Timothy A. Donlon

FOXO3A genotype is strongly associated with human longevity

Human longevity is a complex phenotype with a significant familial component, yet little is known about its genetic antecedents. Increasing evidence from animal models suggests that the insulin/IGF-1 signaling (IIS) pathway is an important, evolutionarily conserved biological pathway that influences aging and longevity. However, to date human data have been scarce. Studies have been hampered by small sample sizes, lack of precise phenotyping, and population stratification, among other challenges. Therefore, to more precisely assess potential genetic contributions to human longevity from genes linked to IIS signaling, we chose a large, homogeneous, long-lived population of men well-characterized for aging phenotypes, and we performed a nested-case control study of 5 candidate longevity genes. Genetic variation within the FOXO3A gene was strongly associated with human longevity. The OR for homozygous minor vs. homozygous major alleles between the cases and controls was 2.75 (P = 0.00009; adjusted P = 0.00135). Long-lived men also presented several additional phenotypes linked to healthy aging, including lower prevalence of cancer and cardiovascular disease, better self-reported health, and high physical and cognitive function, despite significantly older ages than controls. Several of these aging phenotypes were associated with FOXO3A genotype. Long-lived men also exhibited several biological markers indicative of greater insulin sensitivity and this was associated with homozygosity for the FOXO3A GG genotype. Further exploration of the FOXO3A gene, human longevity and other aging phenotypes is warranted in other populations.

Identification of cDNA clones for the human microtubule-associated protein tau and chromosomal localization of the genes for tau and microtubule-associated protein 2

We have previously identified a partial human cDNA for MAP2, and we now report the isolation of human cDNA clones for tau. The RNA species recognized by the tau clones is a 6 kilobase (kb) message that is expressed in the human brain but not in other human tissues, and exhibits a developmental shift in size. We also report the human chromosomal localization of the MAP2 and tau genes. The MAP2 cDNA pKN7 was used to localize the MAP2 gene to chromosome 2q34-35. The tau cDNAs were used to confirm the presence of a tau gene on chromosome 17q21 and an additional region of homology on chromosome 6p21.

Detection of bcr-abl fusion in chronic myelogeneous leukemia by in situ hybridization.

Chronic myelogeneous leukemia (CML) is genetically characterized by fusion of the bcr and abl genes on chromosomes 22 and 9, respectively. In most cases, the fusion involves a reciprocal translocation t(9;22)(q34;q11), which produces the cytogenetically distinctive Philadelphia chromosome (Ph1). Fusion can be detected by Southern (DNA) analysis or by in vitro amplification of the messenger RNA from the fusion gene with polymerase chain reaction (PCR). These techniques are sensitive but cannot be applied to single cells. Two-color fluorescence in situ hybridization (FISH) was used with probes from portions of the bcr and abl genes to detect the bcr-abl fusion in individual blood and bone marrow cells from six patients. The fusion event was detected in all samples analyzed, of which three were cytogenetically Ph1-negative. One of the Ph1-negative samples was also PCR-negative. This approach is fast and sensitive, and provides potential for determining the frequency of the abnormality in different cell lineages.

Performance-based measures of physical function for high-function populations

OBJECTIVES: To improve and broaden the applicability of performance‐based measures of function for use in clinical and research settings.

B-vitamin intake, metabolic genes, and colorectal cancer risk (United States)

Objective: This population-based case–control study was designed to investigate the interrelationships between polymorphisms in the methylenetetrahydrofolate (MTHFR C677T and A1298C) gene and other genes (MTR A2756G; MTRR A66G and CBS 844ins68), intake of B-vitamins and colorectal cancer risk (CRC). Methods: We interviewed 727 CRC cases of Japanese, Caucasian, or Native Hawaiian origin and 727 controls matched on sex, age, and ethnicity. Results: Compared to the homozygous wild-type genotype, the odds ratios for subjects with one or two MTHFR 677T variant alleles were 0.8 (0.6–1.1) and 0.7 (0.5–1.1), respectively (p for gene–dosage effect: 0.04). The TT genotype was associated with a 50–60% decrease in CRC risk among subjects with high intake of folate or vitamin B6, compared to those with the CC genotype and low levels of intake. The MTHFR 1298C and CBS8 44ins68 variant alleles were also found to be weakly protective against CRC and to act jointly with the 677T allele. Conclusions: This study provides additional evidence for a decreased CRC risk for subjects with the MTHFR 677T allele, particularly at high levels of folate and vitamin B6 intake. Our data also suggest that the relationships between CRC and the MTHFR A1298C and CBS 844ins68 polymorphisms warrant further study.

Well-done red meat, metabolic phenotypes and colorectal cancer in Hawaii.

Heterocyclic amines (HAAs) and polycyclic hydrocarbons are suspected colorectal cancer (CRC) carcinogens that are found in well-done meat. They require metabolic activation by phase I enzymes, such as the smoking-inducible CYP1A isoenzymes. N-acetyltransferase 2 (NAT2) also play a role in the further activation of HAAs. We conducted a population-based case-control study in Hawaii to test the associations of preference for well-done red meat and HAA intake with colon and rectal cancers, as well as the modifying effects of NAT2 and CYP1A2. We interviewed 727 Japanese, Caucasian or Native Hawaiian cases and 727 controls matched on sex, age, and ethnicity. HAA intake was estimated based on consumption of meat and fish for each of several cooking methods and doneness levels. A subgroup of 349 cases and 467 controls was phenotyped for CYP1A2 by a caffeine test. We found that preference for well-done red meat was associated with a 8.8-fold increased risk of CRC (95% CI: 1.7-44.9) among ever-smokers with the NAT2 and CYP1A2 rapid phenotypes, compared to ever-smokers with low NAT2 and CYP1A2 activities and who preferred their red meat rare or medium. A dose-dependent association was also found between the HAA intake estimates and male rectal cancer, with a two- to three-fold increase in risk from the low (T(1)) to high (T(3)) tertile of intake for each HAA. This association was strongest for MeIQx. HAA intake was not associated with male colon cancer or colon or rectal cancer in women. These data provide support to the hypothesis that exposure to pyrolysis products through consumption of well-done meat increases the risk of CRC, particularly in individuals who smoke and are genetically susceptible (as determined by a rapid phenotype for both NAT2 and CYP1A2). An attempt to examine the risk associated with specific HAAs suggested that the main HAAs increase risk of rectal cancer in men and that they do not appreciably affect risk of rectal cancer in women or of colon cancer in either sex.

Estrogen Metabolism–Related Genes and Breast Cancer Risk: The Multiethnic Cohort Study

Common polymorphisms in genes that affect estrogen levels may be associated with breast cancer risk. We investigated the associations between breast cancer and sequence variants in several genes in the estradiol/estrone metabolism pathway (CYP1A1*2A, CYP1A2*1F, CYP1B1 Leu432Val, CYP3A4*1B, COMT Val158Met, SULT1A1Arg213His) as well as the Arg554Lys variant in AHR (a transcription factor for CYP1A1, CYP1A2, and CYP1B1) in a case-control study of 1,339 breast cancer cases and 1,370 controls nested in the Multiethnic Cohort Study. The Multiethnic Cohort Study is a large prospective study of men and predominantly postmenopausal women of Japanese, White, African American, Latino, and Native Hawaiian ancestry, residing in Hawaii and Los Angeles. We found no association between breast cancer and these polymorphisms, except for CYP1A2*1F which was inversely associated with risk. The odds ratio (95% confidence interval) for the AA, AC, and CC genotype was 1.0, 0.9 (0.7-1.0), and 0.7 (0.5-1.0), respectively (P for gene dosage effect = 0.03). This association seemed somewhat stronger for estrogen receptor (ER)/progesterone receptor (PR)–negative tumors than for ER/PR-positive tumors, and no statistically significant interaction with estrogen-related risk factors was detected. The findings provide no evidence for a role of COMT Val58Met, CYP1A1*2A, CYP3A4*1B, CYP1B1 Leu432Val, SULT1A1 Arg213His, and AHR Arg554Lys in breast cancer etiology. They also provide support for an inverse association between CYP1A2*1F and breast cancer, which is consistent with the observation of lower circulating estrogen levels in premenopausal women with the CC genotype in a previous study.

Similar molecular deletions on chromosome 15q11.2 are encountered in both the Prader-Willi and Angelman syndromes

SummaryComparative molecular analysis of chromosome 15, sub-band q11.2 of patients with the Prader-Willi or Angelman syndromes demonstrates that they have a similar deletion. An hypothesis is presented that attempts to explain the tremendous degree of clinical heterogeneity in these diverse deletion-associated syndromes based on abnormal haplotypes present on the cytogenetically normal homolog. This hypothesis also addresses genetic similarities between patients who have deletion and those who have the inv dup (15) by postulating that these syndromes are caused by relative dosage ratios of normal versus abnormal alleles.

Immunohistochemical and cytogenetic studies indicate that malignant angioendotheliomatosis is a primary intravascular (angiotropic) lymphoma

The authors performed immunohistochemical and cytogenetic studies in a 73‐year old man with malignant angioendotheliomatosis. The patient was referred for evaluation of fever of unknown origin, hepatic failure, and neurologic deterioration. Examination of a muscle biopsy revealed numerous, noncohesive atypical mononuclear cells within small vessels. These cells stained positively with a pan‐leukocyte marker CD45(PD7/26/16) and with a B‐cell marker L26 but negatively with Factor VIII‐related antigen, an endothelial cell marker. Peripheral blood obtained before chemotherapy was cultured and analyzed by the G‐band method. A new translocation and numerous chromosomal aberrations were identified. The major cell line karyotype was 53, XY,+X,+5q?,‐6,+i(6p),+7,‐10,+11,‐12,+12p‐,+12p‐,+18,+marl,+mar2, t(1;3)(p22;p21),3q+,8p+. This is the first cytogenetic study performed in a case of malignant angioendotheliomatosis. Our findings demonstrate that the neoplastic cells in this disorder circulate in the peripheral blood and provide further evidence that malignant angioendotheliomatosis is a diffuse intravascular neoplasm of lymphoid origin. Furthermore, the authors conclude that this malignant lymphoproliferative disorder should be reclassified as a primary intravascular (angiotropic) lymphoma.

Methyl green is a substitute for distamycin A in the formation of distamycin A/DAPI C-bands

SummaryThe DA/DAPI technique has been found to be useful in the identification of specific chromosomal regions on human chromosomes. The realization that distamycin A (DA) is no longer commercially available has necessitated the development of an alternative technique. We describe a technique, MG/DAPI, which substitutes the AT-specific dye methyl green for distamycin A and gives results identical to those of the DA/DAPI technique.