Merrill D. Benson

Amyloid fibril protein nomenclature: 2012 recommendations from the Nomenclature Committee of the International Society of Amyloidosis

The Nomenclature Committee of the International Society of Amyloidosis (ISA) met during the XIIIth International Symposium, May 6–10, 2012, Groningen, The Netherlands, to formulate recommendations on amyloid fibril protein nomenclature and to consider newly identified candidate amyloid fibril proteins for inclusion in the ISA Amyloid Fibril Protein Nomenclature List. The need to promote utilization of consistent and up to date terminology for both fibril chemistry and clinical classification of the resultant disease syndrome was emphasized. Amyloid fibril nomenclature is based on the chemical identity of the amyloid fibril forming protein; clinical classification of the amyloidosis should be as well. Although the importance of fibril chemistry to the disease process has been recognized for more than 40 years, to this day the literature contains clinical and histochemical designations that were used when the chemical diversity of amyloid diseases was poorly understood. Thus, the continued use of disease classifications such as familial amyloid neuropathy and familial amyloid cardiomyopathy generates confusion. An amyloid fibril protein is defined as follows: the protein must occur in body tissue deposits and exhibit both affinity for Congo red and green birefringence when Congo red stained deposits are viewed by polarization microscopy. Furthermore, the chemical identity of the protein must have been unambiguously characterized by protein sequence analysis when so is practically possible. Thus, in nearly all cases, it is insufficient to demonstrate mutation in the gene of a candidate amyloid protein; the protein itself must be identified as an amyloid fibril protein. Current ISA Amyloid Fibril Protein Nomenclature Lists of 30 human and 10 animal fibril proteins are provided together with a list of inclusion bodies that, although intracellular, exhibit some or all of the properties of the mainly extracellular amyloid fibrils.

The molecular biology and clinical features of amyloid neuropathy

Neuropathy is often a major manifestation of systemic amyloidosis. It is most frequently seen in patients with hereditary transthyretin (TTR) amyloidosis, but is also present in 20% of patients with systemic immunoglobulin light chain (primary) amyloidosis. Familial amyloid polyneuropathy (FAP) is the most common form of inherited amyloidotic polyneuropathy, with clinical and electrophysiologic findings similar to neuropathies with differing etiologies (e.g., diabetes mellitus). Hereditary amyloidosis is an adult‐onset autosomal‐dominant disease with varying degrees of penetrance. It is caused by specific gene mutations, but demonstration that a patient has one such mutation does not confirm the diagnosis of amyloidosis. Diagnosis requires tissue biopsy with demonstration of amyloid deposits either by special histochemical stains or electron microscopy. Transthyretin amyloidosis is treated by liver transplantation, which eliminates the mutated transthyretin from the blood, but for some patients continued amyloid deposition can occur from wild‐type (normal) transthyretin. Presently, a study is ongoing to determine whether amyloid deposition can be inhibited by small organic molecules that are hypothesized to affect the fibril‐forming ability of transthyretin. Proposed gene therapy with antisense oligonucleotides (ASOs) to suppress hepatic transthyretin synthesis is effective in a transgenic mouse model but has not yet been tested in humans. Muscle Nerve, 2007

A primer of amyloid nomenclature

The increasing knowledge of the exact biochemical nature of the localized and systemic amyloid disorders has made a logical and easily understood nomenclature absolutely necessary. Such a nomenclature, biochemically based, has been used for several years but the current literature is still mixed up with many clinical and histochemically based designations from the time when amyloid in general was poorly understood. All amyloid types are today preferably named by their major fibril protein. This makes a simple and rational nomenclature for the increasing number of amyloid disorders known in humans and animals.

Amyloid: Toward terminology clarification Report from the Nomenclature Committee of the International Society of Amyloidosis

The modern nomenclature of amyloidosis now includes 25 human and 8 animal fibril proteins. To be included in the list, the protein has to be a major fibril protein in extracellular deposits, which have the characteristics of amyloid, including affinity for Congo red with resulting green birefringence. Synthetic fibrils with amyloid properties are best named ‘amyloid-like’. With increasing knowledge, however, the borders between different protein aggregates tend to become less sharp.

Nomenclature 2014: Amyloid fibril proteins and clinical classification of the amyloidosis

The Nomenclature Committee of the International Society of Amyloidosis (ISA) met during the XIVth Symposium of the Society, April 27–May 1, 2014, Indianapolis, IN, to assess and formulate recommend...

Variant apolipoprotein AI as a major constituent of a human hereditary amyloid

Amyloid fibrils were isolated from spleen and liver of a patient who died with Familial Amyloidotic Polyneuropathy Type III (Iowa). The major protein constituent of the fibrils was found to be the amino terminal portion (residues 1-83) of apolipoprotein AI with an arginine for glycine substitution at position 26. This is the first report of an apolipoprotein as a major amyloid constituent in a form of autosomal dominant hereditary amyloidosis in humans.

Biochemical and molecular genetic characterization of a new variant prealbumin associated with hereditary amyloidosis.

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant late-onset disorder characterized by the extracellular deposition of amyloid fibrils. In all cases studied these fibrils have been found to be composed of plasma prealbumin (transthyretin) containing a single amino acid substitution. Biochemical studies were conducted on amyloid from one patient and plasma prealbumin from his affected brother, both part of a large kindred from the Appalachian region of the United States. Sequence analysis of the amyloid subunit protein showed it to be prealbumin with about two-thirds of the molecules containing a substitution of alanine for threonine at position 60. Studies of the plasma prealbumin showed that the same substitution was present in 40-45% of the protein. Based on this substitution and the prealbumin cDNA sequence, a Pvu II restriction fragment length DNA polymorphism (RFLP) was predicted and demonstrated in DNA of both patients as well as other family members. This RFLP confirms the predicted DNA mutation responsible for the protein variant, and represents an accurate method for detection of this gene.

Polymorphism of human plasma thyroxine binding prealbumin

Amyloid fibrils from an individual with heredofamilial amyloidosis were found to be composed of plasma prealbumin. To study this protein a three step procedure to isolate prealbumin from plasma was developed. It entailed ion exchange chromatography on DEAE Sephadex, affinity chromatography on Affi-gel Blue and gel filtration on AcA-34. Trypsin Digests of prealbumin were separated by reverse phase HPLC and the pattern compared to that from the normal protein. Only one unexpected peptide was found and it represented the substitution of a methionine for a valine at position 30 in the molecule. This substitution accounts for about 1/3 of the isolated molecules and it represents the first point mutation identified in human plasma prealbumin.

A mutation in apolipoprotein A-I in the Iowa type of familial amyloidotic polyneuropathy.

Immunoblotting of isoelectric focusing gels of plasma and direct genomic DNA sequencing have been used to characterize a mutation in apolipoprotein A-I associated with the familial amyloidotic polyneuropathy originally described by Van Allen in an Iowa kindred. An arginine for glycine substitution in apolipoprotein A-I identified in the probands amyloid fibrils was determined to be the result of a mutation of guanine to cytosine in the apolipoprotein A-I gene at the position corresponding to the first base of codon 26. Direct sequencing of genomic DNA of three affected individuals who died in the 1960s confirmed the inheritance of the disorder. Immunoblot analysis detected the variant apolipoprotein A-I in the probands plasma and in several at-risk members of the kindred. In addition, allele-specific amplification by the polymerase chain reaction was used to detect carriers of the variant gene.

Direct sequencing of the gene for Maryland/German familial amyloidotic polyneuropathy type II and genotyping by allele-specific enzymatic amplification.

Direct genomic DNA sequencing has been used to characterize the mutation associated with familial amyloidotic polyneuropathy in the Maryland/German kindred. A mutation of thymine to adenine in the prealbumin (transthyretin) gene at the position corresponding to the second base of codon 58 in the prealbumin mRNA gives a histidine for leucine substitution in the plasma protein. Since the mutation does not result in a change in the restriction pattern of the prealbumin gene, a new method for the direct detection of single base changes in genomic DNA was developed using the polymerase chain reaction and an allele-specific oligonucleotide primer.