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Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome, caused by genetic mutations that principally affect telomere biology. Approximately 35% of cases remain uncharacterised at the genetic level. To explore the genetic landscape, we conducted genetic studies on a large collection of clinically diagnosed cases of DC as well as cases exhibiting features resembling DC, referred to as 'DC-like' (DCL). This led us to identify several novel pathogenic variants within known genetic loci and in the novel X-linked gene, POLA1. In addition, we have also identified several novel variants in POT1 and ZCCHC8 in multiple cases from different families expanding the allelic series of DC and DCL phenotypes. Functional characterisation of novel POLA1 and POT1 variants, revealed pathogenic effects on protein-protein interactions with primase, CTC1-STN1-TEN1 (CST) and shelterin subunit complexes, that are critical for telomere maintenance. ZCCHC8 variants demonstrated ZCCHC8 deficiency and signs of pervasive transcription, triggering inflammation in patients' blood. In conclusion, our studies expand the current genetic architecture and broaden our understanding of disease mechanisms underlying DC and DCL disorders., (© 2024. The Author(s).)

Biallelic germ line excision repair cross-complementing 6 like 2 (ERCC6L2) variants strongly predispose to bone marrow failure (BMF) and myeloid malignancies, characterized by somatic TP53-mutated clones and erythroid predominance. We present a series of 52 subjects (35 families) with ERCC6L2 biallelic germ line variants collected retrospectively from 11 centers globally, with a follow-up of 1165 person-years. At initial investigations, 32 individuals were diagnosed with BMF and 15 with a hematological malignancy (HM). The subjects presented with 19 different variants of ERCC6L2, and we identified a founder mutation, c.1424delT, in Finnish patients. The median age of the subjects at baseline was 18 years (range, 2-65 years). Changes in the complete blood count were mild despite severe bone marrow (BM) hypoplasia and somatic TP53 mutations, with no significant difference between subjects with or without HMs. Signs of progressive disease included increasing TP53 variant allele frequency, dysplasia in megakaryocytes and/or erythroid lineage, and erythroid predominance in the BM morphology. The median age at the onset of HM was 37.0 years (95% CI, 31.5-42.5; range, 12-65 years). The overall survival (OS) at 3 years was 95% (95% CI, 85-100) and 19% (95% CI, 0-39) for patients with BMF and HM, respectively. Patients with myelodysplastic syndrome or acute myeloid leukemia with mutated TP53 undergoing hematopoietic stem cell transplantation had a poor outcome with a 3-year OS of 28% (95% CI, 0-61). Our results demonstrated the importance of early recognition and active surveillance in patients with biallelic germ line ERCC6L2 variants., (© 2023 by The American Society of Hematology.)

Despite the inclusion of inherited myeloid malignancies as a separate entity in the World Health Organization Classification, many established predisposing loci continue to lack functional characterization. While germline mutations in the DNA repair factor ERCC excision repair 6 like 2 (ERCC6L2) give rise to bone marrow failure and acute myeloid leukaemia, their consequences on normal haematopoiesis remain unclear. To functionally characterise the dual impact of germline ERCC6L2 loss on human primary haematopoietic stem/progenitor cells (HSPCs) and mesenchymal stromal cells (MSCs), we challenged ERCC6L2-silenced and patient-derived cells ex vivo. Here, we show for the first time that ERCC6L2-deficiency in HSPCs significantly impedes their clonogenic potential and leads to delayed erythroid differentiation. This observation was confirmed by CIBERSORTx RNA-sequencing deconvolution performed on ERCC6L2-silenced erythroid-committed cells, which demonstrated higher proportions of polychromatic erythroblasts and reduced orthochromatic erythroblasts versus controls. In parallel, we demonstrate that the consequences of ERCC6L2-deficiency are not limited to HSPCs, as we observe a striking phenotype in patient-derived and ERCC6L2-silenced MSCs, which exhibit enhanced osteogenesis and suppressed adipogenesis. Altogether, our study introduces a valuable surrogate model to study the impact of inherited myeloid mutations and highlights the importance of accounting for the influence of germline mutations in HSPCs and their microenvironment., (© 2022 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Inherited bone marrow (BM) failure syndromes are a diverse group of disorders characterized by BM failure, usually in association with ≥1 extrahematopoietic abnormalities. BM failure, which can involve ≥1 cell lineages, often presents in the pediatric age group. Furthermore, some children initially labeled as having idiopathic aplastic anemia or myelodysplasia represent cryptic cases of inherited BM failure. Significant advances in the genetics of these syndromes have been made, identifying more than 100 disease genes, giving insights into normal hematopoiesis and how it is disrupted in patients with BM failure. They have also provided important information on fundamental biological pathways, including DNA repair: Fanconi anemia (FA) genes; telomere maintenance: dyskeratosis congenita (DC) genes; and ribosome biogenesis: Shwachman-Diamond syndrome and Diamond-Blackfan anemia genes. In addition, because these disorders are usually associated with extrahematopoietic abnormalities and increased risk of cancer, they have provided insights into human development and cancer. In the clinic, genetic tests stemming from the recent advances facilitate diagnosis, especially when clinical features are insufficient to accurately classify a disorder. Hematopoietic stem cell transplantation using fludarabine-based protocols has significantly improved outcomes, particularly in patients with FA or DC. Management of some other complications, such as cancer, remains a challenge. Recent studies have suggested the possibility of new and potentially more efficacious therapies, including a renewed focus on hematopoietic gene therapy and drugs [transforming growth factor-β inhibitors for FA and PAPD5, a human poly(A) polymerase, inhibitors for DC] that target disease-specific defects., (© 2022 by The American Society of Hematology.)

Dyskeratosis congenita (DC) is an inherited bone-marrow-failure disorder characterized by a triad of mucocutaneous features that include abnormal skin pigmentation, nail dystrophy, and oral leucoplakia. Despite the identification of several genetic variants that cause DC, a significant proportion of probands remain without a molecular diagnosis. In a cohort of eight independent DC-affected families, we have identified a remarkable series of heterozygous germline variants in the gene encoding thymidylate synthase (TYMS). Although the inheritance appeared to be autosomal recessive, one parent in each family had a wild-type TYMS coding sequence. Targeted genomic sequencing identified a specific haplotype and rare variants in the naturally occurring TYMS antisense regulator ENOSF1 (enolase super family 1) inherited from the other parent. Lymphoblastoid cells from affected probands have severe TYMS deficiency, altered cellular deoxyribonucleotide triphosphate pools, and hypersensitivity to the TYMS-specific inhibitor 5-fluorouracil. These defects in the nucleotide metabolism pathway resulted in genotoxic stress, defective transcription, and abnormal telomere maintenance. Gene-rescue studies in cells from affected probands revealed that post-transcriptional epistatic silencing of TYMS is occurring via elevated ENOSF1. These cell and molecular abnormalities generated by the combination of germline digenic variants at the TYMS-ENOSF1 locus represent a unique pathogenetic pathway for DC causation in these affected individuals, whereas the parents who are carriers of either of these variants in a singular fashion remain unaffected., Competing Interests: Declaration of interests The authors declare no competing interest., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Gene expression profiling has long been used in understanding the contribution of genes and related pathways in disease pathogenesis and susceptibility. We have performed whole-blood transcriptomic profiling in a subset of patients with inherited bone marrow failure (IBMF) whose diseases are clinically and genetically characterized as Fanconi anemia (FA), Shwachman-Diamond syndrome (SDS), and dyskeratosis congenita (DC). We hypothesized that annotating whole-blood transcripts genome wide will aid in understanding the complexity of gene regulation across these IBMF subtypes. Initial analysis of these blood-derived transcriptomes revealed significant skewing toward upregulated genes in patients with FA when compared with controls. Patients with SDS or DC also showed similar skewing profiles in their transcriptional status revealing a common pattern across these different IBMF subtypes. Gene set enrichment analysis revealed shared pathways involved in protein translation and elongation (ribosome constituents), RNA metabolism (nonsense-mediated decay), and mitochondrial function (electron transport chain). We further identified a discovery set of 26 upregulated genes at stringent cutoff (false discovery rate < 0.05) that appeared as a unified signature across the IBMF subtypes. Subsequent transcriptomic analysis on genetically uncharacterized patients with BMF revealed a striking overlap of genes, including 22 from the discovery set, which indicates a unified transcriptional drive across the classic (FA, SDS, and DC) and uncharacterized BMF subtypes. This study has relevance in disease pathogenesis, for example, in explaining the features (including the BMF) common to all patients with IBMF and suggests harnessing this transcriptional signature for patient benefit., (© 2021 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Telomere biology disorders are complex clinical conditions that arise due to mutations in genes required for telomere maintenance. Telomere length has been utilised as part of the diagnostic work-up of patients with these diseases; here, we have tested the utility of high-throughput STELA (HT-STELA) for this purpose. HT-STELA was applied to a cohort of unaffected individuals (n = 171) and a retrospective cohort of mutation carriers (n = 172). HT-STELA displayed a low measurement error with inter- and intra-assay coefficient of variance of 2.3% and 1.8%, respectively. Whilst telomere length in unaffected individuals declined as a function of age, telomere length in mutation carriers appeared to increase due to a preponderance of shorter telomeres detected in younger individuals (< 20 years of age). These individuals were more severely affected, and age-adjusted telomere length differentials could be used to stratify the cohort for overall survival (Hazard Ratio = 5.6 (1.5-20.5); p < 0.0001). Telomere lengths of asymptomatic mutation carriers were shorter than controls (p < 0.0001), but longer than symptomatic mutation carriers (p < 0.0001) and telomere length heterogeneity was dependent on the diagnosis and mutational status. Our data show that the ability of HT-STELA to detect short telomere lengths, that are not readily detected with other methods, means it can provide powerful diagnostic discrimination and prognostic information. The rapid format, with a low measurement error, demonstrates that HT-STELA is a new high-quality laboratory test for the clinical diagnosis of an underlying telomeropathy.

Inherited bone marrow failure (BMF) syndromes are a heterogeneous group of diseases characterized by defective hematopoiesis and often predisposing to myelodysplastic syndrome (MDS) and acute myelogenous leukemia. We have studied a large family consisting of several affected individuals with hematologic abnormalities, including one family member who died of acute leukemia. By whole-exome sequencing, we identified a novel frameshift variant in the ubiquitously expressed transcription factor specificity protein 1 ( SP1 ). This heterozygous variant (c.1995delA) truncates the canonical Sp1 molecule in the highly conserved C-terminal DNA-binding zinc finger domains. Transcriptomic analysis and gene promoter characterization in patients' blood revealed a hypermorphic effect of this Sp1 variant, triggering superactivation of Sp1-mediated transcription and driving significant up-regulation of Sp1 target genes. This familial genetic study indicates a central role for Sp1 in causing autosomal dominant transmission of BMF, thereby confirming its critical role in hematopoiesis in humans., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

The inclusion of familial myeloid malignancies as a separate disease entity in the revised WHO classification has renewed efforts to improve the recognition and management of this group of at risk individuals. Here we report a cohort of 86 acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) families with 49 harboring germline variants in 16 previously defined loci (57%). Whole exome sequencing in a further 37 uncharacterized families (43%) allowed us to rationalize 65 new candidate loci, including genes mutated in rare hematological syndromes (ADA, GP6, IL17RA, PRF1 and SEC23B), reported in prior MDS/AML or inherited bone marrow failure series (DNAH9, NAPRT1 and SH2B3) or variants at novel loci (DHX34) that appear specific to inherited forms of myeloid malignancies. Altogether, our series of MDS/AML families offer novel insights into the etiology of myeloid malignancies and provide a framework to prioritize variants for inclusion into routine diagnostics and patient management.

Standardized variant curation is essential for clinical care recommendations for patients with inherited disorders. Clinical Genome Resource (ClinGen) variant curation expert panels are developing disease-associated gene specifications using the 2015 American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines to reduce curation discrepancies. The ClinGen Myeloid Malignancy Variant Curation Expert Panel (MM-VCEP) was created collaboratively between the American Society of Hematology and ClinGen to perform gene- and disease-specific modifications for inherited myeloid malignancies. The MM-VCEP began optimizing ACMG/AMP rules for RUNX1 because many germline variants have been described in patients with familial platelet disorder with a predisposition to acute myeloid leukemia, characterized by thrombocytopenia, platelet functional/ultrastructural defects, and a predisposition to hematologic malignancies. The 28 ACMG/AMP codes were tailored for RUNX1 variants by modifying gene/disease specifications, incorporating strength adjustments of existing rules, or both. Key specifications included calculation of minor allele frequency thresholds, formulating a semi-quantitative approach to counting multiple independent variant occurrences, identifying functional domains and mutational hotspots, establishing functional assay thresholds, and characterizing phenotype-specific guidelines. Preliminary rules were tested by using a pilot set of 52 variants; among these, 50 were previously classified as benign/likely benign, pathogenic/likely pathogenic, variant of unknown significance (VUS), or conflicting interpretations (CONF) in ClinVar. The application of RUNX1-specific criteria resulted in a reduction in CONF and VUS variants by 33%, emphasizing the benefit of gene-specific criteria and sharing internal laboratory data., (© 2019 by The American Society of Hematology.)

Biallelic variants in the ERCC excision repair 6 like 2 gene ( ERCC6L2 ) are known to cause bone marrow failure (BMF) due to defects in DNA repair and mitochondrial function. Here, we report on eight cases of BMF from five families harboring biallelic variants in ERCC6L2 , two of whom present with myelodysplasia. We confirm that ERCC6L2 patients' lymphoblastoid cell lines (LCLs) are hypersensitive to DNA-damaging agents that specifically activate the transcription coupled nucleotide excision repair (TCNER) pathway. Interestingly, patients' LCLs are also hypersensitive to transcription inhibitors that interfere with RNA polymerase II (RNA Pol II) and display an abnormal delay in transcription recovery. Using affinity-based mass spectrometry we found that ERCC6L2 interacts with DNA-dependent protein kinase (DNA-PK), a regulatory component of the RNA Pol II transcription complex. Chromatin immunoprecipitation PCR studies revealed ERCC6L2 occupancy on gene bodies along with RNA Pol II and DNA-PK. Patients' LCLs fail to terminate transcript elongation accurately upon DNA damage and display a significant increase in nuclear DNA-RNA hybrids (R loops). Collectively, we conclude that ERCC6L2 is involved in regulating RNA Pol II-mediated transcription via its interaction with DNA-PK to resolve R loops and minimize transcription-associated genome instability. The inherited BMF syndrome caused by biallelic variants in ERCC6L2 can be considered as a primary transcription deficiency rather than a DNA repair defect., Competing Interests: The authors declare no conflict of interest., (Copyright © 2018 the Author(s). Published by PNAS.)

Summary: Phenopolis is an open-source web server providing an intuitive interface to genetic and phenotypic databases. It integrates analysis tools such as variant filtering and gene prioritization based on phenotype. The Phenopolis platform will accelerate clinical diagnosis, gene discovery and encourage wider adoption of the Human Phenotype Ontology in the study of rare genetic diseases., Availability and Implementation: A demo of the website is available at https://phenopolis.github.io . If you wish to install a local copy, source code and installation instruction are available at https://github.com/phenopolis . The software is implemented using Python, MongoDB, HTML/Javascript and various bash shell scripts., Contact: n.pontikos@ucl.ac.uk., Supplementary Information: Supplementary data are available at Bioinformatics online., (© The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com)

Deep phenotyping has been defined as the precise and comprehensive analysis of phenotypic abnormalities in which the individual components of the phenotype are observed and described. The three components of the Human Phenotype Ontology (HPO; www.human-phenotype-ontology.org) project are the phenotype vocabulary, disease-phenotype annotations and the algorithms that operate on these. These components are being used for computational deep phenotyping and precision medicine as well as integration of clinical data into translational research. The HPO is being increasingly adopted as a standard for phenotypic abnormalities by diverse groups such as international rare disease organizations, registries, clinical labs, biomedical resources, and clinical software tools and will thereby contribute toward nascent efforts at global data exchange for identifying disease etiologies. This update article reviews the progress of the HPO project since the debut Nucleic Acids Research database article in 2014, including specific areas of expansion such as common (complex) disease, new algorithms for phenotype driven genomic discovery and diagnostics, integration of cross-species mapping efforts with the Mammalian Phenotype Ontology, an improved quality control pipeline, and the addition of patient-friendly terminology., (© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Short telomeres are associated with chronic disease and early mortality. Recent studies in adults suggest an association between telomere length and exposure to particulate matter, and that ethnicity may modify the relationship. However associations in children are unknown., Objectives: We examined associations between air pollution and telomere length in an ethnically diverse group of children exposed to high levels of traffic derived pollutants, particularly diesel exhaust, and to environmental tobacco smoke., Methods: Oral DNA from 333 children (8-9years) participating in a study on air quality and respiratory health in 23 inner city London schools was analysed for relative telomere length using monochrome multiplex qPCR. Annual, weekly and daily exposures to nitrogen oxides and particulate matter were obtained from urban dispersion models (2008-10) and tobacco smoke by urinary cotinine. Ethnicity was assessed by self-report and continental ancestry by analysis of 28 random genomic markers. We used linear mixed effects models to examine associations with telomere length., Results: Telomere length increased with increasing annual exposure to NO x (model coefficient 0.003, [0.001, 0.005], p<0.001), NO 2 (0.009 [0.004, 0.015], p<0.001), PM 2.5 (0.041, [0.020, 0.063], p<0.001) and PM 10 (0.096, [0.044, 0.149], p<0.001). There was no association with environmental tobacco smoke. Telomere length was increased in children reporting black ethnicity (22% [95% CI 10%, 36%], p<0.001) CONCLUSIONS: Pollution exposure is associated with longer telomeres in children and genetic ancestry is an important determinant of telomere length. Further studies should investigate both short and long-term associations between pollutant exposure and telomeres in childhood and assess underlying mechanisms., (Copyright © 2016. Published by Elsevier Ltd.)

Dyskeratosis congenita is a highly pleotropic genetic disorder. This heterogeneity can lead to difficulties in making an accurate diagnosis and delays in appropriate management. The aim of this study was to determine the underlying genetic basis in patients presenting with features of dyskeratosis congenita and who were negative for mutations in the classical dyskeratosis congenita genes. By whole exome and targeted sequencing, we identified biallelic variants in genes that are not associated with dyskeratosis congenita in 17 individuals from 12 families. Specifically, these were homozygous variants in USB1 (8 families), homozygous missense variants in GRHL2 (2 families) and identical compound heterozygous variants in LIG4 (2 families). All patients had multiple somatic features of dyskeratosis congenita but not the characteristic short telomeres. Our case series shows that biallelic variants in USB1, LIG4 and GRHL2, the genes mutated in poikiloderma with neutropenia, LIG4/Dubowitz syndrome and the recently recognized ectodermal dysplasia/short stature syndrome, respectively, cause features that overlap with dyskeratosis congenita. Strikingly, these genes also overlap in their biological function with the known dyskeratosis congenita genes that are implicated in telomere maintenance and DNA repair pathways. Collectively, these observations demonstrate the marked overlap of dyskeratosis congenita with four other genetic syndromes, confounding accurate diagnosis and subsequent management. This has important implications for establishing a genetic diagnosis when a new patient presents in the clinic. Patients with clinical features of dyskeratosis congenita need to have genetic analysis of USB1, LIG4 and GRHL2 in addition to the classical dyskeratosis congenita genes and telomere length measurements., (Copyright© Ferrata Storti Foundation.)

A substantial number of individuals with bone marrow failure (BMF) present with one or more extra-hematopoietic abnormality. This suggests a constitutional or inherited basis, and yet many of them do not fit the diagnostic criteria of the known BMF syndromes. Through exome sequencing, we have now identified a subgroup of these individuals, defined by germline biallelic mutations in DNAJC21 (DNAJ homolog subfamily C member 21). They present with global BMF, and one individual developed a hematological cancer (acute myeloid leukemia) in childhood. We show that the encoded protein associates with rRNA and plays a highly conserved role in the maturation of the 60S ribosomal subunit. Lymphoblastoid cells obtained from an affected individual exhibit increased sensitivity to the transcriptional inhibitor actinomycin D and reduced amounts of rRNA. Characterization of mutations revealed impairment in interactions with cofactors (PA2G4, HSPA8, and ZNF622) involved in 60S maturation. DNAJC21 deficiency resulted in cytoplasmic accumulation of the 60S nuclear export factor PA2G4, aberrant ribosome profiles, and increased cell death. Collectively, these findings demonstrate that mutations in DNAJC21 cause a cancer-prone BMF syndrome due to corruption of early nuclear rRNA biogenesis and late cytoplasmic maturation of the 60S subunit., (Copyright © 2016. Published by Elsevier Inc.)

Telomeric dysfunction is linked to colorectal cancer (CRC) initiation. However, the relationship of normal tissue and tumor telomere lengths with CRC progression, molecular features and prognosis is unclear. Here, we measured relative telomere length (RTL) by real-time quantitative PCR in 90 adenomas (aRTL), 419 stage I-IV CRCs (cRTL) and adjacent normal mucosa (nRTL). Age-adjusted RTL was analyzed against germline variants in telomere biology genes, chromosome instability (CIN), microsatellite instability (MSI), CpG island methylator phenotype (CIMP), TP53, KRAS, BRAF mutations and clinical outcomes. In 509 adenoma or CRC patients, nRTL decreased with advancing age. Female gender, proximal location and the TERT rs2736100 G allele were independently associated with longer age-adjusted nRTL. Adenomas and carcinomas exhibited telomere shortening in 79% and 67% and lengthening in 7% and 15% of cases. Age-adjusted nRTL and cRTL were independently associated with tumor stage, decreasing from adenoma to stage III and leveling out or increasing from stage III to IV, respectively. Cancer MSI, CIMP, TP53, KRAS and BRAF status were not related to nRTL or cRTL. Near-tetraploid CRCs exhibited significantly longer cRTLs than CIN- and aneuploidy CRCs, while cRTL was significantly shorter in CRCs with larger numbers of chromosome breaks. Age-adjusted nRTL, cRTL or cRTL:nRTL ratios were not associated with disease-free or overall survival in stage II/III CRC. Taken together, our data show that both normal mucosa and tumor RTL are independently associated with CRC progression, and highlight divergent associations of CRC telomere length with tumor CIN profiles., Competing Interests: No conflicts of interest to disclose.

We have used polysome profiling coupled to microarray analysis to examine the translatome of a panel of peripheral blood (PB) B cells isolated from 34 chronic lymphocytic leukaemia (CLL) patients. We have identified a 'ribosome-related' signature in CLL patients with mRNAs encoding for ribosomal proteins and factors that modify ribosomal RNA, e.g. DKC1 (which encodes dyskerin, a pseudouridine synthase), showing reduced polysomal association and decreased expression of the corresponding proteins. Our data suggest a general impact of dyskerin dysregulation on the translational apparatus in CLL and importantly patients with low dyskerin levels have a significantly shorter period of overall survival following treatment. Thus, translational dysregulation of dyskerin could constitute a mechanism by which the CLL PB B cells acquire an aggressive phenotype and thus have a major role in oncogenesis.

Dyskeratosis congenita (DC) and related syndromes are inherited, life-threatening bone marrow (BM) failure disorders, and approximately 40% of cases are currently uncharacterized at the genetic level. Here, using whole exome sequencing (WES), we have identified biallelic mutations in the gene encoding poly(A)-specific ribonuclease (PARN) in 3 families with individuals exhibiting severe DC. PARN is an extensively characterized exonuclease with deadenylation activity that controls mRNA stability in part and therefore regulates expression of a large number of genes. The DC-associated mutations identified affect key domains within the protein, and evaluation of patient cells revealed reduced deadenylation activity. This deadenylation deficiency caused an early DNA damage response in terms of nuclear p53 regulation, cell-cycle arrest, and reduced cell viability upon UV treatment. Individuals with biallelic PARN mutations and PARN-depleted cells exhibited reduced RNA levels for several key genes that are associated with telomere biology, specifically TERC, DKC1, RTEL1, and TERF1. Moreover, PARN-deficient cells also possessed critically short telomeres. Collectively, these results identify a role for PARN in telomere maintenance and demonstrate that it is a disease-causing gene in a subset of patients with severe DC.

Background: The effectiveness of intermittent montelukast for wheeze in young children is unclear. We aimed to assess whether intermittent montelukast is better than placebo for treatment of wheeze in this age group. Because copy numbers of the Sp1-binding motif in the arachidonate 5-lipoxygenase (ALOX5) gene promoter (either 5/5, 5/x, or x/x, where x does not equal 5) modifies response to montelukast in adults, we stratified by this genotype., Methods: We did this multicentre, parallel-group, randomised, placebo-controlled trial between Oct 1, 2010, and Dec 20, 2013, at 21 primary care sites and 41 secondary care sites in England and Scotland. Children aged 10 months to 5 years with two or more wheeze episodes were allocated to either a 5/5 or 5/x+x/x ALOX5 promoter genotype stratum, then randomly assigned (1:1) via a permuted block schedule (size ten), to receive intermittent montelukast or placebo given by parents at each wheeze episode over a 12 month period. Clinical investigators and parents were masked to treatment group and genotype strata. The primary outcome was number of unscheduled medical attendances for wheezing episodes. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01142505., Findings: We randomly assigned 1358 children to receive montelukast (n=669) or placebo (n=677). Consent was withdrawn for 12 (1%) children. Primary outcome data were available for 1308 (96%) children. There was no difference in unscheduled medical attendances for wheezing episodes between children in the montelukast and placebo groups (mean 2·0 [SD 2·6] vs 2·3 [2·7]; incidence rate ratio [IRR] 0·88, 95% CI: 0·77-1·01; p=0·06). Compared with placebo, unscheduled medical attendances for wheezing episodes were reduced in children given montelukast in the 5/5 stratum (2·0 [2·7] vs 2·4 [3·0]; IRR 0·80, 95% CI 0·68-0·95; p=0·01), but not in those in the 5/x+x/x stratum (2·0 [2·5] vs 2·0 [2·3]; 1·03, 0·83-1·29; p=0·79, pinteraction=0·08). We recorded one serious adverse event, which was a skin reaction in a child allocated to placebo., Interpretation: Our findings show no clear benefit of intermittent montelukast in young children with wheeze. However, the 5/5 ALOX5 promoter genotype might identify a montelukast-responsive subgroup., Funding: Medical Research Council (UK) and National Institute for Health Research., (Copyright © 2014 Nwokoro et al. Open Access article distributed under the terms of CC BY. Published by .. All rights reserved.)

Exome sequencing was performed in three index cases with bone marrow failure and neurological dysfunction and whose parents are first-degree cousins. Homozygous truncating mutations were identified in ERCC6L2 in two of the individuals. Both of these mutations affect the subcellular localization and stability of ERCC6L2. We show here that knockdown of ERCC6L2 in human A549 cells significantly reduced their viability upon exposure to the DNA-damaging agents mitomycin C and Irofulven, but not etoposide and camptothecin, suggesting a role in nucleotide excision repair. ERCC6L2-knockdown cells also displayed H2AX phosphorylation, which significantly increased upon genotoxic stress, suggesting an early DNA-damage response. Intriguingly, ERCC6L2 was seen to translocate to the mitochondria and the nucleus in response to DNA damage, and ERCC6L2 knockdown induced intracellular reactive oxygen species (ROS). Treatment with the ROS scavenger N-acetyl cysteine attenuated the Irofulven-induced cytotoxicity in ERCC6L2-knockdown cells and abolished ERCCGL2 traffic to the mitochondria and nucleus in response to this DNA-damaging agent. Collectively, these observations identify a distinct bone-marrow-failure syndrome due to mutations in ERCC6L2, a gene implicated in DNA repair and mitochondrial function., (Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)