Periodontal Ehlers-Danlos syndrome is associated with leukoencephalopathy

Non-oral manifestations in adults with a clinical and molecularly confirmed diagnosis of periodontal Ehlers-Danlos syndrome

Introduction: Periodontal Ehlers-Danlos Syndrome (pEDS) is a rare autosomal dominant type of EDS characterised by severe early-onset periodontitis, lack of attached gingiva, pretibial plaques, joint hypermobility and skin hyperextensibility as per the 2017 International EDS Classification. In 2016, deleterious pathogenic heterozygous variants were identified in C1R and C1S, which encode components of the complement system. Materials and Methods: Individuals with a clinical suspicion of pEDS were clinically and molecularly assessed through the National EDS Service in London and Sheffield and in genetic services in Austria, Sweden and Australia. Transmission electron microscopy and fibroblast studies were performed in a small subset of patients. Results: A total of 21 adults from 12 families were clinically and molecularly diagnosed with pEDS, with C1R variants in all families. The age at molecular diagnosis ranged from 21-73 years (mean 45 years), male: female ratio 5:16. Features of easy bruising (90%), pretibial plaques (81%), skin fragility (71%), joint hypermobility (24%) and vocal changes (38%) were identified as well as leukodystrophy in 89% of those imaged. Discussion: This cohort highlights the clinical features of pEDS in adults and contributes several important additional clinical features as well as novel deleterious variants to current knowledge. Hypothetical pathogenic mechanisms which may help to progress understanding and management of pEDS are also discussed.

PRDM10 directs FLCN expression in a novel disorder overlapping with Birt-Hogg-Dubé syndrome and familial lipomatosis

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant disorder characterized by fibrofolliculomas, pulmonary cysts, pneumothoraces and renal cell carcinomas. Here, we reveal a novel hereditary disorder in a family with skin and mucosal lesions, extensive lipomatosis and renal cell carcinomas. The proband was initially diagnosed with BHD based on the presence of fibrofolliculomas, but no pathogenic germline variant was detected in FLCN, the gene associated with BHD. By whole exome sequencing we identified a heterozygous missense variant (p.(Cys677Tyr)) in a zinc-finger encoding domain of the PRDM10 gene which co-segregated with the phenotype in the family. We show that PRDM10Cys677Tyr loses affinity for a regulatory binding motif in the FLCN promoter, abrogating cellular FLCN mRNA and protein levels. Overexpressing inducible PRDM10Cys677Tyr in renal epithelial cells altered the transcription of multiple genes, showing overlap but also differences with the effects of knocking out FLCN. We propose that PRDM10 controls an extensive gene program and acts as a critical regulator of FLCN gene transcription in human cells. The germline variant PRDM10Cys677Tyr curtails cellular folliculin expression and underlies a distinguishable syndrome characterized by extensive lipomatosis, fibrofolliculomas and renal cell carcinomas.

Oral characteristics in adult individuals with periodontal Ehlers-Danlos syndrome

AIM

Periodontal Ehlers-Danlos syndrome (pEDS) is a monogenic type of Ehlers-Danlos syndrome characterized by periodontal destruction at a young age. The present study aimed to document the oral phenotype of pEDS based on prospective clinical investigations.

MATERIALS AND METHODS

Thirty-five adult individuals from 13 families with a clinically and genetically confirmed diagnosis of pEDS underwent a systematic oral assessment.

RESULTS

Periodontitis stage 3 or 4 or edentulism due to periodontal destruction were diagnosed in 94% of the individuals. First permanent tooth loss was reported at the age of 21.5 years (median; range 13-43 years). Deep periodontal pockets were infrequent, with 94% measuring <4 mm. However, there was increased clinical attachment loss (CAL) averaging 8 mm (range 4-13 mm), and the probability of being edentate between the age of 35 and 44 years was 28-47% compared with less than 0.25% of the general population. Radiographic anomalous findings were only found in a portion of subjects and consisted of fused roots of maxillary second molars (81%), root hypoplasia (57%), taurodontism (26%) and tooth rotation of premolars (67%). As such, radiographic findings are not considered common characteristics of pEDS.

CONCLUSIONS

Characteristic oral traits of pEDS in adults are severe CAL with shallow probing depths and marked gingival recession. This is complemented by a lack of attached gingiva. These indications need to be paralleled by genetic analyses to diagnose pEDS unambiguously.

Multifocal periapical cemental dysplasia in periodontal Ehlers–Danlos syndrome combined with leukoencephalopathy in the mutation of c. 890G > a, G297D [ pEDS ]

Periodontal Ehlers‐Danlos syndrome (pEDS) is a rare disorder caused by heterozygous mutations in complement 1 subunit genes C1R and C1S. To date, 148 cases have been described in the literature.We describe a case of a suspected de novo‐mutation of pEDS with generalized Periapical cemental dysplasia (PCD) and cerebral leukoencephalopathy.

Ehlers-Danlos syndromes and their manifestations in the visual system

Ehlers-Danlos syndrome (EDS) is a rare, genetically variable, heterogenous group of (currently recognized) thirteen connective tissue disorders characterized by skin hyperextensibility, tissue fragility, and generalized joint hypermobility. In addition to these commonly recognized phenotypes, recent studies have notably highlighted variable ophthalmic features in EDS. In this review, we comprehensively gather and discuss the ocular manifestations of EDS and its thirteen subtypes in the clinical setting.

The yin and the yang of early classical pathway complement disorders

The classical pathway of the complement cascade has been recognized as a key activation arm, partnering with the lectin activation arm and the alternative pathway to cleave C3 and initiate the assembly of the terminal components. While deficiencies of classical pathway components have been recognized since 1966, only recently have gain-of-function variants been described for some of these proteins. Loss-of-function variants in C1, C4, and C2 are most often associated with lupus and systemic infections with encapsulated bacteria. C3 deficiency varies slightly from this phenotypic class with membranoproliferative glomerulonephritis and infection as the dominant phenotypes. The gain-of-function variants recently described for C1r and C1s lead to periodontal Ehlers Danlos syndrome, a surprisingly structural phenotype. Gain-of-function in C3 and C2 are associated with endothelial manifestations including hemolytic uremic syndrome and vasculitis with C2 gain-of-function variants thus far having been reported in patients with a C3 glomerulopathy. This review will discuss the loss-of-function and gain-of-function phenotypes and place them within the larger context of complement deficiencies.

Complement System and Alarmin HMGB1 Crosstalk: For Better or Worse

Our immune system responds to infectious (PAMPs) and tissue damage (DAMPs) signals. The complement system and alarmin High-Mobility Group Box 1 (HMGB1) are two powerful soluble actors of human host defense and immune surveillance. These systems involve molecular cascades and amplification loops for their signaling or activation. Initially activated as alarm raising systems, their function can be finally switched towards inflammation resolution, where they sustain immune maturation and orchestrate repair mechanisms, opening the way back to homeostasis. However, when getting out of control, these defense systems can become deleterious and trigger serious cellular and tissue damage. Therefore, they can be considered as double-edged swords. The close interaction between the complement and HMGB1 pathways is described here, as well as their traditional and non-canonical roles, their functioning at different locations and their independent and collective impact in different systems both in health and disease. Starting from these systems and interplay at the molecular level (when elucidated), we then provide disease examples to better illustrate the signs and consequences of their roles and interaction, highlighting their importance and possible vicious circles in alarm raising and inflammation, both individually or in combination. Although this integrated view may open new therapeutic strategies, future challenges have to be faced because of the remaining unknowns regarding the molecular mechanisms underlying the fragile molecular balance which can drift towards disease or return to homeostasis, as briefly discussed at the end.

Periodontal (formerly type VIII) Ehlers-Danlos syndrome: Description of 13 novel cases and expansion of the clinical phenotype

Periodontal Ehlers-Danlos syndrome (pEDS) is a rare condition caused by pathogenic variants in the C1R and C1S genes, encoding subunits C1r and C1s of the first component of the classical complement pathway. It is characterized by early-onset periodontitis with premature tooth loss, pretibial hyperpigmentation and skin fragility. Rare arterial complications have been reported, but venous insufficiency is rarely described. Here we report 13 novel patients carrying heterozygous pathogenic variants in C1R and C1S including three novel C1S variants (c.962G > C, c.961 T > G and c.961 T > A). In addition to the pEDS phenotype, three patients and one relative displayed widespread venous insufficiency leading to persistent varicose leg ulcers. One patient suffered an intracranial aneurysm with familial vascular complications including thoracic and abdominal aortic aneurysm and dissection and intracranial aneurysm rupture. This work confirms that vascular complications can occur, although they are not frequent, which leads us to propose to carry out a first complete non-invasive vascular evaluation at the time of the diagnosis in pEDS patients. However, larger case series are needed to improve our understanding of the link between complement pathway activation and connective tissue alterations observed in these patients, and to better assess the frequency, type and consequences of the vascular complications.

Prepubertal Periodontitis in a Patient with Combined Classical and Periodontal Ehlers-Danlos Syndrome

We report an extremely rare case of combined classical and periodontal Ehlers−Danlos syndrome (EDS) with early severe periodontitis and a generalized lack of attached gingiva. A German family with classical EDS was investigated by physical and dental evaluation and exome and Sanger sequencing. Due to the specific periodontal phenotype in the affected child, an additional diagnosis of periodontal EDS was suspected. Physical and genetic examination of two affected and three unaffected family members revealed a family diagnosis of classical EDS with a heterozygous mutation in COL5A1 (c.1502del; p.Pro501Leufs*57). Additional to the major clinical criteria for classical EDS—generalized joint hypermobility, hyperelastic skin, and atrophic scarring —the child aged four years presented with generalized alveolar bone loss up to 80%, early loss of two lower incisors, severe gingival recession, and generalized lack of attached gingiva. Due to these clinical findings, an additional diagnosis of periodontal EDS was suspected. Further genetic analysis revealed the novel missense mutation c.658T>G (p.Cys220Gly) in C1R in a heterozygous state. Early severe periodontitis in association with generalized lack of attached gingiva is pathognomonic for periodontal EDS and led to the right clinical and genetic diagnosis in the present case.

Weighted burden analysis of exome-sequenced late-onset Alzheimer's cases and controls provides further evidence for a role for PSEN1 and suggests involvement of the PI3K/Akt/GSK-3β and WNT signalling pathways

Previous studies have implicated common and rare genetic variants as risk factors for late-onset Alzheimer's disease (LOAD). Here, weighted burden analysis was applied to over 10,000 exome-sequenced subjects from the Alzheimer's Disease Sequencing Project. Analyses were carried out to investigate whether rare variants predicted to have a functional effect within a gene were more commonly seen in cases or in controls. Confirmatory results were obtained for TREM2, ABCA7, and SORL1. Additional support was provided for PSEN1 (p = 0.0002), which previously had been only weakly implicated in LOAD. There was suggestive evidence that functional variants in PIK3R1, WNT7A, C1R, and EXOC5 might increase risk and that variants in TIAF1 and/or NDRG2 might have a protective effect. Overall, there was strong evidence (p = 5 × 10-6 ) that variants in tyrosine phosphatase genes reduce the risk of developing LOAD. Because PIK3R1 variants are expected to impair PI3K/Akt/GSK-3β signalling while variants in tyrosine phosphatase genes would enhance it, these findings are in line with those from animal models, suggesting that this pathway is protective against Alzheimer's disease.

Two Different Missense C1S Mutations, Associated to Periodontal Ehlers-Danlos Syndrome, Lead to Identical Molecular Outcomes

Ehlers-Danlos syndromes (EDS) are clinically and genetically heterogeneous disorders characterized by soft connective tissue alteration like joint hypermobility and skin hyper-extensibility. We previously identified heterozygous missense mutations in the C1R and C1S genes, coding for the complement C1 proteases, in patients affected by periodontal EDS, a specific EDS subtype hallmarked by early severe periodontitis leading to premature loss of teeth and connective tissue alterations. Up to now, there is no clear molecular link relating the nominal role of the C1r and C1s proteases, which is to activate the classical complement pathway, to these heterogeneous symptoms of periodontal EDS syndrome. We aim therefore to elucidate the functional effect of these mutations, at the molecular and enzymatic levels. To explore the molecular consequences, a set of cell transfection experiments, recombinant protein purification, mass spectroscopy and N-terminal analyses have been performed. Focusing on the results obtained on two different C1S variants, namely p.Val316del and p.Cys294Arg, we show that HEK293-F cells stably transfected with the corresponding C1s variant plasmids, unexpectedly, do not secrete the full-length mutated C1s, but only a truncated Fg40 fragment of 40 kDa, produced at very low levels. Detailed analyses of the Fg40 fragments purified for the two C1s variants show that they are identical, which was also unexpected. This suggests that local misfolding of the CCP1 module containing the patient mutation exposes a novel cleavage site, between Lys353 and Cys354, which is not normally accessible. The mutation-induced Fg40 fragment contains the intact C-terminal serine protease domain but not the N-terminal domain mediating C1s interaction with the other C1 subunits, C1r, and C1q. Thus, Fg40 enzymatic activity escapes the normal physiological control of C1s activity within C1, potentially providing a loss-of-control. Comparative enzymatic analyses show that Fg40 retains the native esterolytic activity of C1s, as well as its cleavage efficiency toward the ancillary alarmin HMGB1 substrate, for example, whereas the nominal complement C4 activation cleavage is impaired. These new results open the way to further molecular explorations possibly involving subsidiary C1s targets.

C1R Mutations Trigger Constitutive Complement 1 Activation in Periodontal Ehlers-Danlos Syndrome

Heterozygous missense or in-frame insertion/deletion mutations in complement 1 subunits C1r and C1s cause periodontal Ehlers-Danlos Syndrome (pEDS), a specific EDS subtype characterized by early severe periodontal destruction and connective tissue abnormalities like easy bruising, pretibial haemosiderotic plaques, and joint hypermobility. We report extensive functional studies of 16 C1R variants associated with pEDS by in-vitro overexpression studies in HEK293T cells followed by western blot, size exclusion chromatography and surface plasmon resonance analyses. Patient-derived skin fibroblasts were analyzed by western blot and Enzyme-linked Immunosorbent Assay (ELISA). Overexpression of C1R variants in HEK293T cells revealed that none of the pEDS variants was integrated into the C1 complex but cause extracellular presence of catalytic C1r/C1s activities. Variants showed domain-specific abnormalities of intracellular processing and secretion with preservation of serine protease function in the supernatant. In contrast to C1r wild type, and with the exception of a C1R missense variant disabling a C1q binding site, pEDS variants had different impact on the cell: retention of C1r fragments inside the cell, secretion of aggregates, or a new C1r cleavage site. Overexpression of C1R variants in HEK293T as well as western blot analyses of patient fibroblasts showed decreased levels of secreted C1r. Importantly, all available patient fibroblasts exhibited activated C1s and activation of externally added C4 in the supernatant while control cell lines secreted proenzyme C1s and showed no increase in C4 activation. The central elements in the pathogenesis of pEDS seem to be the intracellular activation of C1r and/or C1s, and extracellular presence of activated C1s that independently of microbial triggers can activate the classical complement cascade.