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

A mouse model of a novel missense mutation (Gly83Arg) in a Chinese kindred manifesting vitreous amyloidosis only

The purpose of this study is to establish a mouse model of transthyretin (TTR) Gly83Arg gene mutation by the technique of gene targeting for research on hereditary vitreous amyloidosis (HVA) and to confirm whether this point mutation is a genetic feature of HVA. A vector (pBR322-MK-TTR) was constructed to target ES cells. The successfully transfected ES cells were used for blastocyst injection, thus generating F0. F0 and Flp mice were mated to generate F1 (TTR+/-, Flp +/-) mice that lacked the neo gene but carried the Flp gene. F1 mice were mated with C57BL/6N wild type mice to generate F2 (TTR+/-) mice. F3 homozygous and heterozygous mice were generated by mating F2 mice with each other. PCR and sequencing were performed for F3 mice. Amyloid was detected using Congo red stain and polarized light. Immunohistochemistry was used to detect the expression of TTR in the tissues. Quantitative fluorescent PCR and Western blotting were used to detect the expression of TTR mRNA and TTR protein, respectively. Two F0-generation, 2 F1-generation and 15 F3-generation mice were obtained. The gene sequencing of F3 mice showed TTR Gly83Arg mutation. When examined with Congo red and polarized light, the vitreous of TTR Gly83Arg mutant mice tested positive for amyloid. The hearts, livers, brains and kidneys of the experimental group and control group were all negative by Congo red staining. Immunohistochemical staining showed that the vitreous of TTR Gly83Arg mutant mice and the livers of the control mice were positive, but the kidneys, hearts and brains of both groups were negative. Quantitative fluorescent PCR showed that the mRNA expression of mutant mice was significantly lower than that of wild-type mice (F = 0.295, P = 0.023). Western blotting showed that the expression of TTR protein was significantly lower in the model mice than in the wild-type mice (t = 3.224, P = 0.018). TTR gene mutation is indeed a molecular characteristic of HVA and manifest in the eye disease only. A C57BL/6 mouse line carrying the TTR Gly83Arg gene mutation was successfully established. This strain of mice can be used for the study of HVA.

Role of VLDL/chylomicron in amyloid formation in familial amyloidotic polyneuropathy

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.

Polymorphisms of mouse apolipoprotein A-II: seven alleles found among 41 inbred strains of mice

In mice, apolipoprotein A-II (apoA-II) associates to form amyloid fibrils in an age-associated manner. We determined the complete nucleotide sequences of the apoA-II gene (Apoa2) cDNA in 41 inbred strains of mice including Mus musculus domesticus (laboratory mouse), Mus musculus castaneus, Mus musculus molossinus, Mus musculus musculus and Mus spretus. Among these strains we identified 7 alleles (Apoa2a1, Apoa2a2, Apoa2b, Apoa2c, Apoa2d, Apoa2e and Apoa2f). Polymorphisms of nucleotides at 15 positions were detected and amino acid substitutions were found at 8 positions. Apoa2a1 was found in all mouse subspecies, but Apoa2b and Apoa2c were found only in Mus musculus domesticus. Two strains of Mus spretus have the unique alleles Apoa2e and Apoa2f which resemble Apoa2c. We confirmed that VICS in which we found severe amyloidosis here and other amyloidoneic strains in published reports have Apoa2c allele. We determined the plasma concentrations of total and HDL cholesterol in the strains of Mus musculus domesticus with the Apoa2a1, Apoa2b and Apoa2c alleles. Significantly higher concentrations of plasma cholesterol were observed in mouse strains with the Apoa2b allele. These findings provide fundamental data on mouse Apoa2 alleles. Furthermore, differences in these alleles likely have considerable influence on traits related to amyloidosis and lipid metabolism.

Low serum apolipoprotein AI levels in amyloidosis related to familial Mediterranean fever

Amyloidosis (A) related to familial Mediterranean fever (FMF) causes serious morbidity and mortality in children. Our study evaluates serum levels of apolipoprotein (Apo) AI, AII, B, and E and Apo AII/AI ratios as a non-invasive diagnostic tool for amyloidosis in children with FMF and FMF-A. Results were compared with those of patients with childhood nephrotic syndrome (NS) and healthy children (controls). Significantly lower serum levels of Apo AI (90.20+/-28.30 mg/dl) were documented in patients with FMF-A than in all other groups (FMF 126.89+/-51.07 mg/dl, NS 140.38+/-33.73 mg/dl, and controls 134.67+/-12.73 mg/dl) ( P<0.01). Diagnostic sensitivity, specificity, and predictive value for this test were 85%, 80%, and 85%, respectively. Apo AII/AI ratio results were essentially equal in all groups ( P>0.05). It is concluded that a decreased Apo AI serum level, but not Apo AII/AI ratio, is a useful, non-invasive test for the early diagnosis of FMF-A in children.

Japanese monozygotic twins with familial amyloidotic polyneuropathy (FAP) (ATTR Val30Met)

Twenty-nine-year-old twin brothers having the amyloidogenic transthyretin (ATTR) Val30Met gene developed the clinical symptoms of familial amyloidotic polyneuropathy (FAP) in 1995. The twins had the same educational background and lived in the same district. FAP manifestations were similar in both cases, although electromyographic examinations revealed sensorimotor polyneuropathy in No. 1 and sensory polyneuropathy in No. 2. DNA analysis revealed that they were monozygotic twins. In addition to environmental factors, genetic factors may play an important role in determining the onset of FAP.

Decreased serum apolipoprotein AII/AI ratio in systemic amyloidosis

OBJECTIVE

To investigate if serum apolipoprotein A-I and A-II (apoAI and apAII) concentrations change in subjects with systemic amyloidosis secondary to underlying disorders.

METHODS

Serum concentrations of apoAI and apoAII were measured in 21 multiple myeloma patients, including eight with amyloidosis; 95 rheumatoid arthritis patients, including 45 with amyloidosis; and 73 haemodialysis patients, including 32 with amyloidosis.

RESULTS

ApoAII values tended to be reduced in subjects with amyloidosis in each group, but could not effectively distinguish amyloidosis. However, apoAII/AI ratios were significantly lower in subjects with amyloidosis in all groups. The ratio of 0.2 had diagnostic sensitivity and specificity for amyloidosis; 50% and 100%, respectively, in multiple myeloma; 80% and 78%, respectively, in rheumatoid arthritis; and 46% and 90%, respectively, in patients requiring long term haemodialysis.

CONCLUSION

The apoAII/AI ratio can be a useful biochemical marker of suspect amyloidosis in patients with underlying diseases, especially those with rheumatoid arthritis.

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.