Developmental Anatomy in the Zonular Connection with Lens Capsule in Macaque Eye

Morphological analyses of zonule conjugated with lens capsule were performed on the developmental change in eyes from the age of fetus to 7 years old of the rhesus macaques (Macaca fuscata). The zonule was filamentous network in late fetus. After birth, the zonular microfibrils originated from the nonpigmented epithelium of the ciliary process. On the extending path toward the lens capsule through the chamber, microfibril assembled with neighbor fibril and also cohered with one another forming bundle. With growth, these bundles bifurcated into anterior and posterior groups on the equatorial region of capsule. The developmental distribution of bundles in the capsule was characteristic on anterior group, that is, bifurcation into radial and circumferential extension. On the other hand, the posterior bundle undivided but radially extended within short distance from the equator. In the process of fixating with capsule, bundles untangled into fibrils and penetrated circumferentially into the superficial layer and radially into deep apical layer of the capsule. Zonule was composed fibrillin 1 microfibrils and on the extending path toward the lens capsule through the chamber, microfibril self‐assembled with neighbored fibril in composition of fascicle and also cohered with one another forming bundle. Each bundle had alternating pale and dense horizontal bands in the intracapsular extension and the stripe pattern changed in flaccid or extensive tension of zonule between capsule and process. Zonular fibril intermingled with collagen fibril of capsule with interlacing molecule of laminin. At the base of ciliary muscle, elastin‐positive connective tissue intercalated circumferentially between ciliary processes. The developmental changes of the intralamellar distribution and extension of zonule with striped pattern informed the functional role upon the elasticity in coordination with the lens capsule micromolecules. Anat Rec, 296:726–735, 2013. © 2013 Wiley Periodicals, Inc.     

马凡综合征FBN1突变的一个家系分析及产前诊断

目的对一马凡综合征(Marfan's syndrome,MFS)个例进行原纤维蛋白-1基因(FBN1)突变分析并对该家系的1例MFS孕妇进行产前诊断。方法提取先证者及其家族成员外周全血基因组DNA,先证者羊水细胞DNA和培养后羊水细胞的RNA。用PCR和DNA双向测序技术检测存在于FBN1外显子中的潜在突变。RT-PCR扩增RNA检测所发现突变的相应外显子并进行基因测序。结果发现该先证者FBN1基因外显子23错义突变c.2785AC(p.Thr929Pro),其患MFS的父亲和哥哥发现同样突变。该家族其他表型正常的成员该位点未发现突变。胎儿羊水细胞的DNA与羊水培养细胞RNA均未发现该位点的突变。结论 FBN1错义突变c.2785AC(p.Thr929Pro)为该家族的致病原因,该MFS孕妇的胎儿未遗传该FBN1的致病突变。     

Quantitation of fibrillin immunofluorescence in fibroblast cultures in the Marfan syndrome

The Marfan syndrome (MFS) is a heritable connective tissue disorder manifested by defects in the skeletal, ocular, and cardiovascular systems. Diagnosis of MFS is based on clinical findings. At present there are no laboratory tests for specific determination of this disorder. Defects in fibrillin, an elastin-associated microfibrillar glycoprotein, are now known to cause the variable and pleiotropic manifestations of MFS. Immunofluorescence studies of skin sections and dermal fibroblast cultures were the first to show this association. Most unequivocal cases of the Maffan syndrome exhibited an apparent reduction in fibrillin immunofluorescence. The prospect of examining patients whose clinical findings suggest a possible diagnosis of the Marfan syndrome has stimulated us to attempt quantitation of immunofluorescence. In the study described here we used computer-enhanced image analysis to establish "normal" and "abnormal" (Marfan) parameters of fibrillin immunofluorescence in dermal fibroblast cultures. Quantitation of fluorescence from control individuals showed a median of 21%, while the median fibrillin fluorescence in MFS patients was 6% with a confidence interval of 15%. These findings were statistically significant to p<0.01. It is hoped that these analyses may become a useful adjunct in the clinical diagnosis of MFS.     

A Deficiency of Cysteine Impairs Fibrillin-1 Deposition: Implications for the Pathogenesis of Cystathionine β-Synthase Deficiency

Cystathionine β-synthase (CBS) deficiency is an inborn error of amino acid metabolism that has pleiotropic manifestations and is commonly called “homocystinuria.” The features include skeletal, ocular, and vascular defects, some of which are reminiscent of those found in Marfan syndrome (MFS). Because of the spectrum of clinical effects, the pathogenesis of homocystinuria has long been thought to involve the extracellular matrix (ECM), and the condition has been classified as a heritable disorder of connective tissue. Because of the superficial similarities with MFS, we and others (Pyeritz, in McKusicks Heritable Disorders of Connective Tissue, St. Louis, Mosby–Year Book Inc., 5th ed., pp 137–178, 1993; Pyeritz, in Principles and Practice of Medical Genetics, New York, Churchill Livingstone, 3rd ed., pp 1027–1066, 1997; Mudd, Levy, and Skovby, in The Metabolic and Molecular Bases of Inherited Disease, New York, McGraw-Hill Publishing Co., 7th ed., pp 1279–1327, 1995) have speculated how CBS deficiency might affect fibrillin-1, the protein altered in MFS. For example, the altered plasma concentrations of homocysteine and/or cysteine in patients with CBS deficiency may hinder fibrillin-1 synthesis, deposition, or both. When arterial smooth muscle cells were cultured under conditions of cysteine deficiency, fibrillin-1 deposition into the ECM was greatly diminished as revealed by immunocytochemistry. Excessive homocysteine, in contrast, had little, if any, effect on fibrillin-1 deposition. When cysteine concentrations were returned to normal, the smooth muscle cells began to accumulate a matrix rich in fibrillin-1. Type I collagen, the major matrix component synthesized by these smooth muscle cells, was not reduced by low cysteine concentrations nor high homocysteine concentrations. These results demonstrate that a deficiency of cysteine and subsequent inhibition of fibrillin-1 accumulation in CBS deficient patients may be at least partly responsible for their phenotype, and suggest that maintenance of normal plasma cyst(e)ine levels may be an important therapeutic goal.     

Ectopia lentis as the presenting and primary feature in Marfan syndrome

Marfan syndrome (MFS) is a multisystem connective tissue disorder with primary involvement of the ocular, cardiovascular, and skeletal systems. We report on eight patients, all presenting initially with bilateral ectopia lentis (EL) during early childhood. These individuals did not have systemic manifestations of MFS, and did not fulfill the revised Ghent diagnostic criteria. However, all patients had demonstratable, disease-causing missense mutations in the FBN1 gene. Based on molecular results, cardiovascular imaging was recommended and led to the identification of mild aortic root changes in seven of the eight patients. The remaining patient had mitral valve prolapse with a normal appearing thoracic aorta. The findings presented in this paper validate the necessity of FBN1 gene testing in all individuals presenting with isolated EL. As we observed, these individuals are at increased risk of cardiovascular complications. Furthermore, we also noted that the majority of our patient cohort's mutations occurred in the 5' portion of the FBN1 gene, and were found to affect highly conserved cysteine residues, which may indicate a possible genotype-phenotype correlation. We conclude that in patients with isolated features of EL, FBN1 mutation analysis is necessary to aid in providing prompt diagnosis, and to identify patients at risk for potentially life-threatening complications. Additionally, knowledge of the type and location of an FBN1 mutation may be useful in providing further clinical correlation regarding phenotypic progression and appropriate medical management.     

马凡综合征原纤蛋白质-1突变的蛋白质三维结构分析

目的 分析马凡综合征(Marfan syndrome,MFS)患者原纤蛋白质1（fibrillin 1, Fib-1）基因（FBN1）错义突变的蛋白质三维结构变化。 方法 应用Swiss-Model 软件分析福建地区已发现的4例MFS患者的FBN1错义突变c.5015G>C (p.C1672S)、c.5309G>A(p.C1770Y)、c.7241G>A(p.R2414Q)与c.7769G>A (p.C2590Y),模拟突变后的蛋白质三维结构变化。 结果 Swiss-Model 模拟蛋白质结构显示,4个错义突变中,3个发生在半胱氨酸位的错义突变(p.C1672S、p.C1770Y与p.C2590Y)蛋白质三维结构发生明显改变。 结论 用计算机模拟基因突变后的蛋白质三维结构结果有助于了解突变对FBN 1蛋白质三维结构的影响。     

Ocular Findings of Beals Syndrome

Background In this report of two Okinawan patients with Beals syndrome and accompanying ocular complications, the symptoms of Beals syndrome and Marfan syndrome are compared. The etiology of these two syndromes is considered in relation to fibrillin.Cases Case 1 was a 5-year-old boy who showed blue sclera and bilateral enlargement of optic disc cupping. Case 2 was a 24-year-old man who had partial coloboma of the lens, mild cataract, and bilateral glaucomatous disc cupping.Observations Beals syndrome was diagnosed in these two patients based on the initial examination. In further investigations, while the patients were being observed without treatment, the intra ocular pressure of both patients remained within normal range. Funduscopy showed that the cup-to-disc ratio was 0.8 bilaterally in both patients. Case 1 was followed up for 6 years with no changes. Ultrasound biomicroscopy examination in case 2 revealed hypoplasia of the ciliary body, leading to a diagnosis of glaucoma. This patient remains under observation.Conclusions Two cases of Beals syndrome with ocular complications including glaucomatous optic disc cupping are reported. Ophthalmic examinations are recommended to identify the ocular complications of Beals syndrome. Further studies are needed to elucidate the relation between fibrillin abnormality and ocular complications in Beals syndrome. Jpn J Ophthalmol 2004;48:470–474 © Japanese Ophthalmological Society 2004     

Late Deposition of Elastin to Vertical Microfibrillar Fibers in the Presumptive Dermis of the Chick Embryonic Tarsometatarsus

Fibrillin microfibrils are integral components of elastic fibers and serve as a scaffold for elastin deposition. However, microfibrillar fibers (MFs) are not necessarily committed to develop into so‐called elastic fibers. In dermis, elastin‐free oxytalan MFs originating from the dermoepidermal junction are continuous to elaunin‐type MFs (with a small amount of elastin) in the deeper papillary dermis, whereas the reticular dermis contains elastic fibers, or MFs embedded largely in elastin. In this study, we have investigated temporospatial patterns of elastin deposition on the MFs in tarsometatarsal presumptive dermis. While the earliest expression of elastin was demonstrated immunohistochemically as early as embryonic day 4 (ED4) in the wall of cardiac outflow and pharyngeal arch arteries, its deposition in the tarsometatarsus was first detected at ED6 in the deeper mesenchyme and at ED13 in the subectodermal mesenchyme. In the latter tissue, MFs had been organized perpendicularly to the covering ectoderm by ED4, well before an overt accumulation of collagenous matrix. Elastin deposition was observed initially in a punctate manner at ED13 and afterward became continuous along MFs. However, a characteristic spaced array of subectodermal vertical MFs was disorganized by ED17. These findings suggest that elastin deposition in the subectodermal MFs is not deployed by continuous, orderly propagation from elastic fibers in the deeper mesenchyme but occurs de novo in multiple foci along vertical MFs. Moreover, the present chronology of elastin deposition indicates that subectodermal, elastin‐free MFs function as a transient, but primary fibrous structure in the presumptive dermis before the accumulation of collagenous matrix. Anat Rec, 290:1300‐1308, 2007. © 2007 Wiley‐Liss, Inc.