Longer genotypically-estimated leukocyte telomere length is associated with increased adult glioma risk

Telomere maintenance has emerged as an important molecular feature with impacts on adult glioma susceptibility and prognosis. Whether longer or shorter leukocyte telomere length (LTL) is associated with glioma risk remains elusive and is often confounded by the effects of age and patient treatment. We sought to determine if genotypically-estimated LTL is associated with glioma risk and if inherited single nucleotide polymorphisms (SNPs) that are associated with LTL are glioma risk factors. Using a Mendelian randomization approach, we assessed differences in genotypically-estimated relative LTL in two independent glioma case-control datasets from the UCSF Adult Glioma Study (652 patients and 3735 controls) and The Cancer Genome Atlas (478 non-overlapping patients and 2559 controls). LTL estimates were based on a weighted linear combination of subject genotype at eight SNPs, previously associated with LTL in the ENGAGE Consortium Telomere Project. Mean estimated LTL was 31bp (5.7%) longer in glioma patients than controls in discovery analyses (P = 7.82×10-8) and 27bp (5.0%) longer in glioma patients than controls in replication analyses (1.48×10-3). Glioma risk increased monotonically with each increasing septile of LTL (O.R.=1.12; P = 3.83×10-12). Four LTL-associated SNPs were significantly associated with glioma risk in pooled analyses, including those in the telomerase component genes TERC (O.R.=1.14; 95% C.I.=1.03-1.28) and TERT (O.R.=1.39; 95% C.I.=1.27-1.52), and those in the CST complex genes OBFC1 (O.R.=1.18; 95% C.I.=1.05-1.33) and CTC1 (O.R.=1.14; 95% C.I.=1.02-1.28). Future work is needed to characterize the role of the CST complex in gliomagenesis and further elucidate the complex balance between ageing, telomere length, and molecular carcinogenesis.     

人急性淋巴母细胞白血病细胞株Molt-4遗传学特性的研究

本研究探讨人急性淋巴母细胞白血病细胞株Molt-4的遗传学特性,评价其在Flow—FISH方法检测细胞端粒长度中的应用价值。悬浮培养Molt-4细胞并进行规律传代,选取8代不同代数、处于对数生长期的Molt-4细胞进行研究。应用细胞计数法描绘细胞生长曲线并计算细胞倍增时间,流式细胞术检测细胞DNA倍体指数,常规G显带进行染色体核型分析,Southernblot检测细胞端粒长度。结果显示：Molt-4细胞的倍增时间为（1．315±0．062）d、DNA倍体指数为（2．085±0．0093）、端粒长度为（32．05±5．27）kb,不同代数之间无显著性差异（P值分别为0．931、0．888和0．935）。染色体核型分析结果显示,Molt-4细胞染色体数量为91—99条,多数为超四倍体,并且具有稳定的、特征性染色体结构异常。结论：Molt-4细胞具有稳定的遗传特性和较长的端粒长度,可作为Flow—HSH的内对照细胞。     

人肝癌细胞中端粒酶RNA的克隆及序列分析

目的：比较不同组织细胞中端粒酶ＲＮＡ（ｈＴＲ）的序列，建立以ｈＴＲ为基础的肿瘤诊断与治疗新技术。方法：采用逆转录聚合酶链反应（ＲＴ－ＰＣＲ）技术从人肝癌细胞株（ＨｅｐＧ２）中扩增出了ｈＴＲ部分ｃＤＮＡ序列，并通过电泳的方法鉴定了其特异性。通过分子克隆技术将上述产物插入Ｔ－质粒后转化入大肠杆菌ＪＭ１０９中，经聚合酶链反应（ＰＣＲ）鉴定了插入片段的特异性及方向，最后采用自动ＤＮＡ序列分析仪分析了上述插     

Phosphorylation of TPP1 regulates cell cycle-dependent telomerase recruitment

Telomere maintenance is essential for organisms with linear chromosomes and is carried out by telomerase during cell cycle. The precise mechanism by which cell cycle controls telomeric access of telomerase and telomere elongation in mammals remains largely unknown. Previous work has established oligonucleotide/oligosaccharide binding (OB) fold-containing telomeric protein TPP1, formerly known as TINT1, PTOP, and PIP1, as a key factor that regulates telomerase recruitment and activity. However, the role of TPP1 in cell cycle-dependent telomerase recruitment is unclear. Here, we report that human TPP1 is phosphorylated at multiple sites during cell cycle progression and associates with higher telomerase activity at late S/G₂/M. Phosphorylation of Ser111 (S111) within the TPP1 OB fold appears important for cell cycle-dependent telomerase recruitment. Structural analysis indicates that phosphorylated S111 resides in the telomerase-interacting domain within the TPP1 OB fold. Mutations that disrupt S111 phosphorylation led to decreased telomerase activity in the TPP1 complex and telomere shortening. Our findings provide insight into the regulatory pathways and structural basis that control cell cycle-dependent telomerase recruitment and telomere elongation through phosphorylation of TPP1.     

Ambient air pollution,blood mitochondrial DNA copy number and telomere length in a panel of diabetes patients

Abstract

Context: Several previous studies proposed a link between particulate matter (PM) pollution and mitochondrial DNA copy number (MtDNAcn) and telomere length (TL). However, this evidence is quite limited and inconsistent, especially on how the particle size affects the associations and on whether there exists such an association with gaseous pollutants.

Objective: We aimed to investigate the short-term associations of size-fractionated PM and gaseous pollutants with blood MtDNAcn and TL.

Methods: We conducted a longitudinal panel study involving 6 repeated measurements among 35 Type 2 diabetes patients in Shanghai, China from April to June 2013. We measured the real-time concentrations of size-fractionated PM (0.25–10?μm) and criteria gaseous pollutants. Blood MtDNAcn and TL were tested by a quantitative real-time PCR–based assay. Linear mixed-effect models were used to explore their short-term associations using multiple lag periods, after controlling for individual characteristics, time trends and weather conditions.

Results: In general, there were inverse but statistically non-significant associations between all pollutants and MtDNAcn. Coarse PM appeared to be more closely linked with MtDNAcn than smaller PM. The associations between various air pollutants and TL were generally positive but very weak. There were no clear lag patterns for these associations. The associations between air pollutants and MtDNAcn and TL were strengthened but still not significant among those who did not take statins regularly.

Conclusions: This study did not support short-term associations of PM or gaseous pollutants with blood MtDNAcn and TL in type 2 diabetes patients.     

人胚肺成纤维细胞复制性衰老过程中端粒相关因子的表达*

背景：端粒相关蛋白直接影响端粒的功能,调节端粒 DNA 的长度,与细胞的衰老和癌变密切相关。目的：通过观察正常细胞复制性衰老过程中端粒相关因子的变化来找寻细胞正常衰老过程中的关键调控分子。方法：在构建好的细胞复制性衰老模型基础上,利用 RT-PCR 与 western blot 方法在分子与蛋白水平检测端粒相关因子的表达变化,主要检测人胚肺成纤维细胞在复制性衰老过程中端粒相关因子人端粒结合蛋白1、端锚聚合酶1、端粒酶 RNA、端粒末端保护蛋白1以及 P53的表达情况。结果与结论：结果显示,随着细胞的衰老,人端粒结合蛋白1的转录水平未发生改变,而人端粒结合蛋白1的蛋白表达水平有逐渐升高而后快速降低的过程;端锚聚合酶1的 mRNA 水平及蛋白表达水平未发生变化;端粒末端保护蛋白1随着人胚肺成纤维细胞的衰老表达水平逐渐降低;端粒酶 RNA 组分随着细胞的衰老呈递增趋势;P53的蛋白表达未发生变化。综上认为,人端粒结合蛋白1、端粒末端保护蛋白1及端粒酶 RNA 在细胞的复制性衰老过程中起重要作用。     

ALT-associated promyelocytic leukaemia body (APB) detection as a reproducible tool to assess alternative lengthening of telomere stability in liposarcomas

Most cancers maintain telomeres by activating telomerase, but a significant minority, mainly of mesenchymal origin, utilize an alternative lengthening of telomeres (ALT) mechanism. We previously showed the presence of ALT, as detected by ALT-associated promyelocytic leukaemia bodies (APBs) by combined promyelocytic leukaemia immunofluorescence and telomere fluorescence-in situ hybridization, in approximately 25% of frozen specimens obtained from adult patient liposarcomas and proved that ALT negatively affects patient prognosis. In the present study, we assessed the reproducibility of APB detection on frozen versus formalin-fixed, paraffin-embedded specimens from the same liposarcoma specimens and investigated the eventual stability of ALT in 103 different lesions from 40 adult patients followed during their disease. Irrespective of liposarcoma subtype, we (1) confirmed the presence of ALT in 21.4% of tumours; (2) demonstrated the reliability of ALT-associated promyelocytic leukaemia body detection in formalin-fixed, paraffin-embedded sections (with qualitative concordance between matched frozen and formalin-fixed, paraffin-embedded samples in 29/30 specimens, and high quantitative agreement, as indicated by a Spearman correlation coefficient of 0.85); and (3) suggested the stability of ALT status during disease evolution, since the ALT mechanism was never acquired in the 29 patients with initially ALT-negative lesions and lost over time in only two of 11 patients with initially ALT-positive liposarcomas. In conclusion, these results confirm the possibility of investigating the ALT mechanism in archival specimens to obtain biologically relevant information on liposarcoma progression, even when the primary lesion is not available.     

A novel multiplex qPCR method for assessing the comparative lengths of telomeres

BackgroundThe comparative length of telomeres is considered to be related to diseases such as cancer, aging, and cardiovascular diseases. qPCR is currently one of the main methods for detecting telomere length. However, due to the unique sequence of telomeres (highly repetitive six‐base sequence), it is difficult to design primers and probes to expand and detect telomere and to put internal reference gene and telomere into the same tube for detection to reduce the possible inter‐pore errors and improve amplification efficiency. Besides, the stability and accuracy of the test results are greatly affected by the difference between reference genes and telomere copy number.MethodsIn this study, the single‐copy genes were replaced with high‐copy genes (300 copies) as the internal control to reduce the copy number difference of the internal genes and telomere. In addition, a multiplex qPCR system was constructed to detect the telomeres and an internal reference gene product. We also detected the lengths of telomeres in the genomic DNA in immortalized cells (293T and Hela) from different generations of cells.ResultsWe detected the comparative telomere lengths of 1500 random Chinese volunteers of different ages with the multiplex qPCR method; the result shows that the comparative length of telomeres is negatively related to age. In addition, we compared our qPCR detection method with a terminal restriction fragmentation (TRF) method. Both of them were highly consistent, indicating that the qPCR method was reliable.ConclusionsIn conclusion, we developed a stable, convenient, and accurate comparative telomere length detection method.