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Transthyretin (TTR) is an amyloidogenic protein associated with TTR amyloidosis (ATTR). Dissociation of TTR tetramers into TTR monomers causes TTR misfolding, resulting in amyloid fibril formation and triggering the onset of ATTR. Low-molecular-weight tetrameric TTR stabilizers are potential therapeutic agents to delay ATTR progression. However, the currently available drugs are expensive and cannot be used for prophylaxis. Therefore, in this study, we aimed to identify a prophylactic supplement that suppresses TTR amyloid formation. We investigated whether arginine, an amyloidogenic protein aggregation inhibitor, stabilizes tetrameric TTR, thereby preventing amyloid fibril formation. Immunoblotting showed that arginine mixed with wild-type TTR (TTRwt), amyloidogenic TTR Val30Met (ATTR V30M), and human serum samples reduced the amount of monomeric TTR but increased the tetramer/monomer ratio of TTR compared to those in the samples without arginine. Additionally, oral administration of arginine (5000 mg for 5 days) to healthy volunteers effectively increased the tetramer/monomer ratio of TTR in the serum. Thioflavin T test, a quantitative analysis method for amyloid fibril formation, showed that amyloid fibril formation was significantly suppressed with arginine compared to that without arginine. As arginine is a common supplement and non-toxic amino acid, it can be used as a promising prophylactic supplement to suppress amyloid fibril formation in ATTR., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Hiroaki Matsushita reports financial support was provided by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research. Yukio Ando reports financial support was provided by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Misfolding and aggregation of transthyretin (TTR) is associated with numerous ATTR amyloidosis. TTR aggregates extracted from ATTR patients consist of not only full-length TTR, but also N-terminally truncated TTR fragments that can be produced by proteolytic cleavage, suggesting the presence of multiple misfolding pathways. Here, we report mechanistic studies of an early stage of TTR aggregation to probe the oligomerization process for the full-length as well as N-terminally truncated TTR. Our kinetic analyses using size exclusion chromatography revealed that amyloidogenic monomers dissociated from wild-type (WT) as well as pathogenic variants (V30M and L55P) form misfolded dimers, which self-assemble into oligomers, precursors of fibril formation. Dimeric interfaces in the full-length misfolded oligomers were investigated by examining the effect of single-point mutations on the two β-strands (F and H). The single-point mutations on the two β-strands (E92P on strand F and T119W on strand H) inhibited the dimerization of misfolded monomers, while the TTR variants can still form native dimers through the same F and H strands. These results suggest that the two strands are involved in intermolecular associations for both native and misfolded dimers, but detailed intermolecular interactions are different in the two forms of dimers. In the presence of a proteolytic enzyme, TTR aggregation is greatly accelerated. The two mutations on the two β-strands, however, inhibited TTR aggregation even in the presence of a proteolytic enzyme, trypsin. These results suggest that the two β-strands (F and H) play a critical role in aggregation of the N-terminally truncated TTR as well., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hereditary transthyretin amyloidosis with polyneuropathy (ATTR-PN) results from specific TTR gene mutations. In this study, we generated two induced pluripotent stem cell (iPSC) lines derived from ATTR-PN patients with heterozygous TTR gene mutations (Ala97Ser and Phe64Leu). These iPSC lines exhibited normal morphology, karyotype, high pluripotency marker expression, and differentiation into cells representing all germ layers. The generation of these iPSC lines serve as a valuable tool for investigating the mechanisms of ATTR-PN across various cell types and facilitating patient-specific in vitro amyloidosis modeling., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Joseph C. Wu reports a relationship with Greenstone Biosciences that includes: co-founder & scientific advisory board member. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Transthyretin amyloidosis is a severe pathology characterized by the progressive accumulation of transthyretin (TTR) in various organs and tissues. This highly conserved through vertebrate evolution protein transports thyroid hormone thyroxine. In our bodies, TTR can interact with a large number of molecules, including ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) that are broadly used as food supplies. In this study, we investigated the effect of ω-3 and ω-6 PUFAs, as well as their fully saturated analog, on TTR aggregation. Our results showed that both ω-3 and ω-6 PUFAs strongly decreased the rate of TTR aggregation. We also found that in the presence of PUFAs, TTR formed morphologically different fibrils compared to the lipid-free environment. Nano-Infrared imaging revealed that these fibrils had drastically different secondary structures compared to the secondary structure of TTR aggregates formed in the PUFAs-free environment. Furthermore, TTR fibrils formed in the presence of ω-3 and ω-6 PUFAs exerted significantly lower cell toxicity compared to the fibrils formed in the absence of fatty acids., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dmitry Kurouski reports was provided by Texas A&M University., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Amyloidosis is a rare protein misfolding disease caused by the accumulation of amyloid fibrils in various tissues and organs. There are different subtypes of amyloidosis, with light chain (AL) amyloidosis being the most common. Amyloidosis is notoriously difficult to diagnose because it is clinically heterogeneous, no single test is diagnostic for the disease, and diagnosis typically involves multiple specialists. Here, we propose an integrated, multidisciplinary algorithm for efficiently diagnosing amyloidosis. Drawing on research from several medical disciplines, we have combined clinical decisions and best practices into a comprehensive algorithm to facilitate the early detection of amyloidosis. Currently, many patients are diagnosed more than 6 months after symptom onset, yet early diagnosis is the major predictor of survival. Our algorithm aims to shorten the time to diagnosis with efficient sequencing of tests and minimizing uninformative investigations. We also recommend typing and staging of confirmed amyloidosis to guide treatment. By reducing time to diagnosis, our algorithm could lead to earlier and more targeted treatment, ultimately improving prognosis and survival., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

The highly sulfated domains of heparan sulfate (HS), alias HS S-domains, are made up of repeated trisulfated disaccharide units [iduronic acid (2S)-glucosamine (NS, 6S)] and are selectively remodeled by extracellular endoglucosamine 6-sulfatases (Sulfs). Although HS S-domains are critical for signal transduction of several growth factors, their roles in amyloidoses are not yet fully understood. Herein, we found HS S-domains in the kidney of a patient with transthyretin amyloidosis. In in vitro assays with cells stably expressing human Sulfs, heparin, a structural analog of HS S-domains, promoted aggregation of transthyretin in an HS S-domain-dependent manner. Interactions of cells with transthyretin fibrils and cytotoxicity of these fibrils also depended on HS S-domains at the cell surface. Furthermore, glypican-5, encoded by the susceptibility gene for nephrotic syndrome GPC5, was found to be accumulated in the transthyretin amyloidosis kidney. Our study, thus, provides a novel insight into the pathologic roles of HS S-domains in amyloidoses, and we propose that enzymatic remodeling of HS chains by Sulfs may offer an effective approach to inhibiting formation and cytotoxicity of amyloid fibrils., (Copyright © 2019 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Reports of acquired ATTRm in domino liver transplant (DLT) recipients are infrequent and the approach to management is unknown. We describe two patients, an inherited ATTRm patient who underwent liver transplant and his liver recipient who developed acquired ATTRm 8years following transplantation. The clinical manifestations of amyloidosis were similar between patients and consisted of peripheral neuropathy, diarrhea and weight loss. Following liver transplantation, the DLT donor went into remission for 4years, but eventually progressed and died. The DLT recipient was re-transplanted with a healthy liver, but amyloidosis progressed after 5years, with symptoms resembling the progression of the ATTRm liver donor. Proteomic analysis was utilized to type the amyloid deposits present in the DLT recipient fat aspirate specimen obtained prior to the second transplantation and stomach biopsy obtained at disease progression. The fat amyloid deposits contained almost equal amounts of mutant TTR and wild-type TTR peptides, but the stomach biopsy showed only wild-type TTR. There is a high concordance of disease phenotype between inherited and acquired ATTRm, which may help in early recognition of acquired ATTRm in DLT recipients. Liver re-transplantation for acquired ATTRm may not interrupt the cycle of amyloid deposition since normal hepatically produced TTR may co-deposit with trace amount of pre-existing TTRm amyloid., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Overwhelming data suggest that oncogenic and neurodegenerative pathways share several altered cellular responses to insults such as oxidative stress, extracellular matrix remodeling, inflammation, or cell dyscommunication. Protocadherin-10 (Pcdh10) is an adhesion molecule found to protect against tumorigenesis and essential for axonal elongation and actin dynamics during development. Here, by using genome microarrays we identified for the first time Pcdh10 up-regulation in tissues from transgenic mouse models, cultured Schwann cells, and human samples from a familial form of peripheral neuropathy (familial amyloidotic polyneuropathy). Familial amyloidotic polyneuropathy is characterized by poor functional recovery and impaired nerve regenerative response after misfolding and deposition in the peripheral nervous system of mutant transthyretin. Not only increased transcriptional and translational Pcdh10 levels occurred in axons and Schwann cells of nerves with deposited transthyretin aggregates but the pattern also extended to associated cues of axon guidance like neuropilin-1 and F-actin. These findings suggest that Pcdh10 may influence subcellular actin cytoskeletal organization and axon-axon interactions in the course of familial amyloidotic polyneuropathy. Moreover, when preventing nonfibrillar transthyretin deposition with anakinra or transthyretin siRNA, Pcdh10 protein levels were reduced, highlighting its potential as a novel disease biomarker. Whether Pcdh10 overexpression in familial amyloidotic polyneuropathy represents a protective or deleterious response, enhancing survival or promoting cell death will need further investigation., (Copyright © 2016 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this report is to present the diagnosis of familial amyloid polyneuropathy (FAP) based on vitreous biopsy and to demonstrate immunohistochemical images of transthyretin amyloid protein from vitreous samples., Design: Retrospective case series., Methods: Retrospective review of clinical charts of patients with FAP who underwent vitrectomy for vitreous opacities and had immunostaining performed on the vitreous specimens., Participants: Three patients were selected for the study: 2 patients had already been diagnosed with FAP, and in 1 of the patients the vitreous sample served to establish the diagnosis of FAP., Results: Pathology examination of the vitreous specimens confirmed the presence of amyloid with positive Congo red staining, and transthyretin was identified with immunolabeling techniques. In this report, we present immunohistochemical staining images of transthyretin deposits in the vitreous tissues., Conclusions: Transthyretin amyloidosis is usually confirmed with positive Congo red staining for amyloid identified by biopsy of peripheral nerves, salivary glands, or abdominal fat. Ocular manifestation of FAP typically appears years after the onset of the disease, and therefore eye tissue specimens usually are not subject to diagnostic biopsies or transthyretin identification. However, in patients with negative systemic tissue biopsies or early ocular involvement, transthyretin identification from samples obtained during vitrectomy may be useful in establishing the diagnosis, and we present the first immunohistochemical images of transthyretin amyloid of vitreous origin, which confirm the elevated deposition of the altered protein in ocular tissues in FAP., (Copyright © 2015 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.)

Aims: Transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP) is characterized by the systemic accumulation of amyloid fibrils caused by amyloidogenic. Our previous studies demonstrated that albumin played a role in the inhibition of TTR amyloid-formation. The aim of this study was to evaluate the effect of albumin on TTR disposition and tissue deposition in vivo., Main Methods: For pharmacokinetic studies, recombinant wild-type TTR (rTTR) and recombinant amyloidogenic TTR Val30Met (rATTR V30M) were labeled with iodine and administered to Sprague-Dawley rats and analbuminemia rats (NAR: Nagase Analbuminemia Rats). The deposition of ATTR V30M was also analyzed by immunohistochemistry in the transgenic (Tg) rats possessing a human ATTR V30M gene (ATTR V30M Tg rats) and NAR possessing a human ATTR V30M gene (ATTR V30M Tg NAR)., Key Findings: The presence of albumin had no effect on the tissue distribution of either rTTR or rATTR V30M. However, more ATTR V30M was deposited in the hearts, stomachs and small intestines of ATTR V30M Tg NAR rats, compared to ATTR V30M Tg rats., Significance: Although the disposition of TTR and ATTR V30M was unaffected by the presence of albumin, the deposition of ATTR V30M in some organs was apparently increased in the absence of albumin compared to the presence of albumin. These results show that albumin would contribute to suppressing the tissue deposition of TTR in pathogenesis of FAP, but does not affect the disposition of TTR., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: Age and sex differences are closely related to the onset of senile systemic amyloidosis (SSA) caused by wild-type (WT) transthyretin (TTR). However, the effects of these differences on the amyloid formation mechanism in familial amyloid polyneuropathy (FAP) caused by variant TTR, have remained unclear. To elucidate age and sex differences in FAP, we investigated biochemical characteristics of amyloid deposits in different tissue sites of FAP by proteomic analysis., Methods: We used shotgun liquid chromatography/tandem mass spectrometry to analyze the proportions of variant and WT TTR in amyloid deposits in different tissues, such as cardiac, kidney, peripheral nerves, and gastrointestinal tissues, from 23 autopsied FAP cases., Results and Conclusions: The analysis revealed a highly significant correlation between the proportion of WT TTR and age at autopsy in cardiac tissues, whereas the analysis indicated no correlation in kidney, peripheral nerves, and gastrointestinal tissues. In addition, we demonstrated age-related significantly increased WT TTR deposits, but not variant TTR deposits, in cardiac tissues of male patients. Taken together, these data suggest that both age and sex differences affect cardiac amyloid formation, mainly derived from WT TTR, in FAP., (© 2013.)

Objective: The occurrence of ocular complications associated with transthyretin-related familial amyloidotic polyneuropathy increases with time, even after liver transplantation, which leads to a halt in the progression of systemic neurologic complications. This study investigated a new strategy to prevent ocular involvements., Design: Two interventional case reports., Participants: Two patients with familial amyloidotic polyneuropathy who had progressive ocular manifestations., Methods: We used panretinal laser photocoagulation, which damages the retinal pigment epithelium, the main location for synthesis of amyloidogenic transthyretin in ocular tissues, to treat 1 eye of each patient. After laser photocoagulation, we performed general ophthalmic examinations every 3 months for 3 years., Main Outcome Measures: Fundus photography, visual acuity, and intraocular pressure., Results: Panretinal laser photocoagulation clearly prevented progression of amyloid deposition in the vitreous and on the retinal surface in both cases during 3 years of follow-up. No serious complications occurred., Conclusions: Panretinal laser photocoagulation is a safe and well-known procedure that offers a new treatment option to mitigate ocular manifestations in patients with transthyretin-related familial amyloidotic polyneuropathy., (Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Transthyretin (TTR) is a human disease-associated amyloidogenic protein that has been implicated in senile systemic amyloidosis (SSA) and familial amyloidotic polyneuropathy (FAP). FAP typically results in severe and early-onset disease, and the only therapy established so far is liver transplantation; thus, developing new strategies for treating FAP is of paramount interest. Clusterin has recently been proposed to play a role as an extracellular molecular chaperone, affecting the fibril formation of amyloidogenic proteins. The ability of clusterin to influence amyloid fibril formation prompted us to investigate whether clusterin is capable of inhibiting TTR amyloidosis. Here, we report that clusterin strongly interacts with wild-type TTR and TTR variants V30M and L55P under acidic conditions, and blocks the amyloid fibril formation of TTR variants. In particular, the amyloid fibril formation of V30M TTR in the presence of clusterin is reduced to level similar to wild-type TTR. We also demonstrated that clusterin is an effective inhibitor of L55P TTR amyloidosis, the most aggressive form of TTR diseases. The mechanism by which clusterin inhibits TTR amyloidosis appears to be through stabilization of TTR tetrameric structure. These findings suggest the possibility of using clusterin as a therapeutic agent for TTR amyloidosis.

Background: Familial amyloid polyneuropathy (FAP) is distributed worldwide with several endemic foci including two major foci in Japan., Objective: To elucidate a nationwide epidemiology of FAP in Japan., Design, Setting, and Patients: (i) We analyzed the data of FAP patients registered by the Ministry of Health, Labour, and Welfare, Japan, during 2003-2005. (ii) As Ishikawa prefecture was found to be a novel endemic focus, we examined 27 FAP patients in Ishikawa to characterize their clinical and genetic features in comparison with other endemic foci., Results: (i) The prevalence of familial amyloidosis in Japan was estimated to be 0.87-1.1 per 1,000,000 persons. Nagano prefecture had the highest prevalence (11-15.5), followed by Kumamoto (10.1-10.3), and then Ishikawa (3.5-4.2). (ii) All the FAP patients in Ishikawa had transthyretin (TTR) type FAP; all the families had a TTR Val30Met mutation except one family with a Leu58Arg mutation. FAP with Val30Met mutation in Ishikawa was characterized by late onset, high penetrance, and moderate autonomic dysfunction., Conclusions: Ishikawa prefecture is the third endemic focus of FAP in Japan. FAP with TTR Val30Met mutation in Japan can be classified to (i) early-onset and endemic (Nagano and Kumamoto), (ii) late-onset and endemic (Ishikawa), and (iii) late-onset and non-endemic types.

Background: Transthyretin (TTR) variants of familial amyloid neuropathies (FAP) form a heterogenous group of autosomal dominantly inherited diseases. TTR gene analysis in several nationalities (Japanese, Portuguese, French, and British) has shown many distinguishing characteristics in the genotype-phenotype correlation. In Chinese, there are only a few reports of private TTR gene mutations belonging to single kindred., Materials and Methods: We collected five patients with autosomal dominant inheritant sensorimotor polyneuropathy and tissue-proved amyloid deposition. The diagnosis of FAP was established on the mutation of the TTR gene detected by direct sequencing. Haplotype analysis was conducted in four of these patients., Results and Conclusions: These five FAP patients shared an identical missense mutation, Ala97Ser, in the TTR gene. This mutation presented with a constellation of late-onset polyneuropathy, preceding carpal tunnel syndrome, and outstanding autonomic dysfunction. Heart was the most frequently involved vital organ. Haplotype analysis hinted independent origins although the numbers were limited. Our study is the first case series gathering from the Chinese-Taiwanese population. We proposed a possible hot-spot mutation of the TTR gene, Ala97Ser, in this ethnic.

Familial amyloid polyneuropathy (FAP: type IV), known as familial amyloidosis of the Finnish type (FAF), is very rare and reported only in a few countries. The gelsolin mutation G654A is most frequent causative gene in FAF family. The clinical phenotype of FAF possesses several neurological characteristics with multiple cranial nerve signs, in addition to a peculiar exanthema of "lichen amyloidosus" and pendulous skin "cutis laxa", and the carpal tunnel syndrome. We report a new Japanese FAF family presenting bilateral atrophies and fasciculations of the facial muscles and tongue. The patients in our family presented with skin changes as "lichen amyloidosus" and "cutis laxa". In this FAF family, lichen amyloidosus appeared under sunlight and high temperatures in the summer season every year. Two patients in our family presented with common clinical features of FAF, except for the above laboratory results. Including previous cases and our family, this clinical phenotype is similar to the gelsolin gene mutation (G654A) in FAF family members.

Amyloidogenic transthyretin (ATTR) is the pathogenic protein of familial amyloidotic polyneuropathy (FAP). To establish a tool for analyses of ATTR metabolisms including after liver transplantations, we developed a transgenic rat model expressing human ATTR V30M and confirmed expressions of human ATTR V30M in various tissues. Mass spectrometry for purified TTR revealed that rat intrinsic TTR and human ATTR V30M formed tetramers. Congo red staining and immunohistochemistry revealed that nonfibrillar deposits of human ATTR V30M, but not amyloid deposits, were detected in the gastrointestinal tracts of the transgenic rats. At 24h after liver transplantation, serum human ATTR V30M levels in transgenic rats that received livers from normal rats became lower than detectable levels. These results thus suggest that this transgenic rat may be a useful animal model which analyzes the metabolism of human ATTR V30M including liver transplantation studies.

Transthyretin (TTR) tetramer dissociation, misfolding and misassembly are required for the process of amyloid fibril formation associated with familial amyloid polyneuropathy (FAP). Preferential stabilization of the native TTR tetramer over the dissociative transition state by small molecule binding raises the kinetic barrier of tetramer dissociation, preventing amyloidogenesis. Two NSAIDs, diflunisal and flufenamic acid, and trivalent chromium have this ability. Here, we investigated the feasibility of using these molecules for the treatment of FAP utilizing serum samples from 37 FAP patients with 10 different mutations. We demonstrated that the TTR heterotetramer structures in FAP patients serum are significantly less stable than that in normal subjects, indicating the instability of the variant TTR structure is a fundamental cause of TTR amyloidosis. We also demonstrated that therapeutic serum concentrations of diflunisal (100-200 microM) stabilized serum variant TTR tetramer better than those of flufenamic acid (35-70 microM). Trivalent chromium at levels obtained by oral supplementation did not stabilize TTR in a statistically significant fashion. Importantly, diflunisal increased serum TTR stability in FAP patients beyond the level of normal controls.

Objectives: To assess brain metabolic abnormalities in patients with familial amyloid polyneuropathy (FAP) due to the transthyretin (TTR) gene mutations., Background: The TTR-FAP has variable phenotypic expression, which includes abnormalities of the central nervous system (CNS). Several conventional MRI studies have shown brain abnormalities, probably secondary to amyloid accumulation in leptomeningeal and subarachnoid vessels. However, TTR-related amyloid deposits do not seem to significantly affect the brain parenchyma and a prominent CNS impairment is considered to be rare in TTR amyloidosis., Methods: We performed proton MR spectroscopic imaging (1H-MRSI) in the central brain of four unrelated TTR-FAP patients with either minimal or no signs of neurological involvement and eight age- and sex-matched normal controls (NC). Metabolic changes were assessed in the entire volume of interest (VOI) and in the frontal, periventricular and posterior white matter (WM)., Results: Conventional MRI was normal in 2 patients and showed minimal WM lesions in the remaining 2 patients. 1H-MRSI showed N-acetylaspartate to creatine ratio (NAA/Cr) decreases in the central brain VOI in all TTR-FAP patients (p < 0.005). These NAA/Cr decreases were homogeneous in all WM regions (p < 0.05 for all)., Conclusions: 1H-MRSI findings suggest that diffuse metabolic changes, probably related to axonal damage, are present in brains of TTR-FAP patients even when they have no or minimal clinical and MRI signs of CNS involvement. The mechanism leading to sub-clinical metabolic brain changes needs to be identified.

Purpose: To report the clinicopathological findings for a unique ocular amyloid angiopathy in patients with familial amyloidotic polyneuropathy (FAP) caused by amyloidogenic transthyretin Y114C., Design: Three case reports., Methods: Retrospective review of clinicopathological findings, course, and treatment of the 3 patients., Main Outcome Measures: Visual acuity, intraocular pressure, fundus photography, fluorescein angiography (FA), indocyanine green angiography, and histopathological analysis., Results: In the 32-year-old patient, in the early stage of FAP, indocyanine green angiography demonstrated multiple sites of hyperfluorescence, with staining along major choroidal veins. Retinal vessels appeared normal clinically and on FA. In the 48-year-old patient, who had late-stage FAP, examination of the fundus revealed pinpoint white amyloid opacities over the retinal surface, sheathing of retinal vessels, and scattered retinal hemorrhages. Fluorescein angiography showed vascular closure, focal staining, and microaneurysms. Indocyanine green angiography revealed multiple sites of hyperfluorescence, with staining along retinal and choroidal vessels. Examination during follow-up revealed that these vascular changes continued to progress. Histopathological study of an eye obtained at autopsy from the 49-year-old patient revealed marked intravascular and extravascular amyloid deposition., Conclusions: Severe and progressive amyloid angiopathy causing visual disturbance was seen in patients with FAP caused by amyloidogenic transthyretin Y114C.

Familial amyloidotic polyneuropathy (FAP) is a hereditary systemic amyloidosis caused by dominantly acting missense mutations in the gene encoding transthyretin (TTR). The most common mutant TTR is of the Val30Met type, which results from a point mutation. Because the major constituent of amyloid fibrils is mutant TTR, agents that selectively suppress mutant TTR expression could be powerful therapeutic tools. This study has been performed to evaluate the use of small interfering RNAs (siRNAs) for the selective silencing of mutant Val30Met TTR in cell culture systems. We have identified an siRNA that specifically inhibits mutant, but not wild-type, TTR expression even in cells expressing both alleles. Thus, this siRNA-based approach may have potential for the gene therapy of FAP.

Mutation of aspartic acid 187 to asparagine (D187N) or tyrosine (D187Y) in domain 2 of the actin-modulating protein gelsolin causes the neurodegenerative disease familial amyloidosis of Finnish type (FAF). These mutations render plasma gelsolin susceptible to aberrant proteolysis by furin in the trans-Golgi network, the initial proteolytic event in the formation of 71 and 53 residue fragments that assemble into amyloid fibrils. Ca(2+) binding stabilizes wild-type domain 2 gelsolin against denaturation and proteolysis, but the FAF variants are unable to bind and be stabilized by Ca(2+). Though the chain of events initiating FAF has been elucidated recently, uncertainty remains about the mechanistic details that allow the FAF variants to be processed. To test the hypothesis that impaired Ca(2+) binding in the D187 variants, but not other factors specific to residue 187, increases susceptibility to aberrant proteolysis and subsequent amyloidogenesis, we designed the gelsolin variant E209Q to remove a different Ca(2+) ligand from the same Ca(2+) site that is affected in the FAF variants. Here, we show that E209Q domain 2 does not bind Ca(2+) and is not stabilized against denaturation or furin proteolysis, analogous to the behavior exhibited by the FAF variants. Transfection of full-length E209Q into COS cells results in secretion of both the full-length and furin-processed fragments, as observed with D187N and D187Y. Mutation of the furin consensus sequence in D187N and E209Q gelsolin prevents cleavage during secretion, indicating that inhibition of proprotein convertases (furin) represents a viable therapeutic approach for the treatment of FAF. Mutations that diminish domain 2 Ca(2+) binding allow furin access to an otherwise protected cleavage site, initiating the proteolytic cascade that leads to gelsolin amyloidogenesis and FAF.

We examined the affinity of transthyretin (TTR) for lipoproteins and the effect of lipoproteins on TTR-related amyloidogenesis using serum samples from healthy volunteers and patients with familial amyloidotic polyneuropathy (FAP) ATTRVal30Met. In both volunteers and patients, TTR levels were highest in the VLDL fraction containing chylomicrons (VLDL/CM) and next highest in the HDL fraction. Levels were lowest in the LDL fraction. Mass spectrometric analyses of TTR spectra revealed significant TTR association with VLDL/CM and the levels of variant TTR were decreased in the FAP patients. Examination of the affinity of wild-type and variant TTRs for lipoprotein via a quartz crystal microbalance (QCM) revealed the highest affinity of both proteins for VLDL/CM. In in vitro amyloid formation test measured with thioflavin T and electron microscopy, in the presence of VLDL/CM, amyloid formation of TTR was enhanced more than in the presence LDL or in the absence of lipoprotein species. These results suggest that TTR should be highly associated especially with VLDL/CM and amyloidogenicity of TTR should be enhanced around the adipocytes.

A method is presented for direct spatial analysis of amyloid beta peptides in biological tissue sections. The technique takes advantage of the very high sensitivity of matrix-assisted laser desorption/ionization mass spectrometry and is implemented on a commercial instrument with modifications to only a few components and the software. With this setup, hundreds of molecular images can be generated simultaneously and within just a few minutes. The current features are an instrumental resolution of 50 microm and a sensitivity down to the attomol range. This new technology is applied to the study of amyloid beta peptide distribution in brain sections from mice, showing features reminiscent of Alzheimer's disease., (Copyright 2002 Elsevier Science (USA))

A single mutation in the wild-type transthyretin (WT TTR) such as V30M causes a familial amyloidotic polyneuropathy disease. Comparison of the three-dimensional crystal structures of WT and V30M does not tell much about the reason. High-pressure NMR revealed that at neutral pH both WT and V30M exist as equilibrium between the native tetramer and the dissociated/unfolded monomer. The native tetramer is highly stable in WT (deltaG(0)=104 kJ/mol at 37 degrees C, pH 7.1), but the stability is significantly reduced in V30M (deltadeltaG(0)=-18 kJ/mol), increasing the fraction of the unfolded monomer by a 1000-fold. Significant reduction of thermodynamic stability of WT TTR by mutation could be a crucial factor for familial amyloidotic polyneuropathy.

In diseases like Alzheimer's disease and familial amyloidotic polyneuropathy (FAP) amyloid deposits co-localize with areas of neurodegeneration. FAP is associated with mutations of the plasma protein transthyretin (TTR). We can here show an apoptotic effect of amyloidogenic mutants of TTR on a human neuroblastoma cell line. Toxicity could be blocked by catalase indicating a free oxygen radical dependent mechanism. The toxic effect was dependent on the state of aggregation and unexpectedly mature fibrils from FAP-patients who failed to exert an apoptotic response. Morphological studies revealed a correlation between toxicity and the presence of immature amyloid. Thus, we can show that toxicity is associated with early stages of fibril formation and propose that mature full-length fibrils represent an inert end stage, which might serve as a rescue mechanism., ((c) 2002 Elsevier Science (USA).)

Extracellular accumulation of transthyretin (TTR) variants in the form of fibrillar amyloid deposits is the pathological hallmark of familial amyloidotic polyneuropathy (FAP). The TTR Leu55Pro variant occurs in the most aggressive forms of this disease. Inhibition of TTR wild-type (WT) and particularly TTR Leu55Pro fibril formation is of interest as a potential therapeutic strategy and requires a thorough understanding of the fibril assembly mechanism. To this end, we report on the in vitro assembly properties as observed by transmission electron microscopy (TEM), atomic force microscopy (AFM) and quantitative scanning transmission electron microscopy (STEM) for both TTR WT fibrils produced by acidification, and TTR Leu55Pro fibrils assembled at physiological pH. The morphological features and dimensions of TTR WT and TTR Leu55Pro fibrils were similar, with up to 300 nm long, 8 nm wide fibrils being the most prominent species in both cases. Other species were evident; 4-5 nm wide fibrils, 9-10 nm wide fibrils and oligomers of various sizes. STEM mass-per-length (MPL) measurements revealed discrete fibril types with masses of 9.5 and 14.0(+/-1.4) KDa/nm for TTR WT fibrils and 13.7, 18.5 and 23.2(+/-1.5) kDa/nm for TTR Leu55Pro fibrils. These MPL values are consistent with a model in which fibrillar TTR structures are composed of two, three, four or five elementary protofilaments, with each protofilament being a vertical stack of structurally modified TTR monomers assembled with the 2.9 nm axial monomer-monomer spacing indicated by X-ray fibre diffraction data. Ex vivo TTR amyloid fibrils were examined. From their morphological appearance compared to these, the in vitro assembled TTR WT and Leu55Pro fibrils examined may represent immature fibrillar species. The in vitro system operating at physiological pH for TTR Leu55Pro and the model presented for the molecular arrangement of TTR monomers within fibrils may, therefore, describe early fibril assembly events in vivo., (Copyright 2002 Elsevier Science Ltd.)

Familial amyloidotic polyneuropathy (FAP) is a neurodegenerative disorder characterized by extracellular deposition of transthyretin (TTR) amyloid fibrils, particularly in the peripheral nervous system. No systematic immunohistochemical data exists relating TTR deposition with FAP progression. We assessed nerves from FAP patients in different stages of disease progression (FAP 0 to FAP 3) for TTR deposition by immunohistochemistry, and for the presence of amyloid fibrils by Congo Red staining. The nature of the deposited material was further studied by electron microscopy. We observed that early in FAP (FAP 0), TTR is already deposited in an aggregated nonfibrillar form, negative by Congo Red staining. This suggested that in vivo, preamyloidogenic forms of TTR exist in the nerve, in a stage before fibril formation. Cytotoxicity of nonfibrillar TTR was assessed in nerves of different FAP stages by immunohistochemistry for macrophage colony-stimulating factor. FAP 0 patients already presented increased axonal expression of macrophage colony-stimulating factor that was maintained in all other stages, in sites related to TTR deposition. Toxicity of synthetic TTR fibrils formed in vitro at physiological pH was studied on a Schwannoma cell line by caspase-3 activation assays and showed that early aggregates but not mature fibrils are toxic to cells. Taken together, these results show that nonfibrillar cytotoxic deposits occur in early stages of FAP.