Androgen derivatives improve blood counts and elongate telomere length in adult cryptic dyskeratosis congenita.

Dyskeratosis Congenita (DKC) is a systemic disorder caused by mutations resulting in impaired telomere maintenance. Clinical features include bone marrow failure and an increased risk of developing hematological malignancies. There are conflicting data whether androgen derivatives (AD) can elongate telomeres in vivo and whether AD treatment enhances the risk of gaining myelodysplastic syndrome-related mutations. Seven TERC or TERT-mutated DKC patients underwent AD treatment. All patients revealed hematological response. Telomere length of lymphocytes and granulocytes increased significantly and no MDS-related mutations were detected. Pending longer follow-up, treatment with AD seems to represent an efficient and safe therapy for DKC patients.

PRDM8 reveals aberrant DNA methylation in aging syndromes and is relevant for hematopoietic and neuronal differentiation.

BACKGROUND: Dyskeratosis congenita (DKC) and idiopathic aplastic anemia (AA) are bone marrow failure syndromes that share characteristics of premature aging with severe telomere attrition. Aging is also reflected by DNA methylation changes, which can be utilized to predict donor age. There is evidence that such epigenetic age predictions are accelerated in premature aging syndromes, but it is yet unclear how this is related to telomere length. DNA methylation analysis may support diagnosis of DKC and AA, which still remains a challenge for these rare diseases. RESULTS: In this study, we analyzed blood samples of 70 AA and 18 DKC patients to demonstrate that their epigenetic age predictions are overall increased, albeit not directly correlated with telomere length. Aberrant DNA methylation was observed in the gene PRDM8 in DKC and AA as well as in other diseases with premature aging phenotype, such as Down syndrome and Hutchinson-Gilford-Progeria syndrome. Aberrant DNA methylation patterns were particularly found within subsets of cell populations in DKC and AA samples as measured with barcoded bisulfite amplicon sequencing (BBA-seq). To gain insight into the functional relevance of PRDM8, we used CRISPR/Cas9 technology to generate induced pluripotent stem cells (iPSCs) with heterozygous and homozygous knockout. Loss of PRDM8 impaired hematopoietic and neuronal differentiation of iPSCs, even in the heterozygous knockout clone, but it did not impact on epigenetic age. CONCLUSION: Taken together, our results demonstrate that epigenetic aging is accelerated in DKC and AA, independent from telomere attrition. Furthermore, aberrant DNA methylation in PRDM8 provides another biomarker for bone marrow failure syndromes and modulation of this gene in cellular subsets may be related to the hematopoietic and neuronal phenotypes observed in premature aging syndromes.

p53 Mediates Failure of Human Definitive Hematopoiesis in Dyskeratosis Congenita.

Dyskeratosis congenita (DC) is a bone marrow failure syndrome associated with telomere dysfunction. The progression and molecular determinants of hematopoietic failure in DC remain poorly understood. Here, we use the directed differentiation of human embryonic stem cells harboring clinically relevant mutations in telomerase to understand the consequences of DC-associated mutations on the primitive and definitive hematopoietic programs. Interestingly, telomere shortening does not broadly impair hematopoiesis, as primitive hematopoiesis is not impaired in DC cells. In contrast, while phenotypic definitive hemogenic endothelium is specified, the endothelial-to-hematopoietic transition is impaired in cells with shortened telomeres. This failure is caused by DNA damage accrual and is mediated by p53 stabilization. These observations indicate that detrimental effects of telomere shortening in the hematopoietic system are specific to the definitive hematopoietic lineages. This work illustrates how telomere dysfunction impairs hematopoietic development and creates a robust platform for therapeutic discovery for treatment of DC patients.

Clinical and genetic features of dyskeratosis congenita, cryptic dyskeratosis congenita, and Hoyeraal-Hreidarsson syndrome in Japan.

Dyskeratosis congenita (DKC) is an inherited bone marrow failure (BMF) syndrome typified by reticulated skin pigmentation, nail dystrophy, and mucosal leukoplakia. Hoyeraal-Hreidarsson syndrome (HHS) is considered to be a severe form of DKC. Unconventional forms of DKC, which develop slowly in adulthood but without the physical anomalies characteristic of DKC (cryptic DKC), have been reported. Clinical and genetic features of DKC have been investigated in Caucasian, Black, and Hispanic populations, but not in Asian populations. The present study aimed to determine the clinical and genetic features of DKC, HHS, and cryptic DKC among Japanese patients. We analyzed 16 patients diagnosed with DKC, three patients with HHS, and 15 patients with cryptic DKC. We found that platelet count was significantly more depressed than neutrophil count or hemoglobin value in DKC patients, and identified DKC patients with large deletions in the telomerase reverse transcriptase and cryptic DKC patients with RTEL1 mutations on both alleles. This led to some patients previously considered to have unclassifiable BMF being diagnosed with cDKC through identification of new gene mutations. It thus seems important from a clinical viewpoint to re-examine the clinical characteristics, frequency of genetic mutations, and treatment efficacy in DKC, HHS, and cDKC.

Reduced serum levels of anti-Müllerian hormone in females with inherited bone marrow failure syndromes.

CONTEXT: Previously, reduced levels of anti-Müllerian hormone (AMH), a circulating marker of ovarian reserve, were found in females with Fanconi anemia (FA). FA, dyskeratosis congenita (DC), and Diamond-Blackfan anemia (DBA) are inherited bone marrow failure syndromes (IBMFS) associated with high risks of bone marrow failure, leukemia, and solid tumors. OBJECTIVE: The objective of the study was to assess AMH levels in females with DC or DBA. DESIGN AND SETTING: This observational study used the National Cancer Institute's inherited bone marrow failure syndrome cohort at the National Institutes of Health Clinical Center. PARTICIPANTS: The study included females with DC, unaffected female relatives of patients with DC, females with DBA, unaffected female relatives of patients with DBA, and unrelated healthy female volunteers younger than 41 years of age. MAIN OUTCOME MEASURE: Serum AMH levels were measured. RESULTS: Females with DC had significantly lower levels of AMH (median 0.55 ng/mL) compared with unaffected relatives (median 2.28 ng/mL, P = .004) or unrelated healthy volunteers (median 2.69 ng/mL, P = .005). Females with DBA showed a nonsignificant trend for lower levels of AMH (median 0.89 ng/mL) compared with unaffected relatives (median 1.71 ng/mL, P = .21) or unrelated healthy volunteers (P = .11). Patients with DC and DBA had significantly higher levels of AMH (P = .013, P = .003) compared with FA (median 0.05 ng/mL). CONCLUSIONS: Our findings suggest that women with IBMFS have lower levels of AMH than unaffected women. This AMH deficiency could be a primary ovarian defect or a consequence of the pathophysiology of the syndromes. Additional studies of AMH and ovarian function in women with IBMFS are warranted to better understand the underlying biology.

Genetic regulation of fetal haemoglobin in inherited bone marrow failure syndromes.

Patients with inherited bone marrow failure syndromes (IBMFS) have 'stress erythropoiesis', with anaemia, macrocytosis, increased fetal haemoglobin (Hb F) and high erythropoietin levels. In haemoglobinopathies, Hb F levels are regulated by 3 quantitative trait loci, HBS1L-MYB, BCL11A and Xmn1-HBG2. In our study of 97 patients with an IBMFS, increased Hb F was associated with young age, male gender, anaemia, high erythropoietin levels, and alternative alleles in Xmn1-HBG2 [adjusted P = 0·04 for the total group, driven by Fanconi anaemia (P = 0·02) and dyskeratosis congenita (P = 0·09)]. Thus Hb F is regulated in IBMFS by Xmn1-HBG2, as it is in the haemoglobinopathies.

Irreversible leukoencephalopathy after reduced-intensity stem cell transplantation in a dyskeratosis congenita patient with TINF2 mutation.

Hematopoietic stem cell transplantation (HSCT) for dyskeratosis congenita (DC) is challenging due to severe treatment-related adverse effects. Development of pulmonary fibrosis or veno-occlusive disease is well described in DC. However, neurological complication after HSCT has not been reported. A 9-year-old Japanese male with DC harboring the TINF2 mutation received reduced-intensity HSCT. Unfortunately, patient developed posterior reversible encephalopathy syndrome-like symptoms plausibly result by combination of thrombotic microangiopathy, graft-versus-host disease, and persistent hypertension and has been persisted mental retardation. Therefore, to decrease risk in DC cases after HSCT, strict control of hypertension, graft-versus-host disease, and thrombotic microangiopathy is required.

A zebrafish model of dyskeratosis congenita reveals hematopoietic stem cell formation failure resulting from ribosomal protein-mediated p53 stabilization.

Dyskeratosis congenita (DC) is a bone marrow failure disorder characterized by shortened telomeres, defective stem cell maintenance, and highly heterogeneous phenotypes affecting predominantly tissues that require high rates of turnover. Here we present a mutant zebrafish line with decreased expression of nop10, one of the known H/ACA RNP complex genes with mutations linked to DC. We demonstrate that this nop10 loss results in 18S rRNA processing defects and collapse of the small ribosomal subunit, coupled to stabilization of the p53 tumor suppressor protein through small ribosomal proteins binding to Mdm2. These mutants also display a hematopoietic stem cell deficiency that is reversible on loss of p53 function. However, we detect no changes in telomere length in nop10 mutants. Our data support a model of DC whereupon in early development mutations involved in the H/ACA complex contribute to bone marrow failure through p53 deregulation and loss of initial stem cell numbers while their role in telomere maintenance does not contribute to DC until later in life.

Dyskeratosis congenita.

Dyskeratosis congenita (DC) is an inheritable bone marrow failure syndrome characterized by reticulated hyperpigmentation, dystrophic nails and oral leukoplakia. Another name for the condition is Zinsser-Cole-Engman syndrome. Hematologic manifestations usually do not appear in childhood but later in early adulthood. Patients are also prone to carcinomas, particularly of the head and neck. The disease has X-linked or autosomal dominant/recessive inheritance. Early childhood variants (Hoyeraal-Hreidarsson syndrome) are associated with immunological abnormalities in the form of low T- and B-cell numbers. Four genes, namely DKC1 (codes for dyskerin), TERC and TERT (code for telomerase) and NOP10, have been implicated in the pathogenesis; the short telomeres provide a marker for genetic linkage studies. Androgens, with or without granulocyte colony stimulating factor, have been tried in the treatment of the conditions with variable results. Stem cell transplantation from matched sibling donor is currently the treatment of choice. It requires modified nonmyeloablative conditioning protocols, since the patients with DC are prone to pulmonary and hepatic complications.

Telomerase RNA deficiency in peripheral blood mononuclear cells in X-linked dyskeratosis congenita.

Compromised renewal and eventual failure of the hematopoietic system in dyskeratosis congenita (DC) have been proposed to arise from a deficiency in telomerase function. Previously, cultured cell lines from patients with X-linked DC were shown to accumulate less telomerase RNA than cell lines from unaffected family members. Here, we report that telomerase RNA deficiency is also present in the circulating lymphocytes of DC patients. We have compared the accumulation levels of telomerase RNA and a panel of other small RNAs in peripheral blood mononuclear cells from an X-linked DC patient and an unaffected maternal carrier and similarly analyzed cultured lymphoblasts from an X-linked DC patient and maternal carrier in a second family. The DC-patient lymphoid cells show a specific defect in telomerase RNA accumulation with or without cell culture. Our findings support the clinical significance of telomerase deficiency and encourage the use of telomerase activation as a disease therapy.

Inherited aplastic anaemia.

A number of inherited (constitutional/genetic) disorders are characterized by bone marrow (BM) failure/aplastic anaemia (AA) usually in association with one or more somatic abnormality. Occasionally, these patients may present with AA alone and be labelled to have idiopathic AA. In recent years, there have been significant advances in the genetics of Fanconi anaemia (FA), dyskeratosis congenita (DC) and other BM failure syndromes. This is facilitating accurate diagnosis and beginning to unravel their pathophysiology. Furthermore, these advances are also providing important insights into normal haemopoiesis and how this might become defective in some patients presenting with the more common idiopathic AA. Indeed, a link between DC and idiopathic AA and in turn to defective telomerase has now been established. This advance also suggests that treatments directed at correction of telomerase activity might benefit AA patients who do not respond to conventional therapy.

Very short telomeres in the peripheral blood of patients with X-linked and autosomal dyskeratosis congenita.

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome in which patients undergo premature ageing and have a predisposition to malignancy. X-linked and autosomal (dominant and recessive) forms of the disease are recognized. The gene responsible for X-linked DC (DKC1) encodes a highly conserved protein called dyskerin that is believed to be essential in ribosome biogenesis and may also be involved in telomerase RNP assembly. Here we show that in X-linked DC, peripheral blood cells have dramatically reduced telomere lengths but normal levels of telomerase activity. We also find that subjects with autosomal DC have significantly shorter telomeres than age-matched normal controls suggesting that both forms of the disease are associated with rapid telomere shortening in hemopoietic stem cells. The further characterization of these genes will not only lead to a better understanding of the biology of DC but may also provide further insights into the maintenance of telomeres and the biology of aplastic anemia, ageing, and cancer.

Chromosomal breakage analysis in dyskeratosis congenita peripheral blood lymphocytes.

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by reticulate skin pigmentation, nail dystrophy and mucosal leucoplakia. Bone marrow failure occurs in the majority of cases and there is a predisposition to malignancy. Following conflicting reports of increased spontaneous and induced chromosomal breakage in DC lymphocytes, we examined chromosomal breakage with and without clastogen treatment in 10 DC patients from six different families. Peripheral blood cultures were stimulated with phytohaemagglutinin and treated with three clastogenic agents and gamma-irradiation. There was no significant difference in the chromosomal breakage in DC lymphocytes with or without exposure to bleomycin, DEB, MMC or gamma-irradiation. DC can therefore be distinguished from Fanconi's anaemia in which lymphocytes show increased spontaneous and clastogen-induced chromosomal breakage.