CTC1 Mutations in a patient with dyskeratosis congenita.
ABSTRACT Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome caused by mutations in seven genes involved in telomere biology, with approximately 50% of cases remaining genetically uncharacterized. We report a patient with classic DC carrying a compound heterozygous mutation in the CTC1 (conserved telomere maintenance component 1) gene, which has recently implicated in the pleiotropic syndrome Coats plus. This report confirms a molecular link between DC and Coats plus and expands the genotype-phenotype complexity observed in telomere-related genetic disorders.
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ABSTRACT: Germline mutations in telomere biology genes cause dyskeratosis congenita (DC), an inherited bone marrow failure and cancer predisposition syndrome. DC is a clinically heterogeneous disorder diagnosed by the triad of dysplastic nails, abnormal skin pigmentation, and oral leukoplakia; Hoyeraal-Hreidarsson syndrome (HH), a clinically severe variant of DC, also includes cerebellar hypoplasia, immunodeficiency, and intrauterine growth retardation. Approximately 70% of DC cases are associated with a germline mutation in one of nine genes, the products of which are all involved in telomere biology. Using exome sequencing, we identified mutations in Adrenocortical Dysplasia Homolog (ACD) (encoding TPP1), a component of the telomeric shelterin complex, in one family affected by HH. The proband inherited a deletion from his father and a missense mutation from his mother, resulting in extremely short telomeres and a severe clinical phenotype. Characterization of the mutations revealed that the single-amino-acid deletion affecting the TEL patch surface of the TPP1 protein significantly compromises both telomerase recruitment and processivity, while the missense mutation in the TIN2-binding region of TPP1 is not as clearly deleterious to TPP1 function. Our results emphasize the critical roles of the TEL patch in proper stem cell function and demonstrate that TPP1 is the second shelterin component (in addition to TIN2) to be implicated in DC.Genes & Development 09/2014; 28(19). · 12.64 Impact Factor
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ABSTRACT: Dyskeratosis congenita (DC) is an inherited bone marrow failure (BMF) syndrome characterized by the classic triad of abnormal skin pigmentation, nail dystrophy, and oral leukoplakia. However, patients usually develop BMF and are predisposed to cancer, with increased risk for squamous cell carcinoma and hematolymphoid neoplasms. DC is a disease of defective telomere maintenance and is heterogeneous at the genetic level. It can be inherited in X-linked, autosomal dominant, or autosomal recessive patterns. Mutations in at least ten telomere- and telomerase-associated genes have been described in DC. There are no targeted therapies for DC and patients usually die of BMF due to a deficient renewing capability of hematopoietic stem cells. Allogeneic hematopoietic stem cell transplantation is the only curative treatment for BMF.Hematology Research and Reviews 01/2014; 5:157-67.
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ABSTRACT: Telomerase is a ribonucleoprotein enzyme that is necessary for overcoming telomere shortening in human germ and stem cells. Mutations in telomerase or other telomere-maintenance proteins can lead to diseases characterized by depletion of hematopoietic stem cells and bone marrow failure. Telomerase localization to telomeres requires an interaction with a region on the surface of the telomere-binding protein TPP1 known as the TEL patch. Here we identify a family with aplastic anemia and other related hematopoietic disorders, in which a one amino acid deletion in the TEL patch of TPP1 (ΔK170) segregates with disease. All family members carrying this mutation, but not those with wild-type TPP1, have short telomeres. When introduced into 293T cells, TPP1 with the ΔK170 mutation is able to localize to telomeres but fails to recruit telomerase to telomeres, supporting a causal relationship between this TPP1 mutation and bone marrow disorders. ACD/TPP1 is thus a newly-identified telomere-related gene in which mutations cause aplastic anemia and related bone marrow failure disorders.Blood 09/2014; · 9.78 Impact Factor
Pediatr Blood Cancer
CTC1 Mutations in a Patient With Dyskeratosis Congenita
Rachel B. Keller, BS,1,2Katelyn E. Gagne, BS,1,2G. Naheed Usmani, MD,3George K. Asdourian, MD,4
David A. Williams, MD,1,2Inga Hofmann, MD, PhD,1and Suneet Agarwal, MD, PhD1,2*
Dyskeratosis congenita (DC) is an inherited multisystem dis-
order characterized by a classic clinical triad of skin pigmentation
abnormalities, nail changes, and oral leukoplakia [1,2]. Patients
exhibit premature degeneration of several tissues manifesting as
bone marrow failure (BMF), pulmonary fibrosis, hematopoietic
and epithelial malignancies, gray hair, and other defects. DC is
caused by mutations in at least seven genes (DKC1, TERC, TERT,
TINF2, NHP2, NOP10, and TCAB1) involved in the maintenance
of telomere integrity [3,4], but in approximately 50% of cases a
genetic cause has not been identified. DC is one of a wider
phenotypic spectrum of ‘‘telomere diseases’’, including the severe
childhood disorders Hoyeraal–Hreidarsson (HH) and Revesz syn-
dromes, caused by DKC1 and TINF2 mutations [5,6], as well as
more tissue-restricted or later-onset disorders such as isolated
aplastic anemia and familial idiopathic pulmonary fibrosis, caused
by TERC and TERT mutations .
Coats plus is a pleiotropic, autosomal recessive disorder
characterized by retinal telangiectasia and exudates, intracranial
calcification with leukodystrophy and brain cysts, osteopenia
with predisposition to fractures, and gastrointestinal bleeding
and portal hypertension caused by vascular ectasias . A
clinical link between Coats plus and telomere diseases is sug-
gested by the observations that some patients with Coats
plus show premature graying of hair, nail dystrophy and anemia;
that Revesz syndrome patients have Coats retinopathy; and
that both Revesz and HH syndrome patients can have intracranial
calcifications [8,9]. Exome sequencing of patients with Coats
plus and the related disorder cerebroretinal microangiopathy
with calcifications and cysts (CRMCC) has revealed mutations
in the CTC1 gene, encoding ‘‘conserved telomere maintenance
component 1,’’ leading to the hypothesis that CTC1 mutations
may also be found in patients with DC [9–11]. Here we describe
compound heterozygous CTC1 mutations in a patient with
classic DC, confirming the genetic link between Coats plus/
CRMCC and DC.
The patient presented as a previously healthy 15-year-old fe-
male with fatigue and pancytopenia, with an absolute neutrophil
count of 800/ml, hemoglobin 9.4 g/dl, mean corpuscular volume
of 117 fl, and platelets of 56,000/ml. Medical history was notable
only for irregularities in skin pigmentation of unclear etiology and
traumatic fractures of her digits. She had a normal neurocognitive,
developmental and ophthalmological history. Family history was
unremarkable. Physical examination was notable for height 5th
percentile, graying hair, buccal leukoplakia, reticular hypo- and
hyper-pigmented skin lesions over the face, trunk and extremities,
and cracked fingernails and toenails (Fig. 1A). Bone marrow
examination revealed marked hypocellularity (<5%; Fig. 1B)
and no evidence of myelodysplasia or malignancy. Telomere
length testing showed very short age-adjusted telomere length
in five of six peripheral blood cell subsets (Fig. 1C and Supple-
mentary Fig. 1A) [12,13]. She was diagnosed with DC based on
the classic triad of clinical manifestations, BMF and very short
In the 3 years following her initial presentation, the patient
sustained fractures of her femur and metatarsal without significant
trauma, and bone density scan showed osteopenia. Dental evalua-
tion showed numerous caries and shortened incisor roots on
radiography. Her pulmonary function tests showed decreased dif-
fusion capacity of 67% predicted with normal lung volumes and
spirometry. One year after her presentation with BMF the patient
complained of blurry vision, and was found to have myopia
corrected with eyeglasses. Fundoscopic exam was normal except
for sheathed vessels and microaneurysm formation in the periph-
eral retina bilaterally (Fig. 1D). Visual acuity and fundoscopic
Dyskeratosis congenita (DC) is a rare inherited bone marrow
failure syndrome caused by mutations in seven genes involved in
telomere biology, with approximately 50% of cases remaining ge-
netically uncharacterized. We report a patient with classic DC
carrying a compound heterozygous mutation in the CTC1 (con-
served telomere maintenance component 1) gene, which has
recently implicated in the pleiotropic syndrome Coats plus. This
report confirms a molecular link between DC and Coats plus and
expands the genotype–phenotype complexity observed in telomere-
related genetic disorders. Pediatr Blood Cancer
? 2012 Wiley Periodicals, Inc.
aplastic anemia; bone marrow failure; molecular genetics; non-malignant hematology; telomerase
Additional Supporting Information may be found in the online version
of this article.
1Division of Hematology/Oncology, Stem Cell Program, Children’s
Hospital Boston; Department of Pediatric Oncology, Dana-Farber
Cancer Institute; Harvard Medical School, Boston, Massachusetts;
2Harvard Stem Cell Institute, Boston, Massachusetts;
Pediatric Hematology/Oncology, University of Massachusetts Medi-
cal School, Worcester, Massachusetts;4Department of Ophthalmolo-
gy, UMass Memorial Medical Center, Worcester, Massachusetts
Grant sponsor: NIH; Grant numbers: K08HL089150, 5RC1DK086861.
Conflicts of interest: Nothing to declare.
*Correspondence to: Suneet Agarwal, MD, PhD, Children’s Hospital
Boston, CLS3002, 3 Blackfan Circle, Boston, MA 02115.
Received 14 March 2012; Accepted 16 April 2012
? 2012 Wiley Periodicals, Inc.
Published online in Wiley Online Library
exam were stable in follow up. The patient had worsening cyto-
penias and most recently has required red blood cell and platelet
MOLECULAR AND CELLULAR STUDIES
Testing for mutations in DKC1, TERC, TERT, NHP2, NOP10,
and TINF2 was negative. Informed consent was obtained for
research studies. Based on Anderson et al. , we performed
Sanger sequencing on the patient’s DNA to cover the 23 exons
of the CTC1 gene, and identified compound heterozygous muta-
tions in exon 5 (het. c.724_727delAAAG; p.Lys242Leufs?41) and
exon 18 (het. c.2954_2956delGTT; p.Cys985del) (Fig. 2A). Both
alleles produced mRNA detectable by RT-PCR (Supplementary
Fig. 1B,C). The patient’s mother carried only the exon 18 muta-
tion (Supplementary Fig. 1D). No pathogenic CTC1 mutations
were found in three other patients with classic DC of unknown
hypocellular marrow with rare hematopoietic elements. C: Measurement of telomere length by flow-cytometry/fluorescence in situ hybridiza-
tion (flow-FISH) in lymphocytes (left) and granulocytes (right), plotted as percentile of age-adjusted normal values. D: Retinal photograph
showing a normal posterior pole (left panel), but obliterated (black arrows) and sheathed (blue arrow) vessels in the temporal fundus periphery
(right panel). Findings were similar bilaterally.
A: Skin and oral mucosal manifestations in our patient with DC and CTC1 mutations. B: Bone marrow biopsy showing a markedly
2Keller et al.
Pediatr Blood Cancer DOI 10.1002/pbc
each deletion junction is indicated (red arrow), and the bases deleted on one allele are shown (red box). The normal sequence and resulting
mutant allele sequence are depicted. B: Compared to normal fibroblasts (left panel), patient fibroblasts showed several features of senescence
including frequent polygonal forms, ballooning, dendritic-like projections and degeneration [17,18] (middle and right panels). C: Neuroim-
aging. Left panel: Cranial axial computed tomography (CT) scan showing right-sided thalamic calcification (red arrow). Right panel: cervical
spine sagittal T2 magnetic resonance imaging (MRI) showing extensive septated syrinx in cervical to thoracic portions of spinal cord
(demarcated by blue line).
A: Sanger sequencing of CTC1 exons 5 (upper panel) and exon 18 (lower panel) on DNA from peripheral blood cells. The 50site of
CTC1 Mutations in Dyskeratosis Congenita3
Pediatr Blood Cancer DOI 10.1002/pbc
Patient bone marrow cells failed to proliferate for metaphase
karyotype analysis. Stromal cultures from patient bone marrow
yielded only single colonies of senescent fibroblasts after 5 weeks
(n ¼ 2), whereas normal cultures typically produce >106repli-
cating cells after 3–4 weeks. Patient skin biopsy explant cultures
yielded approximately 103–104cells which showed signs of se-
nescence (n ¼ 2; Fig. 2B), in contrast to normal samples which
routinely give >106replicating cells after 5 weeks.
Because of the association of CTC1 mutations with Coats plus/
CRMCC, neuroimaging was performed and revealed a prominent
thalamic calcification and a large septated syrinx extending from
the cervical to mid-thoracic spinal cord (Fig. 2C). The patient has
no neurological complaints except mild, intermittent headaches,
and no deficits on examination.
DC is a rare disease with an estimated annual incidence of <1
in 1 million, with multiple inheritance forms and myriad clinical
manifestations . Genotype–phenotype correlations are com-
plex, due to several factors including a variety of underlying
hypomorphic gene mutations, disease anticipation, and genetic
and environmental modifier effects . Our patient presented
with typical skin, nail and oral mucosal changes, BMF and very
short telomeres, thus fulfilling criteria for DC. She manifested
other DC-associated abnormalities including gray hair, osteope-
nia/fractures, dental disorders, and reduced pulmonary diffusion
capacity. Her fundoscopic exam showed vascular changes which
may represent early signs of retinopathy, but not the exudate,
hemorrhage, or retinal detachment characteristic of Coats disease.
The patient had no significant neurological symptoms, but imag-
ing prompted by the genetic findings revealed significant CNS
abnormalities. There was no history indicative of gastrointestinal
pathology. Therefore, while our patient presented clinically with
classic DC and without cardinal symptoms of Coats plus/
CRMCC, recognition of the common genetic mutation in CTC1
led to the detection of unexpected, overlapping abnormalities.
The mutations found in CTC1 in our patient are identical to
alleles recurrently mutated in patients with Coats plus/CRMCC,
and are not present in dbSNP or in the exome variant server
database, establishing their pathogenicity [9,10]. The specific
combination of alleles in our patient was not described in
the two published series, but compound heterozygosity of a non-
sense lesion with a missense variant was observed frequently.
These data suggest that the phenotypic differences between our
patient with DC and Coats plus/CRMCC patients are due to
genetic and/or environmental modifying factors rather than allelic
differences in CTC1.
We observed a pronounced defect in outgrowth and rapid
senescence of CTC1 mutant fibroblasts, which correlates with
the marked degree of aplasia and indicates depletion of stromal
as well as hematopoietic precursors in the patient’s bone marrow.
CTC1 is a conserved subunit of a-accessory factor, which
stimulates the activity of DNA polymerase a-primase, and may
have a role beyond telomere biology in maintaining general ge-
nomic stability [15,16]. Based on these observations, we speculate
that cellular defects caused by CTC1 mutations will be more
extensive than those caused by DC-related mutations in telome-
In conclusion, we report a patient presenting with classic
DC and BMF with CTC1 mutations identical to those recently
described in Coats plus/CRMCC. This report demonstrates
that CTC1 is a gene mutated in DC, and expands the range of
phenotypic variation observed in genetic diseases of telomere
We thank the patients and families for their participation in
research. This work was supported by NIH grants K08HL089150
to S.A. and by 5RC1DK086861 to D.A.W and I.H.
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