Biomedical subjects
J N Buxbaum
Publications and source records attributed to J N Buxbaum.
Variant-sequence transthyretin (isoleucine 122) in late-onset cardiac amyloidosis in black Americans.
BACKGROUND: After the age of 60, isolated cardiac amyloidosis is four times more common among blacks than whites in the United States; 3.9 percent of blacks are heterozygous for an amyloidogenic allele of the normal serum carrier protein transthyretin in which isoleucine is substituted for valine at position 122 (Ile 122). We hypothesized that the high prevalence of transthyretin Ile 122 is at least partially responsible for the increased frequency of senile cardiac amyloidosis among blacks. METHODS: Paraffin blocks of cardiac tissue were obtained from an earlier study of 52,370 autopsies in Los Angeles and were examined by immunohistochemical and DNA analyses. Samples were available from 32 of 55 blacks and 20 of 78 whites over 60 years of age with isolated cardiac amyloidosis and from two control groups (228 cases). RESULTS: Transthyretin amyloidosis was identified in 31 of the 32 cardiac-tissue samples from the black patients and in 19 of the 20 samples from the white patients. Six of the 26 analyzable DNA samples (23 percent) from the black patients and none of the 19 samples from the white patients were heterozygous for the Ile 122 variant. Four of 125 DNA samples obtained at autopsy (3.2 percent) from a second, more recent, age-matched cohort of blacks without amyloidosis at the same institution were heterozygous for the transthyretin Ile 122 allele. On reexamination the cardiac tissue from these four patients contained small amounts of amyloid not detected at the initial autopsies. All subjects with the Ile 122 variant had ventricular amyloid. CONCLUSIONS: The assessment of elderly black patients with unexplained heart disease should include a consideration of transthyretin amyloidosis, particularly that related to the Ile 122 allele.
Transthyretin ILE20, a new variant associated with late-onset cardiac amyloidosis.
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Familial amyloidosis in one Chinese family: clinical, immunological, and molecular genetic analysis.
Three members of a Taiwanese kindred developed severe, systemic, early onset (< age 25 years), biopsy-proven amyloidosis. Clinical features included upper and lower extremity sensorimotor neuropathy, abdominal pain, vomiting, corneal ulcerations, cardiomyopathy, and syncope. Immunohistochemical analysis indicated that the deposits consisted of transthyretin. Molecular genetic studies revealed a heterozygous codon 55 point mutation, resulting in a proline for leucine-substitution, a mutation previously associated with aggressive familial amyloidosis in a US kindred of Dutch and German descent. The clinical courses and echocardiographic findings are typical for many types of amyloidosis; the pathologic data and genetic studies were necessary to establish a precise diagnosis.
Transthyretin Ile 122 and cardiac amyloidosis in African-Americans. 2 case reports.
Two cases of cardiac amyloidosis resulting from deposition of the Ile 122 variant of transthyretin in African-Americans are presented. These cases illustrate several typical features of this disorder, including electrocardiographic abnormalities and digoxin toxicity. Transthyretin Ile 122 is a common amyloidogenic variant in African-Americans (present as a heterozygous variant in 4% of this population); therefore, the diagnosis of transthyretin Ile 122 cardiac amyloidosis should be considered in African-Americans with unexplained restrictive cardiomyopathy or arrhythmias.
Revised transthyretin Ile 122 allele frequency in African-Americans.
The transthyretin (TTR) Ile 122 variant is associated with cardiac amyloidosis in individuals of African descent. To determine the prevalence of the allele encoding TTR Ile 122 in African-Americans, we have used PCR and restriction analysis to test DNA from African-Americans from various geographic areas, and found an allele frequency of 66/3376 (0.020), which is higher than the value we previously reported in a much smaller pilot study. Our data indicate that this TTR variant is present at equal frequency in African-Americans throughout the U.S., and suggest that this mutation may be a common, often unrecognized cause of cardiac disease in African-Americans.
Transthyretin Ser 6 gene frequency in individuals without amyloidosis.
Transthyretin (TTR) Ser 6 was originally described in a Scottish kindred without amyloidosis. This variant, arising from a G-->A transition in codon 6 that destroys an MspI site and creates a BsrI site, was present in none of 50 controls, and was therefore thought to be rare. This variant has subsequently been found in a normal human cDNA liver library and in two unrelated patients with familial amyloidosis and other TTR variants, raising the question whether it is actually a common polymorphism. To address this question, we performed PCR and restriction digestion of 574 DNA samples from people without evidence of amyloidosis or a known family history of amyloidosis. The TTR Ser 6 allele frequency was 33/558 (.060) in Caucasians (including 8/192 (.04) in North American Ashkenazic Jews, 16/218 (.07) in North American non-Jews, and 9/148 (.06) in Portuguese), 3(242 (.01) in African Americans, 0/140 in Africans, and 0/208 in Asians. These data are most suggestive of a single Caucasian founder and the known 25% admixture of "Caucasian" genes in the African-American population. Alternatively, as this variant arose from a transition at a CG dinucleotide "hot spot," it may have arisen on multiple occasions. These data indicate that TTR Ser 6 is a common non-amyloidogenic population polymorphism in Caucasians.
A double-variant transthyretin allele (Ser 6, Ile 33) in the Israeli patient "SKO" with familial amyloidotic polyneuropathy.
Transthyretin (TTR) isolated from amyloid fibrils from an Israeli patient ("SKO") with familial amyloidotic polyneuropathy has been studied by two groups of investigators. Originally, a position 49 Thr-->Gly substitution was reported; subsequently, a position 33 Phe-->Ile substitution was found instead. We have studied DNA from this patient by single strand conformation polymorphism analysis, restriction analysis, and DNA sequencing. On one allele, exon 2 contained both a T-->A transversion at the first position of codon 33, encoding the previously described Phe-->Ile substitution, and a G-->A transition at the first position of codon 6, encoding a Gly-->Ser substitution. The originally reported position 49 mutation was not encoded in the genomic DNA. This is the first report of a TTR double-variant allele in a patient with TTR amyloidosis.
Transthyretin VAL107, a new variant associated with familial cardiac and neuropathic amyloidosis.
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Detection of transforming oncogenes in rat colon tumors induced by direct perfusion with N-methyl-N-nitrosourea.
We assayed rat colon tumors induced by N-methyl-N-nitrosourea (MNU) for transforming oncogenes by the NIH 3T3 transfection and nude mouse tumorigenicity assays. Transfection of DNA from 3 of 3 adenomas and 3 of 5 carcinomas induced transformed foci on NIH 3T3 cells. DNA from 2 of 3 primary foci also possessed focus-forming activity, and rat-specific sequences were observed in secondary focus DNAs. Furthermore, NIH 3T3 cells transfected with DNA from a carcinoma and from a primary focus derived from it, both positive in the focus-forming assay, induced tumors in nude mice. We found no evidence for rat H-ras, K-ras, or N-ras sequences in the DNA of any of 16 primary foci derived from 6 rat tumors; thus, in contrast to other animal tumor models induced by MNU, activation of the ras genes does not appear to predominantly occur in MNU-induced rat colon tumors. We also did not observe, in any of these foci, sequences corresponding to the rat neu, raf, fms, met, or hst genes, thus indicating that none of these is the transforming oncogene in our model. These results suggest that an as yet unidentified transforming oncogene may be activated in rat colon tumors induced by MNU.
Transthyretin Pro55, a variant associated with early-onset, aggressive, diffuse amyloidosis with cardiac and neurologic involvement.
Mutations in the protein transthyretin cause amyloidosis involving the heart, peripheral nerves, and other organs. A family from West Virginia developed an unusually aggressive form of widespread transthyretin amyloidosis. Single-strand conformation polymorphism analysis revealed a variant in the transthyretin gene, which was found on sequencing to be a T----C transversion at position 2 of codon 55, corresponding to a Leu----Pro substitution. The variant sequence was confirmed by restriction analysis and polymerase chain reaction (PCR)-primer introduced restriction analysis.
Oncogene alterations in rat colon tumors induced by N-methyl-N-nitrosourea.
The authors assayed oncogene alterations in rat colon tumors induced by the direct-acting chemical carcinogen, N-methyl-N-nitrosourea (MNU). DNA isolated from 34 adenomas and eight carcinomas, as well as adjacent normal colon, of 11 rats was assayed by Southern blotting for restriction fragment length polymorphisms and gene amplifications and deletions in 13 oncogenes known to be involved in human or other animal tumors. In addition to finding apparent point mutations or other small alterations in the fos and abl genes in individual rat colon tumors, the authors observed what appear to be larger alterations (ie, rearrangements, or intragenic insertions or deletions) in the H-ras and myb loci in several tumors. In contrast, no changes in the K-ras, N-ras, myc, N-myc, neu, raf, fms, met, and hst genes were seen in any of these tumors. The frequency of myb gene alterations was higher in carcinomas than in adenomas, suggesting that these changes occurred relatively late during tumorigenesis and were not direct effects of the carcinogen. In addition, the finding of alterations in two or three oncogenes in several MNU-induced rat colon tumors suggests the possibility of more widespread genomic lesions in this model.
Enhanced expression of oncogene-encoded mRNA in a rat model of colon cancer.
We have studied the expression of oncogene-encoded mRNAs in a rat model of colon cancer. In this model, rats are intrarectally administered several low doses of the direct-acting carcinogen, N-methyl-N-nitrosourea (MNU). Tumors, predominantly adenomas, develop 5-7 months following administration of the carcinogen, and many of these progress to carcinomas. Upon assaying the steady-state levels of oncogene-encoded transcripts in normal rat colon, we found that fos and N-myc are highly expressed; H-ras, K-ras, myc, myb, and neu messages are present at lower levels; and N-ras, abl, and raf mRNAs are absent. When we compared transcript levels in rat tumors to those in normal colons from the same animal, we observed a 2-4 fold increase in both myc- and H-ras-encoded mRNAs and a 2-7 fold increase in myb message, but no change in expression of any of the 7 other genes. To test whether this increased expression is related to tumor production or is simply a result of the more rapid cellular turnover observed in tumor tissue, the level of oncogene-encoded transcripts was assayed in colonic mucosae of rats given two treatments known to enhance cell turnover and DNA synthesis in the colon. Neither acute application of MNU nor a diet containing 1% cholic acid caused any change in the level of oncogene-encoded mRNAs in rat colons, thus suggesting that the increased abundance of myc, myb, and H-ras messages in tumors is associated with tumor formation. The enhancement of expression of these genes in adenomas, as well as in carcinomas, further suggests that these alterations occur relatively early during the tumorigenic process.
Frequency and genetic background of the position 122 (Val----Ile) variant transthyretin gene in the black population.
Transthyretin (TTR) (122 Val----Ile), caused by a point mutation which destroys a MaeIII restriction site, is associated with cardiac amyloidosis in black individuals. To estimate the frequency of the MaeIII(-) gene in the black population without overt cardiac disease, DNA from 177 black individuals without amyloidosis was amplified by the PCR around TTR codon 122 and was digested with MaeIII. The MaeIII(-) gene frequency was 4/354 (1.1%; 95% confidence interval 0.32%2.7%), suggesting that the variant is relatively common in blacks. HLA genotype testing did not suggest that the TTR (122 Val----Ile) heterozygotes were of a closely related genetic background.
Monoclonal immunoglobulin deposition disease: light chain and light and heavy chain deposition diseases and their relation to light chain amyloidosis. Clinical features, immunopathology, and molecular analysis.
Monoclonal immunoglobulin deposition occurs in tissues as Congo Red binding fibrils in light chain amyloidosis, as less structured deposits in light chain deposition disease, and as similar but distinct deposits in light and heavy chain deposition disease. The nonamyloid forms were found in 13 patients who had evidence of plasmacytic dyscrasia by the immunohistochemical detection of immunoglobulin light chains of kappa or lambda class (with or without staining for a single heavy chain isotype) and by the absence of amyloid P component in tissue sections that did not show the birefringence characteristic of amyloid after Congo Red staining. All but two of the patients presented with proteinuria with or without azotemia. Clinical syndromes involving other organ systems were less common but occasionally severe. Four patients had overt multiple myeloma. Three others had hypercalcemia and mild bone marrow plasmacytosis but no lytic lesions. Analyses of immunoglobulin synthesis in bone marrow cells from seven patients showed excess light chains in all and incomplete light chains or heavy chain fragments in six, regardless of whether an intact monoclonal protein or related subunit was in the serum or urine. The fibrillar (amyloidotic) and nonfibrillar forms of monoclonal immunoglobulin deposition occur either in overt multiple myeloma or in the course of less neoplastically aggressive plasmacytic dyscrasias. Bone marrow cells from patients with either type produce immunoglobulin fragments that are related to those deposited in the affected tissues.
A homozygous transthyretin variant associated with senile systemic amyloidosis: evidence for a late-onset disease of genetic etiology.
Senile systemic amyloidosis (SSA) is a late-onset disease characterized by deposition of amyloid fibrils containing transthyretin (TTR). Amino acid sequencing of protein isolated from the amyloid fibrils of a patient with SSA identified TTR containing a position - 122 isoleucine-for-valine substitution. This change led to the prediction of a genomic G-to-A transition, destroying an MaeIII restriction site. We confirmed the presence of the variant DNA fragment both by Southern blotting and by visualization of MaeIII digests of DNA amplified around codon 122, by using the polymerase chain reaction. The patient's DNA was entirely resistant to MaeIII cleavage; therefore, only the mutant sequence was present. DNA from none of either 24 controls or six other SSA patients contained the variant. Quantitative Southern blotting demonstrated that the patient's DNA contained two copies of the TTR gene per genome; the mutation was therefore homozygous rather than hemizygous. In the present case, the homozygous mutation TTR (122 Val----Ile) is associated with SSA, a finding which is consistent with autosomal recessive inheritance of this condition.
A Thy-1 negative lymphoma cell variant defective in the formation of glycosyl-phosphatidylinositol membrane protein anchors.
Thy-1 is a glycoprotein present on the membrane of murine cells of the T-lineage. The mature Thy-1 is anchored to the membrane via a glycolipid, phosphatidylinositide. In order to study the regulation of the synthesis and membrane insertion of this protein, the biochemical properties of a Thy-1.2 negative variant T-lymphoma cell (RL male 1.4) were studied. It contains intracellular Thy-1 protein but fails to express it on the cell surface. While the wild type and the mutant show similar labelling of the intracellular Thy-1 glycoprotein with amino acids, no ethanolamine is incorporated into the Thy-1 molecule of RL male 1.4. A plasmid, pT1, containing the normal Thy-1.2 gene and bacterial gpt gene was transfected into RL male 1.4 and into the murine plasmacytoma cell, J558L. A transfected plasmacytoma, T1J2, synthesized a normal sized Thy-1 protein and displayed the antigen on the membrane. In contrast, the mycophenolic acid resistant RL male 1.4 transfectants did not display Thy-1.2 on the cell surface, despite the presence of substantial amounts of Thy-1 intracellularly. Two other antigens known to be anchored in the membrane by phospholipid, Ly-6e and Qa-2, were also examined in RL male 1.4. RL male 1.4 did not express Ly-6e after alpha interferon induction. In addition, the expression of Qa-2 antigen was greatly diminished in RL male 1.4 in comparison to RL male 1.3. Thus, the defect in RL male 1.4 is not restricted to Thy-1.2, but includes other similarly anchored glycoproteins as well. This implies that the addition of phospholipid to core proteins is similar, if not identical, for all these molecules and that the RL male 1.4 cell lacks the capacity to from the lipid glycoprotein linkage required for the expression of these proteins on the cell surface.