Improved methods to measure the shortest (not just average) telomere lengths (TLs) are needed. We developed Telomere Shortest Length Assay (TeSLA), a technique that detects telomeres from all chromosome ends from <1 kb to 18 kb using small amounts of input DNA. TeSLA improves the specificity and efficiency of TL measurements that is facilitated by user friendly image-processing software to automatically detect and annotate band sizes, calculate average TL, as well as the percent of the shortest telomeres. Compared with other TL measurement methods, TeSLA provides more information about the shortest telomeres. The length of telomeres was measured longitudinally in peripheral blood mononuclear cells during human aging, in tissues during colon cancer progression, in telomere-related diseases such as idiopathic pulmonary fibrosis, as well as in mice and other organisms. The results indicate that TeSLA is a robust method that provides a better understanding of the shortest length of telomeres.

Alternative splicing is dysregulated in cancer and the reactivation of telomerase involves the splicing of TERT transcripts to produce full-length (FL) TERT. Knowledge about the splicing factors that enhance or silence FL hTERT is lacking. We identified splicing factors that reduced telomerase activity and shortened telomeres using a siRNA minigene reporter screen and a lung cancer cell bioinformatics approach. A lead candidate, NOVA1, when knocked down resulted in a shift in hTERT splicing to non-catalytic isoforms, reduced telomerase activity, and progressive telomere shortening. NOVA1 knockdown also significantly altered cancer cell growth in vitro and in xenografts. Genome engineering experiments reveal that NOVA1 promotes the inclusion of exons in the reverse transcriptase domain of hTERT resulting in the production of FL hTERT transcripts. Utilizing hTERT splicing as a model splicing event in cancer may provide new insights into potentially targetable dysregulated splicing factors in cancer.

Alternative splicing is dysregulated in cancer cells, driving the production of isoforms that allow tumor cells to survive and continuously proliferate. Part of the reactivation of telomerase involves the splicing of hTERT transcripts to produce full-length (FL) TERT . Very few splicing factors to date have been described to interact with hTERT and promote the production of FL TERT . We recently described one such splicing factor, NOVA1, that acts as an enhancer of FL hTERT splicing, increases telomerase activity, and promotes telomere maintenance in cancer cells. NOVA1 is expressed primarily in neurons and is involved in neurogenesis. In the present studies, we describe that polypyrimidine-tract binding proteins (PTBPs), which are also typically involved in neurogenesis, are also participating in the splicing of hTERT to FL in cancer. Knockdown experiments of PTBP1 in cancer cells indicate that PTBP1 reduces hTERT FL splicing and telomerase activity. Stable knockdown of PTBP1 results in progressively shortened telomere length in H1299 and H920 lung cancer cells. RNA pulldown experiments reveal that PTBP1 interacts with hTERT pre-mRNA in a NOVA1 dependent fashion. Knockdown of PTBP1 increases the expression of PTBP2 which also interacts with NOVA1, potentially preventing the association of NOVA1 with hTERT pre-mRNA. These new data highlight that splicing in cancer cells is regulated by competition for splice sites and that combinations of splicing factors interact at cis regulatory sites on pre-mRNA transcripts. By employing hTERT as a model gene, we show the coordination of the splicing factors NOVA1 and PTBP1 in cancer by regulating telomerase that is expressed in the vast majority of cancer cell types.

It is generally recognized that the function of the immune system declines with increased age and one of the major immune changes is impaired T‐cell responses upon antigen presentation/stimulation. Some “high‐performing” centenarians (100+ years old) are remarkably successful in escaping, or largely postponing, major age‐related diseases. However, the majority of centenarians (“low‐performing”) have experienced these pathologies and are forced to reside in long‐term nursing facilities. Previous studies have pooled all centenarians examining heterogeneous populations of resting/unstimulated peripheral blood mononuclear cells (PBMCs). T cells represent around 60% of PBMC and are in a quiescence state when unstimulated. However, upon stimulation, T cells rapidly divide and exhibit dramatic changes in gene expression. We have compared stimulated T‐cell responses and identified a set of transcripts expressed in vitro that are dramatically different in high‐ vs. low‐performing centenarians. We have also identified several other measurements that are different between high‐ and low‐performing centenarians: (a) The amount of proliferation following in vitro stimulation is dramatically greater in high‐performing centenarians compared to 67‐ to 83‐year‐old controls and low‐performing centenarians; (b) telomere length is greater in the high‐performing centenarians; and (c) telomerase activity following stimulation is greater in the high‐performing centenarians. In addition, we have validated a number of genes whose expression is directly related to telomere length and these are potential fundamental biomarkers of aging that may influence the risk and progression of multiple aging conditions.

Mitochondria are involved in a number of diverse cellular functions, including energy production, metabolic regulation, apoptosis, calcium homeostasis, cell proliferation, and motility, as well as free radical generation. Mitochondrial DNA (mtDNA) is present at hundreds to thousands of copies per cell in a tissue-specific manner. mtDNA copy number also varies during aging and disease progression and therefore might be considered as a biomarker that mirrors alterations within the human body. Here, we present a new quantitative, highly sensitive droplet digital PCR (ddPCR) method, droplet digital mitochondrial DNA measurement (ddMDM), to measure mtDNA copy number not only from cell populations but also from single cells. Our developed assay can generate data in as little as 3 h, is optimized for 96-well plates, and also allows the direct use of cell lysates without the need for DNA purification or nuclear reference genes. We show that ddMDM is able to detect differences between samples whose mtDNA copy number was close enough as to be indistinguishable by other commonly used mtDNA quantitation methods. By utilizing ddMDM, we show quantitative changes in mtDNA content per cell across a wide variety of physiological contexts including cancer progression, cell cycle progression, human T cell activation, and human aging.

The steady and dramatic increase in the incidence of Alzheimer's disease (AD) and the lack of effective treatments have stimulated the search for strategies to prevent or delay its onset and/or progression. Since the diagnosis of dementia requires a number of established features that are present when the disease is fully developed, but not always in the early stages, the need for a biological marker has proven to be urgent, in terms of both diagnosis and monitoring of AD. AD has been shown to affect peripheral blood mononuclear cells (PBMCs) that are a critical component of the immune system which provide defence against infection. Although studies are continuously supplying additional data that emphasize the central role of inflammation in AD, PBMCs have not been sufficiently investigated in this context. Delineating biochemical alterations in AD blood constituents may prove valuable in identifying accessible footprints that reflect degenerative processes within the Central Nervous System (CNS). In this review, we address the role of biomarkers in AD with a focus on the notion that PBMCs may serve as a peripheral laboratory to find molecular signatures that could aid in differential diagnosis with other forms of dementia and in monitoring of disease progression.

Telomerase activity is not readily detected in resting human T lymphocytes, however upon antigen presentation, telomerase is transiently upregulated. Presently, it is not known if telomerase activation is necessary for the proliferation of T cells or for the maintenance of telomere lengths. In this study, we found that telomerase activation is not required for the short- term proliferation of T cells and that telomeres progressively shorten in a heterogeneous population of T cells, even if telomerase is detected. By measuring telomerase activity at the single-cell level using quantitative ddPCR techniques (ddTRAP) and by monitoring changes in the shortest telomeres with more sensitive telomere length measurement assays, we show that only a subset of CD28+ T-cells have robust telomerase activity upon stimulation and are capable of maintaining their telomere lengths during induced proliferation. The study of this T-cell subset may lead to a better understanding on how telomerase is regulated and functions in immune cells.

Hutchinson–Gilford progeria syndrome (HGPS) is characterized by accelerated senescence due to a de novo mutation in the LMNA gene. The mutation produces an abnormal lamin A protein called progerin that lacks the splice site necessary to remove a farnesylated domain. Subsequently, progerin accumulates in the nuclear envelope, disrupting nuclear architecture, chromatin organization, and gene expression. These alterations are often associated with rapid telomere erosion and cellular aging. Here, we further characterize the cellular and molecular abnormalities in HGPS cells and report a significant reversal of some of these abnormalities by introduction of in vitro transcribed and purified human telomerase (hTERT) mRNA. There is intra‐individual heterogeneity of expression of telomere‐associated proteins DNA PKcs/Ku70/Ku80, with low‐expressing cells having shorter telomeres. In addition, the loss of the heterochromatin marker H3K9me3 in progeria is associated with accelerated telomere erosion. In HGPS cell lines characterized by short telomeres, transient transfections with hTERT mRNA increase telomere length, increase expression of telomere‐associated proteins, increase proliferative capacity and cellular lifespan, and reverse manifestations of cellular senescence as assessed by β‐galactosidase expression and secretion of inflammatory cytokines. Unexpectedly, mRNA hTERT also improves nuclear morphology. In combination with the farnesyltransferase inhibitor (FTI) lonafarnib, hTERT mRNA promotes HGPS cell proliferation. Our findings demonstrate transient expression of human telomerase in combination with FTIs could represent an improved therapeutic approach for HGPS.