Rational Control of the Activity of a Cu2+-Dependent DNAzyme by Re-engineering Purely Entropic Intrinsically Disordered Domains.

The function and activity of many proteins is finely controlled by the modulation of the entropic contribution of intrinsically disordered domains that are not directly involved in any recognition event. Inspired by this mechanism, we demonstrate here that we could finely regulate the catalytic activity of a model DNAzyme (i.e., a synthetic DNA sequence with enzyme-like properties) by rationally introducing intrinsically disordered nucleic acid portions in its original sequence. More specifically, we have re-engineered here the well-characterized Cu2+-dependent DNAzyme that catalyzes a self-cleavage reaction by introducing a poly(T) linker domain in its sequence. The linker is not directly involved in the recognition event and connects the two domains that fold to form the catalytic core. We demonstrate that the enzyme-like activity of this re-engineered DNAzyme can be modulated in a predictable and fine way by changing the length, and thus entropy, of such a linker domain. Given these attributes, the rational design of intrinsically disordered domains could expand the available toolbox to achieve a control of the activity of DNAzymes and, in analogy, ribozymes through a purely entropic contribution.

Longer TOMM40 poly-T variants associated with higher FDDNP-PET medial temporal tau and amyloid binding.

BACKGROUND: The translocase of outer mitochondrial membrane 40 (TOMM40), which lies in linkage disequilibrium with the apolipoprotein E (APOE) gene, has been implicated in Alzheimer's disease (AD). TOMM40 influences AD pathology through mitochondrial neurotoxicity, and the medial temporal lobe (MTL) is the most likely brain region for identifying early manifestations of AD-related morphology changes. While early reports indicated that the longer length poly-T allele of TOMM40 increases risk for AD, these findings have not been consistently replicated in further studies. We examined the effect of TOMM40 and APOE on regional brain positron emission tomography (PET) 2-(1-{6-[(2 [F18]fluoroethyl) (methyl) amino]-2-naphthyl}ethylidene)malononitrile (FDDNP) binding values in MTL. METHODS: A total of 73 non-demented older adults (42 females; mean age: 62.9(10.9) completed genotyping for both APOE and TOMM40 and received FDDNP-PET scans. For TOMM40, the lengths of the poly-T sequence were classified as short (14-20 repeats; S), long (21-29 repeats, L) or very long (>29 repeats, VL). Using general linear models, we examined medial temporal lobe FDDNP binding and cognitive functioning between TOMM40 and APOE-4 groups, with age, sex, and education as covariates. RESULTS: Data from 30 individuals with APOE-4 and L TOMM40 poly-T length, 11 non E4 TOMM40 S/S, 14 non E4 TOMM40 S/VL and 13 non E4 TOMM40 VL/VL were analyzed. Medial temporal FDDNP binding differed significantly between TOMM40/APOE groups (F(3,62) = 3.3,p = .03). Participants with TOMM40 S/S exhibited significantly lower binding compared to TOMM40 S/VL and APOE-4 carriers. We did not find a significant relationship between TOMM40 poly-T lengths/APOE risk groups and cognitive functioning. CONCLUSIONS: This is the first report to demonstrate a significant association between longer TOMM40 poly-T lengths and higher medial temporal plaque and tangle burden in non-demented older adults. Identifying biomarkers that are risk factors for AD will enhance our ability to identify subjects likely to benefit from novel AD treatments.

Association study between a polymorphic poly-T repeat sequence in the promoter of the somatostatin gene and metabolic syndrome.

BACKGROUND: Metabolic syndrome is a cluster of factors associated with an increased risk of developing type 2 diabetes mellitus (T2D) and coronary artery disease (CAD). It is a complex disorder resulting from the interaction between various environmental factors and genetic susceptibility. The somatostatin (SST) gene has been shown to regulate a wide range of functions, particularly in energy homeostasis. In addition, low levels of SST have been reported to have effects on the progression of metabolic syndrome components. The aim of this study was therefore to evaluate the association between polymorphic T sequences in the promoter of the SST gene and metabolic syndrome expression. METHODS: We studied 1725 French-Canadian subjects from a founder population selected on the basis of having a positive family history of dyslipidemia, CAD or T2D. The analysis were performed on four groups created according to the poly T polymorphism length in the 5' flanking promoter region of SST. Anova, Ancova and logistic regression models and Chi 2 analyses were used to evaluate the association between the poly T polymorphisms and metabolic syndrome components expression. RESULTS: Analyses showed that means, frequencies and odds ratio of metabolic syndrome components expression increase as the number of poly-T repeats in the promoter region of SST increases. Women exhibit more significant differences than men. However, the trends are the same in both genders and differences for most of the components are significant in the entire sample. CONCLUSION: Those results suggest that the poly T polymorphisms in the SST promoter region may influence several metabolic processes implicated in metabolic syndrome expression. More analyses are needed to document the mechanisms that could underlie genetic regulation effect of SST on metabolic syndrome components and to clarify its specific role.

Quantification of Exosome Based on a Copper-Mediated Signal Amplification Strategy.

Exosomes, a class of small extracellular vesicles, play important roles in various physiological and pathological processes by serving as vehicles for transferring and delivering membrane and cytosolic molecules between cells. Since exosomes widely exist in various body fluids and carry molecular information on their originating cells, they are being regarded as potential noninvasive biomarkers. Nevertheless, the development of convenient and quantitative exosome analysis methods is still technically challenging. Here, we present a low-cost assay for direct capture and rapid detection of exosomes based on a copper-mediated signal amplification strategy. The assay involves three steps. First, bulk nanovesicles are magnetically captured by cholesterol-modified magnetic beads (MB) via hydrophobic interaction between cholesterol moieties and lipid membranes. Second, bead-binding nanovesicles of exosomes with a specific membrane protein are anchored with aptamer-modified copper oxide nanoparticles (CuO NPs) to form sandwich complexes (MB-exosome-CuO NP). Third, the resultant sandwich complexes are dissolved by acidolysis to turn CuO NP into copper(II) ions (Cu2+), which can be reduced to fluorescent copper nanoparticles (CuNPs) by sodium ascorbate in the presence of poly(thymine). The fluorescence emission of CuNPs increases with the increase of Cu2+ concentration, which is directly proportional to the concentration of exosomes. Our method allows quantitative analysis of exosomes in the range of 7.5 × 104 to 1.5 × 107 particles/µL with a detection of limit of 4.8 × 104 particles/µL in biological sample. The total working time is about 2 h. The assay has the potential to be a simple and cost-effective method for routine exosome analysis in biological samples.

Molecular characterization of a novel bat-associated circovirus with a poly-T tract in the 3' intergenic region.

The family Circoviridae comprises a large group of small circular single-stranded DNA viruses with several members causing severe pig and poultry diseases. In recent years the number of new viruses within the family has had an explosive increase showing a high level of genetic diversity and a broad host range. In this report we describe two more circoviruses identified from bats in Yunnan and Heilongjiang provinces in China. Full genome sequencing has revealed that these bat associated circoviruses (bat ACV) should be classified as new species within the genus Circovirus based on the demarcation criteria of the International Committee on the Taxonomy of Viruses (ICTV). The most striking result is the novel finding of a 21-28 nt polythymidine (poly-T) tract in the 3' terminal intergenic region of bat ACV isolates from Heilongjiang province. To understand its role in viral replication, a wild type bat ACV and a mutated version with the entire poly-T deleted were rescued through construction of infectious clones. Replication comparison in vitro showed that the poly-T is not essential for viral replication. Identification of additional bat ACV isolates and study of their biological characteristics will be the main task in future to understand the potential roles of bats in transmission of circoviruses to terrestrial mammals and humans.

The effects of the TOMM40 poly-T alleles on Alzheimer's disease phenotypes.

The TOMM40 poly-T is a polymorphism in intron 6 of the TOMM40 gene, which is adjacent to and in linkage disequilibrium with APOE. Roses et al. identified the association between the length of TOMM40 poly-T with the risk and age of onset of late-onset Alzheimer's disease (LOAD). Following the original discovery, additional studies found associations between the TOMM40 poly-T and LOAD-related phenotypes independent of APOE genotypes, while others did not replicate these associations. Furthermore, the identity of the TOMM40 poly-T risk allele has been controversial between different LOAD-related phenotypes. Here, we propose a framework to address the conflicting findings with respect to the TOMM40 poly-T allele associations with LOAD phenotypes and their functional effects. The framework is used to interpret previous studies as means to gain insights regarding the nature of the risk allele, very long versus short. We suggest that the identity of the TOMM40 poly-T risk allele depends on the phenotype being evaluated, the ages of the study subjects at the time of assessment, and the context of the APOE genotypes. In concluding remarks, we outline future studies that will inform the mechanistic interpretation of the genetic data.

[Interaction of Dystamycin Dimeric Analog with Poly(dA) x poly(dT), Poly[d(A-T)] x poly[d(A-T)] and Duplex O23 at Origin of Replication of the Herpes Simplex Virus].

The binding of distamycin dimeric analog (Pt-bis-Dst) to poly[d(A-T)] x poly[d(A-T)1, poly(dA) x poly(dT) and duplex O23 with the sequence 5'-GCCAATATATATATATTATTAGG-3' which is present at the origin of replication of herpes simplex virus OriS is investigated with the use of UV and CD spectroscopy. The distinction of the synthetic polyamide from a natural antibiotic lies in the fact that in the synthetic polyamide there are two distamycin moieties bound via a glycine cis-diamino platinum group. It was shown that the binding of Pt-bis-Dst to poly[d(A-T)] x poly[d(A-T)] and poly(dA) x poly(dT) reaches saturation if one molecule of the ligand occurs at approximately every 8 bp. With further increase in the ratio of the added ligand to the base pairs in CD spectra of complexes with poly[d(A-T)] x poly[d(A-T)], we observed that the maximum wavelength band tend to be shifted towards longer wavelengths, while in the spectral region of 290-310 nm a "shoulder", that was absent in the spectra of the complexes obtained at low polymer coverages by the ligand, appeared. At high molar concentration ratios of ligand to oligonucleotide Pt-bis-Dst can bind to poly[d(A-T)] x poly[d(A-T)] in the form of hairpins or may form associates by the interaction between the distamycin moieties of neighboring molecules of Pt-bis-Dst. The structure of the complexes is stabilized by interactions between pirrolcarboxamide moieties of two molecules of Pt-bis-Dst adsorbed on adjacent overlapping binding sites. These interactions are probably also responsible for the concentration-dependent spectral changes observed during the formation of a complex between Pt-bis-Dst and poly[d(A-T)] x poly[d(A-T)]. Spectral changes are almost absent in binding of Pt-bis-Dst to poly(dA) x poly(dT). Binding of Pt-bis-Dst to duplex O23 reaches saturation if two ligand molecules occur in a duplex that contains a cluster of 18 AT pairs. With increasing the molar concentration ratio of the ligand to the duplex CD spectra undergo concentration-dependent changes similar to those observed during binding of Pt-bis-Dst to poly [d(A-T)] x poly[d(A-T)]. Testing for antiviral efficacy of Pt-bis-Dst showed that the concentration, at which the cytopathic effect produced by the herpes simplex virus in cell culture Vero E6 halved, is equal to 1.5 µg/ml and the selectivity index for evaluating antiviral activity is 65 at a relatively low cytotoxicity. The concentration of Pt-bis-Dst, at which approximately half the cells are killed, is equal to 100 µg/ml.

Association between a polymorphic poly-T repeat sequence in the promoter of the somatostatin gene and hypertension.

Despite the numerous common pathways connecting blood pressure regulation to somatostatin (SST) metabolism, the SST gene has never been seen as a significant blood pressure modulator. The aim of this study was to evaluate the association between a poly-T repeat sequence (rs34872250) in the promoter of the SST gene and blood pressure, according to the obesity status. We genotyped 1918 French-Canadian subjects from a founder population. Analyses were performed according to the length of the poly-T repeat sequence on both alleles and divided into two groups, the 13/13-13/14 group and the 13/15-13/16 group. The effect of age, gender, body mass index, antihypertensive drugs and diabetic status were considered. Systolic, diastolic and mean blood pressures are significantly higher among the 13/15-13/16 group in the whole sample (P<0.05). Whereas the differences remain significant in women, they turn to be non-significant when men are considered alone. The risk of hypertension is increased in the 13/15-13/16 group, particularly among overweight/obese subjects. Systolic blood pressure is significantly higher among overweight/obese carriers of the 13/15-13/16 alleles in the whole sample (P<0.001), in men (P=0.006) and in women (P=0.002), even after correction for age and antihypertensive drugs. These results suggest that the poly-T repeat sequence polymorphism in the promoter of the SST gene is associated with significant variations of blood pressure and could modulate the risk of hypertension, particularly among women.

Associations between TOMM40 Poly-T Repeat Variants and Dementia in Cases with Parkinsonism.

BACKGROUND: Mitochondrial dysfunction has been implicated in the pathophysiology of Parkinson's disease (PD)-related pathologies. OBJECTIVE: To investigate the role of the Translocase of the Outer Mitochondrial Membrane 40 homolog (TOMM40) variants in PD without dementia (PDND), PD with dementia (PDD) and in Dementia with Lewy bodies (DLB). METHODS: 248 individuals, including 92 PDND, 55 PDD, and 101 DLB, were included. The rs10524523 locus in the TOMM40 gene (TOMM40 poly-T repeat) is characterized by a variable number of T residues that were classified into three groups based on length; short (S), long (L), and very long (VL). We tested log-additive genetic model of association with dementia and adjusted for age, sex, and APOEɛ4 carrier status. We analyzed cerebrospinal fluid (CSF) levels of Aß42 and Tau, biomarkers related to Alzheimer's disease (AD). RESULTS: PDD/DBL status and abnormal CSF AD biomarkers (Aß42 and Aß42/Tau ratio) were both associated with the APOEɛ4 allele (p <  0.014) and the L allele of TOMM40 poly-T repeat (p <  0.008). The VL allele was less frequently observed in the PDD/DLB group (p = 0.013). In APOE-ɛ4 adjusted analyses, the relationships between the L and VL alleles and dementia status as well as CSF AD biomarkers were not significant. When adjusting for APOE-ɛ4, however, there were associations between S carrier status and PDD/DLB (p = 0.019) and abnormal CSF levels of Aß42/Tau ratio (p = 0.037) although these were not significant after adjustment for multiple comparisons. CONCLUSION: Our results do not support the notion that TOMM40 poly-T repeat variants have independent effects on PDD and DLB pathology. This relationship seems to be driven by APOE-ɛ4.

Guanine polynucleotides are self-antigens for human natural autoantibodies and are significantly reduced in the human genome.

In the course of investigating anti-DNA autoantibodies, we examined IgM and IgG antibodies to poly-G and other oligonucleotides in the sera of healthy persons and those diagnosed with systemic lupus erythematosus (SLE), scleroderma (SSc), or pemphigus vulgaris (PV); we used an antigen microarray and informatic analysis. We now report that all of the 135 humans studied, irrespective of health or autoimmune disease, manifested relatively high amounts of IgG antibodies binding to the 20-mer G oligonucleotide (G20); no participants entirely lacked this reactivity. IgG antibodies to homo-nucleotides A20, C20 or T20 were present only in the sera of SLE patients who were positive for antibodies to dsDNA. The prevalence of anti-G20 antibodies led us to survey human, mouse and Drosophila melanogaster (fruit fly) genomes for runs of T20 and G20 or more: runs of T20 appear > 170,000 times compared with only 93 runs of G20 or more in the human genome; of these runs, 40 were close to brain-associated genes. Mouse and fruit fly genomes showed significantly lower T20/G20 ratios than did human genomes. Moreover, sera from both healthy and SLE mice contained relatively little or no anti-G20 antibodies; so natural anti-G20 antibodies appear to be characteristic of humans. These unexpected observations invite investigation of the immune functions of anti-G20 antibodies in human health and disease and of runs of G20 in the human genome.

Effect of Polypurine Reverse Hoogsteen Hairpins on Relevant Cancer Target Genes in Different Human Cell Lines.

We studied the ability of polypurine reverse Hoogsteen hairpins (PPRHs) to silence a variety of relevant cancer-related genes in several human cell lines. PPRHs are hairpins formed by two antiparallel polypurine strands bound by intramolecular Hoogsteen bonds linked by a pentathymidine loop. These hairpins are able to bind to their target DNA sequence through Watson-Crick bonds producing specific silencing of gene expression. We designed PPRHs against the following genes: BCL2, TOP1, mTOR, MDM2, and MYC and tested them for mRNA levels, cytotoxicity, and apoptosis in prostate, pancreas, colon, and breast cancer cell lines. Even though all PPRHs were effective, the most remarkable results were obtained with those against BCL2 and mammalian target of rapamycin (mTOR) in decreasing cell survival and mRNA levels and increasing apoptosis in prostate, colon, and pancreatic cancer cells. In the case of TOP1, MDM2, and MYC, their corresponding PPRHs produced a strong effect in decreasing cell viability and mRNA levels and increasing apoptosis in breast cancer cells. Thus, we confirm that the PPRH technology is broadly useful to silence the expression of cancer-related genes as demonstrated using target genes involved in metabolism (DHFR), proliferation (mTOR), DNA topology (TOP1), lifespan and senescence (telomerase), apoptosis (survivin, BCL2), transcription factors (MYC), and proto-oncogenes (MDM2).

The effect of TOMM40 poly-T repeat lengths on age of onset and cerebrospinal fluid biomarkers in Finnish Alzheimer's disease patients.

BACKGROUND: Poly-T repeat lengths of rs10524523 in TOMM40 together with APOE polymorphism have been reported to affect the risk of late-onset Alzheimer's disease (LOAD) and the age of onset (AOO). OBJECTIVE: To explore whether the AOO and cerebrospinal fluid biomarkers Aß42, total tau and phosphorylated tau are associated with different repeat lengths. METHODS: We conducted both the fragment and sequencing analysis of rs10524523 in 336 LOAD patients with a known APOE genotype. RESULTS: AOO and Aß42 levels associated significantly with certain poly-T repeat lengths of rs10524523 in LOAD patients encompassing APOE 34/44 genotype. CONCLUSION: We conclude that the poly-T repeat associations of rs10524523 in TOMM40 reflect the APOE ε4-dependent association in LOAD.

Are APOE ɛ genotype and TOMM40 poly-T repeat length associations with cognitive ageing mediated by brain white matter tract integrity?

Genetic polymorphisms in the APOE ɛ and TOMM40 '523' poly-T repeat gene loci have been associated with significantly increased risk of Alzheimer's disease. This study investigated the independent effects of these polymorphisms on human cognitive ageing, and the extent to which nominally significant associations with cognitive ageing were mediated by previously reported genetic associations with brain white matter tract integrity in this sample. Most participants in the Lothian Birth Cohort 1936 completed a reasoning-type intelligence test at age 11 years, and detailed cognitive/physical assessments and structural diffusion tensor brain magnetic resonance imaging at a mean age of 72.70 years (s.d.=0.74). Participants were genotyped for APOE ɛ2/ɛ3/ɛ4 status and TOMM40 523 poly-T repeat length. Data were available from 758-814 subjects for cognitive analysis, and 522-543 for mediation analysis with brain imaging data. APOE genotype was significantly associated with performance on several different tests of cognitive ability, including general factors of intelligence, information processing speed and memory (raw P-values all<0.05), independently of childhood IQ and vascular disease history. Formal tests of mediation showed that several significant APOE-cognitive ageing associations--particularly those related to tests of information processing speed--were partially mediated by white matter tract integrity. TOMM40 523 genotype was not associated with cognitive ageing. A range of brain phenotypes are likely to form the anatomical basis for significant associations between APOE genotype and cognitive ageing, including white matter tract microstructural integrity.

African-American TOMM40'523-APOE haplotypes are admixture of West African and Caucasian alleles.

BACKGROUND: Several studies have demonstrated a lower apolipoprotein E4 (APOE ε4) allele frequency in African-Americans, but yet an increased age-related prevalence of AD. An algorithm for prevention clinical trials incorporating TOMM40'523 (Translocase of Outer Mitochondria Membrane) and APOE depends on accurate TOMM40'523-APOE haplotypes. METHODS: We have compared the APOE and TOMM40'523 phased haplotype frequencies of a 9.5 kb TOMM40/APOE genomic region in West African, Caucasian, and African-American cohorts. RESULTS: African-American haplotype frequency scans of poly-T lengths connected in phase with either APOE ε4 or APOE ε3 differ from both West Africans and Caucasians and represent admixture of several distinct West African and Caucasian haplotypes. A new West African TOMM40'523 haplotype, with APOE ε4 connected to a short TOMM40'523 allele, is observed in African-Americans but not Caucasians. CONCLUSION: These data have therapeutic implications for the age of onset risk algorithm estimates and the design of a prevention trial for African-Americans or other mixed ethnic populations.

Frequency and distribution of simple and compound microsatellites in forty-eight Human papillomavirus (HPV) genomes.

Simple sequence repeats (SSRs) are tandem-repeated sequences ubiquitously present but differentially distributed across genomes. Present study is a systematic analysis for incidence, composition and complexity of different microsatellites in 48 representative Human papillomavirus (HPV) genomes. The analysis revealed a total of 1868 SSRs and 120 cSSRs. However, four genomes (HPV-60, HPV-92, HPV-112 and HPV-136) lacked any cSSR content; while HPV-31 accounted for a maximum of 10 cSSRs. An overall increase in cSSR% with higher dMAX was observed. The SSRs and cSSRs were prevalent in coding regions. Poly(A/T) repeats were significantly more abundant than poly(G/C) repeats possibly due to high (A/T) content of the HPV genomes. Further, higher prevalence of di-nucleotide repeats over tri-nucleotide repeats may be attributed to instability of former because of higher slippage rate. An in-depth study of the satellite sequences would provide an insight into the imperfections and evolution of microsatellites.

NCS: incorporating positioning data to quantify nucleosome stability in yeast.

MOTIVATION: With the spreading technique of mass sequencing, nucleosome positions and scores for their intensity have become available through several previous studies in yeast, but relatively few studies have specifically aimed to determine the score of nucleosome stability. Based on mass sequencing data, we proposed a nucleosome center score (NCS) for quantifying nucleosome stability by measuring shifts of the nucleosome center, and then mapping NCS scores to nucleosome positions in Brogaard et al.'s study. RESULTS: We demonstrated the efficiency of NCS by known preference of A/T-based tracts for nucleosome formation, and showed that central nucleosomal DNA is more sensitive to A/T-based tracts than outer regions, which corresponds to the central histone tetramer-dominated region. We also found significant flanking preference around nucleosomal DNA for A/T-based dinucleotides, suggesting that neighboring sequences could affect nucleosome stability. Finally, the difference between results of NCS and Brogaard et al.'s scores was addressed and discussed. CONTACTS: jchiang@mail.ncku.edu.tw SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

The specificity and flexibility of l1 reverse transcription priming at imperfect T-tracts.

L1 retrotransposons have a prominent role in reshaping mammalian genomes. To replicate, the L1 ribonucleoprotein particle (RNP) first uses its endonuclease (EN) to nick the genomic DNA. The newly generated DNA end is subsequently used as a primer to initiate reverse transcription within the L1 RNA poly(A) tail, a process known as target-primed reverse transcription (TPRT). Prior studies demonstrated that most L1 insertions occur into sequences related to the L1 EN consensus sequence (degenerate 5'-TTTT/A-3' sites) and frequently preceded by imperfect T-tracts. However, it is currently unclear whether--and to which degree--the liberated 3'-hydroxyl extremity on the genomic DNA needs to be accessible and complementary to the poly(A) tail of the L1 RNA for efficient priming of reverse transcription. Here, we employed a direct assay for the initiation of L1 reverse transcription to define the molecular rules that guide this process. First, efficient priming is detected with as few as 4 matching nucleotides at the primer 3' end. Second, L1 RNP can tolerate terminal mismatches if they are compensated within the 10 last bases of the primer by an increased number of matching nucleotides. All terminal mismatches are not equally detrimental to DNA extension, a C being extended at higher levels than an A or a G. Third, efficient priming in the context of duplex DNA requires a 3' overhang. This suggests the possible existence of additional DNA processing steps, which generate a single-stranded 3' end to allow L1 reverse transcription. Based on these data we propose that the specificity of L1 reverse transcription initiation contributes, together with the specificity of the initial EN cleavage, to the distribution of new L1 insertions within the human genome.

TOMM40 intron 6 poly-T length, age at onset, and neuropathology of AD in individuals with APOE ε3/ε3.

BACKGROUND: This study investigates the association between TOMM40 poly-T length, age at onset, and neuropathology in individuals with Alzheimer's disease (AD) with the apolipoprotein E (APOE) ε3/ε3 allele. METHODS: Thirty-two presenilin 1 (PSEN1) mutation carriers with AD, 27 presenilin 2 (PSEN2) mutation carriers with AD, 59 participants with late-onset AD (LOAD), and 168 autopsied subjects from a community-based cohort were genotyped for TOMM40 intron 6 poly-T (rs10524523) length using short tandem repeat assays. RESULTS: Among AD individuals with PSEN2 mutations, the presence of a long poly-T was associated with an earlier age at onset, whereas there were no such associations for subjects with PSEN1 mutations or LOAD. In community-based participants, the presence of a long poly-T was associated with increased neuritic tangles and a greater likelihood of pathologically diagnosed AD. CONCLUSION: TOMM40 intron 6 poly-T length may explain some of the variation in age at onset in PSEN2 familial AD and may be associated with AD neuropathology in persons with APOE ε3/ε3.

Poly (AT) polymorphism in the XPC gene and smoking enhance the risk of prostate cancer in a low-risk Chinese population.

We investigated two polymorphisms of xeroderma pigmentosum complementary group C (XPC) in 202 subjects with prostate cancer (PCa) and 221 healthy controls in a Chinese Han population. Genotyping was performed using a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique. Our results indicated that smoking is associated with an increased risk for PCa (odds ratio [OR]: 1.51; 95% confidence interval [CI]: 1.02-2.22). Subjects carrying the XPC-PAT+/+ genotype exhibited a significantly increased risk for PCa (OR: 2.11; 95% CI: 1.12-3.99). The combined subjects with either the PAT+/+ or PAT+/- genotype also exhibited a 1.54-fold increased risk associated with PCa (OR: 1.54; 95% CI: 1.04-2.26). Moreover, smokers with PAT+/- or PAT+/+ had a higher risk for PCa (OR: 1.98; 95% CI: 1.08-3.64; P = 0.026 and OR: 3.56; 95% CI: 1.45-8.76; P = 0.004, respectively) compared with never smokers with the PAT-/- genotype. Analyses of the XPC Lys939Gln polymorphism did not show an association with PCa risk. Our findings support the hypothesis that XPC-PAT polymorphisms may contribute to the risk of developing PCa. More important, an elevated risk of PCa associated with a gene-environment (smoking) interaction was determined in a Chinese population.