Marina Colombi

Mutations in the facilitative glucose transporter GLUT10 alter angiogenesis and cause arterial tortuosity syndrome

Arterial tortuosity syndrome (ATS) is an autosomal recessive disorder characterized by tortuosity, elongation, stenosis and aneurysm formation in the major arteries owing to disruption of elastic fibers in the medial layer of the arterial wall. Previously, we used homozygosity mapping to map a candidate locus in a 4.1-Mb region on chromosome 20q13.1 (ref. 2). Here, we narrowed the candidate region to 1.2 Mb containing seven genes. Mutations in one of these genes, SLC2A10, encoding the facilitative glucose transporter GLUT10, were identified in six ATS families. GLUT10 deficiency is associated with upregulation of the TGFβ pathway in the arterial wall, a finding also observed in Loeys-Dietz syndrome, in which aortic aneurysms associate with arterial tortuosity. The identification of a glucose transporter gene responsible for altered arterial morphogenesis is notable in light of the previously suggested link between GLUT10 and type 2 diabetes. Our data could provide new insight on the mechanisms causing microangiopathic changes associated with diabetes and suggest that therapeutic compounds intervening with TGFβ signaling represent a new treatment strategy.

The 2017 international classification of the Ehlers-Danlos syndromes.

The Ehlers–Danlos syndromes (EDS) are a clinically and genetically heterogeneous group of heritable connective tissue disorders (HCTDs) characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. Over the past two decades, the Villefranche Nosology, which delineated six subtypes, has been widely used as the standard for clinical diagnosis of EDS. For most of these subtypes, mutations had been identified in collagen‐encoding genes, or in genes encoding collagen‐modifying enzymes. Since its publication in 1998, a whole spectrum of novel EDS subtypes has been described, and mutations have been identified in an array of novel genes. The International EDS Consortium proposes a revised EDS classification, which recognizes 13 subtypes. For each of the subtypes, we propose a set of clinical criteria that are suggestive for the diagnosis. However, in view of the vast genetic heterogeneity and phenotypic variability of the EDS subtypes, and the clinical overlap between EDS subtypes, but also with other HCTDs, the definite diagnosis of all EDS subtypes, except for the hypermobile type, relies on molecular confirmation with identification of (a) causative genetic variant(s). We also revised the clinical criteria for hypermobile EDS in order to allow for a better distinction from other joint hypermobility disorders. To satisfy research needs, we also propose a pathogenetic scheme, that regroups EDS subtypes for which the causative proteins function within the same pathway. We hope that the revised International EDS Classification will serve as a new standard for the diagnosis of EDS and will provide a framework for future research purposes.

Management of pain and fatigue in the joint hypermobility syndrome (a.k.a. Ehlers–Danlos syndrome, hypermobility type): Principles and proposal for a multidisciplinary approach

Joint hypermobility syndrome (JHS), or Ehlers–Danlos syndrome (EDS) hypermobility type (EDS‐HT), is a underdiagnosed heritable connective tissue disorder characterized by generalized joint hypermobility and a wide range of visceral, pelvic, neurologic, and cognitive dysfunctions. Deterioration of quality of life is mainly associated with pain and fatigue. Except for the recognized effectiveness of physiotherapy for some musculoskeletal features, there are no standardized guidelines for the assessment and treatment of pain and fatigue. In this work, a practical classification of pain presentations and factors contributing in generating painful sensations in JHS/EDS‐HT is proposed. Pain can be topographically classified in articular limb (acute/subacute and chronic), muscular limb (myofascial and fibromyalgia), neuropathic limb, back/neck, abdominal and pelvic pain, and headache. For selected forms of pain, specific predisposing characteristics are outlined. Fatigue appears as the result of multiple factors, including muscle weakness, respiratory insufficiency, unrefreshing sleep, dysautonomia, intestinal malabsorption, reactive depression/anxiety, and excessive use of analgesics. A set of lifestyle recommendations to instruct patients as well as specific investigations aimed at characterizing pain and fatigue are identified. Available treatment options are discussed in the set of a structured multidisciplinary approach based on reliable outcome tools.

Mutations in PRDM5 in Brittle Cornea Syndrome Identify a Pathway Regulating Extracellular Matrix Development and Maintenance

Extreme corneal fragility and thinning, which have a high risk of catastrophic spontaneous rupture, are the cardinal features of brittle cornea syndrome (BCS), an autosomal-recessive generalized connective tissue disorder. Enucleation is frequently the only management option for this condition, resulting in blindness and psychosocial distress. Even when the cornea remains grossly intact, visual function could also be impaired by a high degree of myopia and keratoconus. Deafness is another common feature and results in combined sensory deprivation. Using autozygosity mapping, we identified mutations in PRDM5 in families with BCS. We demonstrate that regulation of expression of extracellular matrix components, particularly fibrillar collagens, by PRDM5 is a key molecular mechanism that underlies corneal fragility in BCS and controls normal corneal development and maintenance. ZNF469, encoding a zinc finger protein of hitherto undefined function, has been identified as a quantitative trait locus for central corneal thickness, and mutations in this gene have been demonstrated in Tunisian Jewish and Palestinian kindreds with BCS. We show that ZNF469 and PRDM5, two genes that when mutated cause BCS, participate in the same regulatory pathway.

Homozygosity mapping of a gene for arterial tortuosity syndrome to chromosome 20q13

Background: Arterial tortuosity syndrome (ATS) is an uncommon connective tissue disorder of unknown aetiology. The most prominent feature is tortuosity of the large arteries, but lengthening, stenosis, and aneurysm formation are also frequent. Methods: We performed a genomewide screen by homozygosity mapping of three consanguineous multiplex families, two from Morocco, and one from Italy, which included 11 ATS patients. The two families from Morocco may possibly have a common ancestor. Results: We mapped the ATS gene to chromosome 20q13. Recombinations within an extended haplotype of 11 microsatellite markers localised the ATS gene between markers D20S836 and D20S109, an interval of 9.5 cM. Conclusions: Cloning and completing functional and structural analysis of the ATS gene may provide new insights into the molecular mechanisms of elastogenesis.

Exclusion of candidate genes in a family with arterial tortuosity syndrome

Arterial tortuosity syndrome (ATS) is a rare hereditary disorder with variable clinical presentation including tortuosity and elongation of the major arteries, often associated with pulmonary artery stenosis, pulmonary hypertension, and skin and joint laxity, suggestive of a connective tissue disorder. ATS is transmitted in an autosomal recessive mode, but the causal gene is unknown. We report an Italian pedigree with three inbred families in which five patients show signs of ATS. In particular, four adult patients present arterial tortuosity and elongation of the main arteries. Two of these patients, with the most severe degree of arterial tortuosity, also show severe peripheral stenosis of the main pulmonary artery. The fifth young patient shows a severe pulmonary valve stenosis in the absence of arterial tortuosity. All patients show signs of Ehlers–Danlos syndrome (EDS): soft skin with abundant subcutaneous tissue and joint laxity, hernias, and disorganization of the extracellular matrix (ECM) of fibronectin (FN) and of actin microfilaments in cultured skin fibroblasts. Linkage analysis of the genes involved in EDS and other connective tissue disorders, excluded COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL5A3, COL6A1, COL6A2, ADAMTS2, ELN, FN1, TNXA, and TNXB as candidate genes in the family under study, thus indicating that ATS is a distinct clinical and molecular entity.

Differential Diagnosis and Diagnostic Flow Chart of Joint Hypermobility Syndrome/Ehlers-Danlos Syndrome Hypermobility Type Compared to Other Heritable Connective Tissue Disorders

Joint hypermobility syndrome/Ehlers–Danlos syndrome hypermobility type (JHS/EDS‐HT) is an evolving and protean disorder mostly recognized by generalized joint hypermobility and without a defined molecular basis. JHS/EDS‐HT also presents with other connective tissue features affecting a variety of structures and organs, such as skin, eye, bone, and internal organs. However, most of these signs are present in variable combinations and severity in many other heritable connective tissue disorders. Accordingly, JHS/EDS‐HT is an “exclusion” diagnosis which needs the absence of any consistent feature indicative of other partially overlapping connective tissue disorders. While both Villefranche and Brighton criteria include such an exclusion as a mandatory item, a systematic approach for reaching a stringent clinical diagnosis of JHS/EDS‐HT is still lacking. The absence of a consensus on the diagnostic approach to JHS/EDS‐HT concerning its clinical boundaries with similar conditions contribute to limit our actual understanding of the pathologic and molecular bases of this disorder. In this review, we revise the differential diagnosis of JHS/EDS‐HT with those heritable connective tissue disorders which show a significant overlap with the former and mostly include EDS classic, vascular and kyphoscoliotic types, osteogenesis imperfecta, Marfan syndrome, Loeys–Dietz syndrome, arterial tortuosity syndrome, and lateral meningocele syndrome. A diagnostic flow chart is also offered with the attempt to support the less experienced clinician in stringently recognizing JHS/EDS‐HT and stimulate the debate in the scientific community for both management and research purposes.

Gynecologic and obstetric implications of the joint hypermobility syndrome (a.k.a. Ehlers–Danlos syndrome hypermobility type) in 82 Italian patients†‡

Joint hypermobility syndrome (JHS) emerges as likely the most common clinical form of Ehlers–Danlos syndrome. Given the striking predominance of affected women, practitioners often face gynecologic and obstetric issues. However, their decisions are still based on personal experience rather than literature due to the lack of a consistent body of evidence. We collected a set of gynecologic and obstetric features in 82 post‐puberal women with JHS attending two Italian centers. Common gynecologic findings were dysmenorrhea (82.9%), meno/metrorrhagias (53.7%), irregular menses (46.3%), and dispareunia/vulvodinia (31.7%). Forty women were nulliparous and 42 had one or more pregnancy for a total of 93 diagnosed conceptions. Of them, 16.1% were spontaneous abortions, 6.5% voluntary interruptions, 10.7% preterm deliveries, and 66.7% deliveries at term. Overall outcome of proceeding pregnancies was good with no stillbirth and fetal/neonatal hypoxic/ischemic event. Non‐operative vaginal delivery was registered in 72.2%, forceps/vacuum use in 5.5% and cesarean in 22.3%. Local/total anesthesia was successfully performed in 17 pregnancies without any problem. Major post‐partum complications included abnormal scar formation after cesarean or episiotomy (46.1%), hemorrhage (19.4%), pelvic prolapses (15.3%), deep venous thrombosis (4.2%), and coccyx dislocation (1.4%). Prolapses were the most clinically relevant complication and associated with episiotomy. Gathered data were discussed for practically oriented considerations.

Loeys-Dietz syndrome type I and type II: clinical findings and novel mutations in two Italian patients

BackgroundLoeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder showing the involvement of cutaneous, cardiovascular, craniofacial, and skeletal systems. In particular, LDS patients show arterial tortuosity with widespread vascular aneurysm and dissection, and have a high risk of aortic dissection or rupture at an early age and at aortic diameters that ordinarily are not predictive of these events. Recently, LDS has been subdivided in LDS type I (LDSI) and type II (LDSII) on the basis of the presence or the absence of cranio-facial involvement, respectively. Furthermore, LDSII patients display at least two of the major signs of vascular Ehlers-Danlos syndrome. LDS is caused by mutations in the transforming growth factor (TGF) beta-receptor I (TGFBR1) and II (TGFBR2) genes. The aim of this study was the clinical and molecular characterization of two LDS patients.MethodsThe exons and intronic flanking regions of TGFBR1 and TGFBR2 genes were amplified and sequence analysis was performed.ResultsPatient 1 was a boy showing dysmorphic signs, blue sclerae, high-arched palate, bifid uvula; skeletal system involvement, joint hypermobility, velvety and translucent skin, aortic root dilatation, tortuosity and elongation of the carotid arteries. These signs are consistent with an LDSI phenotype. The sequencing analysis disclosed the novel TGFBR1 p.Asp351Gly de novo mutation falling in the kinase domain of the receptor. Patient 2 was an adult woman showing ascending aorta aneurysm, with vascular complications following surgery intervention. Velvety and translucent skin, venous varicosities and wrist dislocation were present. These signs are consistent with an LDSII phenotype. In this patient and in her daughter, TGFBR2 genotyping disclosed in the kinase domain of the protein the novel p.Ile510Ser missense mutation.ConclusionWe report two novel mutations in the TGFBR1 and TGFBR2 genes in two patients affected with LDS and showing marked phenotypic variability. Due to the difficulties in the clinical approach to a TGFBR-related disease, among patients with vascular involvement, with or without aortic root dilatation and LDS cardinal features, genotyping is mandatory to clarify the diagnosis, and to assess the management, prognosis, and counselling issues.

Dystrophic epidermolysis bullosa pruriginosa in Italy: clinical and molecular characterization

Dystrophic epidermolysis bullosa (DEB) pruriginosa (DEB‐Pr) is a rare variant of DEB due to COL7A1 dominant and recessive mutations, which is characterized by severe itching and lichenoid or nodular prurigo‐like lesions, mainly involving the extremities. Less than 30 patients have been described showing variable disease expression, and frequently, delayed age of onset. We report the clinical and molecular characterization of seven Italian DEB patients, three affected with recessive DEB‐Pr and four with dominant DEB‐Pr. In all the patients, the signs were typical of a mild DEB phenotype, until the onset of pruritus, which was followed by worsening of the clinical picture, with appearance of the distinctive lichenified lesions of DEB‐Pr. Nine mutations were found in the COL7A1 gene, three of which were novel and one was de novo. DEB‐Pr patients with either dominant or recessive mutations were shown to synthesize a normal or variably reduced amount of type VII collagen, which was correctly deposited at the dermal–epidermal junction. Since six of these mutations have been reported in DEB patients in the absence of intense pruritus, these data implicate a role of yet unidentified phenotype‐modifying factors in the pathogenesis of DEB‐Pr.