Association of FBN1 polymorphism with susceptibility of adolescent idiopathic scoliosis: a case-control study.

BACKGROUND: Fibrillin-1 (FBN1) is an extracellular matrix glycoprotein essential to the structural component of microfibrils and FBN1 gene polymorphisms can be associated with adolescent idiopathic scoliosis (AIS) susceptibility. This study aimed to evaluate the potential role of the FBN1 rs12916536 polymorphism in AIS development or severity and the variation in Cobb angle in relation to patient's characteristics. METHODS: DNA from 563 subjects (185 AIS patients and 378 controls) were genotyped using a validated TaqMan allelic discrimination assay. A multivariate logistic regression model evaluated the association between polymorphism and AIS, using the adjusted odds ratios (OR) with their respective 95% confidence intervals (95% CI). A linear regression analysis evaluated the variation in Cobb angle according to the patient's age and body mass index (BMI). RESULTS: Among the AIS group there was a predominance of females (12:1), low or normal BMI (90%), 58% had a Cobb angle greater than 45° and 74% were skeletally mature. Age was a risk factor (4-fold) for curve progression higher than BMI (P < 0.001). The allelic frequency of the rs12916536 G > A polymorphism was 40% in controls and 31% in AIS cases; and this difference was statistically significant (P = 0.004). FBN1 rs12916536 GA + AA genotypes were associated with a lower risk of AIS susceptibility (OR = 0.58 and 95% CI = 0.35-0.98), after adjustment for age, sex and BMI. However, no significant differences were detected in polymorphism distribution with the severity of the disease (Cobb < 45° or ≥ 45°). CONCLUSION: Age was a risk factor for progression of the scoliotic curve and FBN1 rs12916536 polymorphism a protective factor for AIS susceptibility.

The mgΔlpn mouse model for Marfan syndrome recapitulates the ocular phenotypes of the disease.

PURPOSE: Fibrillin-1 and -2 are major components of tissue microfibrils that compose the ciliary zonule and cornea. While mutations in human fibrillin-1 lead to ectopia lentis, a major manifestation of Marfan syndrome (MFS), in mice fibrillin-2 can compensate for reduced/lack of fibrillin-1 and maintain the integrity of ocular structures. Here we examine the consequences of a heterozygous dominant-negative mutation in the Fbn1 gene in the ocular system of the mgΔlpn mouse model for MFS. METHODS: Eyes from mgΔlpn and wild-type mice at 3 and 6 months of age were analyzed by histology. The ciliary zonule was analyzed by scanning electron microscopy (SEM) and immunofluorescence. RESULTS: Mutant mice presented a significantly larger distance of the ciliary body to the lens at 3 and 6 months of age when compared to wild-type, and ectopia lentis. Immunofluorescence and SEM corroborated those findings in MFS mice, revealing a disorganized mesh of microfibrils on the floor of the ciliary body. Moreover, mutant mice also had a larger volume of the anterior chamber, possibly due to excess aqueous humor. Finally, losartan treatment had limited efficacy in improving ocular phenotypes. CONCLUSIONS: In contrast with null or hypomorphic mutations, expression of a dominant-negative form of fibrillin-1 leads to disruption of microfibrils in the zonule of mice. This in turn causes lens dislocation and enlargement of the anterior chamber. Therefore, heterozygous mgΔlpn mice recapitulate the major ocular phenotypes of MFS and can be instrumental in understanding the development of the disease.

Síndrome de Marfán en la edad adulta / Marfan's Syndrome

El síndrome de Marfán es una enfermedad que integra el grupo de las llamadas colagenopatías no autoinmunes. Etiológicamente consiste en la mutación del gen que codifica la fibrilina 1, que se encarga junto con otras proteínas como la elastina de formar los microfilamentos de sostén de la matriz celular. Este defecto genera diversas manifestaciones clínicas por trastornos en diferentes sistemas (esquelético, cardiovascular, gastrointestinal, ocular). Se presenta un paciente de 43 años de edad, de raza negra, que llegó a la edad adulta sin un diagnóstico de la enfermedad. Incidentalmente sospechamos el diagnóstico al tratar una neumonía adquirida en la comunidad. Se trató su cuadro de neumonía con piperacilina y tazobactam por 7 días. Se recomendó la valoración por parte de cirugía cardiovascular por hallazgos de aneurisma de la aorta ascendente, pero el paciente decidió no continuar con los estudios de su enfermedad. Se aconsejó cambios en el estilo de vida y ejercicios físicos y se diagnosticó alta probabilidad de muerte por el problema vascular descrito(AU)

Marfan's syndrome is a disease that is included in the group of the no autoimmune collagen diseases, the ca use of this syndrome is a mutation in the gen FBN1 that translate the protein fibrillin 1, that is fundamental besides other proteins like elastin to form a part of the extracellular matrix. This defect generates multiple clinical manifestations due to defects in different systems (skeletal, cardiac, big vessels, gastrointestinal, ocular). The reported case is of a patient who reached adulthood without a diagnosis of the diseases, which we incidentally suspect in the context of community acquired pneumonia(AU)

Estudio y análisis comparativo de interacciones entre la proteina integrina con fragmentos de la proteína fibrilina-1 y fragmentos mutados de esta utilizando la metodología de docking molecular / Study and comparative analysis of interactions protein between the integrina with fragments fibrillin-1 and mutated fragments of this by using molecular docking

Resumen Objetivo: Evaluar las interacciones proteína-proteína que pueden generarse entre fragmentos de la proteína fibrilina-1, cuyas mutaciones causan el síndrome de Marfan (SM). Materiales y métodos: Se realizó una serie de cálculos docking proteína-proteína entre las macromoléculas de interés; se empleó el programa Molsoft ICM; se utilizaron las estructuras cristalinas de la proteína integrina αVβ3 y los fragmentos de la proteína fibrilina-1; además se generó una sucesión de mutaciones en la fibrilina-1, las cuales son características de pacientes con síndrome de Marfan, y posteriormente se realizó el acoplamiento molecular. Adicionalmente se determinó los aminoácidos que con mayor frecuencia estaban presentes en el sitio de interacción y su hidrofobicidad. Resultados: Se cuantificó la cantidad de aminoácidos hidrófobos presentes en las zonas de interacción producidas por los acoplamientos, teniendo en cuenta la energía del sistema; esta ponderación estuvo entre el 40 y 50 % de los aminoácidos de la zona de interacción, con un porcentaje mayor con respecto a aminoácidos neutros o cargados. En los resultados obtenidos utilizando las mutaciones realizadas sobre los fragmentos cbEGF22-TB4-cbEGF23 y cbEGF9-hyb2-cbEGF10 de la fibrilina-1 se encontró que no se ubicaron en zonas cercanas al sitio de interacción en la mayoría de los casos. Conclusiones: Las interacciones entre los fragmentos de fibrilina-1, y estos con respecto a la integrina, mostraron en sus zonas de interacción la presencia mayoritariamente de aminoácidos hidrofóbicos, que es lo esperado normalmente.

Abstract Objective: To assess protein-protein interactions between fragments of fibrillin-1 protein, whose mutations cause Marfan syndrome (MS). Materials and Methods: We performed a series of protein-protein docking calculations between the macromolecules of interest for this purpose was used Molsoft ICM program. We used the crystal structures of αVβ3 Integrin protein and fragments of fibrillin-1 protein also were generated mutations in the fibrillin-1, which are characteristic in patients with Marfan syndrome and subsequently to the molecular docking. We determined the amino acids most often present at the site of interaction and its hydrophobicity. Results: The amount of hydrophobic amino acids present in the areas of interaction given by the couplings was quantified. Given the energy of the system, was between 40 and 50% of the amino acids of the interaction zone, with a higher proportion relative to charged or neutral amino acids. In the results obtained using the mutations performed on fragments cbEGF23 cbEGF22-TB4-and-cbEGF10 cbEGF9-HYB2 of fibrillin-1, was found they were not placed in areas near the site of interaction in most cases. Conclusion: The interaction between fragments of fibrillin-1, and those with respect to their integrin showed the presence interaction zones mostly hydrophobic amino acids, which are normally expected.

Revisión Bibliográfica y Presentación de un Caso: Síndrome de Marfán / Bibliographic Review and Presentation of a Case: Marfán Syndrome

El síndrome de Marfán es una patología poco común, causada por una mutación genética de fibrilina 1, imprescindible para la síntesis de fibras elásticas del tejido conectivo. Se caracteriza por una alta penetrancia y mar-cada heterogeneidad fenotípica. Entre las diferentes manifestaciones clínicas, la afectación cardiovascular merece una consideración especial, debido a su impacto en el pronóstico. El diagnóstico requiere una evaluación clínica completa de múltiples órganos y sistemas; por su ampliada sintomatología, la toma de decisiones es compleja, por tanto, cuando se sospeche síndrome de Marfán debe apli-carse la revisión de los criterios de Ghent. Si el diagnóstico es confirmado, debe iniciarse tempranamente su manejo multidisciplinario con un seguimiento minucioso, ya que se dis-pone de tratamientos farmacológicos y qui-rúrgicos que mejoran la esperanza de vida.Se reporta un caso clínico, con la revisión de las manifestaciones clínicas, criterios diagnósticos y manejo.

Marfan syndrome is a rare disease, caused by a genetic mutation of fibrillin-1, essential for the synthesis of connective tissue elastic fibers. It is characterized by a high penetran-ce and a marked phenotypic heterogeneity. Among the different clinical manifestations, cardiovascular involvement deserves a spe-cial consideration because of their impact on prognosis.The diagnosis requires a complete medical evaluation of multiple organs and systems; with expanded symptoms where the decision making is complex, so when Marfan syndro-me is suspected should be applied the revi-sed criteria of Ghent. If the diagnosis is confir-med, it must start early with its multidisciplinary approach carefully monitored because there are pharmacological and surgical treatments that improve life expectancy.Finally a case is reported, with the review of clinical manifestations, diagnostic criteria and management.

Fibrillin-1 mgΔ(lpn) Marfan syndrome mutation associates with preserved proteostasis and bypass of a protein disulfide isomerase-dependent quality checkpoint.

Fibrillin-1 mutations promote Marfan syndrome (MFS) via complex yet unclear pathways. The roles of endoplasmic reticulum (ER) and the major ER redox chaperone protein disulfide isomerase-A1 in the processing of normal and mutated fibrillin-1 and ensuing protein secretion and/or intracellular retention are unclear. Our results in mouse embryonic fibroblasts bearing the exon-skipping mgΔ(lox-P-neo) (mgΔ(lpn)) mutation, which associates in vivo with MFS and in vitro with disrupted microfibrils, indicate a preserved ER-dependent proteostasis or redox homeostasis. Rather, mutated fibrillin-1 is secreted normally through Golgi-dependent pathways and is not intracellularly retained. Similar results occurred for the C1039G point mutation. In parallel, we provide evidence that PDIA1 physically interacts with fibrillin-1 in the ER. Moreover, siRNA against PDIA1 augmented fibrillin-1 secretion rates in wild-type cells. However, fibrillin-1 with the mgΔ(lpn) mutation bypassed PDI checkpoint delay, while the C1039G mutation did not. This heretofore undisclosed PDIA1-mediated mechanism may be important to control the extracellular availability of function-competent fibrillin-1, an important determinant of disease phenotype. Moreover, our results may reveal a novel, holdase-like, PDI function associated with ER protein quality control.

Processamento intracelular da fibrilina-1 mutada na síndrome de Marfan: escape do controle de qualidade pela dissulfeto isomerase proteica / Mutated fibrillin-1 intracellular processing in Marfan syndrome: bypass of a protein disulfide isomerase-mediated quality control

A Síndrome de Marfan (SMF) é a enfermidade hereditária mais comum dentre as que afetam o sistema conjuntivo, causada por mutações da glicoproteína fibrilina-1, o principal componente estrutural das microfibrilas elásticas da matriz extracelular. As manifestações fenotípicas da SMF são sistêmicas e acometem tipicamente os sistemas ocular, esquelético e cardiovascular, este uma importante causa de morbi-mortalidade. Entretanto, não está claro como a mutação induz a doença. Estudos anteriores sugerem anomalias morfológicas do retículo endoplasmático (RE) ou retenção intracelular da fibrilina-1 nos estágios avançados da SMF. Entretanto, a contribuição do enovelamento da fibrilina-1 mutada e do estresse do RE na fisiopatologia celular da SMF não é conhecida. Proteínas mal-enoveladas podem levar à retenção intracelular e/ou aumento da degradação através da via de degradação associada ao RE (ERAD), além da indução da resposta a proteínas mal-enoveladas (UPR), ambas com potencial contribuição à fisiopatologia de doenças, incluindo a SMF. Assim, estudamos em fibroblastos embrionários isolados de camundongos (MEFs) com SMF se a fibrilina-1 mutada é reconhecida pelo controle de qualidade do RE pelo seu mal- enovelamento e induz estresse do RE por sua retenção intracelular. Demonstramos que a mutação na fibrilina-1 per se não promoveu chaperonas marcadoras de UPR ou geração de oxidantes. Além disso, não levou a uma maior sensibilização das células à indução exógena de estresse do RE, nem promoveu maior morte celular após inibição do proteassoma. Além disso, não foi observada retenção intracelular da fibrilina-1 nas células SMF, e mesmo após inibição da via secretora ou indução de estresse do RE, a inibição da secreção da fibrilina-1 foi similar nos MEFs SMF e wild-type (WT). A dissulfeto isomerase proteica (PDI), uma importante chaperona redox do RE, interage com fibrilina-1, e seu silenciamento levou a um aumento na secreção da fibrilina-1 pelos MEFs WT...

Marfan syndrome (MFS) is the most common connective tissue hereditary disease, caused by mutations in the glycoprotein fibrillin-1, the main structural component of extracellular matrix elastic microfibrils. MFS phenotypic manifestations are systemic and typically involve the ocular, skeletal and cardiovascular systems, the latter a major cause of morbidity/mortality. However, how gene mutation induxes disease is yet unclear. Previous studies suggest endoplasmic reticulum (ER) morphological abnormalities or fibrillin-1 intracellular retention in advanced MFS stages. However, the contribution of mutated fibrillin-1 folding and ER stress to MFS cellular pathophysiology is unknown. Un/misfolded proteins may associate with their intracellular retention and/or increased degradation through ER-associated degradation (ERAD), in addition to inducing the unfolded protein response (UPR), both sharing potential contributions to disease pathophysiology, including MFS. Thus, we studied in embryonic fibroblasts (MEFs) isolated from WT and MFS mice, if mutated fibrillin-1 can be recognized by ER quality control as a misfolded protein, able to induce ER stress due to its intracellular retention. We showed that fibrillin-1 mutation by itself did not promote UPR chaperone markers or oxidant generation. Moreover, it did not sensitize cells to exogenous ER stress nor affected cell survival curves after proteasome inhibition. Furthermore, no intracellular retention of fibrillin-1 was observed in MFS cells, and even after secretory pathway inhibition or ER stress induction, fibrillin-1 secretion inhibition was similar in MFS and wild-type (WT) MEFs. Protein disulfide isomerase (PDI), an important ER redox chaperone, interacts with fibrillin-1 and its silencing induced an increased fibrillin-1 secretion in WT...

Candidate gene linkage analysis indicates genetic heterogeneity in Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant disease of the connective tissue that affects the ocular, skeletal and cardiovascular systems, with a wide clinical variability. Although mutations in the FBN1 gene have been recognized as the cause of the disease, more recently other loci have been associated with MFS, indicating the genetic heterogeneity of this disease. We addressed the issue of genetic heterogeneity in MFS by performing linkage analysis of the FBN1 and TGFBR2 genes in 34 families (345 subjects) who met the clinical diagnostic criteria for the disease according to Ghent. Using a total of six microsatellite markers, we found that linkage with the FBN1 gene was observed or not excluded in 70.6 percent (24/34) of the families, and in 1 family the MFS phenotype segregated with the TGFBR2 gene. Moreover, in 4 families linkage with the FBN1 and TGFBR2 genes was excluded, and no mutations were identified in the coding region of TGFBR1, indicating the existence of other genes involved in MFS. Our results suggest that the genetic heterogeneity of MFS may be greater that previously reported.