulfate proteoglycan decorin, confirming β3GalT6 loss of function. Dermal electron microcopy disclosed abnormalities in collagen fibril organization, in line with the important regulatory role of decorin in this process. A strong reduction in heparan sulfate level was also observed, indicating that β3GalT6 deficiency alters synthesis of both main types of glycosaminoglycans. In vitro wound healing assay revealed a significant delay in fibroblasts from two index individuals, pointing to a role for glycosaminoglycan defect in impaired wound repair in vivo. Our study emphasizes a crucial role for β3GalT6 in multiple major developmental and pathophysiological processes.