The Pathophysiological Significance of Fibulin-3

Fibulin-3 (also known as EGF-containing fibulin extracellular matrix protein 1 (EFEMP1)) is a secreted extracellular matrix glycoprotein, encoded by the EFEMP1 gene that belongs to the eight-membered fibulin protein family. It has emerged as a functionally unique member of this family, with a diverse array of pathophysiological associations predominantly centered on its role as a modulator of extracellular matrix (ECM) biology. Fibulin-3 is widely expressed in the human body, especially in elastic-fibre-rich tissues and ocular structures, and interacts with enzymatic ECM regulators, including tissue inhibitor of metalloproteinase-3 (TIMP-3). A point mutation in EFEMP1 causes an inherited early-onset form of macular degeneration called Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD). EFEMP1 genetic variants have also been associated in genome-wide association studies with numerous complex inherited phenotypes, both physiological (namely, developmental anthropometric traits) and pathological (many of which involve abnormalities of connective tissue function). Furthermore, EFEMP1 expression changes are implicated in the progression of numerous types of cancer, an area in which fibulin-3 has putative significance as a therapeutic target. Here we discuss the potential mechanistic roles of fibulin-3 in these pathologies and highlight how it may contribute to the development, structural integrity, and emergent functionality of the ECM and connective tissues across a range of anatomical locations. Its myriad of aetiological roles positions fibulin-3 as a molecule of interest across numerous research fields and may inform our future understanding and therapeutic approach to many human diseases in clinical settings.

A study of optic nerve head drusen in 38 pseudoxanthoma elasticum (PXE) patients (64 eyes). Location of optic nerve head drusen in PXE

PURPOSE

To investigate the prevalence and location of optic nerve head drusen and their potential association with other PXE-related ophthalmic abnormalities.

MATERIALS AND METHODS

Thirty-eight of the 155 patients (57 male and 98 female aged 49±17 years) included in this retrospective study had optic nerve head drusen. All of the patients underwent a comprehensive ophthalmic examination, including color images using red-free, blue and red filters, autofluorescence imaging and late-phase ICG frames. Comparative analysis of both groups (optic nerve head drusen or not) was conducted using R statistical software.

RESULTS

The prevalence of optic nerve head drusen in our cohort was 24.5%. In this study, no evidence of a significant link between optic nerve head drusen and other fundus abnormalities was detected. They were more commonly located in the nasal sector than in the temporal sector of the optic disc (P<0.001). They were more frequently situated superonasally than inferonasally (P<0.004), superotemporally (P<0.001) or inferotemporally (P<0.03). No central visual field defect was observed in OND+ patients who were unaffected by macular disorders.

DISCUSSION

We hypothesized this predominantly nasal primary location may result from greater sensitivity in the nasal optic nerve fibers which follow a much more angular path once they arrive in the scleral canal, accounting for accumulation of axoplasmic debris.

CONCLUSION

In PXE, optic nerve head drusen are mostly located in the superonasal quadrant, causing progressive optic nerve invasion but probably no central visual field defects.

Novel membrane frizzled-related protein gene mutation as cause of posterior microphthalmia resulting in high hyperopia with macular folds

PURPOSE

We present a genetic and clinical analysis of two sisters, 3 and 4 years of age, with nanophthalmos and macular folds.

METHODS

Ophthalmological examination, general paediatric examination and molecular genetic analysis of the MFRP gene were performed in both affected siblings.

RESULTS

Clinical analysis showed high hyperopia (+11 D and +12 D), short axial lengths (15 mm) and the presence of macular folds and optic nerve head drusen. Autofluorescence of the retina was generally normal with subtle macular abnormalities. Sequence analysis showed compound heterozygosity for severe MFRP mutations in both sisters: a previously reported p.Asn167fs (c.498dupC) and a novel stop codon mutation p.Gln91X (c.271C>T).

CONCLUSION

These are the youngest nanophthalmos patients in the literature identified with severe loss of MFRP function, showing already the known structural abnormalities for this disease. Adult patients affected by homozygous or compound heterozygous MFRP mutations generally show signs of retinal dystrophy, with ERG disturbances and RPE abnormalities on autofluorescence imaging. ERG examination could not be performed in these children, but extensive RPE abnormalities were not seen at this young age.

[Retinitis pigmentosa--clinical and genetic aspects with low vision]

PURPOSE

Clinical and genetic study of a case of retinitis pigmentosa following the vision and the quality of life in this disease.

METHOD

This paper presents a female periodically reevaluated in our clinic from the first diagnosis of retinitis pigmentosa which was established ten years ago, with many relatives with the diagnosis of retinitis pigmentosa, has also high hyperopia and optic disc drusen. A particular aspect--she is student at English Faculty and she want to become professor in a school for children with low vision. Clinical evaluation included complete ophthalmic and general examination, family history and also some additional lab and imaging study, In genetic evaluation of this case were used the basic rules of genetics to diagnose the genetic form of retinitis pigmentosa in order to offer a correct genetic counseling.

CONCLUSIONS

Retinitis pigmentosa needs a broad clinical evaluation and a careful socio-professional rehabilitation of these low-vision patients.

A new autosomal recessive syndrome consisting of posterior microphthalmos, retinitis pigmentosa, foveoschisis, and optic disc drusen is caused by a MFRP gene mutation

PURPOSE

To describe the clinical and genetic characteristics of a new ophthalmic syndrome, which consists of posterior microphthalmos, retinitis pigmentosa, foveoschisis, and optic disc drusen, that segregates as an autosomal recessive trait in a family with four affected siblings. The membrane-type frizzled-related protein (MFRP) and CEH10 homeodomain-containing homolog (CHX10) genes, previously implicated in autosomal recessive forms of nanophthalmos/microphthalmos, were analyzed as candidate genes for this novel disease.

METHODS

Complete ophthalmologic examinations were performed in four affected siblings and their parents. Ophthalmologic manifestations, fundus photographs, ultrasonographic (US) assessment, electroretinography (ERG), fluorescein retinal angiography (FA), Goldmann kinetic perimetry (GKP), and optical coherence tomography (OCT), as well as mutational status of MFRP and CHX10 genes in genomic DNA.

RESULTS

In all affected siblings, ophthalmologic examination demonstrated normal horizontal corneal diameters and high hyperopia; funduscopy, ERG, and FA evidenced a progressive retinal dystrophy compatible with retinitis pigmentosa; A- and B-mode ultrasonography revealed decreased axial eye length and optic disc drusen; OCT showed localized macular retinoschisis. MFRP molecular analysis disclosed a one base pair insertion in exon 5 (c.498_499insC) in all affected individuals, a mutation that predicts a truncated protein (P165fsX198). Both parents were heterozygous for this mutation.

CONCLUSIONS

A distinct autosomal recessive ophthalmic syndrome characterized by microphthalmos, retinitis pigmentosa, foveoschisis, and optic disc drusen is described. We demonstrated that this clinical association is caused by a mutation in MFRP, a gene previously implicated in isolated nanophthalmos. Our data indicate that defects in MFRP could be responsible for syndromic forms of microphthalmos/retinal degeneration and that this gene is necessary for photoreceptor maintenance.

Drusen, choroidal neovascularization, and retinal pigment epithelium dysfunction in SOD1-deficient mice: a model of age-related macular degeneration

Oxidative stress has long been linked to the pathogenesis of neurodegenerative diseases; however, whether it is a cause or merely a consequence of the degenerative process is still unknown. We show that mice deficient in Cu, Zn-superoxide dismutase (SOD1) have features typical of age-related macular degeneration in humans. Investigations of senescent Sod1(-/-) mice of different ages showed that the older animals had drusen, thickened Bruch's membrane, and choroidal neovascularization. The number of drusen increased with age, and exposure of young Sod1(-/-) mice to excess light induced drusen. The retinal pigment epithelial cells of Sod1(-/-) mice showed oxidative damage, and their beta-catenin-mediated cellular integrity was disrupted, suggesting that oxidative stress may affect the junctional proteins necessary for the barrier integrity of the retinal pigment epithelium. These observations strongly suggest that oxidative stress may play a causative role in age-related retinal degeneration, and our findings provide evidence for the free radical theory of aging. In addition, these results demonstrate that the Sod1(-/-) mouse is a valuable animal model to study human age-related macular degeneration.

[Optical coherence tomography in Malattia Leventinese]

BACKGROUND

Malattia Leventinese (ML) is a genetically homogeneous macular dystrophy with an autosomal dominant mode of inheritance. Ophthalmoscopically it is recognisable by a radial pattern of drusen-like deposits in the macula and by parapapillary deposits, named Forni's verrucosities. The aim of this study is to describe optical coherence tomographic (OCT) findings and to compare them with histological data.

PATIENTS AND METHODS

Six patients underwent ophthalmological examination, angiography and OCT. Diagnosis was confirmed by genetic analysis of the R345W mutation. A histopathological study of an ML donor eye was performed.

RESULTS

OCT revealed a diffuse RPE-choriocapillaris thickening with nodular features in the macular and parapapillary areas. The protrusions reached as far as the outer nuclear layer.

CONCLUSIONS

OCT is a non-invasive technique that provides a cross-sectional picture of the retina comparable to a histological section. In ML, OCT revealed a diffuse alteration of the RPE-Bruch's membrane complex. The macular and parapapillary nodular lesions are the tomographic equivalents of drusen and Forni's verrucosities.

Optic disc drusen, angioid streaks, and mottled fundus in various combinations in a Sicilian family

BACKGROUND

We describe a Sicilian family in which optic disc drusen, angioid streaks, and mottled fundus--without dermatological signs of pseudoxanthoma elasticum (PXE)--are present in various combinations and segregate as an autosomal dominant trait. Since these ocular manifestations can be part of the clinical signs of PXE, we examined the possible involvement of a mutation in the ABCC6 gene, which is known to be responsible for PXE.

METHODS

Linkage analysis was performed with both intragenic and flanking markers. We used marker D16B9722 and a single-nucleotide polymorphism located in exon 15 of the ABCC6 gene. LOD score values were calculated on the assumption of a gene frequency of 0.0001 and both complete penetrance and reduced penetrance (90%), with theta values between 0.0 and 0.4.

RESULTS

LOD score values excluded the involvement of the ABCC6 gene.

CONCLUSIONS

The dominant transmission of optic disc drusen, mottled fundus, and angioid streaks in this family is not due to alterations in the ABCC6 gene.

[Familial complicated optic disc drusen in a child]

We report a case of a 15-year-old child with optic disc drusen with known familial inheritance and disc swelling. Inheritance and visual field defects are discussed.

[A familial case of drusen of the optic disk]

The present abstract is about a case of drusen of the optic disc (DOD), consisting of three members, belonging to two generations: the mother (41 years) and two daughters (16 and 19 years). Their personal records showed nothing special, except case III-2 with crisis equivalent to the epileptic ones. No changes of the visual acuity and of the visual field were found. Ophthalmoscopy and angiofluorography showed: a bilateral and superficial location of the DOD; no vascular anomalies (discal and peridiscal) or other retinal changes; a trend towards flattening and getting more mat of the DOD, in older cases. It is debated upon the possibility that a single gene might be involved, responsible for an autosomal dominant or autosomal recessive transmission mode.

Are optic disc drusen inherited?

OBJECTIVE

To conduct family studies of the incidence of optic disc drusen and related optic disc anomalies among relatives of those affected.

DESIGN

Retrospective case series with prospective examination of patients and their relatives using B-scan ultrasonography and color photography.

PARTICIPANTS

A total of 27 relatives of 7 probands with bilateral optic disc drusen were examined.

MAIN OUTCOME MEASURES

Presence of optic disc drusen on clinical examination or B-scan ultrasonography and presence of related anomalies, including absence of optic disc cup and presence of anomalous vasculature.

RESULTS

Only 1 of 27 relatives had optic disc drusen (3.7%). Thirty of 53 eyes had anomalous vessels (57%), and 26 eyes had no optic cup (49%).

CONCLUSION

The primary pathology of optic disc drusen is likely to be an inherited dysplasia of the optic disc and its blood supply, which predisposes to the formation of optic disc drusen.

[Fundus autofluorescence in patients with hereditary macular dystrophies, malattia leventinese, familial dominant and aged-related drusen]

PURPOSE

The lack of histopathological material has placed limitation on our knowledge on the composition of focal deposits in eyes with macular dystrophies, malattia leventinese, dominant drusen and age related macular degeneration. This study was designed to study the composition of focal deposits in these eyes by documenting fundus autofluorescence in vivo.

METHODS

Fundus autofluorescence was documented in 343 eyes of 199 subjects with macular dystrophies, malattia leventinese, dominant drusen and age-related macular degeneration using a laser scanning ophthalmoscope (Zeiss, Oberkochen; excitation wavelength: 488 nm, barrier filter at 521 nm).

RESULTS

Autofluorescence of focal deposits was increased in eyes with macular dystrophies. In eyes with malattia leventinese and dominant drusen autofluorescence intensity of focal deposits showed a wide spectrum. In contrast, autofluorescence of age-related drusen was within normal limits. Background autofluorescence intensity was increased in eyes with macular dystrophies and within normal limits in eyes with malattia leventinese, dominant drusen and age-related drusen.

CONCLUSION

The technique of in-vivo recording of fundus autofluorescence allows the differential diagnosis between macular dystrophies/malattia leventinese, dominant drusen/age related drusen when otherwise not possible.

Pigmented paravenous retinochoroidal atrophy (PPRCA) with optic disc drusen

Pigmented paravenous retinochoroidal atrophy (PPRCA) is a rare retinal disorder which is diagnosed primarily on its typical funduscopic appearance of retinal pigment epithelial atrophy and clumping in a paravenous distribution. Pigmented paravenous retinochoroidal atrophy is usually asymptomatic and seldom causes marked decrease in visual acuity or significant impairment of electrophysiologic functions. Optic nerve head drusen, which are thought to be inherited as an autosomal dominant trait, rare in blacks, and known to be associated with retinitis pigmentosa, have not been previously reported with PPRCA. The authors present a case of PPRCA which is classic except for an additional finding of optic nerve head drusen. The heritability of PPRCA remains controversial but the authors' reported association of PPRCA and disc drusen seems to suggest some genetic influence.