Two novel variants of transthyretin identified in Japanese cases with familial amyloidotic polyneuropathy: transthyretin (Glu42 to Gly) and transthyretin (Ser50 to Arg)

Clinical Profile and Prognosis of Hereditary Transthyretin Amyloid Cardiomyopathy: A Single-Center Study in South China

Background

Hereditary transthyretin amyloid cardiomyopathy (ATTR-CM) is a genotypically heterogeneous disorder with a poor prognosis. There is limited literature describing the variants responsible for ATTRv in areas outside the United State, the United Kingdom and Europe. This study was performed to describe the clinical characteristics and genotypic profiles of this disease in South China.

Methods

This was a single-center retrospective study that evaluated 29 patients with a confirmed diagnosis of hereditary transthyretin amyloid cardiomyopathy enrolled from January 2016 to November 2021.

Results

93.1% patients were male and the median age of symptom onset was 53 (46, 62.5) years old. The initial manifestations of ATTR-CM were cardiovascular symptoms (55.2%), neuropathy (41.4%) and vitreous opacity (3.4%). Phenotypes at diagnosis were mixed (82.8%), predominant cardiac (6.9%), neurological (6.9%) and ophthalmic (3.4%). Poor R-wave progression (41%), pseudo-infarct (31%) and low-voltage (31%) patterns were common findings on electrocardiogram. Unexplained increased wall thickness was observed in all 29 patients, with mean septal and posterior wall thicknesses of 14.25 ± 6.26 mm and 15.34 ± 2.84 mm, respectively. Diastolic dysfunction was also seen in all 29 patients, and 17 (58%) had a restrictive fill pattern at diagnosis. Nine different missense mutations of the TTR gene were found in 29 patients from 23 families, with c.349G>T (p.Ala117Ser) the most common mutation. The median survival time after diagnosis was 47.6 (95% CI 37.9-57.4) months, with 1, 3 and 5-year survival rates of 91.2%, 74% and 38% respectively. Patients with advanced heart failure (National Amyloidosis Staging stage II/III) had worse survival than stage I [Breslow (Generalized Wilcoxon), χ2 = 4.693, P = 0.03)].

Conclusions

ATTR amyloidosis genotypes and phenotypes are highly heterogeneous. Advanced heart failure predicts a poor prognosis. Understanding the different clinical profiles of ATTR cardiac amyloidosis with different genotype is important to its early recognition.

mTOR pathway repressing expression of FoxO3 is a potential mechanism involved in neonatal white matter dysplasia

Neonatal white matter dysplasia (NWMD) is characterized by developmental abnormity of CNS white matter, including abnormal myelination. Besides environmental factors such as suffocation at birth, genetic factors are also main causes. Signaling pathway is an important part of gene function and several signaling pathways play important roles in myelination. Here, we performed genetic analysis on a corhort of 138 patients with NWMD and found that 20% (5/25) cause genes which refered to 28.57% (8/28) patients enriched in mTOR signaling pathway. Depletion of mTOR reduced genesis and proliferation of oligodendrocyte progenitor cells (OPC) during embryonic stage and reduced myelination in corpus callosum besides cerebellum and spinal cord during early postnatal stages which is related to not only differentiation but also proliferation of oligodendrocyte (OL). Transcriptomic analyses indicated that depletion of mTOR in OLs upregulated expression of FoxO3, which is a repressor of expression of myelin basic protein (MBP), and downregulating expresion of FoxO3 by siRNA promoted OPCs develop into MBP+ OLs. Thus, our findings suggested that mTOR signaling pathway is NWMD-related pathway and mTOR is important for myelination of the entire CNS during early developmental stages through regulating expression of FoxO3 at least partially.

Caenorhabditis elegans as a model system for target identification and drug screening against neurodegenerative diseases

Over the past decades, Caenorhabditis elegans (C. elegans) has been widely used as a model system because of its small size, transparent body, short generation time and lifespan (~3 days and 3 weeks, respectively), completely sequenced genome and tractability to genetic manipulation. Protein misfolding and aggregation are key pathological features in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Animal models, including C. elegans, have been extensively used to discover and validate new drugs against neurodegenerative diseases. The well-defined and genetically tractable nervous system of C. elegans offers an effective model to explore basic mechanistic pathways of neurodegenerative diseases. Recent progress in high-throughput drug screening also provides a powerful approach for identifying chemical modulators of biological processes. Here, we summarize the latest progress of using C. elegans as a model system for target identification and drug screening in neurodegenerative diseases.

Clinical diagnosis and typing of systemic amyloidosis in subcutaneous fat aspirates by mass spectrometry-based proteomics

Examination of abdominal subcutaneous fat aspirates is a practical, sensitive and specific method for the diagnosis of systemic amyloidosis. Here we describe the development and implementation of a clinical assay using mass spectrometry-based proteomics to type amyloidosis in subcutaneous fat aspirates. First, we validated the assay comparing amyloid-positive (n=43) and -negative (n=26) subcutaneous fat aspirates. The assay classified amyloidosis with 88% sensitivity and 96% specificity. We then implemented the assay as a clinical test, and analyzed 366 amyloid-positive subcutaneous fat aspirates in a 4-year period as part of routine clinical care. The assay had a sensitivity of 90%, and diverse amyloid types, including immunoglobulin light chain (74%), transthyretin (13%), serum amyloid A (%1), gelsolin (1%), and lysozyme (1%), were identified. Using bioinformatics, we identified a universal amyloid proteome signature, which has high sensitivity and specificity for amyloidosis similar to that of Congo red staining. We curated proteome databases which included variant proteins associated with systemic amyloidosis, and identified clonotypic immunoglobulin variable gene usage in immunoglobulin light chain amyloidosis, and the variant peptides in hereditary transthyretin amyloidosis. In conclusion, mass spectrometry-based proteomic analysis of subcutaneous fat aspirates offers a powerful tool for the diagnosis and typing of systemic amyloidosis. The assay reveals the underlying pathogenesis by identifying variable gene usage in immunoglobulin light chains and the variant peptides in hereditary amyloidosis.

Familial amyloidosis with polyneuropathy associated with TTR Ser50Arg mutation

BACKGROUND

The phenotypic heterogeneity of transthyretin amyloidosis (ATTR) familial polyneuropathy may be linked to the type of mutation and to the environmental factors. A gender difference in relation to the severity of the disease has been suspected. More than 100 different pathogenic variants of hereditary transthyretin (TTR) mutations have been reported.

OBJECTIVE

To describe 32 patients with confirmed TTR Ser50Arg mutation from the same geographical origin.

METHODS

Seven families with up to four affected generations underwent genetic testing and prospective clinical and laboratory evaluations.

RESULTS

The mutation was confirmed in seven patients from different families with clinical symptoms compatible with ATTR amyloidosis, and in 25 (62%) of the 40 direct relatives tested. Of the 32 patients with positive test results, 18 (56%) were men. Only 5 (16%) subjects were disease-free at the time of the genetic test (mean age: 20, range: 18-30-year-old). The rest developed symptoms at a young age, between ages 36 and 41. Symptomatic, histologically positive patients were older than carriers and symptomatic patients without a confirmatory biopsy. The later generation displayed symptoms at a younger age. Initial manifestations in the 27 symptomatic patients were neuropathic in 19 (70%), gastrointestinal in 6 (22%) and autonomic in 1 (4%). Significant differences were demonstrated among genders, where men had a considerably worse outcome.

CONCLUSION

ATTR Ser50Arg mutation was associated with an early onset, an unbalanced male to female ratio, a more aggressive course in males and possibly displayed anticipation.

A case of atypical amyloid polyneuropathy with predominant upper-limb involvement with the diagnosis unexpectedly found at lung operation

We present a patient of familial amyloid polyneuropathy (FAP) with predominant upper-limb involvement, the pattern of which resembled a mononeuropathy multiplex pattern. Sural nerve biopsy failed to diagnose the disorder, but lung partial resection performed later for other diagnostic purposes suggested FAP. A rare mutation in the transthyretin gene (S50R) was subsequently confirmed. Diagnostic challenges of FAP with atypical clinical presentations, including difficulties in pathological diagnosis, are discussed with a review of the literature.

Familial amyloid polyneuropathy associated with TTRSer50Arg mutation in two Iberian families presenting a novel single base change in the mutant gene

We present two families, from Spain and Portugal, with familial amyloid polyneuropathy (FAP) associated with the mutation TTRSer50Arg. This mutation was first described in two Japanese patients from independent families and later in a French-Italian patient and a Vietnamese family. The two families presented here, are the first to be diagnosed with this mutation in the Iberian Peninsula. In the patients of both families, FAP was very aggressive as they rapidly developed multiple symptoms with progressive deterioration; we emphasize the presence of severe orthostatic hypotension in the Spanish proband which confined him to a wheelchair. This proband was the first patient with this mutation to have undergone liver transplantation and results were encouraging. The mutation was detected in four patients and one disease-free relative by DNA sequencing of exon 3 and induced mutation restriction analysis. The most outstanding feature was the single base transversion A to C in codon 50 (CGT instead of AGT), whereas in both Japanese patients and the French-Italian patient it was T to G (AGG instead of AGT). To our knowledge only six FAP mutations with more than one single nucleotide mutation for the same codon have been reported to date.

Biochemical characteristics of variant transthyretins causing hereditary leptomeningeal amyloidosis

Transthyretin (TTR) is a tetrameric protein that can dissociate into amyloidogenic monomers and cause TTR-related amyloidosis. A rare phenotype, called hereditary leptomeningeal TTR amyloidosis, in which TTR amyloid deposition occurs mainly in leptomeninges and subarachnoid vessels, has been reported in patients with several different TTR variants. In the present study, we examined TTR variants immunoprecipitated from the serum and cerebrospinal fluid (CSF) of patients with hereditary leptomeningeal TTR amyloidosis using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (IP-Mass method). The leptomeningeal-type TTR variants were not detected in the serum but were found at low levels in the CSF. The undetectable levels of the leptomeningeal-type TTR variants in serum could explain the minute amounts of systemic deposition of these variants. The relatively high level of unstable TTR variants in CSF, probably due to increased secretion from the choroid plexus, is considered to be the pathogenesis of the leptomeningeal-type of TTR amyloidosis.

Transthyretin mutations in hyperthyroxinemia and amyloid diseases

Over 80 different disease-causing mutations in transthyretin (TTR) have been reported. The vast majority are inherited in an autosomal dominant manner and are related to amyloid deposition, affecting predominantly peripheral nerve and/or the heart. A small portion of TTR mutations are apparently non-amyloidogenic. Among these are mutations responsible for hyperthyroxinemia, presenting high affinity for thyroxine (a TTR ligand). Compound heterozygotic individuals for TTR mutants have been described; noteworthy is the clinically protective effect exerted by a non-pathogenic over a pathogenic mutation. Current TTR mutations and their significance are briefly reviewed here.

A new diagnostic procedure to detect unknown transthyretin (TTR) mutations in familial amyloidotic polyneuropathy (FAP)

Two patients with amyloidosis caused by transthyretin (TTR) were investigated by immunohistopathologic, mass spectrometric, and molecular genetic methods. After confirming the immunoreactivity of TTR in the amyloid deposits using anti-TTR polyclonal antibody, a new method: centrifugal concentration and electrospray ionization mass spectrometry (ESI-MS) was employed to detect the variant TTR in the serum. Only 50 microl of the serum and 30 microl of the anti-TTR antibody were needed for the analysis. After incubation with the antibody, the samples were passed through a 1000 kDa cut off centrifugal concentrator to retain the antibody, thereafter, the filtrate was analyzed by ESI-MS. Several forms of normal and variant TTR were detected in the serum samples: unconjugated TTR, cysteine and cysteine-glycine conjugated TTR. In the patients, a variant form of TTR was detected with a 26.0 Da higher molecular weight than that of normal TTR. Single-strand conformation polymorphism (SSCP) and direct sequence analysis confirmed the presence of a one-base substitution situated at the codon 50 from AGT (Ser) to ATT (Ile) in both patients, that corresponded to the increased molecular weight of 26.0. The present diagnostic procedure demonstrates the usefulness of both ESI-MS and SSCP to screen for TTR related amyloidosis rapidly. Moreover, the DNA samples obtained from the band showing abnormal electrophoretic migration pattern in SSCP, facilitate the direct sequence analysis to detect the unknown mutation, and the observed shift in molecular weight of the variant TTR in ESI-MS confirms the base substitution.

Familial amyloid polyneuropathy related to transthyretin mutation Val30 to Leu in a Japanese family

A rare variant transthyretin that has a leucine-for-valine substitution at position 30 was reported in a sporadic case of type 1 familial amyloid polyneuropathy (FAP). We found the same substitution in members of a Japanese family with FAP. Three individuals in this family had a guanine-to-cytosine mutation at the first base of codon 30 in exon 2. This family shows a direct link between a valine-to-leucine substitution at position 30 and type 1 FAP.

A novel variant of transthyretin (Glu42Asp) associated with sporadic late-onset cardiac amyloidosis

A sixty-three year old French man presented with isolated late-onset amyloid cardiomyopathy proven by endomyocardial biopsy. There was no known family history of amyloidosis. Immunohistochemistry of cardiac deposits suggested that amyloi fibrils were derived from transthyretin. DNA sequencing revealed a point mutation in exon 2 of the transthyretin gene responsible for a novel amyloidogenic variant Asp42.

Post-translational modification of transthyretin in plasma

To determine the behavior of transthyretin (TTR) in blood circulation, TTR purified from normal subjects' plasma was injected to rats, and blood and urine were collected time dependently. Although TTR in plasma was proven to be a predominantly cysteine (Cys) conjugated form by electrospray ionization mass spectrometry (ESI-MS) analysis, it was gradually converted into free, 32 Da (dihydroxylation), 80 Da (phosphorylation), and 306 Da (glutathionylation), increased forms in molecular weight of TTR. The plasma levels of TTR were decreased in a time-dependent manner with the half life of 72.4 min. No secretion of TTR into the urine was observed by ESI-MS. In conclusion, this method can be simply performed without loading a radioactive molecule to the targeted protein. It offers a possibility to determine natural protein behaviors in the blood stream.

Three siblings of familial amyloid cardiomyopathy with isoleucine-50 transthyretin mutation

We herein describe three siblings with familial amyloid cardiomyopathy in a Japanese family, who demonstrated an Ile-50 mutation in the transthyretin gene. In their clinical course, the symptoms started at from 50 to 55 years of age, and two cases died within 5 years. However, one case is still alive seven years after onset probably due to either the implantation of a pacemaker for a complete atrio-ventricular block or the administration of dimethylsulphoxide. Based on our findings, some differences were observed not only in the mutation of the transthyretin gene but also in the clinical course between our cases and the previously reported cases.

Peripheral nerve amyloidosis

Peripheral nerve amyloidosis is the cardinal feature of familial amyloid polyneuropathy (FAP) but can also be seen in primary light chain (AL) amyloidosis and dialysis (beta 2-microglobulin) related amyloidosis. The generalized neuropathy seen in all forms of peripheral nerve amyloidosis is similar, characterized by a severe progressive mixed neuropathy with autonomic dysfunction. Pathologically, amyloid is found in the peripheral nervous system as amorphous, eosinophilic, extracellular deposits. FAP is most commonly associated with variant plasma transthyretin (TTR), although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now at least 36 point mutations in the TTR gene associated with FAP and these continue to be described. Recent studies on the possible role individual point mutations in the TTR gene may play in amyloidosis have helped give us an insight into the mechanisms behind peripheral nerve amyloidosis. This article reviews the clinical and pathological features of the peripheral nerve amyloidosis and discusses theories of amyloidogenesis based on studies of FAP.

Familial amyloid polyneuropathy associated with transthyretin Gly42 mutation: a quantitative light and electron microscopic study of the peripheral nervous system

We performed extensive quantitative analyses of the peripheral nervous system (PNS) of two siblings with familial amyloid polyneuropathy (FAP) caused by a transthyretin (TTR) Gly42 mutation. Pronounced amyloid deposition was found in the sympathetic ganglia (SyG), dorsal root ganglia (DRG) and throughout the length of the peripheral nerve fibers with some accumulation in the more proximal portion. There was severe neuronal loss in the SyG and DRG together with nerve fiber depletion in the nerve trunk, while only a small amount of amyloid deposition with mild fiber loss was seen in the spinal roots. Sprouts of regenerating axons were very scanty even in the spinal nerves or roots. A teased fiber study mainly showed demyelinating fibers, but axonal degeneration was also present throughout peripheral nerves. An electron microscopic study showed fine amyloid fibrils in direct contact with the axoplasmic membrane of demyelinated axons and destruction of axons in some areas. Amyloid deposition within the PINS in this type of FAP resembled that in type I FAP (TTR Met30). However, direct axonal damage by amyloid fibrils appeared to be more prominent in our cases than in type I FAP. Lectin histochemistry using Ulex europaeus agglutinin I demonstrated preferential depletion of small neurons in the DRG and their primary afferent fibers in the spinal dorsal horn. Primary axonal degeneration and ganglionopathy due to amyloid deposition appear to be the pathogenetic mechanisms for peripheral neuropathy in this type of FAP.

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.

Genetic abnormalities and pathogenesis of familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is an autosomal inherited disease, characterized by extracellular amyloid deposits and by peripheral neuropathy. Amyloid fibrils derived from most types of FAP consist of variant transthyretin (TTR) with single amino acid substitutions, and methionine 30 TTR is the most common variant TTR. TTR is mainly produced in the liver and the choroid plexus. Biochemical and molecular biological techniques have been revealing the amyloidogenicity of variant TTR in vitro and in vivo using the transgenic mouse as a model. It will be important for the development of effective therapy to find out the factors, other than variant TTR, which affect amyloid deposition and define the tissue specificity of amyloid.

Transthyretin mutations in health and disease

To date, over 40 different mutations in transthyretin (TTR) have been associated with amyloid deposition. The major unresolved problem is the correlation between the clinical heterogeneity and the genetic heterogeneity. For instance, whereas some mutations produce neuropathy and some give rise to cardiomyopathy, others produce vitreous opacities, the vast majority being neuropathic. Moreover, some mutations are not amyloidogenic but are responsible to hyperthyroxinemias (by virtue of the protein function in thyroid transport), whereas others are apparently nonpathogenic. The study of TTR variants is very important to the understanding of the amyloid formation process and to establish a relationship between the structure and function of the molecule. The results of current TTR mutation screening programs and their characterization are summarized.

Role of nitric oxide in the peripheral vessels of patients with familial amyloidotic polyneuropathy (FAP) type I

In order to establish the generation of endothelial derived relaxating factor (EDRF) in patients with familial amyloidotic polyneuropathy (FAP) type I, the muscle temperature of the lower limb was measured with a deep portion thermometer. The temperature of the gastrocunemius muscle in FAP patients was significantly decreased compared with control subjects. In order to investigate the generation of EDRF in FAP patients, we administered NG-monomethyl-L-arginine (L-NMMA), specific inhibitor of nitric oxide, from the brachial artery and measured the changes in blood flow. Although 61.7 +/- 18.2% of the blood flow was transiently decreased after administration of L-NMMA in control subjects, FAP patients showed poor responses. In contrast, in the same way as in control subjects, significant vasodilatation was seen in FAP patients after administration of L-arginine. The urinary secreted NO2-/NO3- levels per day, which reflect the synthesis of nitric oxide in the systemic circulation, was a great deal lower in FAP patients than in control subjects. These results suggest that, although peripheral vessels can be dilated when a large amount of the substrate for NO synthase, L-arginine, is supplied, production of nitric oxide may be suppressed, and, as the result of this phenomenon, blood flow is decreased in the peripheral tissues of FAP patients in a static state.

Two transthyretin mutations (glu42gly, his90asn) in an Italian family with amyloidosis

A family with familial amyloidotic polyneuropathy (FAP) was previously found to have a substitution of asparagine for histidine at position 90 of transthyretin. Members with his90asn developed FAP. However, close examination of the transthyretin gene revealed that glu42gly is coinherited with his90asn in this family. Since glu42gly has already been seen in Japanese FAP patients, and his90asn has been found in Portuguese and German individuals without FAP, we conclude that his90asn is a nonpathogenic variant.

Familial amyloidotic polyneuropathy with late-onset and well-preserved autonomic function: a Japanese kindred with novel mutant transthyretin (Ala97 to Gly)

We report the characteristics of one patient and two asymptomatic carriers from a Japanese family with familial amyloidotic polyneuropathy (FAP). The clinical features were somatic sensory and motor neuropathy with well-preserved autonomic function and late onset with slow insidious progression. These symptoms and signs are different from those of type 1 FAP. There were massive amyloid deposits with transthyretin (TTR) in the myocardium and the sural nerve. DNA sequencing of the TTR gene and amino acid sequence analysis of serum TTR revealed a new mutation in which Gly97 was substituted for Ala. We suggest that patients with somatic sensory and motor neuropathy of unknown origin without apparent autonomic dysfunction should be further studied for TTR mutation.

Type I familial amyloid polyneuropathy and pontine haemorrhage

A Portuguese female, aged 47 years, who had emigrated to Spain, was admitted to the hospital in 1991 for pontine haematoma. The patient, four siblings and her father were affected by a peripheral neuropathy, indicating autosomal dominant inheritance. The patient presented in the 2nd decade with sensory and motor neuropathy beginning in the lower extremities. Alternating constipation and diarrhoea, and urinary incontinence became uncontrollable. She had to be colostomised, and, eventually, confined to a wheelchair from the age of 43. Neurological examination showed bilateral facial involvement, and severe signs of sensory and motor peripheral neuropathy, and later right hemiplegia. There were abnormalities of atrial rhythm and left bundle branch block. Computerised axial tomography and magnetic resonance images demonstrated left-sided pontine haemorrhage. Nerve conduction studies revealed severe diminution of motor conduction velocity and absence or reduction of amplitude of sensory and motor action potentials. Inanition and a respiratory infection led to her death. Clinical diagnosis was type I familial amyloid polyneuropathy (FAP). Postmortem examination demonstrated amyloid deposits in peripheral nerves, including spinal roots and cranial nerves, leptomeninges, thyroid, breasts, heart, adrenal glands, kidneys, intestines, pancreas, and meningeal and some pontine vascular structures. Advanced pontine haematoma was verified. Cerebral haemorrhage usually occurs with cerebrovascular amyloidosis, but exceptionally with FAP. A minority of patients presenting with CNS haemorrhage showed arteriovenous malformation or embolism [Da Silva Horta and Dias Coelho (1960) Arch 'de Vecchi' Anal Patol Med Clin 31 = 163-172].(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoassay for transthyretin variants associated with amyloid neuropathy

An anti-transthyretin (TTR) mouse monoclonal antibody (88.6.FD6) of IgG1 subclass, obtained using as immunogen TTR from the serum of a patient with familial amyloidotic polyneuropathy, was found to bind to sera from carriers of several amyloidogenic TTR variants associated with peripheral neuropathy, but not to normal sera or sera from carriers of non-pathogenic or cardiomyopathic variants, in an ELISA performed under special conditions. Further characterization suggests that it recognizes an epitope near the N-terminal side of the TTR monomer. We propose that this epitope is exposed in amyloid and could be implicated in fibril deposition in the peripheral nervous system.

Transthyretin gene mutations in British and French patients with amyloid neuropathy

Five patients, two British and three French, with late onset amyloid neuropathy were found to have mutations of the transthyretin (TTR) gene associated with the Portuguese and German types of familial amyloid polyneuropathy. Familial amyloid polyneuropathy is rare in the United Kingdom and has not previously been defined at a molecular genetic level. None of the patients had a history of affected antecedents; the role of TTR gene analysis in diagnosing known or suspected amyloid neuropathy, regardless of family history or ethnic background, is emphasised.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathy (FAP) is most commonly associated with variant plasma transthyretin, although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now approximately 26 point mutations in the transthyretin gene associated with FAP. Because of the overlapping clinical phenotypes described with these mutations, it is now more appropriate to classify the various forms of FAP according to the underlying genetic defect rather than on clinical grounds. Many questions concerning the amyloidogenic nature of transthyretin and the variability of organ involvement depending on the underlying mutation remain unanswered. The recent use of liver transplantation for treatment appears to be promising.

Low plasma apolipoprotein AII levels in human and mouse amyloidosis with mutant transthyretin (Met-30) gene

We measured the serum apolipoprotein levels in patients with familial amyloidotic polyneuropathy (FAP). The serum apolipoprotein AII levels were much lower than those of the control subjects, while the levels in asymptomatic carriers of the FAP gene were normal. Other plasma apolipoprotein levels, such as apolipoproteins AI, B, CII, CIII, and E, were all within normal ranges. The decrease of apolipoprotein AII in the plasma of FAP patients correlated with the progression of the disease. In a transgenic mice model of FAP carrying human variant transthyretin gene (Met-30), serum apolipoprotein AII levels were decreased in 1.5-year-old mice compared with control mice, while the 3-month-old mice had normal levels. These results suggest that apolipoprotein AII may play an important role in lipid metabolism or amyloid formation in patients with FAP.

Amyloid polyneuropathy with transthyretin Arg50 in a Japanese case from Osaka

A Japanese patient with systemic amyloidosis associated with a transthyretin (TTR) variant Arg50 is presented. This 41-year-old man became impotent and developed decreased pain sensation in his hands, and then sensory loss and muscle wasting in his lower legs, and cardiomyopathy appeared. The symptoms progressed and he died of congestive heart failure at age 46. There were amyloid deposits in all organs studied and massive amyloid deposition was seen in the peripheral nerves and cardiac muscles. Amyloid fibrils extracted from heart tissue contained TTR. A genetic mutation, causing a Ser50-->Arg substitution of the TTR molecule, was identified in another family member. Plasma TTR was shown to be a mixture of normal TTR Ser50 and mutant TTR Arg50 in the 2 subjects.

Novel variant transthyretin gene (Ser50 to Ile) in familial cardiac amyloidosis

We detected a point mutation in the transthyretin (TTR) gene in a patient with familial cardiac amyloidosis by using PCR-DCP (DNA conformation polymorphism) analysis that is based on the diversity in electrophoretic mobility of single-stranded DNAs and/or heteroduplex DNAs in PCR products. The PCR products of the transthyretin gene were denatured in the presence of formamide and electrophoresed in a non-denaturing polyacrylamide gel to detect an electrophoretic change due to a sequence variation. An unusual DNA fragment was visualized by silver staining in the PCR products of the exon 3 from the patient. Subsequent sequencing analysis revealed a T to A transversion and led to a replacement of Ser by Ile at codon 50 of the TTR gene.

A novel mutant (transthyretin Ile-50) related to amyloid polyneuropathy. Single-strand conformation polymorphism as a new genetic marker

DNA sequence polymorphisms in transthyretin (TTR) genes were investigated by single-strand conformation polymorphism (SSCP) analysis of polymerase chain reaction products. The amplified DNA fragments that encode each exon of the normal TTR gene showed two bands, representing the two complementary single strands of DNA. In one patient with amyloid polyneuropathy, the exon 3 DNA showed a unique, aberrant migration pattern. Direct sequencing analysis of the amplified exon 3 revealed a single base change (G-to-T), resulting in a novel amino acid substitution (Ser-50----Ile). We also present the SSCP patterns for five known Japanese TTR variants.

Familial amyloid polyneuropathy related to transthyretin Gly42 in a Japanese family

A Japanese family is described in which 6 persons showed familial amyloid polyneuropathy (FAP). Mean ages of onset were 38 for 4 males and 54 for 2 females. Three of the 6 became emaciated and died after 4 to 10 years. In 5, muscular weakness and autonomic dysfunction were the initial symptoms followed by sensory disturbances. Amyloidotic cardiomyopathy was present in 3 of the subjects. Amyloid deposits showed an immunohistological relation to transthyretin (TTR). Analysis of 1 patient's TTR gene revealed a single base change (A----G) that led to amino acid substitution (Glu42----Gly). This base change produced a new restriction site for endonuclease Cfr13 I in exon 2. Polymorphic analysis of the length of the Cfr13 I-restriction fragment confirmed the base change, and made it possible to detect the mutant TTR Gly42 gene in the FAP subjects. Amino acid sequencing analysis showed a variant of TTR Gly42 in 1 patient's serum.

Familial amyloidosis: a study of 52 North American-born patients examined during a 30-year period

Between 1961 and 1990, 52 patients with biopsy-proven familial amyloidosis born in North America were examined at the Mayo Clinic. At the time of diagnosis of familial amyloidosis, 83% of these patients had peripheral neuropathy, 33% had autonomic neuropathy, and 27% had cardiomyopathy. Renal disease was noted in fewer than 10%, and liver involvement was rare. The median age at diagnosis was 64 years. The sensitivity of various diagnostic biopsies was similar to that for primary amyloidosis: deposits of amyloid were found in 77 and 78% of the subcutaneous fat aspirates or rectal biopsy specimens, respectively, and in 41% of specimens of bone marrow. The median duration of survival of 5.8 years for patients with inherited amyloidosis was superior to that for patients with primary amyloidosis. When patients were stratified by organ involvement, the survival of patients with familial amyloidosis remained superior. The presence of cardiomyopathy and an interactive variable of age and the presence of autonomic neuropathy were powerful predictors of survival. Of the 52 patients, 22 died, 12 (55%) of cardiac failure or cardiac arrhythmia. Nine patients (41%) died of inanition in conjunction with progressive peripheral or autonomic neuropathy. Transthyretin was identified by immunohistochemical studies in 31 of the 34 tissue specimens tested. A transthyretin mutation was identified in 24 of the 31. A transthyretin mutation was found in five additional patients for whom tissue was unavailable for immunostaining.

Familial amyloidotic polyneuropathy: report of patients heterozygous for the transthyretin Gly42 gene

We studied 2 patients from a Japanese family with familial amyloidotic polyneuropathy (FAP). Their clinical features are similar to type 1 FAP, and the proband's rectal tissue contained amyloid that stained with antihuman transthyretin (TTR) antiserum. Direct DNA sequencing of the proband's TTR gene revealed a guanine-for-adenine substitution in the second base of codon 42, producing a glycine for glutamate substitution in the plasma protein.

A novel transthyretin mutation associated with familial amyloidotic polyneuropathy

We characterized the mutation associated with familial amyloidotic polyneuropathy in a Japanese patient. Sequence analysis of polymerase chain reaction-amplified exons of the transthyretin gene revealed a novel point mutation resulting in a substitution of arginine for glycine at position 47. The mutation was confirmed using allele-specific olgonucleotide hybridization procedures. This most likely represents a de novo mutation since neither parent carries the mutant allele.

New mutant gene (transthyretin Arg 58) in cases with hereditary polyneuropathy detected by non-isotope method of single-strand conformation polymorphism analysis

Single-strand conformation polymorphism (SSCP) was analyzed to detect a mutation in the transthyretin (TTR) gene from the mother and son showing polyneuropathy with carpal tunnel syndrome. DNA segments containing TTR coding sequence were amplified by polymerase chain reaction, heat denatured and electrophoresed on a neutral polyacrylamide gel. The single-stranded DNA fragments in the gel were transferred to a nylon membrane and hybridized with biotinylated TTR cDNA probe, followed with chemiluminescent DNA detection. The mobility shift was found in the fragments of exon 3 from the patients' DNA. Sequencing analyses of the exon 3 confirmed a T----G base change, resulting in a Leu 58----Arg substitution. TTR Arg 58 is the first mutant TTR gene that has been detected by SSCP analysis. The rapid and sensitive detection of new mutations at various sites on the TTR gene is hereafter possible by the present method in the facilities for non-radioactive experiments.

Normal transthyretin and synthetic transthyretin fragments form amyloid-like fibrils in vitro

In two general forms of amyloidosis, senile systemic amyloidosis and several familial amyloidoses the amyloid fibrils are built up by transthyretin and fragments of the molecule. It has previously been demonstrated that other amyloid fibril proteins e.g. atrial natriuretic factor and islet amyloid polypeptide form amyloid-like fibrils in vitro. In this study we used normal transthyretin and synthetic polypeptides corresponding to segments of the transthyretin molecule. We show that normal transthyretin and two of our tested polypeptides, which corresponded to the beta-strands A and G, easily form amyloid-like fibrils in vitro.

Recent advances in the molecular pathology of familial amyloid polyneuropathy

The familial amyloid polyneuropathies (FAP) represent a heterogeneous spectrum of clinical syndromes differing regarding age of onset, rate of progression, and distribution of organ involvement and affecting people from different ethnic groups. Several mutant forms of transthyretin (TTR, formerly referred to as prealbumin) have been identified both in circulating plasma and in amyloid deposits from FAP patients. It is possible that a common factor in the amyloidogenesis process exists among the different forms which might be related to a change produced by the mutation in the three-dimensional structure of TTR. Other genetic or acquired factors affecting tissue composition might also play a role in pathogenesis. The intervening factors in amyloidogenesis in FAP, other than the presence of mutant TTR, are largely unknown and deserve future study.