Syndromic thrombocytopenia and predisposition to acute myelogenous leukemia caused by constitutional microdeletions on chromosome 21q

Familial Acute Promyelocytic Leukemia: A Case Report and Review of the Literature

Acute promyelocytic leukemia (APL) is characterized by a reciprocal translocation t (15;17) (q24;q21), which leads to the fusion of PML and RARα genes known as PML-RARα fusion. A few cases of potentially hereditary leukemia-related genes in APL have been reported, but no instances of familial aggregation of APL have been documented. Here, we describe a family in whom two members successively affected by APL。The potential familial association observed in these two cases of APL highlights the need for further investigation and more definitive genetic lineage tracing in order to understand the genetic basis of this disease.

Over-expression of Dyrk1A affects bleeding by modulating plasma fibronectin and fibrinogen level in mice

Down syndrome is the most common chromosomal abnormality in humans. Patients with Down syndrome have hematologic disorders, including mild to moderate thrombocytopenia. In case of Down syndrome, thrombocytopenia is not associated with bleeding, and it remains poorly characterized regarding molecular mechanisms. We investigated the effects of overexpression of Dyrk1A, an important factor contributing to some major Down syndrome phenotypes, on platelet number and bleeding in mice. Mice overexpressing Dyrk1A have a decrease in platelet number by 20%. However, bleeding time was found to be reduced by 50%. The thrombocytopenia and the decreased bleeding time observed were not associated to an abnormal platelet receptors expression, to a defect of platelet activation by ADP, thrombin or convulxin, to the presence of activated platelets in the circulation or to an abnormal half-life of the platelets. To propose molecular mechanisms explaining this discrepancy, we performed a network analysis of Dyrk1A interactome and demonstrated that Dyrk1A, fibronectin and fibrinogen interact indirectly through two distinct clusters of proteins. Moreover, in mice overexpressing Dyrk1A, increased plasma fibronectin and fibrinogen levels were found, linked to an increase of the hepatic fibrinogen production. Our results indicate that overexpression of Dyrk1A in mice induces decreased bleeding consistent with increased plasma fibronectin and fibrinogen levels, revealing a new role of Dyrk1A depending on its indirect interaction with these two proteins.

[Management of genetic predisposition to hematologic malignancies in patients undergoing allogeneic hematopoietic cell transplantation (HCT): Guidelines from the SFGM-TC]

The advent of new technologies has made it possible to identify genetic predispositions to myelodysplastic syndromes (MDS) and acute leukemias (AL) more frequently. The most frequent and best characterized at present are mutations in CEBPA, RUNX1, GATA2, ETV6 and DDX41 and, either in the presence of one of these mutations with a high allelic frequency, or in the case of a personal or family history suggestive of blood abnormalities such as non-immune thrombocytopenia, it is recommended to look for the possibility of a hereditary hematological malignancy (HHM). Indeed, early recognition of these HHMs allows better adaptation of the management of patients and their relatives, as allogeneic hematopoietic stem cell transplantation (HSCT) is very often proposed for these pathologies. According to current data, with the exception of the GATA2 mutation, the constitutional or somatic nature of the mutations does not seem to influence the prognosis of hematological diseases. Therefore, the indication for an allograft will be determined according to the usual criteria. However, when searching for a family donor, it is important to ensure that there is no hereditary disease in the donor. In order to guarantee the possibility of performing the HSC allograft within a short period of time, it may be necessary to initiate a parallel procedure to find an unrelated donor. Given the limited information on the modalities of HSC transplantation in this setting, it is important to assess the benefit/risk of the disease and the procedure to decide on the type of conditioning (myeloablative or reduced intensity). In view of the limited experience with the risk of secondary cancers in the medium and long-term, it may be appropriate to recommend reduced intensity conditioning, as in the case of better characterized syndromic hematological diseases such as Fanconi anemia or telomere diseases. In summary, it seems important to evoke HHM more frequently, particularly in the presence of a family history, certain mutations or persistent blood abnormalities, in order to discuss the specific modalities of HSC allografting, particularly with regard to the search for a donor and the evaluation of certain modalities of the procedure, such as conditioning. It should be noted that the discovery of HHM, especially if the indication of an allogeneic HSC transplant is retained, will raise ethical and psychological considerations not only for the patient, but also for his family. A multidisciplinary approach involving molecular biologists, geneticists, hematologists and psychologists is essential.

RUNX1-mutated families show phenotype heterogeneity and a somatic mutation profile unique to germline predisposed AML

First reported in 1999, germline runt-related transcription factor 1 (RUNX1) mutations are a well-established cause of familial platelet disorder with predisposition to myeloid malignancy (FPD-MM). We present the clinical phenotypes and genetic mutations detected in 10 novel RUNX1-mutated FPD-MM families. Genomic analyses on these families detected 2 partial gene deletions, 3 novel mutations, and 5 recurrent mutations as the germline RUNX1 alterations leading to FPD-MM. Combining genomic data from the families reported herein with aggregated published data sets resulted in 130 germline RUNX1 families, which allowed us to investigate whether specific germline mutation characteristics (type, location) could explain the large phenotypic heterogeneity between patients with familial platelet disorder and different HMs. Comparing the somatic mutational signatures between the available familial (n = 35) and published sporadic (n = 137) RUNX1-mutated AML patients showed enrichment for somatic mutations affecting the second RUNX1 allele and GATA2. Conversely, we observed a decreased number of somatic mutations affecting NRAS, SRSF2, and DNMT3A and the collective genes associated with CHIP and epigenetic regulation. This is the largest aggregation and analysis of germline RUNX1 mutations performed to date, providing a unique opportunity to examine the factors underlying phenotypic differences and disease progression from FPD to MM.

Distinctive phenotypes in two children with novel germline RUNX1 mutations - one with myeloid malignancy and increased fetal hemoglobin

RUNX1 associated familial platelet disorder (FPD) is a rare autosomal dominant hematologic disorder characterized by thrombocytopenia and/or altered platelet function. There is an increased propensity to develop myeloid malignancy (MM) - acute myeloid leukemia, myeloproliferative neoplasms or myelodysplastic syndrome often in association with secondary somatic variants in other genes. To date, 23 FPD-MM pediatric cases have been reported worldwide. Here, we present two new kindreds with novel RUNX1 pathogenic variants in which children are probands. The first family is a daughter/mother diad, sharing a heterozygous frameshift variant in RUNX1 gene (c.501delT p.Ser167Argfs*9). The daughter, age 13 years, presented with features resembling juvenile myelomonocytic leukemia - severe anemia, thrombocytopenia, high white cell count with blast cells, monocytosis, increased nucleated red cells and had somatic mutations with high allele burden in CUX1, PHF6, and SH2B3 genes. She also had increased fetal hemoglobin and increased LIN28B expression. The mother, who had a long history of hypoplastic anemia, had different somatic mutations- a non-coding mutation in CUX1 but none in PHF6 or SH2B3. Her fetal hemoglobin and LIN28B expression were normal. In the second kindred, the proband, now 4 years old with thrombocytopenia alone, was investigated at 3 months of age for persistent neonatal thrombocytopenia with large platelets. Molecular testing identified a heterozygous intragenic deletion in RUNX1 encompassing exon 5. His father is known to have increased bruising for several years but is unavailable for testing. These two cases illustrate the significance of secondary mutations in the development and progression of RUNX1-FPD to MM.

Emerging roles for multifunctional ion channel auxiliary subunits in cancer

Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.

Thrombocytopenia and Predisposition to Acute Myeloid Leukemia due to Mosaic Ring 21 with Loss of RUNX1: Cytogenetic and Molecular Characterization

Familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML) has been well documented in the literature and is a new entity within the latest revised edition of the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues (OMIM). The disorder arises due to mutations within the RUNX1 gene in chromosome 21; mutations within the Runt-binding domain are the most commonly encountered anomalies that cause decreased platelet count and function. Rare cases of haploinsufficiency have also been shown to cause this disorder. Here, we describe a 12-year-old female with mosaicism for a ring chromosome 21 and monosomy 21 who was born with thrombocytopenia which is now explained by loss of the RUNX1 gene resulting in FPD/AML. We also comment on the structure of the ring and the mechanism of its formation.

Monosomy chromosome 21 compensated by 21q22.11q22.3 duplication in a case with small size and minor anomalies

Background

Partial monosomy 21 is a rare finding with variable sizes and deletion breakpoints, presenting with a broad spectrum of phenotypes.

Case presentation

We report a 10-month-old boy with short stature, minor anomalies and mild motor delay. The patient had a monosomy 21 and duplication of the 21q22.11q22.3 region on the remaining derivative chromosome 21 which represents a partial 21q uniparental disomy of paternal origin, upd(21q22.11q22.3)pat. The abnormalities were characterized by karyotyping, FISH, chromosomal microarray, and genotyping.

Conclusions

This is the first case showing a monosomy 21 compensated by upd(21q22.11q22.3) as a mechanism of genomic rescue. Because there is no strong evidence showing imprinting on chromosome 21, the uniparental disomy itself is not associated with abnormal phenotype but has reduced phenotype severity of monosomy 21. We reviewed the previously published cases with isolated 21q deletions and identified a common deletion of 5.7 Mb associated with low birth weight, length and head circumference in the 21q21.2 region.

Recommendations for Surveillance for Children with Leukemia-Predisposing Conditions

Leukemia, the most common childhood cancer, has long been recognized to occasionally run in families. The first clues about the genetic mechanisms underlying familial leukemia emerged in 1990 when Li-Fraumeni syndrome was linked to TP53 mutations. Since this discovery, many other genes associated with hereditary predisposition to leukemia have been identified. Although several of these disorders also predispose individuals to solid tumors, certain conditions exist in which individuals are specifically at increased risk to develop myelodysplastic syndrome (MDS) and/or acute leukemia. The increasing identification of affected individuals and families has raised questions around the efficacy, timing, and optimal methods of surveillance. As part of the AACR Childhood Cancer Predisposition Workshop, an expert panel met to review the spectrum of leukemia-predisposing conditions, with the aim to develop consensus recommendations for surveillance for pediatric patients. The panel recognized that for several conditions, routine monitoring with complete blood counts and bone marrow evaluations is essential to identify disease evolution and enable early intervention with allogeneic hematopoietic stem cell transplantation. However, for others, less intensive surveillance may be considered. Because few reports describing the efficacy of surveillance exist, the recommendations derived by this panel are based on opinion, and local experience and will need to be revised over time. The development of registries and clinical trials is urgently needed to enhance understanding of the natural history of the leukemia-predisposing conditions, such that these surveillance recommendations can be optimized to further enhance long-term outcomes. Clin Cancer Res; 23(11); e14-e22. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Myeloid Neoplasm With Germline Predisposition: A 2016 Update for Pathologists

CONTEXT.—

Myeloid neoplasms with familial occurrence have been rarely reported in the past. With the advance of molecular technology and better understanding of the molecular pathogenesis of myeloid neoplasms, investigating the genetic causes of familial acute myeloid leukemia or myelodysplastic syndrome has become feasible in the clinical setting. Recent studies have identified a rapidly expanding list of germline mutations associated with increased risks of developing myeloid neoplasm in the affected families. It is important to recognize these entities, as such a diagnosis may dictate a unique approach in clinical management and surveillance for the patients and carriers.

OBJECTIVE.—

To raise the awareness of myeloid neoplasms arising in the setting of familial inheritance among practicing pathologists.

DATA SOURCES.—

Based on recent literature and the 2016 revision of the World Health Organization classification of hematopoietic neoplasms, we provide an up-to-date review of myeloid neoplasm with germline predisposition.

CONCLUSIONS.—

This short review focuses on the clinical, pathologic, and molecular characterization of myeloid neoplasm with germline predisposition. We emphasize the important features that will help practicing pathologists to recognize these newly described entities.

Initial Diagnostic Workup of Acute Leukemia: Guideline From the College of American Pathologists and the American Society of Hematology

CONTEXT

- A complete diagnosis of acute leukemia requires knowledge of clinical information combined with morphologic evaluation, immunophenotyping and karyotype analysis, and often, molecular genetic testing. Although many aspects of the workup for acute leukemia are well accepted, few guidelines have addressed the different aspects of the diagnostic evaluation of samples from patients suspected to have acute leukemia.

OBJECTIVE

- To develop a guideline for treating physicians and pathologists involved in the diagnostic and prognostic evaluation of new acute leukemia samples, including acute lymphoblastic leukemia, acute myeloid leukemia, and acute leukemias of ambiguous lineage.

DESIGN

- The College of American Pathologists and the American Society of Hematology convened a panel of experts in hematology and hematopathology to develop recommendations. A systematic evidence review was conducted to address 6 key questions. Recommendations were derived from strength of evidence, feedback received during the public comment period, and expert panel consensus.

RESULTS

- Twenty-seven guideline statements were established, which ranged from recommendations on what clinical and laboratory information should be available as part of the diagnostic and prognostic evaluation of acute leukemia samples to what types of testing should be performed routinely, with recommendations on where such testing should be performed and how the results should be reported.

CONCLUSIONS

- The guideline provides a framework for the multiple steps, including laboratory testing, in the evaluation of acute leukemia samples. Some aspects of the guideline, especially molecular genetic testing in acute leukemia, are rapidly changing with new supportive literature, which will require on-going updates for the guideline to remain relevant.

Myeloid neoplasms with germ line RUNX1 mutation

Familial platelet disorder with propensity to myeloid malignancies (FPD/AML) is an autosomal dominant disorder characterized by quantitative and/or qualitative platelet defects with a tendency to develop a variety of hematological malignancies. Heterozygous germ line mutations in the RUNX1 gene are responsible genetic events for FPD/AML. Notably, about half of individuals in the family with germ line mutations in RUNX1 develop overt hematological malignancies. The latency is also relatively long as an average age at diagnosis is more than 30 years. Similar to what is observed in sporadic hematological malignancies, acquired additional genetic events cooperate with inherited RUNX1 mutations to progress the overt malignant phase. Reflecting recent increased awareness of hematological malignancies with germ line mutations, FPD/AML was added in the revised WHO 2016 classification. In this review, we provide an update on FPD/AML with recent clinical and experimental findings.

De Novo Truncating Variants in SON Cause Intellectual Disability, Congenital Malformations, and Failure to Thrive

SON is a key component of the spliceosomal complex and a critical mediator of constitutive and alternative splicing. Additionally, SON has been shown to influence cell-cycle progression, genomic integrity, and maintenance of pluripotency in stem cell populations. The clear functional relevance of SON in coordinating essential cellular processes and its presence in diverse human tissues suggests that intact SON might be crucial for normal growth and development. However, the phenotypic effects of deleterious germline variants in SON have not been clearly defined. Herein, we describe seven unrelated individuals with de novo variants in SON and propose that deleterious variants in SON are associated with a severe multisystem disorder characterized by developmental delay, persistent feeding difficulties, and congenital malformations, including brain anomalies.

Braddock-Carey syndrome: A 21q22 contiguous gene syndrome encompassing RUNX1

In 1994, Braddock and Carey first reported two unrelated girls with a new multiple malformation syndrome. The primary features included Pierre Robin sequence, persistent neonatal-onset thrombocytopenia, agenesis of the corpus callosum, a distinctive facies, enamel hypoplasia, and severe developmental delay. Since that time, there have been multiple other reported patients with a similar phenotype. In addition, several reports of thrombocytopenia and developmental delay have been documented in association with deletions in the Down syndrome critical region at 21q22. The similarity of the reported cases with deletions involving 21q22 with the clinical presentation of the two patients with Braddock-Carey syndrome resulted in a reinvestigation of the genetic etiology of these two patients 20 years after the original study. This investigation provides evidence that the etiology of this and other "Fanconi-like" disorders represent a newly recognized contiguous gene deletion syndrome involving 21q22 and specifically, the RUNX1 gene. © 2016 Wiley Periodicals, Inc.

Intronic cleavage and polyadenylation regulates gene expression during DNA damage response through U1 snRNA

The DNA damage response involves coordinated control of gene expression and DNA repair. Using deep sequencing, we found widespread changes of alternative cleavage and polyadenylation site usage on ultraviolet-treatment in mammalian cells. Alternative cleavage and polyadenylation regulation in the 3ʹ untranslated region is substantial, leading to both shortening and lengthening of 3ʹ untranslated regions of genes. Interestingly, a strong activation of intronic alternative cleavage and polyadenylation sites is detected, resulting in widespread expression of truncated transcripts. Intronic alternative cleavage and polyadenylation events are biased to the 5ʹ end of genes and affect gene groups with important functions in DNA damage response and cancer. Moreover, intronic alternative cleavage and polyadenylation site activation during DNA damage response correlates with a decrease in U1 snRNA levels, and is reversible by U1 snRNA overexpression. Importantly, U1 snRNA overexpression mitigates ultraviolet-induced apoptosis. Together, these data reveal a significant gene regulatory scheme in DNA damage response where U1 snRNA impacts gene expression via the U1-alternative cleavage and polyadenylation axis.

Haematological spectrum and genotype-phenotype correlations in nine unrelated families with RUNX1 mutations from the French network on inherited platelet disorders

Background

Less than 50 patients with FPD/AML (OMIM 601309) have been reported as of today and there may an underestimation. The purpose of this study was to describe the natural history, the haematological features and the genotype-phenotype correlations of this entity in order to, first, screen it better and earlier, before leukaemia occurrence and secondly to optimize appropriate monitoring and treatment, in particular when familial stem cell transplantation is considered.

Methods

We have investigated 41 carriers of RUNX1 alteration belonging to nine unrelated French families with FPD/AML and two syndromic patients, registered in the French network on rare platelet disorders from 2005 to 2015.

Results

Five missense, one non-sense, three frameshift mutations and two large deletions involving several genes including RUNX1 were evidenced. The history of familial leukaemia was suggestive of FPD/AML in seven pedigrees, whereas an autosomal dominant pattern of lifelong thrombocytopenia was the clinical presentation of two. Additional syndromic features characterized two large sporadic deletions. Bleeding tendency was mild and thrombocytopenia moderate (>50 x10⁹/L), with normal platelet volume. A functional platelet defect consistent with a δ-granule release defect was found in ten patients regardless of the type of RUNX1 alteration. The incidence of haematological malignancies was higher when the mutated RUNX1 allele was likely to cause a dominant negative effect (19/34) in comparison with loss of function alleles (3/9). A normal platelet count does not rule out the diagnosis of FPD/AML, since the platelet count was found normal for three mutated subjects, a feature that has a direct impact in the search for a related donor in case of allogeneic haematopoietic stem cell transplantation.

Conclusions

Platelet dysfunction suggestive of defective δ-granule release could be of values for the diagnosis of FPD/AML particularly when the clinical presentation is an autosomal dominant thrombocytopenia with normal platelet size in the absence of familial malignancies. The genotype-phenotype correlations might be helpful in genetic counselling and appropriate optimal therapeutic management.

Proximal 21q deletion as a result of a de novo unbalanced t(12;21) translocation in a patient with dysmorphic features, hepatomegaly, thick myocardium and delayed psychomotor development

Background

IInterstitial 21q deletions can cause a wide spectrum of symptoms depending on the size and the location of the deletion. It has previously been suggested that the long arm of chromosome 21 can be divided into three regions based on the clinical severity of the patients and deletion of the region from 32.3 Mb to 37.1 Mb was more crucial than the deletion of other regions.

Case Presentation

In this study we describe a female patient with dysmorphic features, hepatomegaly, thick myocardium and psychomotor delay. Conventional karyotyping was initially interpreted as full monosomy 21, but subsequent chromosome microarray analysis suggested an approximately 18 Mb partial monosomy. Re-evaluation of the karyotype and fluorescence in situ hybridization revealed deletion of the proximal 21q11.2-q22.11 segment and insertion of 21q22.11-qter to 12qter. The deletion of the present case overlaps with two of the proposed regions including part of the proposed crucial region.

Conclusions

This report emphasizes the relevance of investigating suspected full monosomies with high resolution methods and FISH in order to investigate the extent of the deletion and the presence of more complex rearrangements.

Deletion of the App-Runx1 region in mice models human partial monosomy 21

Partial monosomy 21 (PM21) is a rare chromosomal abnormality that is characterized by the loss of a variable segment along human chromosome 21 (Hsa21). The clinical phenotypes of this loss are heterogeneous and range from mild alterations to lethal consequences, depending on the affected region of Hsa21. The most common features include intellectual disabilities, craniofacial dysmorphology, short stature, and muscular and cardiac defects. As a complement to human genetic approaches, our team has developed new monosomic mouse models that carry deletions on Hsa21 syntenic regions in order to identify the dosage-sensitive genes that are responsible for the symptoms. We focus here on the Ms5Yah mouse model, in which a 7.7-Mb region has been deleted from the App to Runx1 genes. Ms5Yah mice display high postnatal lethality, with a few surviving individuals showing growth retardation, motor coordination deficits, and spatial learning and memory impairments. Further studies confirmed a gene dosage effect in the Ms5Yah hippocampus, and pinpointed disruptions of pathways related to cell adhesion (involving App, Cntnap5b, Lgals3bp, Mag, Mcam, Npnt, Pcdhb2, Pcdhb3, Pcdhb4, Pcdhb6, Pcdhb7, Pcdhb8, Pcdhb16 and Vwf). Our PM21 mouse model is the first to display morphological abnormalities and behavioural phenotypes similar to those found in affected humans, and it therefore demonstrates the major contribution that the App-Runx1 region has in the pathophysiology of PM21.

Summary: The Del(16App-Runx1)5Yah mouse model displays morphological abnormalities and behavioural phenotypes similar to those found in humans with partial monosomy 21, and it therefore demonstrates the major contribution of the App-Runx1 region to the pathophysiology of partial monosomy 21.

Inherited predisposition to acute myeloid leukemia

Germline testing for familial predisposition to myeloid malignancies is becoming more common with the recognition of multiple familial syndromes. Currently, Clinical Laboratory Improvement Amendments-approved testing exists for the following: familial platelet disorder with propensity to acute myeloid leukemia, caused by mutations in RUNX1; familial myelodysplastic syndrome/acute myeloid leukemia with mutated GATA2; familial acute myeloid leukemia with mutated CEBPA; and the inherited bone marrow failure syndromes, including dyskeratosis congenita, a disease of abnormal telomere maintenance. With the recognition of additional families with a genetic component to their myeloid diseases, new predisposition alleles are likely to be identified. Awareness of the existence of these syndromes will facilitate proper genetic counseling, appropriate testing, and clinical management of these cases.

A de novo 1.4-Mb deletion at 21q22.11 in a boy with developmental delay

Monosomy 21 is a very rare chromosomal abnormality. At least 45 patients with partial deletion involving 21q11 have been reported. Here, we report a Japanese boy who presented with pre- and postnatal growth delays, psychomotor developmental delay, microcephaly, and iris coloboma. Cytogenetic analysis revealed a de novo 1.4-Mb deletion at 21q22.11 containing 19 protein-coding RefSeq genes. We compared the clinical phenotypes between the present patient and 16 previously reported patients with a deleted region associated with postnatal growth delay and psychomotor developmental delay. Interestingly, ITSN1 was the only gene deleted or disrupted in all cases; this gene is known to be associated with intellectual disability. Microcephaly and brain structural abnormalities including polymicrogyria and agenesis/hypoplasia of the corpus callosum may also result from haploinsufficiency of ITSN1, highlighting its clinical significance for the neurological features of patients with monosomy 21.

Biological and clinical features of trisomy 21 in adult patients with acute myeloid leukemia

INTRODUCTION

Trisomy 21 is frequently noted in patients with AML. In adults, +21 has traditionally been considered an intermediate-risk cytogenetic aberration.

PATIENTS AND METHODS

We analyzed 90 patients with newly diagnosed AML harboring +21. Four cytogenetic subgroups were defined based on associated cytogenetic abnormalities: +21 alone, +21 with favorable, +21 with intermediate, and +21 with unfavorable cytogenetics.

RESULTS

Fifty-four percent of patients with +21 AML achieved a complete remission (CR) or CR with incomplete platelet recovery (CRp) after induction therapy with a trend toward improved CR/CRp rates in patients with +21 alone/+21 with favorable cytogenetics compared with patients with +21 with intermediate/+21 with unfavorable cytogenetics (76% vs. 50%; P = .057). Time to progression (TTP) was 12 months (range, 5-19) and overall survival (OS) was 9 months (range, 7-11) for the entire group. TTP was longer for patients with +21 alone (not reached) or with +21 with favorable cytogenetics (101 months) compared with those with +21 with intermediate cytogenetics (2 months) or +21 with unfavorable cytogenetics (11 months) (P = .02). Similarly, OS was improved in patients with +21 with favorable cytogenetics (not reached) or +21 alone (107 months), compared with +21 with unfavorable cytogenetics (9 months) or +21 with intermediate cytogenetics (8 months) (P < .001). The differences in TTP and OS were maintained on multivariate analysis (P = .04 and P = .001; respectively).

CONCLUSION

Isolated +21 hitherto classified as intermediate-risk cytogenetics might actually behave as a favorable-risk cytogenetics in adult AML patients.

Recognizing familial myeloid leukemia in adults

Germline testing for familial cases of myeloid leukemia in adults is becoming more common with the recognition of multiple genetic syndromes predisposing people to bone marrow disease. Currently, Clinical Laboratory Improvement Amendments approved testing exists for several myeloid leukemia predisposition syndromes: familial platelet disorder with propensity to acute myeloid leukemia (FPD/AML), caused by mutations in RUNX1; familial AML with mutated CEBPA; familial myelodysplastic syndrome and acute leukemia with mutated GATA2; and the inherited bone marrow failure syndromes, including dyskeratosis congenita, a disease of abnormal telomere maintenance. With the recognition of additional families with a genetic component to their leukemia, new predisposition alleles will likely be identified. We highlight how to recognize and manage these cases as well as outline the characteristics of the major known syndromes. We look forward to future research increasing our understanding of the scope of inherited myeloid leukemia syndromes.

A 2.84 Mb deletion at 21q22.11 in a patient clinically diagnosed with Marden-Walker syndrome

We present a girl with the characteristic clinical picture associated with Marden-Walker syndrome (MWS; OMIM 248700), including mask-like face with blepharophimosis, joint contractures, intellectual disability, a multicystic dysplastic kidney and cerebral dysgenesis. The long-term follow-up allowed us to monitor the evolution of the phenotype in this patient, and among the main findings we highlight the following: demyelination of the pyramidal tract demonstrated by transcranial magnetic stimulation and the involvement of the levator muscles of angle of mouth in fixed facial expression with relative integrity of the rest of the facial expression muscles. A 244 k array comparative genomic hybridization (aCGH) was carried out and showed a de novo interstitial deletion of approximately 2.84 Mb affecting only the cytoband 21q22.11 (genome coordinates chr21:31,874,016-34,711,763). We selected 10 of the most recent published cases with either total or partial deletions of cytoband 21q22.11 that provided good characterization of the genomic size or the genes in the deleted regions. We observed that in nine of the 10 cases the deleted regions included the RUNX1 gene in 21q22.12, which is not affected in the current patient's deletion or in that of Patient 3 from Roberson et al. [2011]. After a comparison of shared deleted genes between cases, and correlation of their potential phenotypes, we concluded that the pattern of defects considered for a diagnosis of MWS may represent part of the phenotypic expression of a partial or total deletion of 21q22.11.

RUNX1 meets MLL: epigenetic regulation of hematopoiesis by two leukemia genes

A broad range of human leukemias carries RUNX1 and MLL genetic alterations. Despite such widespread involvements, the relationship between RUNX1 and MLL has never been appreciated. Recently, we showed that RUNX1 physically and functionally interacts with MLL, thereby regulating the epigenetic status of critical cis-regulatory elements for hematopoietic genes. This newly unveiled interaction between the two most prevalent leukemia genes has solved a long-standing conundrum: leukemia-associated RUNX1 N-terminal point mutants that exhibit no obvious functional abnormalities in classical assays for the assessment of transcriptional activities. These mutants turned out to be defective in MLL interaction and subsequent epigenetic modifications that can be examined by the histone-modification status of cis-regulatory elements in the target genes. RUNX1/MLL binding confirms the importance of RUNX1 function as an epigenetic regulator. Recent studies employing next-generation sequencing on human hematological malignancies identified a plethora of mutations in epigenetic regulator genes. These new findings would enhance our understanding on the mechanistic basis for leukemia development and may provide a novel direction for therapeutic applications. This review summarizes the current knowledge about the epigenetic regulation of normal and malignant hematopoiesis by RUNX1 and MLL.

A neonate with congenital amegakaryocytic thrombocytopenia associated with a chromosomal microdeletion at 21q22.11 including the gene RUNX1

We observed a neonate who had severe thrombocytopenia wherein evaluations for neonatal immune-mediated thrombocytopenia and congenital infections were negative, and the marrow findings were consistent with congenital amegakaryocytic thrombocytopenia (CAMT). A genomic microarray identified a microdeletion at 21q22.11 including the gene RUNX1. Two somewhat similar cases were recently reported, but with multiple congenital anomalies that are not present in our case. We propose that a 21q22 deletion resulting in RUNX1 haploinsufficiency can produce a phenotype similar to CAMT with various associated anomalies depending on which adjacent genes are absent or disrupted.

A unique combination of 17pter trisomy and 21qter monosomy in a boy with developmental delay, severe intellectual disability, growth retardation and dysmorphisms

BACKGROUND

Microduplication at 17p13.3 and microdeletion at 21q22 are both rare chromosomal aberrations. The presence of both genomic imbalances in one patient has not been previously reported in literature. In this study, we performed a molecular diagnostic testing with a whole genome microarray on a 3-year-old boy with developmental delay, mental retardation and multiple malformations.

METHODS

A routine G-banding karyotype analysis was performed using peripheral lymphocytes. Chromosome microarray analysis (CMA) was done using Affymetrix CytoScan™ HD array. Genomic imbalances were further confirmed by multiple ligation-dependent probe amplification (MLPA).

RESULTS

The result of karyotyping was normal but CMA detected a 9.8 Mb microduplication at 17p13.3-13.1 (chr17: 1-9,875,545) and a 2.8 Mb microdeletion involving 21q22.3-qter (chr21: 45,239,077-48,097,372). The imbalances were due to a balanced translocation present in patient's mother. The patient was characterized with short stature, profound developmental delay, non-verbal, intellectual disability as well as craniofacial dysmorphism, subtle brain structural anomaly and sparse scalp hair.

CONCLUSIONS

This is the first patient reported with a combination of a microduplication at 17p13.3-13.1 and a microdeletion at 21q22.3-qter. Both genomic imbalances were undetected by conventional karyotyping but were delineated with CMA test. Synergistic effect from the two rare genomic imbalances is likely responsible for the severe clinical phenotypes observed in this patient.

1.9 Mb microdeletion of 21q22.11 within Braddock-Carey contiguous gene deletion syndrome region: dissecting the phenotype

Braddock-Carey syndrome is characterized by Pierre Robin sequence, agenesis of the corpus callosum, facial dysmorphisms, developmental delay, and congenital thrombocytopenia. Recently, Braddock-Carey syndrome was demonstrated to be caused by chromosomal microdeletion in 21q22 including the RUNX1 gene, whose haploinsufficiency is responsible for thrombocytopenia phenotype. Therefore, the syndrome has emerged as a contiguous gene deletion syndrome. Here, we describe an infant with Pierre Robin sequence, facial anomalies, congenital heart defects, hypotonia, and the absence of thrombocytopenia, who was found to have a 1.9 Mb microdeletion within the Braddock-Carey contiguous deletion syndrome region. This deletion spares the RUNX1 gene, narrowing the genomic region responsible for a part of the Braddock-Carey syndrome phenotype. Further studies are awaited to understand the role of the genes located within 21q22 in the pathogenesis of Braddock-Carey syndrome.

Hereditary leukemia due to rare RUNX1c splice variant (L472X) presents with eczematous phenotype

Deleterious mutations in the RUNX1 gene cause hereditary leukemia due to a rare syndrome called Familial platelet Disorder with Associated Myeloid Malignancy (FPDMM). We describe the characteristics of a family with FPDMM due to a novel RUNX1 mutation (L472X), located in the most 3-prime end of the gene reported to date. Our 36-year old proband presented with incidentally detected thrombocytopenia and a family history suggestive of FPDMM. Contrary to previously described families, affected members of our kindred express an eczematous phenotype, reportedly most severe in members who develop leukemia. Pedigree analysis shows that the L472X mutation tracks with thrombocytopenia, acute leukemia, and eczema. The L472X mutation produces a stably expressed RUNX1 protein product with a corresponding decrease in wild type RUNX1 expression. Our data supports the inclusion of eczema in the FPDMM phenotype and suggests the possibility that the RUNX1 L472X mutant causes the type of dominant negative affect that is associated with an elevated risk of leukemia in FPDMM families.

Array CGH in human leukemia: from somatics to genetics

During the past decade, array CGH has been applied to study copy number alterations in the genome in human leukemia in relation to prediction of prognosis or responsiveness to therapy. In the first segment of this review, we will focus on the identification of acquired mutations by array CGH, followed by studies on the pathogenesis of leukemia associated with germline genetic variants, phenotypic presentation and response to treatment. In the last section, we will discuss constitutional genomic aberrations causally related to myeloid leukemogenesis.

Application of microarray-based comparative genomic hybridization in prenatal and postnatal settings: three case reports

Microarray-based comparative genomic hybridization (array CGH) is a newly emerged molecular cytogenetic technique for rapid evaluation of the entire genome with sub-megabase resolution. It allows for the comprehensive investigation of thousands and millions of genomic loci at once and therefore enables the efficient detection of DNA copy number variations (a.k.a, cryptic genomic imbalances). The development and the clinical application of array CGH have revolutionized the diagnostic process in patients and has provided a clue to many unidentified or unexplained diseases which are suspected to have a genetic cause. In this paper, we present three clinical cases in both prenatal and postnatal settings. Among all, array CGH played a major discovery role to reveal the cryptic and/or complex nature of chromosome arrangements. By identifying the genetic causes responsible for the clinical observation in patients, array CGH has provided accurate diagnosis and appropriate clinical management in a timely and efficient manner.

Down-regulation of the RUNX1-target gene NR4A3 contributes to hematopoiesis deregulation in familial platelet disorder/acute myelogenous leukemia

RUNX1 encodes a DNA-binding α subunit of the core-binding factor, a heterodimeric transcription factor. RUNX1 is a master regulatory gene in hematopoiesis and its disruption is one of the most common aberrations in acute leukemia. Inactivating or dominant-negative mutations in the RUNX1 gene have been also identified in pedigrees of familial platelet disorders with a variable propensity to develop acute myeloid leukemia (FPD/AML). We performed analysis of hematopoiesis from 2 FPD/AML pedigrees with 2 distinct RUNX1 germline mutations, that is, the R139X in a pedigree without AML and the R174Q mutation in a pedigree with AML. Both mutations induced a marked increase in the clonogenic potential of immature CD34(+)CD38(-) progenitors, with some self-renewal capacities observed only for R174Q mutation. This increased proliferation correlated with reduction in the expression of NR4A3, a gene previously implicated in leukemia development. We demonstrated that NR4A3 was a direct target of RUNX1 and that restoration of NR4A3 expression partially reduced the clonogenic potential of patient progenitors. We propose that the down-regulation of NR4A3 in RUNX1-mutated hematopoietic progenitors leads to an increase in the pool of cells susceptible to be hit by secondary leukemic genetic events.

Familial myelodysplastic syndromes: a review of the literature

Familial cases of myelodysplastic syndromes are rare, but are immensely valuable for the investigation of the molecular pathogenesis of myelodysplasia in general. The best-characterized familial myelodysplastic syndrome is that of familial platelet disorder with propensity to myeloid malignancy, caused by heterozygous germline RUNX1 mutations. Recently, there has been an increase in the number of reported cases, allowing for better understanding of the incidence, clinical features, and pathogenesis of this disorder. These recent cases have highlighted the clinical variability of the disorder and confirmed that many patients lack a bleeding and/or thrombocytopenia history. Additionally, several cases of T-acute lymphoblastic leukemia have now been reported, confirming a risk of lymphoid leukemia in patients with inherited RUNX1 mutations. Furthermore, an increased awareness of clinicians has helped detect a number of additional families affected by inherited myelodysplastic syndromes, resulting in the identification of novel causative mechanisms of disease, such as RUNX1 deficiency resulting from constitutional microdeletions of 21q22 and myelodysplasia-associated with telomerase deficiency. Awareness of predisposition to myelodysplastic syndromes and acute myeloid leukemia in families may be of critical importance in the management of younger patients with myelodysplasia in whom allogeneic hematopoietic stem cell transplantation is considered. Such families should be investigated for inherited deficiencies of RUNX1 and/or telomerase to prevent the use of an affected sibling as a donor for transplantation. Here we provide an update on familial platelet disorder in addition to a review of other known familial myelodysplastic syndromes.

Clonal evolution of adult T-cell leukemia/lymphoma takes place in the lymph nodes

Adult T-cell leukemia/lymphoma (ATLL) is the neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). We performed oligo-array comparative genomic hybridization (CGH) against paired samples comprising peripheral blood (PB) and lymph node (LN) samples from 13 patients with acute ATLL. We found that the genome profiles of the PB frequently differed from those of the LN samples. The results showed that 9 of 13 cases investigated had a log2 ratio imbalance among chromosomes, and that chromosome imbalances were more frequent in LN samples. Detailed analysis revealed that the imbalances were likely caused by the presence of multiple subclones in the LN samples. Five of 13 cases showed homozygous loss regions in PB samples, which were not found in the LN samples, indicating that tumors in the PB were derived from LN subclones in most cases. Southern blot analysis of TCRγ showed that these multiple subclones originated from a common clone. We concluded that in many ATLL cases, multiple subclones in the LNs originate from a common clone, and that a selected subclone among the LN subclones appears in the PB.

Clinical manifestations of the deletion of Down syndrome critical region including DYRK1A and KCNJ6

A relatively small region of human chromosome 21 (Hsa21) is considered to play a major role in Down syndrome (DS) phenotypes, and the concept of a Down syndrome critical region (DSCR) has been proposed. The goal of the phenotype-genotype correlation study is to discover which genes are responsible for each DS phenotype. Loss of the genomic copy numbers of Hsa21 can give us important suggestion to understand the functions of the involved genes. Genomic copy number aberrations were analyzed by micro-array-based comparative genomic hybridization (aCGH) in 300 patients with developmental delay. Partial deletions of Hsa21 were identified in three patients with developmental delay, epilepsy, microcephaly, and distinctive manifestations. Two of the patients had mosaic deletions of 21q22-qter including a part of DSCR; one of whom whose mosaic ratio was higher than the other showed more severe brain morphogenic abnormality with colpocephaly, which was similar to the previously reported patients having pure deletions of 21q22-qter, indicating the critical region for cortical dysplasia at this region. The remaining patient had the smallest microdeletion with 480 kb in DSCR including DYRK1A and KCNJ6. Although we could not identify any nucleotide alteration in DYRK1A and KCNJ6 in our cohort study for 150 patients with mental retardation with/without epilepsy, this study underscores the clinical importance of DSCR not only for DS but also for developmental disorders.

Current Clinical and Pharmaceutical Applications of Microarrays: From Disease Biomarkers Discovery to Automated Diagnostics

Microarrays used for measuring chromosomal aberrations in genomic DNA and for defining gene expression patterns have become almost routine. A microarray consists of an arrayed series of microscopic spots each containing either DNA or protein molecules known as feature reporters. Advances in microarray fabrication and in feature detection systems, such as high-resolution scanners and their associated software, lead to high-throughput screening of the genome or the transcriptome of a cell or a group of cells in only few days. Despite the potential of high-density microarrays, several problems about data interpretation are still to be solved. In addition, targeted microarrays are shown to be useful tools for rapid and accurate diagnosis of diseases. The aim of this review was to discuss the impact of microarrays on different application levels from the definition of disease biomarkers to pharmaceutical and clinical diagnostics.

Syndromic mental retardation with thrombocytopenia due to 21q22.11q22.12 deletion: Report of three patients

During the last few years, an increasing number of microdeletion/microduplication syndromes have been delineated. This rapid evolution is mainly due to the availability of microarray technology as a routine diagnostic tool. Microdeletions of the 21q22.11q22.12 region encompassing the RUNX1 gene have been reported in nine patients presenting with syndromic thrombocytopenia and mental retardation. RUNX1 gene is responsible for an autosomal dominant platelet disorder with predisposition to acute myelogenous leukemia. We report on three novel patients with an overlapping "de novo" interstitial deletion involving the band 21q22 characterized by array-CGH. All our patients presented with severe developmental delay, dysmorphic features, behavioral problems, and thrombocytopenia. Comparing the clinical features of our patients with the overlapping ones already reported two potential phenotypes related to 21q22 microdeletion including RUNX1 were highlighted: thrombocytopenia with +/- mild dysmorphic features and syndromic thrombocytopenia with growth and developmental delay.

Distinctive Phenotypic Abnormalities Associated with Submicroscopic 21q22 Deletion Including DYRK1A

Partial monosomy 21 has been reported, but the phenotypes described are variable with location and size of the deletion. We present 2 patients with a partially overlapping microdeletion of 21q22 and a striking phenotypic resemblance. They both presented with severe psychomotor delay, behavioral problems, no speech, microcephaly, feeding problems with frequent regurgitation, idiopathic thrombocytopenia, obesity, deep set eyes, down turned corners of the mouth, dysplastic ears, and small chin. Brain MRI showed cerebral atrophy mostly evident in frontal and temporal lobes, widened ventricles and thin corpus callosum in both cases, and in one patient evidence of a migration disorder. The first patient also presented with epilepsy and a ventricular septum defect. The second patient had a unilateral Peters anomaly. Microarray analysis showed a partially overlapping microdeletion spanning about 2.5 Mb in the 21q22.1-q22.2 region including the DYRK1A gene and excluding RUNX1. These patients present with a recognizable phenotype specific for this 21q22.1-q22.2 locus. We searched the literature for patients with overlapping deletions including the DYRK1A gene, in order to define other genes responsible for this presentation.