Finnish hereditary amyloidosis. Amino acid sequence homology between the amyloid fibril protein and human plasma gelsoline

Construction of Remote Sensing Model of Fresh Corn Biomass Based on Neural Network

Corn has a high yield and is widely used. Therefore, developing corn production and accurately estimating corn biomass yield are of great significance to improving people's lives, developing rural economy and climate issues. In this paper, a 3-layer BP neural network model is constructed by using the LM algorithm as the training algorithm of the corn biomass BP network model. From the three aspects of elevation, slope, and aspect, combined with the BP neural network model of corn biomass, the spatial distribution of corn biomass in the study area is analyzed. The results showed that the average biomass per unit area of maize increased with the increase in altitude below 1000 m. There are relatively more human activities in low altitude areas, which are more active in forestry production. The best planting altitude of corn is 0 ∼ 1000 m. When the altitude is higher than 1000 m, the corn biomass gradually decreases. In terms of slope, if the slope is lower than 15°, the biomass of maize increases with the increase in slope. If the slope is lower than 15°, the biomass of maize decreases gradually with the increase in slope. The biomass of maize on sunny slope was higher than that on shady slope.

Selective and Sensitive Pull Down of Amyloid Fibrils Produced in Vitro and in Vivo by the Use of Pentameric-Thiophene-Coupled Resins

Protein aggregation is a hallmark of several degenerative diseases, including Alzheimer's disease, Parkinson's disease and familial amyloidosis (Finnish type) (FAF). A method to isolate and detect amyloids is desired for the diagnosis of amyloid diseases. Here, we report the synthesis of pentameric thiophene amyloid ligand (p-FTAA) linked to agarose resin for selective purification of amyloid aggregates produced in vitro and in vivo. Using amyloid fibrils produced in vitro from α-synuclein, gelsolin, and Aβ_1-40 and gelsolin amyloid aggregates extracted from tissue homogenates of a mouse model of FAF, we observed that p-FTAA resin was able to pull down amyloid aggregates. The functionalized resin was also able to pull down oligomers produced in vitro from the A30P variant of α-synuclein. The methodology described here can be useful for the diagnosis of amyloidogenic disease and also can be used to purify amyloid fibrils from biological samples, rendering the fibrils available for more accurate structural and biochemical characterization.

AAV9 delivered bispecific nanobody attenuates amyloid burden in the gelsolin amyloidosis mouse model

Gelsolin amyloidosis is a dominantly inherited, incurable type of amyloidosis. A single point mutation in the gelsolin gene (G654A is most common) results in the loss of a Ca2+  binding site in the second gelsolin domain. Consequently, this domain partly unfolds and exposes an otherwise buried furin cleavage site at the surface. During secretion of mutant plasma gelsolin consecutive cleavage by furin and MT1-MMP results in the production of 8 and 5 kDa amyloidogenic peptides. Nanobodies that are able to (partly) inhibit furin or MT1-MMP proteolysis have previously been reported. In this study, the nanobodies have been combined into a single bispecific format able to simultaneously shield mutant plasma gelsolin from intracellular furin and extracellular MT1-MMP activity. We report the successful in vivo expression of this bispecific nanobody following adeno-associated virus serotype 9 gene therapy in gelsolin amyloidosis mice. Using SPECT/CT and immunohistochemistry, a reduction in gelsolin amyloid burden was detected which translated into improved muscle contractile properties. We conclude that a nanobody-based gene therapy using adeno-associated viruses shows great potential as a novel strategy in gelsolin amyloidosis and potentially other amyloid diseases.

Clinical, biopsy, and mass spectrometry findings of renal gelsolin amyloidosis

Gelsolin amyloidosis is a rare type of amyloidosis typically involving the cranial and peripheral nerves, but rarely the kidney. Here we report the clinical, kidney biopsy, and mass spectrometry findings in 12 cases of renal gelsolin amyloidosis. Of the 12 patients, five were men and seven were women with mean age at diagnosis of 63.8 years. Gelsolin amyloidosis was most common in Caucasians (six patients) and Asians (four patients), and included one each African-American and Hispanic patients. Nephrotic syndrome was the most common cause of biopsy, although most patients also had progressive loss of kidney function. Hematological and serological evaluation was negative in 11 patients, while one patient had a monoclonal gammopathy. The renal biopsy showed large amounts of pale eosinophilic Congo red-positive amyloid deposits typically restricted to the glomeruli. Immunofluorescence studies were negative for immunoglobulins in nine cases with three cases of smudgy glomerular staining for IgG. Electron microscopy showed mostly random arrangement of amyloid fibrils with focally parallel bundles/sheets of amyloid fibrils present. Laser microdissection of the amyloid deposits followed by mass spectrometry showed large spectra numbers for gelsolin, serum amyloid P component, and apolipoproteins E and AIV. Furthermore, the p. Asn211Lys gelsolin mutation on mass spectrometry studies was detected in three patients by mass spectrometry, which appears to represent a renal-limited form of gelsolin amyloidosis. Thus, renal gelsolin amyloidosis is seen in older patients, presents with nephrotic syndrome and progressive chronic kidney disease, and histologically exhibits glomerular involvement. The diagnosis can be confirmed by mass spectrometry studies.

Hereditary renal amyloidosis caused by a heterozygous G654A gelsolin mutation: a report of two cases

Finnish-type familial amyloidosis (FAF) is a rare hereditary systemic amyloidosis that mainly exhibits cranial neuropathy. We describe a Japanese family with FAF manifested predominantly as renal amyloidosis. The proband was a 42-year-old woman with a 21-year history of proteinuria due to renal amyloidosis. Her mother was subsequently diagnosed with a similar disorder. After the first renal biopsy, both patients were followed up routinely for a period of 14 years. Genetic analysis of DNA samples revealed a heterozygous G654A gelsolin mutation. Severe renal involvement has not been reported previously in patients with FAF bearing a heterozygous gelsolin mutation.

Clinical characteristics and SAP scintigraphic findings in 10 patients with AGel amyloidosis

The clinical features of hereditary gelsolin (AGel) amyloidosis include corneal lattice dystrophy, distal sensorimotor, cranial neuropathy and cutis laxa. To date, four mutations of the gelsolin (GSN) gene encoding the following variants have been identified as the cause of this malady; p.D214N, p.D214Y, p.G194R and p.N211K (this nomenclature includes the 27-residue signal peptide). Interestingly, the latter two variants are associated exclusively with a renal amyloidosis phenotype. Here we report the clinical features in 10 patients with AGel amyloidosis associated with the p.D214N mutation, all of whom underwent whole body (123)I-SAP scintigraphy and were followed up in a single UK Centre for a prolonged period. Two patients, from the same kindred presented with proteinuria; eight subjects had a characteristic AGel amyloidosis phenotype including cranial neuropathy and/or corneal lattice dystrophy. (123)I-SAP scintigraphy revealed substantial renal amyloid deposits in all 10 patients, including those with preserved renal function, and usually without tracer uptake into other visceral organs. (123)I-SAP scintigraphy is a non-invasive technique that aids early diagnosis of patients with this rare disease, especially those who lack a family history and/or present with an unusual clinical phenotype.

Immunoprecipitation of amyloid fibrils by the use of an antibody that recognizes a generic epitope common to amyloid fibrils

Amyloid fibrils are associated with many maladies, including Alzheimer's disease (AD). The isolation of amyloids from natural materials is very challenging because the extreme structural stability of amyloid fibrils makes it difficult to apply conventional protein science protocols to their purification. A protocol to isolate and detect amyloids is desired for the diagnosis of amyloid diseases and for the identification of new functional amyloids. Our aim was to develop a protocol to purify amyloid from organisms, based on the particular characteristics of the amyloid fold, such as its resistance to proteolysis and its capacity to be recognized by specific conformational antibodies. We used a two-step strategy with proteolytic digestion as the first step followed by immunoprecipitation using the amyloid conformational antibody LOC. We tested the efficacy of this method using as models amyloid fibrils produced in vitro, tissue extracts from C. elegans that overexpress Aβ peptide, and cerebrospinal fluid (CSF) from patients diagnosed with AD. We were able to immunoprecipitate Aβ(1-40) amyloid fibrils, produced in vitro and then added to complex biological extracts, but not α-synuclein and gelsolin fibrils. This method was useful for isolating amyloid fibrils from tissue homogenates from a C. elegans AD model, especially from aged worms. Although we were able to capture picogram quantities of Aβ(1-40) amyloid fibrils produced in vitro when added to complex biological solutions, we could not detect any Aβ amyloid aggregates in CSF from AD patients. Our results show that although immunoprecipitation using the LOC antibody is useful for isolating Aβ(1-40) amyloid fibrils, it fails to capture fibrils of other amyloidogenic proteins, such as α-synuclein and gelsolin. Additional research might be needed to improve the affinity of these amyloid conformational antibodies for an array of amyloid fibrils without compromising their selectivity before application of this protocol to the isolation of amyloids.

Molecular diagnosis of genodermatoses

The progress of molecular genetics helps clinicians to prove or exclude a suspected diagnosis for a vast and yet increasing number of genodermatoses. This leads to precise genetic counselling, prenatal diagnosis and preimplantation genetic haplotyping for many inherited skin conditions. It is also helpful in such occasions as phenocopy, late onset and incomplete penetrance, uniparental disomy, mitochondrial inheritance and pigmentary mosaicism. Molecular methods of two genodermatoses are explained in detail, i.e. genodermatoses with skin fragility and neurofibromatosis type 1.

Hereditary gelsolin amyloidosis

Hereditary gelsolin amyloidosis (HGA) is an autosomally dominantly inherited form of systemic amyloidosis, characterized mainly by cranial and sensory peripheral neuropathy, corneal lattice dystrophy, and cutis laxa. HGA, originally reported from Finland and now increasingly from other countries in Europe, North and South America, and Asia, may still be underdiagnosed worldwide. It is the first and so-far only known disorder caused by a gelsolin gene defect, namely a G654A or G654T mutation. Gelsolin is a principal actin-modulating protein, implicated in multiple biological processes, also in the nervous system, e.g. axonal transport, myelination, neurite outgrowth, and neuroprotection. The gelsolin gene defect causes expression of variant gelsolin, followed by systemic deposition of gelsolin amyloid (AGel) in HGA patients and even other consequences on the metabolism and function of gelsolin. In HGA, specific therapy is not yet available but correct diagnosis enables adequate symptomatic treatment which decisively improves the quality of life in these patients. A transgenic murine model of HGA expressing AGel is available, in anticipation of new treatment options targeted toward this slowly progressive but devastating amyloidosis. Present and future lessons learned from HGA may be applicable even in diagnosis and treatment of other hereditary and sporadic amyloidoses.

Regulation of actin dynamics by protein kinase R control of gelsolin enforces basal innate immune defense

Primary resistance to pathogens is reliant on both basal and inducible immune defenses. To date, research has focused upon inducible innate immune responses. In contrast to resistance via cytokine induction, basal defense mechanisms are less evident. Here we showed that the antiviral protein kinase R (PKR) inhibited the key actin-modifying protein gelsolin to regulate actin dynamics and control cytoskeletal cellular functions under homeostatic conditions. Through this mechanism, PKR controlled fundamental innate immune, actin-dependent processes that included membrane ruffling and particle engulfment. Accordingly, PKR counteracted viral entry into the cell. These findings identify a layer of host resistance, showing that the regulation of actin-modifying proteins during the innate immune response bolsters first-line defense against intracellular pathogens and has a sustained effect on virus production. Moreover, these data provide proof of principle for a concept in which the cell cytoskeleton could be targeted to elicit broad antiviral protection.

Protein aggregation: mechanisms and functional consequences

Understanding the mechanisms underlying protein misfolding and aggregation has become a central issue in biology and medicine. Compelling evidence show that the formation of amyloid aggregates has a negative impact in cell function and is behind the most prevalent human degenerative disorders, including Alzheimer's Parkinson's and Huntington's diseases or type 2 diabetes. Surprisingly, the same type of macromolecular assembly is used for specialized functions by different organisms, from bacteria to human. Here we address the conformational properties of these aggregates, their formation pathways, their role in human diseases, their functional properties and how bioinformatics tools might be of help to study these protein assemblies.

Amyloidosis

The term amyloid describes the deposition in the extracellular space of certain proteins in a highly characteristic, insoluble fibrillar form. Amyloidosis describes the various clinical syndromes that occur as a result of damage by amyloid deposits in tissues and organs throughout the body. The clinical significance of amyloid varies enormously, ranging from incidental asymptomatic deposits to localized disease through to rapidly fatal systemic forms that can affect multiple vital organs. Currently available therapy is focused on reducing the supply of the respective amyloid fibril precursor protein and supportive medical care, which together have greatly improved survival. Chemotherapy and anti-inflammatory treatment for the disorders that underlie AL and AA amyloidosis are guided by serial measurements of the respective circulating amyloid precursor proteins, i.e. serial serum free light chains in AL and serum amyloid A protein in AA type. Quality of life and prognosis of some forms of hereditary systemic amyloidosis can be improved by liver and other organ transplants. Various new therapies, ranging from silencing RNA, protein stabilizers to monoclonal antibodies, aimed at inhibiting fibril precursor supply, fibril formation or the persistence of amyloid deposits, are in development; some are already in clinical phase.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

Transgenic analysis of the anterior eye-specific enhancers of the zebrafish gelsolin-like 1 (gsnl1) gene

The anterior segment of the eye includes such structures as the cornea, lens, iris, and ciliary body and is essential for many visual and physiological functions of the eye. The zebrafish gelsolin-like 1 (gsnl1) gene encodes an actin regulatory protein and is expressed in the anterior segment of the eye. We report the transgenic analyses of the gsnl1 promoter and enhancer that are required for expression in the anterior segment of the eye. A 6.4-kb genomic fragment upstream from the translation initiation site (ATG) was capable of driving green fluorescent protein (GFP) expression in transient transgenic embryos and stable transgenic adult fish, which mimics the endogenous gsnl1 expression. The GFP expression was localized in the corneal epithelium (CE) and the annular ligament (AL) at the iridocorneal angle. A unique enhancer for each of these two tissues was identified at 3.7-kb upstream from the ATG. The 60-bp AL and 25-bp CE enhancers were separated by 100-bp and functioned independently from each other. Deletion analysis indicated that the proximal promoter was located 1.6-kb upstream from the ATG. Stable GFP transgenic lines were established for future studies of genetic regulation in the anterior segment of the fish eye.

[Finnish amyloid polyneuropathy in a French patient]

INTRODUCTION

Finnish amyloid variety is a rare familial amiloidosis polyneuropathy essentially observed in Finland. It concerns about six hundred people in the world in which five hundred reside in Finland.

OBSERVATION

We report a case of a 58-year-old French woman with a 10-year history of lattice cornea dystrophy. She consulted in January 2004 for impaired swallowing, facial paralysis principally of the right superior territory and symptoms of arthritis which had developed a few months earlier. Observation revealed facial cutis laxa, tongue amyotrophy and some fasciculation. Electroneuromyography showed chronic neurogenic involvement of the facial muscles. Limbs and the sympathetic neuronal system were free of involvement. Pathological examination revealed areas of peri vascular amiloid deposits. Molecular biology confirmed the diagnosis of Finnish amiloidosis: substitution of aspartic acid by tyrosine in the 187 codon in the 9th chromosome (gelsoline gene). This mutation has been previously found in Denmark and the Czech Republic.

CONCLUSION

Finnish amiloidosis is a familial polyneuropathy characterized by an association of cornea lattice dystrophy, cutis laxa and a chronic neurogenic involvement of the cranial nerves. Two mutations are known. Life expectancy is not affected, but quality of life is altered.

Checking the conformational stability of cystatin C and its L68Q variant by molecular dynamics studies: why is the L68Q variant amyloidogenic?

Human L68Q cystatin C is one of the known human amyloidogenic proteins. In its native state it is a monomer with alpha/beta structure. Experimental evidence suggests that L68Q variant associates into dimeric intermediates and that the dimers subsequently self-assemble to form amyloid deposits and insoluble fibrils. Details of the pathway of L68Q mutant amyloid formation are unclear; however, different experimental approaches with resolutions at molecular level have provided some clues. Probably, the stability and flexibility of monomeric L68Q variant play essential roles in the early steps of amyloid formation; thus, it is necessary to characterize early conformational changes of L68Q cystatin C monomers. In this paper, we demonstrate the possibility that the differences between the monomeric forms of wild-type (wt) cystatin C and its L68Q variant are responsible for higher tendency of the L68Q cystatin C amyloidogenesis. We started our studies with the simulations of wt and L68Q cystatin C monomers. Nanosecond time scale molecular dynamics simulations at 308K were performed using AMBER7.0 program. The results show that the structure of the L68Q monomer was changed, relative to the wt cystatin C structure. The results support earlier speculation that the L68Q point mutation would easily lead to dimer formation.

Metalloendoprotease cleavage triggers gelsolin amyloidogenesis

Amyloid diseases like Alzheimer's disease and familial amyloidosis of Finnish type (FAF) stem from endoproteolytic cleavage of a precursor protein to generate amyloidogenic peptides that accumulate as amyloid deposits in a tissue-specific manner. FAF patients deposit both 8 and 5 kDa peptides derived from mutant (D187Y/N) plasma gelsolin in the extracellular matrix (ECM). The first of two aberrant sequential proteolytic events is executed by furin to yield a 68 kDa (C68) secreted fragment. We now identify the metalloprotease MT1-matrix metalloprotease (MMP), an integral membrane protein active in the ECM, as a protease that processes C68 to the amyloidogenic peptides. We further demonstrate that ECM components are capable of accelerating gelsolin amyloidogenesis. Proteolysis by MT1-MMP-like proteases proximal to the unique chemical environment of the ECM offers an explanation for the tissue-specific deposition observed in FAF and provides critical insight into new therapeutic strategies.

Towards gelsolin amyloid formation

Amyloid diseases result from protein misfolding and aggregation into fibrils. Some features of gelsolin amyloidogenic fragments comprised of residues 173-243 (G173-243) and residues 173-202 (G173-202) were investigated by the method of molecular dynamics (MD). The alpha-helical structure of G173-243 present in the whole protein unwinds during the course of MD simulation of the fragment G173-243, suggesting that the G173-243 structure is not stable and could unfold before becoming involved in gelsolin amyloid fibril formation. Twelve fragments of G173-202 were used to build a possible beta-fibril. During the course of the simulation, G173-202 fragments formed hydrogen bonds and tended to turn by an angle of 10 degrees -20 degrees towards each other.

Cardiac conduction alterations in a French family with amyloidosis of the finnish type with the p.Asp187Tyr mutation in theGSN gene

Familial amyloidosis of the Finnish type (FAF) is a rare autosomal-dominant disorder caused by the accumulation of a 71-amino acid amyloidogenic fragment of mutant gelsolin, an actin-modulating protein. The main symptoms include corneal lattice dystrophy, progressive cranial and peripheral neuropathy, and skin changes. To date, only two mutations in the GSN gene have been described: the p.Asp187Asn mutation in most patients and the p.Asp187Tyr mutation in a Danish and Czech family. We report on the third family with the p.Asp187Tyr mutation and the first French FAF family. Severe cardiac conduction alterations in three patients were mainly caused by cardiac sympathetic denervation. These findings demonstrate the cardiological involvement of the FAF phenotype and suggest that cardiological follow-up is required in FAF patients.

Gelsolin-related familial amyloidosis, Finnish type, in a Portuguese family: Clinical and neurophysiological studies

We report a Portuguese family with familial amyloid polyneuropathy related to gelsolin. There were no known Finnish ancestors, but the same mutation as described in Finnish patients (G654A) was carried. Clinical and neurophysiological investigations were performed in four patients. Corneal lattice dystrophy affected all four patients; an axonal lesion of the facial nerve occurred in three patients; visual tract involvement was documented in one case; and corticospinal and posterior column dysfunction was present in one patient. Polarizing microscopy of skin and muscle samples demonstrated amyloid deposits in two patients; anti-gelsolin immunohistochemistry was positive for amyloidogenic gelsolin. The Finnish mutation of gelsolin protein (G654A) was detected in five family members. The utility of neurophysiological testing in the evaluation and follow-up of this type of amyloidosis is discussed.

The Finnish Disease Heritage III: the individual diseases

This article is the third and last in a series entitled The Finnish Disease Heritage I-III. All the 36 rare hereditary diseases belonging to this entity are described for clinical and molecular genetic purposes, based on the Finnish experience gathered over a period of half a century. In addition, five other diseases are mentioned. They may be included in the list of the "Finnish diseases" after adequate complementary studies.

A family with gastrointestinal amyloidosis associated with variant lysozyme

Hereditary nonneuropathic systemic lysozyme amyloidosis is a very rare form of amyloidosis, and only 4 families with this condition have been detailed until now in the literature. Clinical manifestations of lysozyme amyloidosis observed until now mainly concerned the kidneys, liver, and digestive tract. We report here a new family with hereditary lysozyme amyloidosis who presented predominantly with gastrointestinal involvement. The proband, a middle-aged woman, underwent partial gastrectomy for a hemorrhagic "gastric peptic ulcer" in 1984. Gastrointestinal amyloidosis was diagnosed in 1998 on biopsies performed on the gastroduodenal anastomosis, which appeared to be very congestive at presentation. Immunohistochemical stainings in tissue sections were positive for lysozyme. Amyloid was also observed in the colonic mucosa. The patient had a mutation in the lysozyme gene characterized by substitution of the amino acid at position 64 in the mature protein from tryptophan to arginine, previously described in only 1 French family with prominent nephropathy. It is interesting to note that her father had died many years before with an uncharacterized digestive amyloidosis. Our observation shows that a search for gastrointestinal amyloidosis is important, particularly when physicians are faced with congestive mucosa, unexplained abdominal hemorrhage, or abdominal symptoms. When gastrointestinal amyloidosis is diagnosed, it is important to determine with precision the nature of the amyloid fibril proteins, because various types of amyloidosis can involve the gastrointestinal tract.

Hereditary renal amyloidosis caused by a new variant lysozyme W64R in a French family

BACKGROUND

The number of proteins with mutations resulting in amyloidosis has continued to increase. Five proteins--transthyretin, fibrinogen alpha-A chain, apolipoprotein AI, lysozyme, apolipoprotein AII, cystatin C and gelsolin--can be associated with hereditary amyloidosis involving the kidney.

METHODS

A French family with a history of autosomal dominant hereditary amyloidosis with early sicca syndrome and nephropathy leading to renal failure after the fifth to the seventh decade was studied. Several tissue specimens obtained from the proband and his relatives were examined. Immunohistochemistry was performed on paraffin embedded sections using the indirect immunoperoxidase technique. We searched for mutations in the five exons and flanking introns of the lysozyme gene.

RESULTS

Amyloid deposits from the bowel, labial salivary gland and kidney were intensively stained by anti-lysozyme antibody. Sequence analysis of lysozyme exon 2 from the affected individuals revealed a nucleotide substitution predicting a substitution of the amino acid at position 64 in the mature protein from tryptophane, an aromatic residue to the cationic residue arginine (W64R).

CONCLUSION

We report a novel mutation (W64R) of the lysozyme that is associated with hereditary amyloidosis and prominent nephropathy. Since the treatment of hereditary amyloidosis greatly varies with the nature of the amyloid protein, thorough characterization of the latter is crucial for the management of the disease.

Furin initiates gelsolin familial amyloidosis in the Golgi through a defect in Ca(2+) stabilization

Hereditary familial amyloidosis of Finnish type (FAF) leading to amyloid in the peripheral and central nervous systems stems from deposition of a 71 residue fragment generated from the D187N/Y variants of plasma gelsolin by two sequential endoproteolytic events. We identify the protease accomplishing the first cleavage as furin, a proprotein convertase. Endoproteolysis of plasma gelsolin occurs in the trans-Golgi network due to the inability of the FAF variants to bind and be stabilized by Ca(2+). Secretion and processing of the FAF variants by furin can be uncoupled by blocking the convergence of the exocytic pathway transporting plasma gelsolin and the endocytic recycling of furin. We propose that coincidence of membrane trafficking pathways contributes to the development of proteolysis-initiated amyloid disease.

Destabilization of Ca2+-free gelsolin may not be responsible for proteolysis in Familial Amyloidosis of Finnish Type

Mutations at position 187 in secreted gelsolin enable aberrant proteolysis at the 172-173 and 243-244 amide bonds, affording the 71-residue amyloidogenic peptide deposited in Familial Amyloidosis of Finnish Type (FAF). Thermodynamic comparisons of two different domain 2 constructs were carried out to study possible effects of the mutations on proteolytic susceptibility. In the construct we consider to be most representative of domain 2 in the context of the full-length protein (134-266), the D187N FAF variant is slightly destabilized relative to wild type (WT) under the conditions of urea denaturation, but exhibits a T(m) identical to WT. The D187Y variant is less stable to intermediate urea concentrations and exhibits a T(m) that is estimated to be approximately 5 degrees C lower than WT (pH 7.4, Ca(2+)-free). Although the thermodynamic data indicate that the FAF mutations may slightly destabilize domain 2, these changes are probably not sufficient to shift the native to denatured state equilibrium enough to enable the proteolysis leading to FAF. Biophysical data indicate that these two FAF variants may have different native state structures and possibly different pathways of amyloidosis.

Ultrastructural localization of gelsolin in lattice corneal dystrophy type I

In the light of recent studies into lattice corneal dystrophies, with particular reference to gelsolin immunoreactivity, the authors set out to determine the ultrastructural localization of gelsolin molecules in lattice corneal dystrophy type I. Immunoelectron microscopy with a monoclonal antibody against the COOH-terminal of the native gelsolin molecule (clone GS-2C4) was used to compare antigelsolin reactivity in normal and dystrophic corneas. A gelsolin-like protein was observed at the level of the rough endoplasmic reticulum in both epithelial and endothelial cells, together with mild positive staining in stromal keratocytes of normal corneas; increased keratocytic immunoreactivity with positive staining within and/or around corneal amyloid deposits was revealed in dystrophic corneas. Observed intra- and extracellular immunoreactivity suggests that amyloid deposition may induce gelsolin synthesis; this actin-related protein could be involved in the rearrangement of corneal stroma in lattice corneal dystrophy.

Evidence for gelsolin as a corneal crystallin in zebrafish

We have shown that gelsolin is one of the most prevalent water-soluble proteins in the transparent cornea of zebrafish. There are also significant amounts of actin. In contrast to actin, gelsolin is barely detectable in other eye tissues (iris, lens, and remaining eye) of the zebrafish. Gelsolin cDNA hybridized intensely in Northern blots to RNA from the cornea but not from the lens, brain, or headless body. The deduced zebrafish gelsolin is approximately 60% identical to mammalian cytosolic gelsolin and has the characteristic six segmental repeats as well as the binding sites for actin, calcium, and phosphatidylinositides. In situ hybridization tests showed that gelsolin mRNA is concentrated in the zebrafish corneal epithelium. The zebrafish corneal epithelium stains very weakly with rhodamine-phalloidin, indicating little F-actin in the cytoplasm. In contrast, the mouse corneal epithelium contains relatively little gelsolin and stains intensely with rhodamine-phalloidin, as does the zebrafish extraocular muscle. We propose, by analogy with the diverse crystallins of the eye lens and with the putative enzyme-crystallins (aldehyde dehydrogenase class 3 and other enzymes) of the mammalian cornea, that gelsolin and actin-gelsolin complexes act as water-soluble crystallins in the zebrafish cornea and contribute to its optical properties.

Danish type gelsolin related amyloidosis: 654G-T mutation is associated with a disease pathogenetically and clinically similar to that caused by the 654G-A mutation (familial amyloidosis of the Finnish type)

BACKGROUND

Familial amyloidosis of the Finnish type (FAF, Finnish hereditary amyloidosis) is caused by a 654G-A mutation in the gelsolin gene on chromosome 9 resulting in the expression of mutant Asn-187 gelsolin which is abnormally proteolytically processed generating amyloidogenic fragments that polymerize into amyloid fibrils. We have recently shown that in a Danish and a Czech family with a clinical syndrome similar to FAF, including corneal lattice dystrophy, cranial neuropathy and skin changes, the disease is caused by another mutation at the same position, namely 654G-T predicting a Try-for-Asp substitution at 187 in secreted gelsolin.

AIM

To undertake a closer examination of the Danish subtype of FAF and report immunohistochemical and biochemical findings.

RESULTS

Immunostaining of plasma gelsolin isolated from heterozygous FAF of the Danish subtype revealed a pattern similar to that found in FAF-Asn 187. The > 60 kDa gelsolin species contain an epitope characteristic of the amyloid forming region as revealed by an amyloid specific antibody, whereas the approximately 50 kDa fragments are devoid of it. Compared with the wild-type gelsolin peptide (Asp-187), the corresponding mutant peptide (Tyr-187) showed dramatically increased fibrillogenicity as revealed by quantitative thioflavine-T based fluorimetry; ultrastructurally, amyloid-like fibrils were formed by the mutant peptide. Immunohistochemistry showed that antibodies directed against residues 231-242 of secreted gelsolin, representing the carboxy terminus of the sequence forming the amyloid protein (residues 173-243) laid down in the tissues in a fibrillar form in FAF, specifically labelled the amyloid deposited in rectum and skin in the Danish (654G-T) subtype.

CONCLUSIONS

The 654G-T mutation in the gelsolin gene gives rise to an amyloid disease clinically and pathogenetically similar to that caused by the 654G-A mutation.

Regulation of neural differentiation by normal and mutant (G654A, amyloidogenic) gelsolin

Gelsolin belongs to a family of proteins that modulate the structural dynamics of cytoskeletal actin. Gelsolin activity is required for the redistribution of actin occurring during membrane ruffling, cell crawling, and platelet activation. A point mutation (G654A) in the gelsolin gene causes a dominantly inherited systemic amyloidosis called familial amyloidosis of the Finnish type (FAF). This disease is characterized by a cranial neuropathy that cannot be explained solely by amyloid deposits. To address the question of whether gelsolin has a specific role in neural cell development, we transfected cDNA for wild type and G654A point-mutated gelsolin into a neural cell line, Paju, which can be induced to differentiate by treatment with phorbol 12-myristate 13-acetate. Overexpressed wild type gelsolin inhibited neural differentiation whereas mutated gelsolin did not, indicating that appropriate gelsolin activity is essential for neural sprouting. The G654A mutant gelsolin induced stabilization of F-actin and reduced the plasticity of neural development. This provides a novel etiopathogenetic mechanism for the neuronal dysfunction in FAF.

Functional consequences of amyloidosis mutation for gelsolin polypeptide -- analysis of gelsolin-actin interaction and gelsolin processing in gelsolin knock-out fibroblasts

Gelsolin, an actin-modulating protein, derived from a single gene exists in intracellular and secreted forms. A point mutation at position 187 of both forms of gelsolin causes familial amyloidosis of the Finnish type (FAF). Here, we expressed both isoforms of the wild-type and FAF mutant gelsolin in mouse embryonic gelsolin-null fibroblasts. We demonstrate that the FAF mutation does not interfere with the normal actin-modulating function of intracellular gelsolin, and that aberrant processing of secreted FAF gelsolin to FAF amyloid precursor takes place in the gelsolin-negative background. These results suggest that, in patients with FAF, symptoms are caused by the accumulation in their tissues of amyloid derived from plasma gelsolin and are not due to functional differences in cytoplasmic gelsolin.

The amyloidogenicity of gelsolin is controlled by proteolysis and pH

BACKGROUND

Normally, gelsolin functions in plasma as part of the actin-scavenging system to assemble and disassemble actin filaments. The Asp 187-->Asn (D187N) Asp 187-->Tyr (D187Y) gelsolin mutations facilitate two proteolytic cuts in the parent protein generating a 71-residue fragment that forms amyloid fibrils in humans, putatively causing Finnish type familial amyloidosis (FAF). We investigated the role of the D187N mutation in amyloidogenicity using biophysical studies in vitro.

RESULTS

Both the recombinant wild-type and D187N FAF-associated gelsolin fragments adopt an ensemble of largely unfolded structures that do not self-associate into amyloid at pH 7. 5. Incubation of either fragment at low pHs (6.0-4.0) leads to the formation of well-defined fibrils within 72 hours, however.

CONCLUSIONS

The D187N mutation has been suggested to destabilize the structure of the gelsolin parent protein (specifically domain 2), facilitating two proteolytic cleavage events. Our studies demonstrate that generating the largely unstructured peptide is not sufficient alone for amyloid formation in vitro (on a time scale of months). A drop in pH or an analogous environmental change appears necessary to convert the unstructured fragment into amyloid fibrils, probably through an associative mechanism. The wild-type gelsolin fragment will make amyloid fibrils from pH 6 to 4 in vitro, but neither the wild-type fragment nor fibrils have been observed in vivo. It is possible that domain 2 of wild-type gelsolin is stable in the context of the whole protein and not susceptible to the proteolytic degradation that affords the 71-residue FAF-associated peptide.

Cells of the neuronal lineage play a major role in the generation of amyloid precursor fragments in gelsolin-related amyloidosis

Gelsolin-related amyloidosis or familial amyloidosis, Finnish type (FAF) (OMIM No105120) is a hereditary amyloid disease caused by a mutation in a precursor protein for amyloid (gelsolin) and characterized by corneal dystrophy and polyneuropathy. In vitro expression of the FAF-mutant (Asp187 --> Asn/Tyr) secretory gelsolin in COS cells leads to generation of an aberrant polypeptide presumably representing the precursor for tissue amyloid. Here, we provide evidence that this abnormal processing results from defective initial folding of the secreted FAF gelsolin due to the lack of the Cys188-Cys201 disulfide bond, normally formed next to the FAF mutation site. We compared cells of different tissue origin and discovered a dramatic difference between the amount of cleavage of FAF gelsolin to the amyloid precursor in neuronal and non-neuronal cells. More than half of the mutant gelsolin was cleaved in PC12 and in vitro differentiated human neuronal progenitor cells. In contrast, human fibroblasts and Schwannoma cell cultures showed only a limited capacity to cleave FAF gelsolin, although the cleavage mechanism per se seems to be similar in the various cell types. The present findings of processing and distribution of secreted FAF gelsolin in the neuronal cells emphasize the role of neurons in the tissue pathogenesis of this amyloid polyneuropathy.

Gelsolin-related familial amyloidosis, Finnish type (FAF), and its variants found worldwide

Gelsolin-related familial amyloidosis, Finnish type, occurs worldwide, most likely as a result of sporadic low-frequency mutations. Two mutations at nucleotide 654 in the gelsolin gene have been demonstrated, which result in a characteristic triad of ophthalmologic, neurologic and dermatologic manifestations distinct from other amyloidoses. Some phenotypic variation, particularly in the age of onset and severity of manifestations, occurs but in general the disease is clinically rather homogeneous. Systemic deposition of amyloid is found in most tissues, predominantly in blood vessel walls and associated with basement membranes. The mutations result in amino acid substitutions with a charge change in the gelsolin molecule, postulated to alter the susceptibility for proteases thereby rendering the molecule amyloidogenic. Gelsolin fragments constitute the amyloid fibrils, but abnormal fragments also occur in patients' plasma and CSF providing evidence for the role of aberrant proteolysis in the disease pathomechanism. This is further strengthened by in vitro expression analyses showing both disease-related mutations to result in secretion of an abnormal gelsolin fragment, the likely precursor protein of gelsolin amyloid. Of the two forms of gelsolin, secretory and cytoplasmic, the secretory plasma form is the likely source of amyloid. The origin of the systemic amyloid deposits is not known but, beside a circulatory origin, local synthesis and deposition is an attractive pathomechanical alternative. The final goal of preventing or curing this disease has come closer, but still awaits further comprehensive pathological, functional and experimental studies in order to dissect all pathogenetically important events.

The crystal structure of plasma gelsolin: implications for actin severing, capping, and nucleation

The structure of gelsolin has been determined by crystallography and comprises six structurally related domains that, in a Ca2+-free environment, pack together to form a compact globular structure in which the putative actin-binding sequences are not sufficiently exposed to enable binding to occur. We propose that binding Ca2+ can release the connections that join the N- and C-terminal halves of gelsolin, enabling each half to bind actin relatively independently. Domain shifts are proposed in response to Ca2+ as bases for models of how gelsolin acts to sever, cap, or nucleate F-actin filaments. The structure also invites discussion of polyphosphoinositide binding to segment 2 and suggests how mutation at Asp-187 could initiate a series of events that lead to deposition of amyloid plaques, as observed in victims of familial amyloidosis (Finnish type).

Comparison of amyloid deposition in two lines of transgenic mouse that model familial amyloidotic polyneuropathy, type I

We previously produced a transgenic mouse line designated MT-hMet30 by introducing the human mutant transthyretin (TTR) gene carrying the mouse metallothionein promoter, and showed that the presence of human variant TTR is sufficient for amyloid deposition in various tissues of these transgenic mice. However, the expression pattern of human mutant transthyretin gene in the mouse was different from that in man. To analyse pathologic processes, it is essential to establish a transgenic mouse line in which the development and tissue-specific expression of the human mutant TTR gene is the same as in man. Thus, we produced two additional transgenic mouse lines carrying the human mutant TTR gene containing either 0.6 kb (0.6-hMet30) or 6.0 kb (6.0- hMet30) of the upstream region. The expression levels of 6.0-hMet 30 gene in the liver and serum were the same as in man and about 10 times higher than those of 0.6-hMet30 gene in the liver and serum were the same as similar tissues to human patients except for the peripheral and autonomic nervous tissues. The amyloid deposition started earlier and was more extensive in 6.0-hMet30 than 0.6-hMet30 mice, suggesting that the serum levels of human mutant TTR are correlated with the occurrence and degree of amyloid deposition, to some extent. Neither amyloid deposition nor degenerative changes were observed in the peripheral and autonomic nervous systems despite the transgene expression in the choroid plexus of the 6.0-hMet30 mice. In the 6.0-hMet30 mice, amyloid deposition started at 9 months of age, although the serum level of human mutant TTR reached the adult level at 1 month. These results suggest that intrinsic environmental factors other than the mutant gene are involved in the late-onset deposition of amyloid fibrils. Transgenic mice described here should be useful for analysing such factors.

Tissue distribution and levels of gelsolin mRNA in normal individuals and patients with gelsolin-related amyloidosis

We measured quantitatively the mRNA levels of intracellular and secretory forms of gelsolin, an actin-modulating protein, in human tissues from subjects of different ages. The intracellular gelsolin mRNA constituted the major type of gelsolin steady-state mRNA in all tissues analyzed. Both forms of gelsolin were expressed in most adult tissues, with particularly high mRNA levels in all types of muscle and interestingly in skin. Between the adult and infantile tissues the most striking difference in expression levels was found in liver, as the adult liver contained only a subtle amount of gelsolin mRNA. Skin and muscle samples from patients with gelsolin-related amyloidosis (FAF), with significantly increased concentrations of serum gelsolin, did not reveal an increased expression of the gene, and both mutant and wild-type alleles were expressed in equal amounts. The high level of expression of the gelsolin gene in the skin in general could locally contribute to the characteristic skin amyloidosis in FAF patients.

Vitreous amyloidosis in familial amyloidotic polyneuropathy. Report of a case with the Val30Met transthyretin mutation

We present a clinical pathological review of vitreous amyloidosis in a case of familial amyloidotic polyneuropathy, type I. Vitreous opacification was the first manifestation of disease in the proband, who was successfully treated with vitrectomy. The eyes were obtained at autopsy after the patient died from an unrelated cause, and the histopathology is presented here. Analysis of DNA from the pathology specimen revealed the most commonly reported transthyretin mutation, Val30Met. The classification of systemic and ocular amyloidosis as well as the genetics of familial amyloidotic polyneuropathy are briefly reviewed.

Ocular amyloidosis, with special reference to the hereditary forms with vitreous involvement

The complex of diseases referred to as amyloidosis is characterized by the deposition of amyloid substance in various tissues. The amyloid protein differs in the various forms of amyloidosis. This variation is the basis of the differences in affected tissues and subsequent clinical dissimilarities. Vitreous involvement in amyloidosis seems to be especially linked to some of the hereditary neuropathies associated with the amyloid protein transthyretin. Characterization of the amyloid proteins during recent decades has allowed a chemical and immunologic classification of amyloid fibrils. This paper presents the basis for classification of amyloidosis, reviews the literature on ocular amyloidosis, with special reference to vitreous involvement, and summarizes clinical findings and frequency of vitreous amyloid involvement in Swedish patients with familial amyloidotic polyneuropathy.

Identification of the trapped calcium in the gelsolin segment 1-actin complex: implications for the role of calcium in the control of gelsolin activity

The X-ray structure of the complex of actin with gelsolin segment 1 revealed the presence of two calcium ions, one bound at an intramolecular site within segment 1 and the other bridging the segment directly to actin. Although earlier calcium binding studies at pH 8.0 revealed only a single calcium trapped in the complex (and also in the binary gelsolin-actin complex), it is here shown that two calcium ions are bound under the conditions of crystallization at physiological pH. Mutation of acidic residues in either actin or segment 1 involved in ligation of the intermolecular calcium ion resulted in loss of one of the bound calcium ions at pH < 7, but not at pH 8. Thus the calcium ion trapped in the segment 1-actin complex is that located at the intramolecular site. The implications of this for gelsolin function are discussed.

Haplotype analysis in gelsolin-related amyloidosis reveals independent origin of identical mutation (G654A) of gelsolin in Finland and Japan

Familial amyloidosis, Finnish type (FAF) (gelsolin-related amyloidosis) is an autosomal dominant form of systemic amyloidosis characterized by corneal lattice dystrophy and peripheral polyneuropathy. The accumulating protein in FAF consists of fragments of gelsolin, an actin-modulating protein. The gelsolin mutation G654A has been found in both Finnish and Japanese patients. To study the origin of the gelsolin mutation in these patients we performed haplotype analysis in 10 Finnish and 2 Japanese FAF families. Poymorphic DNA markers GSN, D9S103, AFMa061xd9, and AFMa139xb9 revealed a uniform disease haplotype in all the disease-associated chromosomes of the Finnish FAF families, which was different from the one observed in the Japanese families. The present results and the previously detected gelsolin mutation G654T in Czech and Danish FAF patients suggest that nucleotide 654 may represent a mutation hot spot in the gelsolin gene. The DNA markers studied here will be useful in future genealogical analyses of FAF.

Autonomic nervous system and cardiac involvement in familial amyloidosis, Finnish type (FAF)

Familial amyloidosis, Finnish type (FAF), is a gelsolin-related inherited systemic amyloidosis. We report autonomic nervous system and cardiac findings in a study of 30 FAF patients (18 females, 12 males aged 27-74 years; mean 53.9 years). Cardiovascular reflex tests showed a significant decrease in heart rate variation in FAF patients compared with healthy controls. Orthostatic hypotension was found in 9 of 28 FAF patients, but only in 3 of 69 controls. Signs of amyloid cardiopathy were rare at clinical examination and in radio-, echocardio- and electrocardiographic examinations. Histological and immunohistochemical studies revealed amyloid deposition and immunoreactivity against the gelsolin-related FAF amyloid subunit in autonomic nervous system structures and in cardiac tissue in 3 autopsied FAF patients. The results show that minor autonomic nervous system dysfunction can be found in FAF, while clinically significant amyloid cardiopathy or autonomic neuropathy is not characteristic of this type of amyloidosis.

Idiopathic AA amyloidosis manifested by autonomic neuropathy, vestibulocochleopathy, and lattice corneal dystrophy

A 69-year-old Japanese woman with non-familial amyloidosis had polyneuropathy and profound autonomic neuropathy, and kappa chain monoclonal gammopathy. Immunohistopathological examination showed protein AA and protein AP in the amyloid deposits. She showed involvement of the vestibulocochlear nerve and lattice dystrophy of the cornea. Vestibulocochleopathy and corneal lattice dystrophy have been reported in familial amyloid polyneuropathy type IV, Finnish type, but never in non-familial amyloidosis.

Neuropathy in familial amyloidosis , Finnish type (FAF): electrophysiological studies

We report, for the first time, electrophysiological findings in the Finnish type of familial amyloidosis (FAF), a gelsolin-related form of systemic amyloidosis. Electromyography, nerve conduction studies, and blink reflex examinations were performed in 30 patients (age range 27-74 years). Cranial nerve involvement was detected in all, and peripheral nerve involvement in the majority of patients. Carpal tunnel syndrome was a characteristic feature of FAF, previously unrecognized. Myokymia-type short spontaneous bursts in frontal muscles were found in 3 younger patients. In addition to signs of axonal degeneration we found slow nerve conduction, prolonged distal motor latencies, and conduction blocks suggestive of demyelination. Most nerve conduction velocities correlated remarkably with age. We conclude that FAF is characterized not only by distinct clinical and molecular biological features but also by electrophysiological findings, which enable differentiation from other hereditary amyloidoses.