Interstitial lung diseases associated with mutations of poly(A)-specific ribonuclease: A multicentre retrospective study

BACKGROUND AND OBJECTIVE

Poly(A)-specific ribonuclease (PARN) mutations have been associated with familial pulmonary fibrosis. This study aims to describe the phenotype of patients with interstitial lung disease (ILD) and heterozygous PARN mutations.

METHODS

We performed a retrospective, observational, non-interventional study of patients with an ILD diagnosis and a pathogenic heterozygous PARN mutation followed up in a centre of the OrphaLung network.

RESULTS

We included 31 patients (29 from 16 kindreds and two sporadic patients). The median age at ILD diagnosis was 59 years (range 54 to 63). In total, 23 (74%) patients had a smoking history and/or fibrogenic exposure. The pulmonary phenotypes were heterogenous, but the most frequent diagnosis was idiopathic pulmonary fibrosis (n = 12, 39%). Haematological abnormalities were identified in three patients and liver disease in two. In total, 21 patients received a specific treatment for ILD: steroids (n = 13), antifibrotic agents (n = 11), immunosuppressants (n = 5) and N-acetyl cysteine (n = 2). The median forced vital capacity decline for the whole sample was 256 ml/year (range -363 to -148). After a median follow-up of 32 months (range 18 to 66), 10 patients had died and six had undergone lung transplantation. The median transplantation-free survival was 54 months (95% CI 29 to ∞). Extra-pulmonary features were less frequent with PARN mutation than telomerase reverse transcriptase (TERT) or telomerase RNA component (TERC) mutation.

CONCLUSION

IPF is common among individuals with PARN mutation, but other ILD subtypes may be observed.

Genetic predisposition to long telomeres is associated with increased mortality after melanoma: A study of 2101 melanoma patients from hospital clinics and the general population

Whether there is an association between measured and genetically predicted telomere length and melanoma mortality is unclear. We tested the hypothesis that measured and genetically predicted telomere length is associated with mortality after a melanoma diagnosis. We followed 2,101 patients with melanoma from hospital clinics and the general population for risk of death for up to 26 years. All had telomere length measured in DNA from leukocytes, and 2052 of these were genotyped for the three single nucleotide polymorphisms rs7726159 (TERT), rs1317082 (TERC), and rs2487999 (OBFC1); all three genotypes are associated with telomere length and combined into an allele count from 0 to 6. For each telomere-lengthening allele, the hazard ratios (HRs) for mortality in the age-adjusted and multivariable-adjusted Cox analysis were 1.12 (95% confidence interval: 1.02-1.23) and 1.11 (1.01-1.23). However, for each standard deviation increase in measured telomere length, HR for mortality was 0.97 (0.88-1.08). In conclusion, in more than 2000 melanoma patients from hospital clinics and from the general population, genetically predicted long telomeres were associated with increased mortality, but measured leukocyte telomere length was not.

Molecular Pathways of Cellular Senescence and Placental Aging in Late Fetal Growth Restriction and Stillbirth

Abnormally accelerated, premature placental senescence plays a crucial role in the genesis of pregnancy pathologies. Abnormal growth in the third trimester can present as small for gestational age fetuses or fetal growth restriction. One differs from the other by the presence of signs of placental insufficiency and the risk of stillbirth. The majority of stillbirths occur in normally grown fetuses and are classified as "unexplained", which often leads to conclusions that they were unpreventable. The main characteristic of aging is a gradual decline in the function of cells, tissues, and organs. These changes result in the accumulation of senescent cells in mitotic tissues. These cells begin the aging process that disrupts tissues' normal functions by affecting neighboring cells, degrading the extracellular matrix, and reducing tissues' regeneration capacity. Different degrees of abnormal placentation result in the severity of fetal growth restriction and its sequelae, including fetal death. This review aims to present the current knowledge and identify future research directions to understand better placental aging in late fetal growth restriction and unexplained stillbirth. We hypothesized that the final diagnosis of placental insufficiency can be made only using markers of placental senescence.

The Interactions of DNA Repair, Telomere Homeostasis, and p53 Mutational Status in Solid Cancers: Risk, Prognosis, and Prediction

The disruption of genomic integrity due to the accumulation of various kinds of DNA damage, deficient DNA repair capacity, and telomere shortening constitute the hallmarks of malignant diseases. DNA damage response (DDR) is a signaling network to process DNA damage with importance for both cancer development and chemotherapy outcome. DDR represents the complex events that detect DNA lesions and activate signaling networks (cell cycle checkpoint induction, DNA repair, and induction of cell death). TP53, the guardian of the genome, governs the cell response, resulting in cell cycle arrest, DNA damage repair, apoptosis, and senescence. The mutational status of TP53 has an impact on DDR, and somatic mutations in this gene represent one of the critical events in human carcinogenesis. Telomere dysfunction in cells that lack p53-mediated surveillance of genomic integrity along with the involvement of DNA repair in telomeric DNA regions leads to genomic instability. While the role of individual players (DDR, telomere homeostasis, and TP53) in human cancers has attracted attention for some time, there is insufficient understanding of the interactions between these pathways. Since solid cancer is a complex and multifactorial disease with considerable inter- and intra-tumor heterogeneity, we mainly dedicated this review to the interactions of DNA repair, telomere homeostasis, and TP53 mutational status, in relation to (a) cancer risk, (b) cancer progression, and (c) cancer therapy.

Prognostic impact of telomeric repeat-containing RNA expression on long-term oncologic outcomes in colorectal cancer

Telomeres are transcribed into long, noncoding telomeric repeat-containing RNAs (TERRA) that have been implicated in the regulation of telomerase, the enzyme that lengthens telomeres, in heterochromatin formation at telomeres, and in telomere stability. This study aimed to evaluate the correlation between TERRA expression and long-term oncologic outcomes in colorectal cancer (CRC).We evaluated 18p TERRA expression and telomere length using quantitative real-time PCR in 60 patients who underwent surgical resection for CRC between June 2008 and November 2010.Patients were grouped according to 18p TERRA expression, with 29 (48.3%) and 31 (51.7%) patients in the low and high TERRA expression groups, respectively. The median follow-up period was 80 months (range 2-103). The 18p TERRA expression was marginally significantly associated with preoperative carcinoembryonic antigen (CEA; P = .082) and was significantly associated with telomere length (P < .05). Multivariate analysis revealed that preoperative CEA (hazard ratio [HR], 2.728; 95% confidence interval [CI], 0.832-8.944, P = .098) and 18p TERRA expression (HR, 0.113; 95% CI, 0.011-1.126, P = .071) were marginally significant independent prognostic factors for overall survival (OS), whereas preoperative CEA (HR, 4.254; 95% CI, 1.394-12.985, P = .011) and 18p TERRA expression (HR, 0.108; 95% CI, 0.011-1.037, P = .054) were significant independent prognostic factors for disease-free survival (DFS). According to our prognostic model with 2 prognostic factors, the OS and DFS rate increased to 76.2% and 80.63%, respectively, in patients with high 18p TERRA expression and CEA levels ≤5 (P = .178, P = .057, respectively).18p TERRA expression was marginally significantly associated with preoperative CEA and significantly associated with telomere length, rendering it a potential prognostic factor for long-term oncologic outcomes in CRC.

The RNA interactome of human telomerase RNA reveals a coding-independent role for a histone mRNA in telomere homeostasis

Telomerase RNA (TR) provides the template for DNA repeat synthesis at telomeres and is essential for genome stability in continuously dividing cells. We mapped the RNA interactome of human TR (hTR) and identified a set of non-coding and coding hTR-interacting RNAs, including the histone 1C mRNA (HIST1H1C). Disruption of the hTR-HIST1H1C RNA association resulted in markedly increased telomere elongation without affecting telomerase enzymatic activity. Conversely, over-expression of HIST1H1C led to telomere attrition. By using a combination of mutations to disentangle the effects of histone 1 RNA synthesis, protein expression, and hTR interaction, we show that HIST1H1C RNA negatively regulates telomere length independently of its protein coding potential. Taken together, our data provide important insights into a surprisingly complex hTR-RNA interaction network and define an unexpected non-coding RNA role for HIST1H1C in regulating telomere length homeostasis, thus offering a glimpse into the mostly uncharted, vast space of non-canonical messenger RNA functions.

Shepherding DNA ends: Rif1 protects telomeres and chromosome breaks

Cells have evolved conserved mechanisms to protect DNA ends, such as those at the termini of linear chromosomes, or those at DNA double-strand breaks (DSBs). In eukaryotes, DNA ends at chromosomal termini are packaged into proteinaceous structures called telomeres. Telomeres protect chromosome ends from erosion, inadvertent activation of the cellular DNA damage response (DDR), and telomere fusion. In contrast, cells must respond to damage-induced DNA ends at DSBs by harnessing the DDR to restore chromosome integrity, avoiding genome instability and disease. Intriguingly, Rif1 (Rap1-interacting factor 1) has been implicated in telomere homeostasis as well as DSB repair. The protein was first identified in Saccharomyces cerevisiae as being part of the proteinaceous telosome. In mammals, RIF1 is not associated with intact telomeres, but was found at chromosome breaks, where RIF1 has emerged as a key mediator of pathway choice between the two evolutionary conserved DSB repair pathways of non-homologous end-joining (NHEJ) and homologous recombination (HR). While this functional dichotomy has long been a puzzle, recent findings link yeast Rif1 not only to telomeres, but also to DSB repair, and mechanistic parallels likely exist. In this review, we will provide an overview of the actions of Rif1 at DNA ends and explore how exclusion of end-processing factors might be the underlying principle allowing Rif1 to fulfill diverse biological roles at telomeres and chromosome breaks.

BRCA1/2 mutations perturb telomere biology: characterization of structural and functional abnormalities in vitro and in vivo

BRCA1 mutation is associated with carcinogenesis, especially of breast tissue. Telomere maintenance is crucial for malignant transformation. Being a part of the DNA repair machinery, BRCA1 may be implicated in telomere biology. We explored the role of BRCA1 in telomere maintenance in lymphocytes of BRCA1/2 mutation carriers and in in vitro system by knocking down its expression in non-malignant breast epithelial cells.The results in both systems were similar. BRCA1/2 mutation caused perturbation of telomere homeostasis, shortening of the single stranded telomere overhang and increased the intercellular telomere length variability as well as the number of telomere free chromosomal ends and telomeric circles. These changes resulted in an increased DNA damage status. Telomerase activity, inducibility and expression remained unchanged. BRCA1 mutation resulted also in changes in the binding of shelterin proteins to telomeres. DNMT-1 levels were markedly reduced both in the carriers and in in vitro system. The methylation pattern of the sub-telomeric regions in carriers suggested hypomethylation in chromosome 10. The expression of a distinct set of genes was also changed, some of which may relate to pre-disposition to malignancy.These results show that BRCA gene products have a role in telomere length homeostasis. It is plausible that these perturbations contribute to malignant transformation in BRCA mutants.

Cellular aging in depression: Permanent imprint or reversible process?: An overview of the current evidence, mechanistic pathways, and targets for interventions

Depression might be associated with accelerated cellular aging. However, does this result in an irreversible state or is the body able to slow down or recover from such a process? Telomeres are DNA-protein complexes that protect the ends of chromosomes and generally shorten with age; and therefore index cellular aging. The majority of studies indicate that persons with depression have shorter leukocyte telomeres than similarly aged non-depressed persons, which may contribute to the observed unfavorable somatic health outcomes in the depressed population. Some small-scale preliminary studies raise the possibility that behavioral or pharmacological interventions may either slow down or else reverse this accelerated telomere shortening, possibly through increasing the activity of the telomere-lengthening enzyme telomerase. This paper covers the current state of evidence in the relationship between depression and the telomere-telomerase system and debates whether depression-related cellular aging should be considered a reversible process or permanent damage.