Genome Wide Linkage Analysis Suggests Genetic Heterogeneity in Autosomal Recessive Dyskeratosis Congenita, with One Locus on Chromosome 15.

Abstract Dyskeratosis congenita (DC) is a severe inherited premature aging syndrome characterised by muco-cutaneous abnormalities, bone marrow failure and an increased predisposition to cancer. X-linked recessive, autosomal dominant (AD) and autosomal recessive (AR) forms of the disease are recognised. Mutations in DKC1 and TERC have been identified in X-linked recessive and AD-DC, respectively. The products encoded by both of these genes are key components of the telomerase complex, which is responsible for maintaining telomere length after cell division. This has led to the suggestion that DC is primarily a disease of defective telomere maintenance. The international dyskeratosis congenita registry (Hammersmith Hospital, London) has information on 244 families with DC. Of these 30% have mutations in DKC1 and 6% have mutations in TERC. Disease causing mutations in the remaining 64% of patients have yet to be characterised. In an attempt to identify a candidate locus through homozygosity mapping, we performed a genome-wide scan using a maximum of 475 microsatellite markers (LMS-MD 10/5 ABI PRISM) on DNA from 19 affected individuals from 13 families with consanguineous marriage. No single marker was found to be homozygous in all individuals, although not all markers were typed in all individuals. 19% of markers were homozygous in four or more families across the chromosomes, but this dropped to 4% when the number of families that were homozygous was increased to six. Only six markers (1% approx.) were homozygous in seven or more families. This suggests there is considerable genetic heterogeneity amongst the AR-DC subset. To investigate this further we selected one family that showed a recessive pattern of inheritance with samples available from three affected individuals, three unaffected siblings and parents. Affected members in this family had the classical DC features of nail dystrophy, abnormal skin pigmentation, abnormal dentition and severe bone marrow failure in the index case. To try to identify a disease locus in this family, we typed the whole family at the markers where the affected individuals shared common homozygosity and analysed the data using Genehunter, a multi-point linkage analysis program, to obtain a LOD score (log10 of the odd ratio in favour of linkage). The maximum LOD score obtained for this family was 2.7 on chromosome 15, suggesting that a disease-causing locus is at chromosome 15q14. This particular location seems to be unique to this family as there is no overlap in homozygosity with any other family studied. It remains to be established how many loci there are, and whether a single gene causes DC in many of the AR families, or if each gene identified causes the disease in a small subset of families. In conclusion this work highlights the extent of genetic heterogeneity that exists in DC, with AR-DC being a very heterogeneous subtype which may involve several genes, but the locus of one AR-DC gene has been assigned to chromosome 15q14.

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Germline Mutations in RTEL1 cause Dyskeratosis Congenita

Blood ◽

10.1182/blood.v120.21.515.515 ◽

2012 ◽

Vol 120 (21) ◽

pp. 515-515

Author(s):

Bari J. Ballew ◽

Kevin B. Jacobs ◽

Meredith Yeager ◽

Neelam Giri ◽

Joseph F. Boland ◽

...

Keyword(s):

Bone Marrow ◽

Missense Mutation ◽

Autosomal Recessive ◽

Autosomal Dominant ◽

Bone Marrow Failure ◽

Germline Mutations ◽

Dyskeratosis Congenita ◽

Telomere Maintenance ◽

Targeted Sequencing ◽

Telomere Elongation

Abstract Abstract 515 Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome that results from impaired telomere maintenance. The classic triad (dysplastic nails, skin pigmentation, and oral leukoplakia) is diagnostic of DC but significant clinical heterogeneity can exist, even within a family. Leukocyte telomere lengths less than the first percentile for age are diagnostic of DC. Patients with DC are at high risk of bone marrow failure (BMF), myelodysplastic syndrome, cancer, pulmonary fibrosis, liver disease and other complications. Currently, germline mutations in 1 of 8 telomere biology genes (DKC1, TERC, TERT, TINF2, NOP10, NHP2, WRAP53, and CTC1) are known to cause ∼50–60% of DC cases. Our longitudinal cohort study conducts detailed medical record review and clinical examinations of patients with DC and their family members. DC is diagnosed based on the presence of the diagnostic triad or 1 of the triad plus BMF. All DC patients had telomeres <1st percentile. Patients are classified as DC-like if they have telomeres <1st percentile and other features, such as BMF or family history, suggestive of DC. All participants in this study were negative for mutations in the known DC genes. We performed whole exome sequencing (WES) on two DC families using an enriched multiplexed sequencing library (Nimblegen v2) and sequenced on an Illumina HiSeq™. Variants were removed from analyses if they did not pass quality control filters or were present more than 3 times in publically available databases (1000Genomes, ESP, Kaviar, and dbSNP). Since DC can be inherited in autosomal dominant, autosomal recessive, and X-linked manners, we evaluated all inheritance models in our families. Additionally, if healthy family members had very short telomeres, they were also evaluated as potential silent carriers, since this approach has facilitated the identification of other DC genes. Nonsynonymous variants were considered deleterious if SIFT, PolyPhen 2, and Condel predictions were consistent. Family 1 has 2 siblings with the Hoyeraal Hreidarsson syndrome (HH) variant of DC, which includes features of DC plus cerebellar hypoplasia. In that family, WES revealed autosomal dominant inheritance of a nonsense mutation in RTEL1 (Regulator of Telomere Elongation Helicase 1), p.Arg1010Stop. Their mother, who has lymphocyte telomere lengths at the 1st percentile, is a clinically silent carrier of this mutation; the severe phenotypes present in her children are likely an example of genetic anticipation. In family 2, we found 2 RTEL1 mutations, a nonsense (p.Arg998Stop) and a deleterious missense (p.Glu615Asp) mutation, that were inherited from the father and mother, respectively. One clinically healthy child inherited only the missense mutation, but has telomeres <1st percentile. The other child has HH and extremely short telomeres; he is a compound heterozygote, having inherited both the missense and nonsense mutations in RTEL1. We subsequently performed targeted sequencing of the entire RTEL1 gene in all of our mutation-negative DC (n=11) and DC-like (n=14) families. We identified missense mutations in RTEL1 in 2 additional families. Family 3 has 2 DC-like siblings, but only the proband's DNA was available for sequencing. He was heterozygous for a deleterious missense mutation (p.Ala645Thr) in a conserved helicase domain of RTEL1. In family 4, a mutation was inherited in an autosomal recessive manner by a proband with HH. This mutation is intronic except for a read-through transcript of RTEL1-TNFRSF6B, which utilizes an alternative exon 34. If translated, this variant results in the amino acid change p.Arg1264His, which is likely deleterious; if not, this mutation may affect nonsense-mediated decay or induce a regulatory change in RTEL1 expression. RTEL1 is an essential, evolutionarily conserved DNA helicase that is important for DNA replication and telomere elongation. Depletion of mRTEL1 from mouse embryonic stem cells results in telomeric loss and chromosomal instability. All individuals with germline RTEL1 mutations in this study have short telomeres, which underscores the functional importance of RTEL1 in human telomere maintenance. In summary, by employing WES followed by targeted sequencing, we discovered mutations in RTEL1 in 4 DC families, indicating that dysfunctional RTEL1 is a biologically plausible cause of DC. Disclosures: No relevant conflicts of interest to declare.

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Homozygous and Compound Heterozygous Mutations in the Telomerase Reverse Transcriptase Gene in Two Families with Spontaneous Dyskeratosis Congenita and Idiopathic Aplastic Anemia.

Blood ◽

10.1182/blood.v110.11.1675.1675 ◽

2007 ◽

Vol 110 (11) ◽

pp. 1675-1675

Author(s):

Hong-Yan Du ◽

Elena Pumbo ◽

Peter Manley ◽

David B. Wilson ◽

Philip Mason ◽

...

Keyword(s):

Bone Marrow ◽

Autosomal Recessive ◽

Amino Acid Change ◽

Autosomal Dominant ◽

Bone Marrow Failure ◽

Gene Mutations ◽

Dyskeratosis Congenita ◽

Compound Heterozygous ◽

The Family ◽

Tert Gene

Abstract Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome. Classically, DC presents with progressive bone marrow failure, abnormal skin pigmentation, nail dystrophy, and mucosal leukoplakia. The pattern of inheritance in families with DC suggests an X-linked recessive, an autosomal dominant, and an autosomal recessive form of DC. However, in the majority of patients the occurrence of the disease is sporadic or the family history is unknown. Mutations in four different genes have been associated with DC so far. Mutations in DKC1 have been shown to account for the X-linked form of DC and DKC1 de novo mutations account for about one third of male patients with sporadic disease. Mutations in the telomerase RNA TERC and in the catalytic subunit of telomerase, TERT, have been shown to be responsible for the autosomal dominant form of DC. Interestingly, patients with heterozygous mutations in TERC and TERT often show a milder form of disease and a later age of onset and often lack the classic mucocutaeous features, thus are classified as atypical DC. Very recently homozygosity for a mutation in NOP10 has been identified in one family with autosomal recessive disease. The products of the genes mutated in DC are all components of the telomerase complex, suggesting that disease in patients with DC is caused by a defect in telomere maintenance. Here we investigated two patients, one UPN # 199.001 presenting with the classic manifestations of DC and the other UPN# 284.001 presenting with progressive bone marrow failure but no other clinical features suggestive of DC. In both patients the telomeres measured in peripheral blood mononuclear cells were very short, being defined as being below the 1st percentile. Mutation analysis in the genes associated with DC revealed that patient 199.001 was homozygous for a novel TERT (C2110T) gene mutation, causing an amino acid change (P704S) within the RT domain of TERT. Both parents were heterozygous for the C to T transition. Interestingly however, the father was in addition heterozygote for a second mutation in TERT (C1234T; H412Y) a mutation which has previously been described and has been shown to reduce telomerase activity by 50%. Investigations of the family revealed that the parent’s were distantly related, explaining the same TERT sequence alteration in both parents. Both arms of the family contained members with pulmonary fibrosis. In the second patient 284.001 we identified two different novel TERT gene mutations. One A2537G causes the amino acid change Y846C in the RT domain of TERT whereas the other C2628G causes H876Q also in the RT domain. One of the mutations was inherited from each parent and the parent with the A2537G mutation also had very short telomeres. These two families illustrate that the pattern of inheritance in patients with DC may be complex and show for the first time that homozygous or compound heterozygous TERT gene mutation may be associated with DC. Co-dominance of the three different TERT gene mutations and the inheritance of short telomeres have possibly contributed to development of disease in these patients who were thought to have sporadic DC and idiopathic aplastic anemia.

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DNA Damage Accumulation, Accelerated Hematopoietic Stem Cell Aging, and Partial Reversal by Antioxidant Treatment in a Mouse Model of Dyskeratosis Congenita.

Blood ◽

10.1182/blood.v114.22.498.498 ◽

2009 ◽

Vol 114 (22) ◽

pp. 498-498

Author(s):

Baiwei Gu ◽

JianMeng Fan ◽

Monica Bessler ◽

Philip Mason

Keyword(s):

Bone Marrow ◽

Stem Cell ◽

Cell Function ◽

Bone Marrow Failure ◽

Dyskeratosis Congenita ◽

Telomere Maintenance ◽

Cell Aging ◽

Female Mice ◽

Stem Cell Aging ◽

Population Doublings

Abstract Abstract 498 X-linked dyskeratosis congenita (DC) caused by mutations in DKC1, encoding the protein dyskerin, is the most common form of DC, a severe inherited bone marrow failure (BMF) syndrome associated with a predisposition to malignancy. Dyskerin is a component of small nucleolar ribonucleoprotein particles(snoRNPs) that modify specific residues in nascent ribosomal RNA(rRNA) molecules and also forms part of the telomerase complex responsible for synthesizing the telomere repeats at the ends of chromosomes. Strong evidence suggests that compromised telomerase function is the major cause of DC but defects in ribosome biogenesis may contribute to the disease. Excessive telomere shortening resulting in premature cellular senescence is thought to be the primary cause of bone marrow failure in dyskeratosis congenita. Our previous data showed that, in mice, cells expressing a Dkc1 mutation (Dkc1Δ15) had a telomerase dependent but telomere length independent growth defect. Here we show that the growth rate of Δ15 MEF cells was lower when cultured at both ambient oxygen (21%) and low (3%) oxygen. In 21% oxygen both Δ15 and WT cells stopped growing and entered senescence after 8-10 population doublings, with the Δ15 cells growing more slowly than the WT cells. In 3% oxygen Δ15 cells grew more slowly and entered senescence earlier than WT cells. Further investigations reveal that both γ-H2AX foci number and reactive oxygen species (ROS) levels in Δ15 cells were significantly higher than in WT cells with increased passage number even when cultured in low oxygen. Increased levels of γ-H2AX and p53 in Dkc1Δ15 mice, particularly in older mice, were also detected in liver, spleen and bone marrow. To study the effect of the mutation on stem cell function during aging, we carried out competitive repopulation experiments using the CD45.1/CD45.2 congenic system. Irradiated mice were injected with a 1:1 mixture of Dkc1Δ15 and Dkc1+ bone marrow from old (77-88w) or young (10w) animals. Old Dkc1Δ15cells are less able to compete with age matched WT cells in primary recipients, making up only 20% of cells after 12 weeks compared with 40% for the young cells. Moreover, serial transplantation results show that, in secondary recipients, BM cells from old Dkc1Δ15 mice were not detectable while Dkc1Δ15 cells from young mice still comprise 10-30% of the bone marrow after 12 weeks. These results strongly indicate the Dkc1Δ15 mutation causes decay of stem cell function with age. Because of the association with ROS we asked whether treatment with an antioxidant could rescue the growth disadvantage of Δ15 cells. We grew primary MEF cells from Dkc1Δ15/+ female mice in the presence or absence of 100 M N-acetyl cysteine (NAC), a clinically approved antioxidant. These cultures consist in early passages of 50% cells expressing WT and 50% expressing Δ15 dyskerin, reflecting random X-chromosome inactivation, Without NAC the WT cells almost completely outgrew the Δ15 cells after 11 population doublings but in the presence of NAC the Δ15 cells are still clearly present after 15 population doublings, suggesting that NAC at least partially rescues the growth disadvantage of dyskerin mutant cells. More impressively, the growth disadvantage of the Δ15 cells is also rescued in vivo in Dkc1Δ15/+ female mice given the NAC (1mg/ml) in their drinking water. Although the precise mechanism will be the subject of further investigation, these results point to a functional link between increased oxidative stress, defective telomere maintenance and stem cell aging in the pathogenesis of BMF in dyskeratosis congenita. Disclosures: Bessler: Alexion: Membership on an entity's Board of Directors or advisory committees.

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Antioxidant Treatment Rescues An Accelerated Aging Phenotype In Dyskerin Mutated Bone Marrow Stem Cells.

Blood ◽

10.1182/blood.v116.21.2614.2614 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2614-2614

Author(s):

Baiwei Gu ◽

Jian-meng Fan ◽

Monica Bessler ◽

Philip J Mason

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Cell Function ◽

Bone Marrow Failure ◽

Dyskeratosis Congenita ◽

Untreated Group ◽

Telomere Maintenance ◽

Antioxidant Treatment ◽

Transplantation Experiments

Abstract Abstract 2614 X-linked Dyskeratosis Congenita (DC) is due to mutations in the DKC1 gene, which encodes the protein dyskerin. Dyskerin is a highly conserved nucleolar protein that, as part of a specialized nucleolar RNP, catalyzes the pseudouridylation of specific residues in newly synthesized ribosomal RNAs and spliceosomal snRNAs. Dyskerin also associates with telomerase and is involved in telomere maintenance. In addition to the well known effect of telomere homeostasis on cancer, it is evident that telomere maintenance may also be important in replicative aging because of telomere shortening due to the limited expression of telomerase activity in dividing somatic cells. Accumulating evidence suggests that dysfunctional telomeres resulting in premature cellular senescence is the primary cause of bone marrow failure in dyskeratosis congenita. It is important to determine the mechanism whereby Dkc1 mutations lead to premature cellular senescence in bone marrow. We have produced a line of mice containing a mutation, Dkc1Δ15, which is a copy of a pathogenic human mutation. Male Dkc1Δ15 mice showed a decrease in the proportion of B and T lymphocytes in peripheral blood and reduced body weight with age but no overt bone marrow failure syndrome phenotypes. Our previous competitive bone marrow transplantation experiments showed that the Dkc1Δ15 mutation caused decay of stem cell function with age. Bone marrow from older Dkc1Δ15 mice was markedly inefficient in repopulation studies compared with bone marrow from age matched wild type mice. We also found that N-acetyl cysteine (NAC) could at least partially rescue the growth disadvantage of dyskerin mutant spleen cells or fibroblasts which was associated with accumulation of DNA damage and reactive oxygen species. To determine if NAC, or other antioxidants might be useful therapeutically it is important to determine their effects on stem cell function, which is defective in DC. To this end we established a cohort of mice that were given NAC in their drinking water (1mg/ml) from 3-weeks of age and maintained on NAC for 1 year. We found that long term NAC treatment did not show significant side effects on the mice. They had slightly increased neutrophils, but no difference in life span and body weight compared with the untreated group. Impressively, old male Dkc1Δ15 mice showed corrected B and T cell proportions in peripheral blood after treatment with NAC. Competitive bone marrow transplantation experiments were carried out in which a 1:1 mixture of BM cells from mutant and WT mice was used to repopulated lethally irradiated recipient mice. These experiments showed that, when taken from NAC treated animals, old Dkc1Δ15 BM cells could compete with age matched WT cells with 40–45% of Dkc1Δ15 cells in primary recipients compared with only 20% for the untreated group. Moreover, after secondary transplantation, cells from the NAC treated group still represent 15–20% of Dkc1Δ15 cells in recipients while those from the untreated group could not be detected. These results strongly suggest that NAC treatment can partially restore the bone marrow repopulating ability of Dkc1Δ15 stem cells. Together with our previous results these data suggest that a pathogenic Dkc1 mutation, through its effect on telomerase, initiates stem cell aging before telomeres are short and that increased oxidative stress might play a role in this process. Moreover the effects of the mutation may be prevented or delayed by antioxidant treatment, although the precise mechanism will be the subject of future investigation. Disclosures: Bessler: Alexion Pharmaceutical Inc: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Taligen: Consultancy.

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Genetic Analysis of a Large Family with Migraine, Vertigo, and Motion Sickness

Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques ◽

10.1017/cjn.2019.64 ◽

2019 ◽

Vol 46 (5) ◽

pp. 512-517 ◽

Cited By ~ 2

Author(s):

Leema Reddy Peddareddygari ◽

Phillip D. Kramer ◽

Philip A. Hanna ◽

Mark A. Levenstien ◽

Raji P. Grewal

Keyword(s):

Linkage Analysis ◽

Motion Sickness ◽

Autosomal Recessive ◽

Large Family ◽

American Family ◽

Chromosome 4 ◽

Microsatellite Repeat ◽

Lod Score ◽

Genome Wide ◽

Multipoint Linkage

ABSTRACT:Background: Migraine is a common disorder most typically presenting as headache and often associated with vertigo and motion sickness. It is a genetically complex condition with multiple genes ultimately contributing to the predisposition and development of this episodic neurological disorder. We identified a large American family of 29 individuals of which 17 members suffered from at least one of these disorders, migraine, vertigo, or motion sickness. Many of these individuals suffered from several simultaneously. We hypothesized that vertigo and motion sickness may involve genes that are independent to those directly contributing to migraine susceptibility. Methods: Genome-wide linkage analysis performed using 400 microsatellite repeat markers spaced at 10 cM throughout the genome. The members of this family were phenotyped for each condition, migraine, vertigo, and motion sickness and analyzed separately. Statistical analysis was performed using two-point and multipoint linkage analysis employing a number of models including autosomal recessive or dominant patterns of inheritance with high and low genetic penetrance. Results: We identified a novel locus for migraine, 9q13-q22 (maximum two-point logarithm of odds [LOD] score-2.51). In addition, there are suggestive LOD scores that localize to different chromosomes for each phenotype; vertigo (chromosome 18, LOD score of 1.82) and motion sickness (chromosome 4, LOD score of 2.09). Conclusions: Our analysis supports our hypothesis that the migraine-associated vertigo and motion sickness may involve distinct susceptibility genes.

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Significance of Telomere Length Measurement in the Diagnosis of Dyskeratosis Congenita.

Blood ◽

10.1182/blood.v110.11.836.836 ◽

2007 ◽

Vol 110 (11) ◽

pp. 836-836

Author(s):

Hong-Yan Du ◽

Elena Pumbo ◽

Akiko Shimamura ◽

Adrianna Vlachos ◽

Jeffrey M. Lipton ◽

...

Keyword(s):

Bone Marrow ◽

Aplastic Anemia ◽

Telomere Length ◽

Bone Marrow Failure ◽

Skin Pigmentation ◽

Screening Method ◽

Dyskeratosis Congenita ◽

Telomere Maintenance ◽

Healthy Controls ◽

Mutation Carriers

Abstract Dyskeratosis congenita (DC) is a rare inherited bone marrow failure (BMF) syndrome. The classical features of DC include nail dystrophy, abnormal skin pigmentation, and mucosal leukoplakia. The diagnosis of DC can be difficult. Originally, the diagnosis was based on the presence of the classical mucocutaneous features. However, the identification of four genes responsible for DC (DKC1, TERC, TERT, and NOP10) showed that these mucocutaneous features are only present in a proportion of patients with DC. Additionally, screening for mutations in the affected genes is expensive and is negative in about 50% of patients with classical features of DC. The products of the genes mutated in DC are the components of the telomerase ribonucleoprotein complex, which is essential for telomere maintenance. Therefore it has been postulated that DC is a disease arising from excessive telomere shortening. Here we examined whether the measurement of telomeres could be used as a screening test to identify individuals with DC. For this purpose we examined telomere length in peripheral blood mononuclear cells from 169 patients who presented with bone marrow failure including 17 patients with DC, diagnosed by the presence of classical cutaneous features or the identification of mutations in DKC1, TERC or TERT, 28 patients with paroxysmal nocturnal hemoglobinuria, 25 patients with Diamond Blackfan anemia, 5 patients with Shwachman-Diamond syndrome, 8 patients with myelodysplastic syndrome, and 74 patients with aplastic anemia of unknown cause classified as idiopathic aplastic anemia. In addition we measured telomere length in 12 patients with idiopathic pulmonary fibrosis and in 45 individuals with a de novo deletion of chromosome 5p including the TERT gene. Their telomere lengths were compared with those of 202 age-matched healthy controls. Moreover, mutations were screened in the genes associated with DC. In cases where a mutation was identified, telomere length and mutations were also examined in all the family members. Our results show that all patients with DC and bone marrow failure have very short telomeres far below the first percentile of healthy controls. Not all mutation carriers, including some carriers of apparently dominant mutations, have very short telomeres. What is more, very short telomeres could be found in healthy individuals in these families, some of whom were not mutation carriers. These findings indicate that in patients with BMF the measurement of telomere length is a sensitive screening method for DC, whether very short telomeres in this setting are also specific for DC remains to be determined. However, in contrast to a previous study, we find that telomere length does not always identify mutation carriers in the families of DC.

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Very short telomere length by flow fluorescence in situ hybridization identifies patients with dyskeratosis congenita

Blood ◽

10.1182/blood-2007-02-075598 ◽

2007 ◽

Vol 110 (5) ◽

pp. 1439-1447 ◽

Cited By ~ 217

Author(s):

Blanche P. Alter ◽

Gabriela M. Baerlocher ◽

Sharon A. Savage ◽

Stephen J. Chanock ◽

Babette B. Weksler ◽

...

Keyword(s):

Bone Marrow ◽

T Cells ◽

In Situ Hybridization ◽

Fluorescence In Situ Hybridization ◽

Telomere Length ◽

Bone Marrow Failure ◽

Correct Diagnosis ◽

Dyskeratosis Congenita ◽

Telomere Maintenance

Abstract Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome in which the known susceptibility genes (DKC1, TERC, and TERT) belong to the telomere maintenance pathway; patients with DC have very short telomeres. We used multicolor flow fluorescence in situ hybridization analysis of median telomere length in total blood leukocytes, granulocytes, lymphocytes, and several lymphocyte subsets to confirm the diagnosis of DC, distinguish patients with DC from unaffected family members, identify clinically silent DC carriers, and discriminate between patients with DC and those with other bone marrow failure disorders. We defined “very short” telomeres as below the first percentile measured among 400 healthy control subjects over the entire age range. Diagnostic sensitivity and specificity of very short telomeres for DC were more than 90% for total lymphocytes, CD45RA+/CD20− naive T cells, and CD20+ B cells. Granulocyte and total leukocyte assays were not specific; CD45RA− memory T cells and CD57+ NK/NKT were not sensitive. We observed very short telomeres in a clinically normal family member who subsequently developed DC. We propose adding leukocyte subset flow fluorescence in situ hybridization telomere length measurement to the evaluation of patients and families suspected to have DC, because the correct diagnosis will substantially affect patient management.

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Dyskeratosis congenita: rare case report of Syria

Oxford Medical Case Reports ◽

10.1093/omcr/omab041 ◽

2021 ◽

Vol 2021 (11) ◽

Author(s):

Firas Hussein ◽

Zainab Omar

Keyword(s):

Bone Marrow ◽

Autosomal Recessive ◽

Replicative Senescence ◽

Bone Marrow Failure ◽

Skin Pigmentation ◽

Dyskeratosis Congenita ◽

Inherited Disease ◽

Nail Dystrophy ◽

Cell Counts ◽

Rare Case Report

ABSTRACT Dyskeratosis congenita (DC) is an inherited disease characterized by the triad of abnormal skin pigmentation, nail dystrophy and mucosal leukoplakia. Non-cutaneous abnormalities (dental, gastrointestinal, genitourinary, neurological, ophthalmic, pulmonary and skeletal) have also been reported. Bone marrow failure (BMF) is the main cause of early mortality, with an additional predisposition to malignancy. DC results from an anomalous progressive shortening of telomeres resulting in DNA replication problems inducing replicative senescence. Men are more affected than women are and X-linked recessive, autosomal dominant and autosomal recessive forms of the disease are recognized. There are no targeted therapies for DC. Patients treated with androgens had a hematological response. We herein describe case of a 32-year-old man, presented with several characteristic systemic features of this condition, including the classic triad of lesions, dysplastic bone marrow, epiphora and liver cirrhosis with grade I esophageal varices. Therefore, a prophylactic propranolol was started in additional to danazol. Three-week later, the patient had subsequent increases in his platelet, red cell and white cell counts.

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Germline mutation of MDM4, a major p53 regulator, in a familial syndrome of defective telomere maintenance

Science Advances ◽

10.1126/sciadv.aay3511 ◽

2020 ◽

Vol 6 (15) ◽

pp. eaay3511

Author(s):

Eléonore Toufektchan ◽

Vincent Lejour ◽

Romane Durand ◽

Neelam Giri ◽

Irena Draskovic ◽

...

Keyword(s):

Bone Marrow ◽

Mouse Model ◽

Bone Marrow Failure ◽

Dyskeratosis Congenita ◽

Telomere Maintenance ◽

Negative Regulator ◽

Telomere Dysfunction ◽

Genetic Modifiers ◽

Bone Marrow Failure Syndrome ◽

Telomere Biology

Dyskeratosis congenita is a cancer-prone inherited bone marrow failure syndrome caused by telomere dysfunction. A mouse model recently suggested that p53 regulates telomere metabolism, but the clinical relevance of this finding remained uncertain. Here, a germline missense mutation of MDM4, a negative regulator of p53, was found in a family with features suggestive of dyskeratosis congenita, e.g., bone marrow hypocellularity, short telomeres, tongue squamous cell carcinoma, and acute myeloid leukemia. Using a mouse model, we show that this mutation (p.T454M) leads to increased p53 activity, decreased telomere length, and bone marrow failure. Variations in p53 activity markedly altered the phenotype of Mdm4 mutant mice, suggesting an explanation for the variable expressivity of disease symptoms in the family. Our data indicate that a germline activation of the p53 pathway may cause telomere dysfunction and point to polymorphisms affecting this pathway as potential genetic modifiers of telomere biology and bone marrow function.

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Genome wide whole blood transcriptome profiling across inherited bone marrow failure subtypes

Blood Advances ◽

10.1182/bloodadvances.2021005360 ◽

2021 ◽

Author(s):

Amanda J Walne ◽

Thomas J Vulliamy ◽

Findlay Bewicke-Copley ◽

Jun Wang ◽

Jenna Alnajar ◽

...

Keyword(s):

Bone Marrow ◽

Whole Blood ◽

Bone Marrow Failure ◽

Enrichment Analysis ◽

Protein Translation ◽

Dyskeratosis Congenita ◽

Gene Set Enrichment Analysis ◽

Disease Pathogenesis ◽

Genome Wide ◽

Upregulated Genes

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 inherited bone marrow failure (IBMF) cases that are clinically and genetically characterised as Fanconi anemia (FA), dyskeratosis congenita (DC) and Shwachman Diamond syndrome (SDS). 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 towards upregulated genes in FA cases when compared to controls. Both DC and SDS cases 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 cut-off (FDR<0.05) that appeared as a unified signature across the IBMF subtypes. Subsequent transcriptomic analysis on genetically uncharacterised BMF cases revealed a striking overlap of genes, including 22 from the discovery set indicating a unified transcriptional drive across the classic (FA, DC and SDS) and uncharacterised BMF subtypes. This study has relevance in disease pathogenesis, for example in explaining the features (including the BMF) common to all IBMF cases and suggests harnessing this "transcriptional signature" for patient benefit.

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