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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., Familial myeloid malignancies have recently been classified as separate disease entities. Here, using whole-exome sequencing of affected pedigrees - the authors highlight genetic variants associated with these conditions.

An asymptomatic 36-year-old woman presented with significantly elevated white blood cells (165.9 × 109/L) at antenatal booking, in her first pregnancy. Further investigations revealed the diagnosis of chronic lymphocytic leukaemia with monoallelic deletion of chromosome 13q14. She was supported and monitored through out pregnancy, without treatment, and delivered a healthy baby boy at term with no complications and is currently being followed up by the haem-oncology team.

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.

Aplastic anemia (AA) and myelodysplasia (MDS) are forms of bone marrow failure that are often part of the same progressive underlying disorder. While most cases are simplex and idiopathic, some show a clear pattern of inheritance; therefore, elucidating the underlying genetic cause could lead to a greater understanding of this spectrum of disorders. We used a combination of exome sequencing and SNP haplotype analysis to identify causative mutations in a family with a history of autosomal-dominant AA/MDS. We identified a heterozygous mutation in SRP72, a component of the signal recognition particle (SRP) that is responsible for the translocation of nascent membrane-bound and excreted proteins to the endoplasmic reticulum. A subsequent screen revealed another autosomal-dominant family with an inherited heterozygous SRP72 mutation. Transfection of these sequences into mammalian cells suggested that these proteins localize incorrectly within the cell. Furthermore, coimmunoprecipitation of epitope-tagged SRP72 indicated that the essential RNA component of the SRP did not fully associate with one of the SRP72 variants. These results suggest that inherited mutations in a component of the SRP have a role in the pathophysiology of AA/MDS, identifying a third pathway for developing these disorders alongside transcription factor and telomerase mutations.

Dyskeratosis congenita (DC) is a heterogeneous disorder, both genetically and phenotypically (1). Clinical presentation is classically defined by a triad of mucocutaneous features: abnormal reticulate skin pigmentation, nail dystrophy and leukoplakia. Bone marrow failure and a spectrum of other somatic abnormalities are also commonly observed (2). In its severe form, DC overlaps with the Hoyeraal–Hreidarsson (HH) syndrome, characterized by immunodeficiency, cerebellar hypoplasia, microcephaly and growth retardation as well as aplastic anaemia (AA). Because of this wide range of phenotypes, a clinical diagnosis of DC can often be quite difficult, although we would usually define a DC patient as having at least two of the three mucocutaneous features with either evidence of bone marrow failure or two or more other somatic abnormalities (3). In some cases a genetic diagnosis can be made, based on the identification of a mutation in one of the seven genes (DKC1, TERC, TERT, NOP10, NHP2, TINF2 and C16orf57). Through genome-wide linkage analysis and candidate gene sequencing, the TINF2 gene was initially identified as the cause of DC in one family showing autosomal dominant inheritance of the disease (4). It has subsequently become clear that mutations in this gene usually arise de novo in sporadic cases, causing a relatively severe form of DC (4, 5). The gene encodes a core component of the shelterin complex – a group of proteins that interact to protect telomeres. This protein is called TIN2, the telomeric repeat binding factor 1 (TRF1)-interacting nuclear factor 2; it is an essential mediator of TRF1 function and acts as an important regulator of telomere length (6, 7). TIN2 acts as the central component of the shelterin complex, binding not only TRF1 but also TRF2, a second telomere DNA-binding protein (8) and TPP1, the TIN2-interacting protein (9). TIN2-anchored TPP1 plays a major role in the recruitment of telomerase to telomeres in human cells (10). TPP1 is also important for recruiting POT1 (protection of telomeres), which is the third DNA-binding protein of the shelterin complex. POT1 binds to telomeric single-stranded DNA, protecting chromosome ends from the DNA-damage response (11). A second larger isoform of TIN2 has recently been identified, and this appears to have a role in tethering telomeres to the nuclear matrix (12). Since our previous report in 2008 (5), we have been screening for TINF2 mutations in all patients referred to our DC registry with various forms of bone marrow failure. This has led to the identification of 16 new families with eight previously unreported variants. They show that the phenotype associated with TINF2 mutation is broader than previously thought, but also raise the question as to whether all of these novel variants are pathogenic.

The bone marrow failure syndrome dyskeratosis congenita (DC) has been considered to be a disorder of telomere maintenance in which disease features arise due to accelerated shortening of telomeres. By screening core components of the telomerase and shelterin complexes in patients with DC and related bone marrow failure syndromes we have identified 24 novel mutations: 11 in the RNA component of telomerase (TERC), 8 in the reverse transcriptase component (TERT), 4 in dyskerin (DKC1) and 1 in TRF1-interacting nuclear factor 2 (TINF2). This has prompted us to review these genetic subtypes in terms of telomere length, telomerase activity and clinical presentation among 194 genetically characterised index cases recruited onto the registry in London. While those with DKC1 and TINF2 mutations present at a younger age and have more disease features than those with TERC or TERT mutations, there is no difference in telomere length between these groups. There is no difference in the age of onset and numbers of disease features seen in those with TERC and TERT mutations despite the fact that the latter show higher levels of telomerase activity in vitro. The incidence of aplastic anaemia is greater in patients with TERC or TINF2 mutations compared to patients with DKC1 mutations, and cancer incidence is highest in patients with TERC mutations. These data are the first to provide robust comparisons between different genetic subtypes of telomerase and shelterin mutations (the “telomereopathies”) and clearly demonstrate that disease severity is not explained by telomere length alone.

Dyskeratosis congenita (DC) is a heterogeneous bone marrow failure disorder with known mutations in components of telomerase and telomere shelterin. Recent work in a mouse model with a dyskerin mutation has implicated an increased DNA damage response as part of the cellular pathology, while mouse models with Terc and Tert mutations displayed a normal response. To clarify how these contradictory results might apply to DC pathology in humans, we studied the cellular phenotype in primary cells from DC patients of several genetic subtypes, focussing on T lymphocytes to remain close to the haematopoietic system. We observed novel cell cycle abnormalities in conjunction with impaired growth and an increase in apoptosis. Using flow cytometry and confocal microscopy we examined induction of the DNA damage proteins γ-H2AX and 53BP1 and the cell cycle protein TP53 (p53). We found an increase in damage foci at telomeres in lymphocytes and an increase in the basal level of DNA damage in fibroblasts, but crucially no increased response to DNA damaging agents in either cell type. As the response to induced DNA damage was normal and levels of global DNA damage were inconsistent between cell types, DNA damage may contribute differently to the pathology in different tissues.

To address the association between travel and deep vein thrombosis (DVT) we examined the risk factors for DVT in 568 consecutive patients with suspected DVT attending King's College Hospital in London. No significant link between DVT and long-haul travel was demonstrable in this cohort, with an odds ratio of 1.3 (CI 0.6-2.8). Risk of DVT was only increased in long-haul travellers if one or more additional risk factors were present, with an odds ratio of 3.0 (CI 1.1-8.2). Such individuals may benefit from prophylactic measures to minimize risk.