Protein Fibrillin-1 Research Articles

Linkage of regulators of TGF‐β activity in the fetal ovary to polycystic ovary syndrome

Although not often discussed, the ovaries of women with polycystic ovary syndrome (PCOS) show all the hallmarks of increased TGF-β activity, with increased amounts of fibrous tissue and collagen in the ovarian capsule or tunica albuginea and ovarian stroma. Recent studies suggest that PCOS could have fetal origins. Genetic studies of PCOS have also found linkage with a microsatellite located in intron 55 of the extracellular matrix protein fibrillin 3. Fibrillins regulate TGF-β bioactivity in tissues by binding latent TGF-β binding proteins. We therefore examined expression of fibrillins 1-3, latent TGF-β binding proteins 1-4, and TGF-β 1-3 in bovine and human fetal ovaries at different stages of gestation and in adult ovaries. We also immunolocalized fibrillins 1 and 3. The results indicate that TGF-β pathways operate during ovarian fetal development, but most important, we show fibrillin 3 is present in the stromal compartments of fetal ovaries and is highly expressed at a critical stage early in developing human and bovine fetal ovaries when stroma is expanding and follicles are forming. These changes in expression of fibrillin 3 in the fetal ovary could lead to a predisposition to develop PCOS in later life.

The Elastin Fiber System between and Adjacent to Collector Channels in the Human Juxtacanalicular Tissue

To determine the composition and investigate the elastin fiber system in the juxtacanalicular tissue adjacent to and between collector channel orifices in normal human eyes. Normal human eyes (71.0 ± 8.6 years; mean ± SD; n = 4) were perfusion fixed at low (10 mm Hg) and high pressure (20 mm Hg) with 3% paraformaldehyde/0.1 M phosphate buffer. Frontal serial sections were cut from paraffin blocks, and regions with and without collector channels were selected. Sections were stained using Weigert's resorcin-fuchsin stain with oxidation. Immunohistochemistry was performed using antibodies against elastin, fibrillin-1, and microfibrillar-associated protein-1/2. Elastin, elaunin, and oxytalan fibers were identified within the juxtacanalicular tissue of the inner and outer walls in low- and high-pressure eyes. These fibers were found at collector channel orifices, between collector channels, and within collector channel walls. Fibrillin-1 was located at the base and lateral edges of Schlemm's canal endothelial cells. Microfibrillar-associated protein-1/2 was found with elastin-like fibers at the base of Schlemm's canal endothelium cells, in the juxtacanalicular tissue, and in the uveal region. Elastin, elaunin, oxytalan, and elastin-associated proteins fibrillin-1 and microfibrillar-associated protein-1/2 were identified within the juxtacanalicular tissue of the inner and outer walls and within collector channel walls of human eyes perfused at low and high pressure. No differences in labeling patterns for elastin, elaunin, and oxytalan were found in the juxtacanalicular tissue adjacent to or between collector channel orifices. The elastin fiber system appears to have a significant role in the support and distensibility of the juxtacanalicular region under collector channels.

Fibrillin-3 expression in human development

Fibrillin proteins are the major components of extracellular microfibrils found in many connective tissues. Fibrillin-1 and fibrillin-2 are well studied and mutations in these proteins cause a number of fibrillinopathies including Marfan syndrome and congenital contractural arachnodactyly, respectively. Fibrillin-3 was more recently discovered and is much less well characterized. Fibrillin-1 is expressed throughout life, whereas fibrillins-2 and -3 are thought to be primarily present during development. Here, we report detailed fibrillin-3 expression patterns in early human development.A polyclonal antiserum against a C-terminal recombinant half of human fibrillin-3 was produced in rabbit. Anti-fibrillin-3 antibodies were affinity-purified and antibodies cross-reacting with the other fibrillins were removed by absorption resulting in specific anti-fibrillin-3 antibodies. Immunohistochemical analyses with these purified antibodies demonstrate that fibrillin-3 is temporally expressed in numerous tissues relatively evenly from the 6th to the 12th gestational week. Fibrillin-3 was found spatially expressed in perichondrium, perineurium, perimysium, skin, developing bronchi, glomeruli, pancreas, kidney, heart and testis and at the prospective basement membranes in developing epithelia and endothelia. Double immunohistochemical analyses showed that all fibrillins are globally expressed in the same organs, with a number of differences on the tissue level in cartilage, perichondrium and developing bronchi. These results suggest that fibrillin-3, compared to the other fibrillins, fulfills both overlapping and distinct functions in human development.

Fibrillins in Adult Human Ovary and Polycystic Ovary Syndrome: Is Fibrillin-3 Affected in PCOS?

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age. Although genetic linkage analyses have demonstrated a susceptibility locus for PCOS mapping to the fibrillin-3 gene, the presence of fibrillin proteins in normal and polycystic ovaries has not been characterized. This study compared and contrasted fibrillin-1, -2, and -3 localization in normal and polycystic ovaries. Immunohistochemical stainings of ovaries from 21 controls and 9 patients with PCOS were performed. Fibrillin-1 was ubiquitous in ovarian connective tissue. Fibrillin-2 localized around antral follicles and in areas of folliculolysis. Fibrillin-3 was present in a restricted distribution within the specialized perifollicular stroma of follicles in morphological transition from primordial to primary type [transitional follicles (TFs)]. Fibrillin-1 and -2 stainings of PCOS ovaries were similar to those of the controls. However, in eight of the nine PCOS ovaries, there was a decrease in the number of TFs associated with fibrillin-3, including no staining in five PCOS samples; decreased number of fibrillin-3-associated TFs/mm(2) was confirmed by quantitative analysis. Our findings support a role for fibrillin-3 in the pathogenesis of PCOS and suggest fibrillin-3 may function in primordial to primary follicle transition. We propose that loss of fibrillin-3 during folliculogenesis may be an important factor in PCOS pathogenesis.

Corneal curvature, pachymetry, and endothelial cell density in Marfan syndrome

To evaluate corneal curvature, pachymetry, and endothelial cell density (ECD) in Marfan syndrome (MFS). A case-control study in which K values, pachymetry, and ECD were compared in 39 MFS eyes and 40 control eyes matched for age and refraction was conducted. MFS eyes with lens subluxation also were compared with eyes without subluxation. The mean K(med) value in MFS eyes was lower than in the control eyes, 42.2 ± 1.9 versus 43.4 ± 1.4 dioptres (D), respectively (p = 0.02). Fifteen MFS eyes (38%) and three control eyes (8%) had K(med) values below 41.5 D (p = 0.0012). MFS eyes had generally more corneal astigmatism than control eyes, 1.1 ± 0.9 versus 0.8 ± 0.4 D (p = 0.035), and MFS eyes with lens subluxation had more corneal astigmatism than those without, 1.6 ± 1.1 versus 0.6 ± 0.3 D (p = 0.0002). Nine MFS eyes with corneal astigmatism exceeding 1.5 D also had a subluxated lens. No eyes had keratoconus. The mean pachymetry value was lower in MFS eyes compared to the controls, 485 ± 54.5 versus 514 ± 37.3 μm (p = 0.007); 24 MFS eyes (62%) and 10 control eyes (25%) had measurements below 500 μm (p = 0.01). The mean ECD values were similar in MFS and control eyes, 2815 ± 430 versus 2858 ± 458 cells/mm(2) (p = 0.66). The mean K value, pachymetry, and ECD values did not differ between MFS eyes with and without lens subluxation. Decreased K values and pachymetry could indicate MFS regardless of subluxation. High corneal astigmatism is associated with subluxation in MFS. Subluxation should be identified in MFS eyes with high corneal astigmatism.

Plant lipid‐associated fibrillin proteins condition jasmonate production under photosynthetic stress

The role of a subfamily of lipid globule-associated proteins, referred to as plant fibrillins (FIB1a, -1b, -2), was determined using a RNA interference (RNAi) strategy. We show that Arabidopsis plants with reduced levels of these plastid structural proteins are impaired in long-term acclimation to environmental constraint, namely photooxidative stress imposed by high light combined with cold. As a result, their photosynthetic apparatus is inefficiently protected. This leads to the prevalence of an abnormal granal and stromal membrane arrangement, as well as higher photosystem II photoinhibition under stress. The visible phenotype of FIB1-2 RNAi lines also includes retarded shoot growth and a deficit in anthocyanin accumulation under stress. All examined phenotypic effects of lower FIB levels are abolished by jasmonate (JA) treatment. An atypical expression pattern of several JA-induced genes was observed in RNAi plants. A JA-deficient mutant was found to share similar stress phenotypic characteristics with FIB RNAi plants. We conclude a new physiological role for JA, namely acclimation of chloroplasts, and that light/cold stress-related JA biosynthesis is conditioned by the accumulation of plastoglobule-associated FIB1-2 proteins. Consistent correlative data suggest that this FIB effect is mediated by plastoglobule (and triacylglycerol) accumulation as the potential site for initiating the chloroplast stress-related JA biosynthesis.

Functional Consequences of Homocysteinylation of the Elastic Fiber Proteins Fibrillin-1 and Tropoelastin

Homocystinuria caused by cystathionine-beta-synthase deficiency represents a severe form of homocysteinemias, which generally result in various degrees of elevated plasma homocysteine levels. Marfan syndrome is caused by mutations in fibrillin-1, which is one of the major constituents of connective tissue microfibrils. Despite the fundamentally different origins, both diseases share common clinical symptoms in the connective tissue such as long bone overgrowth, scoliosis, and ectopia lentis, whereas they differ in others. Fibrillin-1 contains approximately 13% cysteine residues and can be modified by homocysteine. We report here that homocysteinylation affects functional properties of fibrillin-1 and tropoelastin. We used recombinant fragments spanning the entire fibrillin-1 molecule to demonstrate that homocysteinylation, but not cysteinylation leads to abnormal self-interaction, which was attributed to a reduced amount of multimerization of the fibrillin-1 C terminus. The deposition of the fibrillin-1 network by human dermal fibroblasts was greatly reduced by homocysteine, but not by cysteine. Furthermore, homocysteinylation, but not cysteinylation of elastin-like polypeptides resulted in modified coacervation properties. In summary, the results provide new insights into pathogenetic mechanisms potentially involved in cystathionine-beta-synthase-deficient homocystinuria.

2009 George E. Brown Memorial Lecture—Marfan Syndrome and Related Disorders: From Molecules to Medicines

Our lab studies molecular determinants of vessel wall homeostasis, with particular emphasis on molecules and pathways that contribute to aortic aneurysm. The study of Marfan syndrome (MFS), an autosomal dominant condition with a strong predisposition for aortic root aneurysm and dissection, has provided a tractable means to gain a foothold in the pathogenesis of this complex phenotype. Our initial studies demonstrated that MFS is caused by mutations in the extracellular matrix protein fibrillin-1. Early pathogenetic models that singularly invoked inherent weakness of the tissues as the driving force in disease progression boded poorly for the development of productive treatment strategies and failed to reconcile multiple disease manifestations, including bone overgrowth, myxomatous valve changes, and muscle and fat hypoplasia. Using mouse models of MFS, we demonstrated that fibrillin-1 is not simply a structural protein but rather regulates the local bioavailability and activation of the growth factor transforming growth factor (TGF) β . Many important manifestations of MFS, including emphysema, valve degeneration, myopathy, and aortic aneurysm, could be attenuated or prevented in fibrillin-1–deficient mice upon systemic administration of TGF β antagonists. Similar protection was achieved through the use of the angiotensin II type 1 receptor blocker (ARB) losartan, which lowers both blood pressure and TGF β signaling and is in widespread clinical use for the treatment of hypertension. These observations led to the first clinical trial for MFS that is based upon a refined mechanistic understanding of disease. We now have performed comprehensive interrogation of a modifier network in mouse models of MFS. These data reveal parsing of the angiotensin II signaling cascades in the pathogenesis and prevention of aortic aneurysm. Signaling through the type 2 (AT2) receptor is protective, whereas loss of AT2 signaling accelerates disease and attenuates the protection afforded by ARBs, suggesting that losartan provides protection, at least in part, through shunting of angiotensin II signaling through AT2. We also demonstrate a predominant role of noncanonical TGF β signaling in the pathogenesis of ascending aortic aneurysm and show that the mechanism of AT2-mediated protection derives from cross-talk with this pathway. Taken together, these data explain why ARBs markedly outperform angiotensin-converting enzyme inhibitors in our mouse model of MFS. They also define noncanonical TGF β and AT2 signaling as prognostic and therapeutic modifiers of vascular disease and provide rationale and incentive for additional clinical trials in MFS and related disorders.

Comparative gene expression profiling of post-natal and post-pneumonectomy lung growth

Although increasing numbers of patients suffer from chronic destructive lung diseases, there are no effective therapeutic options apart from transplantation. Understanding the mechanisms of physiological and regenerative alveolar septation is prerequisite for the development of regenerative therapies for the lung. We compared lung gene expression in the phase of induction of post-natal and post-pneumonectomy alveolarisation to identify regulatory genes involved in both processes. We performed genome-wide microarray screenings of newborn and pneumonectomised mouse lungs 1 and 3 days after birth or surgery. Selected candidates were validated by real-time PCR, Western blot and in situ hybridisation. We found 58 genes to be regulated in both models with 40 candidates being changed likewise. Many of these genes participated in growth and differentiation processes. Additionally, immune system, structural molecules, respiratory chain, signal transduction and metabolism were involved. Some candidates were not yet linked to specific functions. The highest regulatory concordance was observed for various isoforms of (pro-)collagen molecules, elastin and the elastin-associated protein fibrillin1 being corporately upregulated. Our findings do not definitively support a common regulating mechanism for induction of post-natal and adult alveolarisation, but some candidates in the intersection of both models are promising for further investigations.

Computer construction and analysis of protein models of mutant fibrillin-1 gene in Marfan's syndrome

Fibrillin-1, the major constituent of extracellular microfibrils, plays an important role in the molecular pathogenesis of Marfan syndrome (MFS, #54700). The aim of this study was to analyze protein models of the mutation of the fibrillin-1 (FBN1) gene on Arg545Cys and Arg1530Cys which have been reported to cause predominant ectopia lentis in Chinese patients. We constructed and analyzed the protein models of the mutant FBN1 gene on Arg545Cys and Arg1530Cys. Fibrillin-1 protein structures were predicted by SWISS-MODEL. Models were viewed in Swiss-Pdb Viewer. Computer construction and analysis of protein models of the mutant FBN1 gene revealed that the mutant Arg545Cys FBN1 protein had various changes on protein's secondary structure with an absence of a helix, decreased hydrogen bond distance, different protein surface solvent-accessibility and decreased negative electrostatic potential. The mutant Arg1530Cys FBN1 showed lost of hydrogen bonds, different protein surface solvent-accessibility and increased negative electrostatic potential. Protein models of the mutant FBN1 gene shows significant alterations on the protein's secondary structure based on computer construction and analysis technology. This study provides further evidence for the important effect of the mutant FBN1 on the pathogenesis of human ectopia lentis.

Transforming Growth Factor-β

Marfan syndrome is an autosomal dominant disorder of connective tissue due to abnormal fibrillin-1 caused by mutations in the FBN1 gene on chromosome 15. Affecting 1 in ≈5000 individuals, Marfan syndrome has widespread features involving the cardiovascular system, eye, skeleton, lung, dura, and skin. After evaluation of individuals and families with Marfan syndrome over the years, it is remarkable how variable the phenotype and age of onset of various manifestations may be among affected individuals, even in the same family. Some individuals with Marfan syndrome require aortic root replacement early in childhood, whereas others may not require aortic surgery until late in life, if at all. This highlights the importance of thorough screening of all first-degree relatives of the Marfan patient, long-term follow-up, and consideration of mutation analysis for those with ambiguous features. Article see p 526 The past 2 decades have witnessed remarkable scientific discovery and progress, providing hope to those affected by Marfan syndrome. In 1991, it was discovered that Marfan syndrome was due to a mutation in FBN1 , the gene that encodes fibrillin-1.1 Hundreds of different mutations in FBN1 have subsequently been described, with most families having their own private mutation. Because fibrillin-1 is present in tissues affected by Marfan syndrome, it was considered that the underlying defect in fibrillin-1 led to a primary structural weakness in this connective tissue protein. Because of recent discovery, this concept has come into question. Genetically engineered mouse models of Marfan syndrome, which recapitulate the phenotype observed in humans, have revolutionized understanding of basic pathophysiological mechanisms of this disease.2–4 Fibrillin-1 is a 350-kDa glycoprotein with multiple repeating, cysteine-rich, epidermal growth factor–like motifs, most of which are calcium binding. Fibrillin-1 also has motifs with homology to latent transforming growth factor-β–binding proteins. Fibrillin-1 proteins aggregate and associate to form microfibrils, …

Experimental and bioinformatic characterisation of the promoter region of the Marfan syndrome gene, FBN1

Mutations in the FBN1 gene, encoding the extracellular matrix protein fibrillin-1, result in the dominant connective tissue disease Marfan syndrome. Marfan syndrome has a variable phenotype, even within families carrying the same FBN1 mutation. Differences in gene expression resulting from sequence differences in the promoter region of the FBN1 gene are likely to be involved in causing this phenotypic variability. In this report, we present an analysis of FBN1 transcription start site (TSS) use in mouse and human tissues. We found that transcription of FBN1 initiated primarily from a single CpG-rich promoter which was highly conserved in mammals. It contained potential binding sites for a number of factors implicated in mesenchyme differentiation and gene expression. The human osteosarcoma line MG63 had high levels of FBN1 mRNA and secreted fibrillin-1 protein to form extracellular matrix fibres. The human embryonic kidney line HEK293 and two breast cancer lines MCF7 and MDA-MB-231 had levels of FBN1 mRNA 1000 fold lower and produced negligible amounts of fibrillin-1 protein. Therefore MG63 appears to be the optimal cell line for examining tissue-specific, biologically relevant promoter activity for FBN1. In reporter assays, the conserved promoter region was more active in MG63 cells than in non- FBN1-expressing lines but additional elements outside the proximal promoter are probably required for optimal tissue-specific expression. Understanding the regulation of the FBN1 gene may lead to alternative therapeutic strategies for Marfan syndrome.

Decreased gene expression of fibrillin‐1 in stress urinary incontinence

Studies to show impairments in the pelvic floor extracellular matrix (ECM) associated with stress urinary incontinence (SUI) has earlier been performed, but the results are contradictory. Collagen I and III, the elastin associated proteins fibrillin-1 and fibulin-5 and the small leucine-rich repeat proteoglycans (SLRPs) decorin, lumican and fibromodulin are involved in giving the tissue its mechanical properties. Their gene signals and tissue localizations were investigated. Para-urethral punch biopsies were obtained from 24 women, 12 pre- and 12 postmenopausals, during surgery for SUI. As controls, biopsies were collected from 14 women, 8 pre- and 6 postmenopausals, undergoing surgery for other benign conditions. The mRNA expression by real-time RT-PCR and protein localization by immunohistochemistry were analyzed concerning collagen I and III, the small leucine rich repeat proteoglycans (SLRPs) decorin, lumican and fibromodulin and the elastic fiber associated proteins fibulin-5 and fibrillin-1. Statistical comparisons controlled for age changes in gene expressions. A significant decrease in mRNA expression of fibrillin-1 was discovered in all SUI women compared to all controls, P = 0.03. All molecules were down-regulated by age, but no other differences between SUI and controls reached significance. All proteins were adequately expressed by immunohistochemistry. A weaker staining for fibrillin-1 was seen in the pre-menopausal SUI group compared to the pre-menopausal controls. A decreased gene signal and weaker immunoreactivity for fibrillin-1, important for the elastic fiber assembly, was discovered in women with SUI. Loss of tissue elasticity could lead to increased urethra hypermobility and SUI.

Fibrillins and latent TGFβ binding proteins in bovine ovaries of offspring following high or low protein diets during pregnancy of dams

The microsatellite D19S884, located in intron 55 of fibrillin-3 (FBN3) gene, associates with polycystic ovary syndrome (PCOS) in familial studies. The family of fibrillin proteins (FBN1-3), which includes latent TGF-β binding proteins (LTBP-1 to -4), are extracellular matrix proteins. We localized and examined the expression of these proteins in the adult bovine ovaries (n=7–10 per group, average age 681 days) born to mothers fed high (13% protein per total dry weight) or a low protein diet (5%) in each of the first and second trimesters of pregnancy (n=4 groups). FBN1 and LTBP-1 and -2 were the major members expressed in the mature ovary. Each protein had a unique localization pattern but all were associated with stromal tissue including the tunica albuginea (FBN1 and LTBP-2 near surface, and FBN1 and LTBP-1 deeper in the tunica), cortical stroma (FBN1 and LTBP-1) and follicular thecal layers (FBN1 in theca interna, LTBP-1 in the inner regions of the theca externa, and LTBP-2 in the outer regions of the theca externa). No significant (P>0.05) effects of maternal diet were observed on either the localization or the levels of mRNA of any of these proteins in the tunica. Expression levels of all three FBNs were positively correlated with each other, and FBN1 and 2 were positively correlated with LTBP-2, suggesting some level of co-ordinate regulation. This is the first study to investigate the expression and localization of these genes affecting TGFβ bioavailability in the ovary.

Gene expressions of small leucine-rich repeat proteoglycans and fibulin-5 are decreased in pelvic organ prolapse

Few studies are performed on the sustainability of the pelvic floor extracellular matrix important for preventing development of pelvic organ prolapse (POP). Collagens I and III, the elastin-associated proteins fibrillin-1 and fibulin-5 and the small leucine-rich repeat proteoglycans (SLRPs) decorin, lumican and fibromodulin are involved in giving the tissue its mechanical properties. Para-urethral biopsies were obtained from 15 women, 6 pre- and 9 post-menopausal, with POP. Real-time reverse transcription-polymerase chain reaction and immunohistochemistry for collagen I, collagen III, fibrillin-1, fibulin-5, decorin, lumican and fibromodulin were performed and compared with 14 controls, 8 pre- and 6 post-menopausal. Statistical comparisons controlled for age changes in gene expressions. A 16-fold decrease in decorin mRNA expression, P = 0.0001, and 8-fold in lumican mRNA expression, P = 0.001, were discovered in premenopausal POP compared with matched controls. In all women with POP, there were lower gene expressions of fibromodulin, P = 0.004, and fibulin-5, P = 0.001, compared with all controls. All proteins were detectable by immunohistochemistry, showing a weaker staining for decorin in premenopausal POP. For the first time, we show substantially decreased gene signal for production of SLRPs, regulators of collagen fiber assembly and impairment in elastic fiber assembly by down-regulation of fibulin-5 in POP.

P38 MAPK Is an Early Determinant of Promiscuous Smad2/3 Signaling in the Aortas of Fibrillin-1 (Fbn1)-null Mice

Excessive transforming growth factor-beta (TGF-beta) signaling characterizes the progression of aortic aneurysm in mouse models of Marfan syndrome, a systemic disorder of the connective tissue that is caused by mutations in the gene encoding the extracellular matrix protein fibrillin-1. Fibrillin-1 mutations are believed to promote abnormal Smad2/3 signaling by impairing the sequestration of latent TGF-beta complexes into the extracellular matrix. Here we report that promiscuous Smad2/3 signaling is the cell-autonomous phenotype of primary cultures of vascular smooth muscle cells (VSMC) explanted from the thoracic aortas of Fbn1 mutant mice with either neonatal onset or progressively severe aortic aneurysm. This cellular phenotype was characterized in VSMC isolated from Fbn1-null (mgN/mgN) mice, which recapitulate the most severe form of Marfan syndrome. We found that loss of fibrillin-1 deposition promotes the production of intracellular reactive oxygen species and abnormal accumulation of phosphorylated TGF-beta-activated kinase 1 and p38 MAPK, in addition to increasing the levels of endogenous phospho-Smad2. We showed that improper Smad2/3 signaling in Fbn1-null VSMC is in part stimulated by phospho-p38 MAPK, which is in turn activated in response to signals other than those mediated by the kinase activity of the ALK5 receptor. Consistent with these cell culture data, in vivo analyses documented that phospho-p38 MAPK accumulates earlier than phospho-Smad2 in the aortic wall of mgN/mgN mice and that systemic inhibition of phospho-p38 MAPK activity lowers the levels of phospho-Smad2 in this tissue. Collectively, these findings indicate that improper activation of p38 MAPK is a precursor of constitutive Smad2/3 signaling in the aortic wall of a mouse model of neonatal lethal Marfan syndrome.

Heparan Sulfate Regulates Fibrillin-1 N- and C-terminal Interactions

Fibrillin-1 N- and C-terminal heparin binding sites have been characterized. An unprocessed monomeric N-terminal fragment (PF1) induced a very high heparin binding response, indicating heparin-mediated multimerization. Using PF1 deletion and short fragments, a heparin binding site was localized within the domain encoded by exon 7 after the first hybrid domain. Rodent embryonic fibroblasts adhered to PF1 and deletion fragments, and, when cells were plated on fibrillin-1 or fibronectin Arg-Gly-Asp cell-binding fragments, cells showed heparin-dependent spreading and focal contact formation in response to soluble PF1. Within domains encoded by exons 59-62 near the fibrillin-1 C terminus are novel conformation-dependent high affinity heparin and tropoelastin binding sites. Heparin disrupted tropoelastin binding but did not disrupt N- and C-terminal fibrillin-1 interactions. Thus, fibrillin-1 N-terminal interactions with heparin/heparan sulfate directly influence cell behavior, whereas C-terminal interactions with heparin/heparan sulfate regulate elastin deposition. These data highlight how heparin/heparan sulfate controls fibrillin-1 interactions.

The expanding cardiovascular phenotype of Marfan syndrome

In this issue of the journal, Kiotsekoglou et al. report on right ventricular systolic dysfunction in patients with Marfan syndrome (MFS). Over the past years, several studies have demonstrated mild, though significant, left ventricular systolic and diastolic dysfunction in patients with MFS.1–5 This is the first study indicating impaired right ventricular function. Marfan syndrome is an autosomal dominant connective-tissue disorder caused by mutations in the fibrillin-1 gene ( FBN1 ). Cardiovascular manifestations are mainly characterized by progressive dilatation of the aortic root, leading to aneurysm formation which may—when left untreated—lead to aortic dissection or rupture. Other established cardiovascular manifestations include mitral valve prolapse, dilatation of the pulmonary artery, and dilatation or dissection of the descending thoracic or abdominal aorta. Although not commonly related to MFS, dilated cardiomyopathy, beyond that explained by aortic or mitral valve regurgitation, seems to occur with higher prevalence in patients with MFS, implicating involvement of the extracellular matrix protein fibrillin-1 in ventricular structure and/or function.6 Whether left ventricular dysfunction is a rare but severe complication of MFS or rather a widespread but generally asymptomatic finding was unclear until recently. Several studies have now demonstrated that both systolic and diastolic left ventricular functions are impaired in patients with MFS. These alterations may already be present in childhood.1–4 This study by Kiotsekoglou … Corresponding author. Tel: +32 9 332 3476; fax: +32 9 332 3462. E-mail address : julie.debacker{at}UGent.be

Conservation of 5′-upstream region of the FBN1 gene in primates

Fibrillin-1 is a multifunctional extracellular protein encoded by the FBN1 gene. FBN1 is 237 kb in size and is located on chromosome 15q21. FBN1 mutations are known to cause Marfan syndrome and other fibrillinopathies. FBN1 is composed of 65 exons and 3 additional alternatively spliced exons at the 5' end. The absence of the peptide sequence from the extreme N-terminus of the fibrillin-1 protein and the presence of in-frame and alternatively spliced exons at the 5' end of the FBN1 gene create some ambiguity about the translation start site and indicate a functional role of these alternatively spliced exons. We demonstrate here the conservation of 5'-upstream region of the FBN1 gene among humans and non-human primates.

Coupling LCM to gene expression and microproteomics: Novel approaches to molecularly define pediatric coronary artery intimal occlusive lesions

Background‐Cardiac allografts fail due to post‐transplant vasculopathy, a progressive loss of the lumen in coronary arteries. The arterial injury is characterized pathologically by a concentric intimal expansion as a result of the proliferation of smooth muscle cells and the accumulation of extracellular matrix (ECM). The precise pathogenesis of graft arteriosclerosis is unknown.Methods and Results‐Samples from coronary artery occlusive lesions were captured using LCM. The tissue was then incubated in Liquid Tissue Reagent (Expression Pathology, Gaithersburg, MD), enabling subsequent proteolysis and LC‐MS/MS analysis using a nanoflow HPLC system and a linear ion trap/orbitrap mass spectrometer. Proteins for multiple ECM components were detected in the neointima, including a variety of collagens, fibrillin, laminin, fibronectin and specific proteoglycan core proteins. The findings were validated by immunohistochemical analysis.Conclusions‐Microproteomic analysis demonstrates multiple ECM components including collagens and specific proteoglycan core proteins in the intimal lesions of post‐transplant vasculopathy. This accumulation of ECM components was present in all lesions, suggesting it plays an important role in their pathogenesis. Further analysis of the ECM in these lesions may provide new insights into the pathobiology of post‐transplant arteriopathy.NIH/NHLBI 1 P50 HL74734