Kamran Hamidi Asl

Hereditary amyloid cardiomyopathy caused by a variant apolipoprotein A1.

Autosomal dominant hereditary amyloidosis with a unique cutaneous and cardiac presentation and death from heart failure by the sixth or seventh decade was found to be associated with a previously unreported point mutation (thymine to cytosine, nt 1389) in exon 4 of the apolipoprotein A1 (apoA1) gene. The predicted substitution of proline for leucine at amino acid position 90 was confirmed by structural analysis of amyloid protein isolated from cardiac deposits of amyloid. The subunit protein is composed exclusively of NH2-terminal fragments of the variant apoA1 with the longest ending at residue 94 in the wild-type sequence. Amyloid fibrils derived from four previously described apoA1 variants are composed of similar fragments with carboxyl-terminal heterogeneity, but contrary to those variants, which all carry one extra positive charge, the substitution Leu90Pro does not result in any charge modification. It is unlikely, therefore, that amyloid fibril formation is related to change of charge for a specific residue of the precursor protein. This is in agreement with studies on transthyretin amyloidosis in which no unifying factor such as change of charge for amino acid residues has been noted.

A prospective evaluation of the transthyretin Ile122 allele frequency in an African-American population.

Transthyretin Val122Ile is one of greater than 80 mutations in transthyretin (TTR) that are associated with hereditary amyloidosis. Retrospective studies have shown a prevalence of this mutation as high as 3.9% in African-Americans. The present study was undertaken to determine in a prospective fashion the prevalence of the TTR Val122Ile allele in African-Americans in a Midwestern American city. DNA was isolated from cord bloods collected at the time of birth in the County hospital of Indianapolis, Indiana. Samples were identified only as to ethnic origin of the mother. Analysis was performed by PCR amplification of TTR exon 4 followed by SSCP and RFLP. Cord bloods from 1,973 children born at the County hospital were analyzed. Thirty of 1,000 DNA samples from African-American newborns were positive for TTR Val122Ile (3%). Two of 453 DNA samples from Caucasian newborns were positive (0.44%). Zero of 490 DNA samples from newborns of Hispanic mothers and 0 of 30 from newborns with mothers classified as other (including Asian) were positive. This prospective study demonstrates that 3% of newborns of African-American women in an urban population have the TTR Val122Ile mutation which is associated with late-onset cardiomyopathy. The degree of penetrance of this mutation at the clinical level has not yet been determined.

Local synthesis of amyloid fibril precursor in AL amyloidosis of the urinary tract

An amyloid tumor localized to the urethra was resected and shown by immunohistochemistry to contain fibril deposits that stained with antisera specific for lambda VI immunoglobulin light chain. The amino acid sequence of the fibril protein was homologous to lambda VI Positive staining of subepithelial plasma cells with lambda VI specific monoclonal antibody was consistent with the hypothesis that the fibril precursor light chain protein is synthesized and processed locally to give this type of localized amyloidosis.

A novel variant of transthyretin (Glu89Lys) associated with familial amyloidotic polyneuropathy

We detected a point mutation in the transthyretin (TTR) gene associated with familial amyloidotic polyneuropathy (FAP) in a 57-year old male presenting with sensorimotor polyneuropathy, severe autonomic dysfunction and cardiomyopathy using a non-isotopic RNase cleavage assay (NIRCA). NIRCA suggested that the mutation site was near either amino acid position 58 of mature TTR or the 3′ end of exon 3. Direct DNA sequencing showed both a normal GA G (Glu) and a variantAAG (Lys) codon at amino acid position 89 of mature TTR, which has not been previously reported. The site of this mutation is near the 3′ end of exon 3, consistent with the result of NIRCA. This mutation was also confirmed by polymerase chain reaction-induced mutation restriction analysis (PCR-IMRA).

Cardiac amyloidosis associated with the transthyretin Ile122 mutation in a Caucasian family.

The Ile 122 transthyretin variant associated with restrictive cardiomyopathy has been described in African-Americans and estimated to be present in approximately 4% of the Black population. We report the first American-Caucasian family with cardiomyopathy due to the TTR lie122 mutation. The high prevalence of this mutation in the Black population and the discovery that it may cause disease in other ethnic populations highlights the importance of considering this autosomal dominant systemic amyloidosis in all individuals with restrictive cardiomyopathy. Inadequate diagnosis combined with inappropriate treatment may have a significant impact on morbidity and mortality.

Transthyretin isoleucine-122 mutation in African and American blacks

The gene frequency of the transthyretin (TTR) mutation (Vall22Ile) was studied in African and African-American populations. The African populations analyzed included the Zulu and Xhosa of South Africa, and Yorubas from the city of Ibadan, Nigeria. The African-American population included patients at the Veterans Affairs (VA) Medical Center, Indianapolis, and newborns from a local hospital in Indianapolis. The Vall22Ile TTR mutation was identified in I of 55 Zulu, 0 of 34 Xhosa, 0 of 9 Nigerian subjects, 5 of 51 Veteran patients, and 3 of 103 newborns. Assuming the 2.91% prevalence in newborns to be the norm, there is a significant increased prevalence in the VA patient population.

Identification of a New Transthyretin Variant (Ile49) in Familial Amyloidotic Polyneuropathy Using Electrospray Ionization Mass Spectrometry and Nonisotopic RNase Cleavage Assay

Mutation of the transthyretin (TTR) plasma protein and gene in a Japanese patient with amyloid polyneuropathy was investigated by electrospray ionization mass spectrometry (ESI-MS) and nonisotopic RNase cleavage assay (NIRCA), respectively. ESI-MS analysis showed normal TTR peaks and additionally a variant TTR with 12-dalton-higher molecular weight than normal TTR. NIRCA suggested that the mutation existed near either the 5′ or 3′ end of exon 3. Direct DNA sequencing revealed both a normal ACC (threonine) and a variant ATC (isoleucine) at codon 49, which was located near the 5′ end of exon 3. The molecular weight shift of this mutation was 12 D, consistent with the result of ESI-MS.

Kappa III immunoglobulin light chain origin of localized orbital amyloidosis.

Isolated orbital amyloidosis is a rare condition in which intra-muscular deposits result in proptosis and restriction of eye movement. Previous reports have suggested an immunoglobulin origin of the amyloid fibrils, but this has not been proven biochemically. A case is presented in which initial unilateral orbital amyloidosis progressed to bilateral disease. Biochemical analysis of resected ocular muscle determined that the amyloid fibrils were derived from a kappa III immunoglobulin light chain. Questions of pathogenesis and tissue tropism are considered.