Project description:Mammalian telomeres are formed by tandem repeats of the TTAGGG sequence, and shorten with each round of cell division in the absence of telomerase. Telomere shortening and dysfunction has been implicated in the pathology of several age-related diseases and premature ageing syndromes. Telomerase is important for telomere length maintenance. Telomerase RNA component, also known as TERC, is a component of telomerase. Terc knockout leads to telomerase deficiency and telomere shortening. Heterozygous telomerase-deficient (Terc+/-) mice were housed and bred for homozygous generation. ESC lines were generated with high efficiency from wild-type (WT, Terc+/+), heterozygous (Het, Terc+/-) and early- to late-generation (G1, G3 and G4) Terc-/- mouse blastocysts. Telomeres were shorter in Terc+/- ES cells than in WT ES cells, and further shortened from G1 to G4 Terc-/- ES cells. We took advantage of ES cell lines with various telomere lengths to investigate roles of telomere length on differentiation capacity of ES cells. We found that telomere length, but not telomerase activity, is required for differentiation of ES cells into epidermis. We performed microarray analysis to investigate differential gene expression profile at genome-wide levels between WT and G3/G4 Terc-/- (KO) mouse ES cells and during differentiation in vitro of WT and G4 Terc-/- mouse ES cells.
Project description:We asked whether telomere shortening impairs differentiation of ESCs into germ cell lineage. Terc-/- ESCs were used to investigate the effects of short telomeres on germ cell specification by in vitro differentiation. Short telomeres greatly reduced induction of PGCLCs from ESCs. Mechanistically, short telomeres resulted in excessive chromatin accessibility, which in turn activated the genes regulated by chromatin. Notably, Fst overexpression reduced BMP-Smad signaling and thus induction of PGCLCs, meanwhile upregulation of MAPK signaling pathway increase somatic lineage differentiation in short telomeres sampels. Moreover, knockin of Terc gene by CRISPR/Cas9 in Terc-/- ESCs restored telomere length and normal gene expression profile, and rescued PGCLC induction, revealing important roles of telomeres in PGC fate decision.
Project description:Telomeres play vital roles in ensuring chromosome stability and are thus closely linked with the onset of aging and human disease. Telomeres undergo extensive lengthening during early embryogenesis. However, the detailed molecular mechanism of telomere resetting in early embryos remains unknown. Here, we show that Dcaf11 (Ddb1- and Cul4-associated factor 11) participates in telomere elongation in early embryos and 2-cell-like embryonic stem cells (ESCs). The deletion of Dcaf11 in embryos and ESCs leads to reduced telomere sister-chromatid exchange (T-SCE) and impairs telomere lengthening. Importantly, Dcaf11-deficient mice exhibit gradual telomere erosion with successive generations, and hematopoietic stem cell (HSC) activity is also greatly compromised. Mechanistically, Dcaf11 targets Kap1 (KRAB-associated protein 1) for ubiquitination-mediated degradation, leading to the activation of Zscan4 downstream enhancer and the removal of heterochromatic H3K9me3 at telomere/subtelomere regions. Our study therefore demonstrates that Dcaf11 plays important roles in telomere elongation in early embryos and ESCs through activating Zscan4.
Project description:Telomere shortening is universally acquired with aging in humans, but the contribution of telomere shortening to immune aging is not fully understood. Here, we studied T cells derived from short telomere syndrome patients and compared their T cell profile and function to controls and elderly individuals who had normal age-adjusted telomere length. The short telomere syndrome patients were all under age 40 and carried mutant telomerase or telomere genes and had telomere lengths below the 1st age-adjusted percentile. The T cell profile of young short telomere syndrome patients resembled those that were five decades older including a depletion of naive T cell population and accumulation of terminally differentiated effector cells. To test whether short telomeres affect the quality of these cells, we performed a gene expression microarray. The data are summarized here. We found that although numerically expanded in both short telomere and elderly cases, the gene expression microarrays were distinct with short telomere cells predominately upregulating gene expression of DNA damage pathways and elderly T cells upregulating cell extrinsic apoptotic pathways. The goal of the experiment is to highlight important genes and pathways that may drive immune aging in short telomere syndromes and which may also contribute to normal immune aging.
Project description:The telomerase RNA component (TERC) is a critical determinant of cellular self renewal. Poly(A)-specific ribonuclease (PARN) is required for post-transcriptional maturation of TERC. PARN mutations lead to incomplete 3â² end processing and increased destruction of nascent TERC RNA transcripts, resulting in telomerase deficiency and telomere diseases. Here, we determined that overexpression of TERC increased telomere length in PARN-deficient cells and hypothesized that decreasing post-transcriptional 3â² oligo-adenylation of TERC would counteract the deleterious effects of PARN mutations. Inhibition of the noncanonical poly(A) polymerase PAP-associated domainâcontaining 5 (PAPD5) increased TERC levels in PARN-mutant patient cells. PAPD5 inhibition was also associated with increases in TERC stability, telomerase activity, and telomere elongation. Our results demonstrate that manipulating post-transcriptional regulatory pathways may be a potential strategy to reverse the molecular hallmarks of telomere disease. mRNA sequencing of induced pluripotent stem cells and 293 cell line.