Prevalence and natural history of variants in the ANKRD26 gene: a short review and update of reported cases

Genome-first determination of the prevalence and penetrance of eight germline myeloid malignancy predisposition genes: a study of two population-based cohorts

It is estimated that 10% of individuals with a myeloid malignancy carry a germline susceptibility. Using the genome-first approach, in which individuals were ascertained on genotype alone, rather than clinical phenotype, we quantified the prevalence and penetrance of pathogenic germline variants in eight myeloid malignancy predisposition (gMMP) genes. ANKRD26, CEBPA, DDX41, MECOM, SRP72, ETV6, RUNX1 and GATA2, were analyzed from the Geisinger MyCode DiscovEHR (n = 170,503) and the United Kingdom Biobank (UKBB, n = 469,595). We identified a high risk of myeloid malignancies (MM) (odds ratio[OR] all genes: DiscovEHR, 4.6 [95% confidential interval (CI) 2.1-9.7], p < 0.0001; UKBB, 6.0 [95% CI 4.3-8.2], p = 3.1 × 10-27), and decreased overall survival (hazard ratio [HR] DiscovEHR, 1.8 [95% CI 1.3-2.6], p = 0.00049; UKBB, 1.4 [95% CI 1.2-1.8], p = 8.4 × 10-5) amongst heterozygotes. Pathogenic DDX41 variants were the most commonly identified, and in UKBB showed a significantly increased risk of MM (OR 5.7 [95% CI 3.9-8.3], p = 6.0 × 10-20) and increased all-cause mortality (HR 1.35 [95% CI 1.1-1.7], p = 0.0063). Through a genome-first approach, this study genetically ascertained individuals with a gMMP and determined their MM risk and survival.

Genetic predisposition to myelodysplastic syndrome: Genetic counseling and transplant implications

The development of myelodysplastic syndromes (MDS) is influenced by various genetic predispositions. Several important genes contribute to disease susceptibility. This paper explores common genetic predisposition genes in MDS, including DDX41, CEBPA, and SAMD9/SAMD9L, which are linked to hereditary conditions presenting diagnostic and clinical challenges. It delves into hereditary conditions that affect platelet production and count, such as RUNX1, ETV6, and ANKRD26, detailing their clinical features and how they contribute to an increased risk of MDS. The discussion extends to additional genetic syndromes like GATA2 deficiency, telomere biology disorders, Fanconi anemia, and Li-Fraumeni syndrome, along with new findings on genes like ERG that offer new insights into disease etiology. The importance of genetic counseling in MDS is underscored, outlining its goals, methods for evaluating family history, risk assessment, and the ethical considerations involved. Furthermore, the role of hematopoietic cell transplantation in managing MDS, particularly in patients with germline syndromes, is reviewed, emphasizing the need for optimal donor selection and personalized treatment approaches. This comprehensive overview illustrates the critical role of genetic factors in MDS and highlights the need for continued research and tailored clinical practices to improve patient outcomes.

Molecular pathophysiology of germline mutations in acute myeloid leukemia

Germline (GL) predisposition to acute myeloid leukemia (AML) has been established as an independent disease entity in the latest World Health Organization classification. Following the American College of Medical Genetics and Genomics guidelines, GL variants were interpreted as causal if they were classified as "pathogenic." GL predisposition can be divided into three groups with different phenotypes, and play an important role in the pathogenesis of adult-onset AML. The clinical course and age of onset of myeloid neoplasms varied considerably for each gene. For example, patients with GATA2 GL variants develop AML before the age of 30 along with bone marrow failure, whereas those with DDX41 GL variants tend to develop AML after the age of 50 without any preceding hematological abnormalities or organ dysfunction. A comprehensive analysis of adult-onset myelodysplastic syndromes in transplant donors showed a 7% frequency of pathogenic GL variants, with DDX41 being the most frequent gene mutation at approximately 3.8%. Future research on GL predisposition at any age of myeloid neoplasm onset will assist in early and accurate diagnosis, development of effective treatment strategies, and selection of suitable donors for stem cell transplantation.

Inherited thrombocytopenia associated with a variant in the FLI1 binding site in the 5' UTR of ANKRD26

Variants in the 5' UTR of ANKRD26 are a common cause of inherited thrombocytopenia (ANKRD26-RT), and are associated with sustained ANKRD26 expression, which inhibits megakaryocyte maturation and proplatelet formation. ANKRD26 expression is controlled by the binding of a RUNX1/FLI1 complex to the 5' UTR. To date, all reported ANKRD26-RD associated variants have been within the RUNX1 binding site and a 22 base pair flanking region. Here, we report a novel variant in the 5' UTR of ANKRD26, c.-107C>T. This variant is in the FLI1 binding site, and is predicted to disrupt FLI1 binding due to loss of a hydrogen bond with FLI1. Differentiated PBMCs from affected family members showed impaired megakaryocyte maturation and proplatelet formation and sustained expression of ANKRD26, and platelets from affected family members had higher ANKRD26 expression than control platelets. The variant increased activity of the ANKRD26 promotor in a reporter assay. We also provide evidence that the previously reported c.-140C>G ANKRD26 5' UTR variant is benign and not associated with thrombocytopenia. Identification of the c.-107C>T variant extends the range of the regulatory region in the 5' UTR of ANKRD26 that is associated with ANKRD26-RT.

Updates on germline predisposition in pediatric hematologic malignancies: What is the role of flow cytometry?

Hematologic neoplasms with germline predisposition have been increasingly recognized as a distinct category of tumors over the last few years. As such, this category was added to the World Health Organization (WHO) 4th edition as well as maintained in the WHO 5th edition and International Consensus Classification (ICC) 2022 classification systems. In practice, these tumors require a high index of suspicion and confirmation by molecular testing. Flow cytometry is a cost-effective diagnostic tool that is routinely performed on peripheral blood and bone marrow samples. In this review, we sought to summarize the current body of research correlating flow cytometric immunophenotype to assess its utility in diagnosis of and clinical decision making in germline hematologic neoplasms. We also illustrate these findings using cases mostly from our own institution. We review some of the more commonly mutated genes, including CEBPA, DDX41, RUNX1, ANKRD26, GATA2, Fanconi anemia, Noonan syndrome, and Down syndrome. We highlight that flow cytometry may have a role in the diagnosis (GATA2, Down syndrome) and screening (CEBPA) of some germline predisposition syndromes, although appears to show nonspecific findings in others (DDX41, RUNX1). In many of the others, such as ANKRD26, Fanconi anemia, and Noonan syndrome, further studies are needed to better understand whether specific flow cytometric patterns are observed. Ultimately, we conclude that further studies such as large case series and organized data pipelines are needed in most germline settings to better understand the flow cytometric immunophenotype of these neoplasms.

GATA binding protein 2 mediated ankyrin repeat domain containing 26 high expression in myeloid-derived cell lines

BACKGROUND

Thrombocytopenia 2, an autosomal dominant inherited disease characterized by moderate thrombocytopenia, predisposition to myeloid malignancies and normal platelet size and function, can be caused by 5'-untranslated region (UTR) point mutations in ankyrin repeat domain containing 26 (ANKRD26). Runt related transcription factor 1 (RUNX1) and friend leukemia integration 1 (FLI1) have been identified as negative regulators of ANKRD26. However, the positive regulators of ANKRD26 are still unknown.

AIM

To prove the positive regulatory effect of GATA binding protein 2 (GATA2) on ANKRD26 transcription.

METHODS

Human induced pluripotent stem cells derived from bone marrow (hiPSC-BM) and urothelium (hiPSC-U) were used to examine the ANKRD26 expression pattern in the early stage of differentiation. Then, transcriptome sequencing of these iPSCs and three public transcription factor (TF) databases (Cistrome DB, animal TFDB and ENCODE) were used to identify potential TF candidates for ANKRD26. Furthermore, overexpression and dual-luciferase reporter experiments were used to verify the regulatory effect of the candidate TFs on ANKRD26. Moreover, using the GENT2 platform, we analyzed the relationship between ANKRD26 expression and overall survival in cancer patients.

RESULTS

In hiPSC-BMs and hiPSC-Us, we found that the transcription levels of ANKRD26 varied in the absence of RUNX1 and FLI1. We sequenced hiPSC-BM and hiPSC-U and identified 68 candidate TFs for ANKRD26. Together with three public TF databases, we found that GATA2 was the only candidate gene that could positively regulate ANKRD26. Using dual-luciferase reporter experiments, we showed that GATA2 directly binds to the 5'-UTR of ANKRD26 and promotes its transcription. There are two identified binding sites of GATA2 that are located 2 kb upstream of the TSS of ANKRD26. In addition, we discovered that high ANKRD26 expression is always related to a more favorable prognosis in breast and lung cancer patients.

CONCLUSION

We first discovered that the transcription factor GATA2 plays a positive role in ANKRD26 transcription and identified its precise binding sites at the promoter region, and we revealed the importance of ANKRD26 in many tissue-derived cancers.

Germline Variants and Characteristic Features of Hereditary Hematological Malignancy Syndrome

Due to the proliferation of genetic testing, pathogenic germline variants predisposing to hereditary hematological malignancy syndrome (HHMS) have been identified in an increasing number of genes. Consequently, the field of HHMS is gaining recognition among clinicians and scientists worldwide. Patients with germline genetic abnormalities often have poor outcomes and are candidates for allogeneic hematopoietic stem cell transplantation (HSCT). However, HSCT using blood from a related donor should be carefully considered because of the risk that the patient may inherit a pathogenic variant. At present, we now face the challenge of incorporating these advances into clinical practice for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) and optimizing the management and surveillance of patients and asymptomatic carriers, with the limitation that evidence-based guidelines are often inadequate. The 2016 revision of the WHO classification added a new section on myeloid malignant neoplasms, including MDS and AML with germline predisposition. The main syndromes can be classified into three groups. Those without pre-existing disease or organ dysfunction; DDX41, TP53, CEBPA, those with pre-existing platelet disorders; ANKRD26, ETV6, RUNX1, and those with other organ dysfunctions; SAMD9/SAMD9L, GATA2, and inherited bone marrow failure syndromes. In this review, we will outline the role of the genes involved in HHMS in order to clarify our understanding of HHMS.

A familial deletion of 10p12.1 associated with thrombocytopenia

Thrombocytopenia can be inherited or acquired from a variety of causes. While hereditary causes of thrombocytopenia are rare, several genes have been associated with the condition. In this report, we describe an 18-year-old man and his mother, both of whom have congenital thrombocytopenia. Exome sequencing in the man revealed a 1006 kb maternally inherited deletion in the 10p12.1 region (arr[GRCh37] 10p12.1(27378928_28384564)x1) of uncertain clinical significance. This deletion in the THC2 locus includes genes ANKRD26, known to be involved in normal megakaryocyte differentiation, and MASTL, which some studies suggest is linked to autosomal dominant thrombocytopenia. In the family presented here, the deletion segregated with the congenital thrombocytopenia phenotype, suggesting that haploinsufficiency of one or both genes may be the cause. To our knowledge, this is the first report of a deletion of the THC2 locus associated with thrombocytopenia. Future functional studies of deletions of the THC2 locus may elucidate the mechanism for this phenotype observed clinically.

Diagnostic work-up of hematological malignancies with underlying germline predisposition disorders (GPD)

Hematological malignancies with underlying germline predisposition disorders have been recognized by the World Health Organization 5th edition and International Consensus Classification (ICC) classification systems. The list of genes and the associated phenotypes are expanding and involve both pediatric and adult populations. While the clinical presentation and underlying molecular pathogenesis are relatively well described, the knowledge regarding the bone marrow morphologic features, the landscape of somatic aberrations associated with progression to hematological malignancies is limited. These pose challenges in the diagnosis of low-grade myelodysplastic syndrome (MDS) to hematopathologists which carries direct implication for various aspects of clinical management of the patient, donor selection for transplantation, and family members. Here in, we provide a focused review on the diagnostic work-up of hematological malignancies with underlying germline predisposition disorders with emphasis on the spectrum of hematological malignancies associated with each entity, and characteristic bone marrow morphologic, somatic cytogenetic and molecular alterations at the time of diagnosis of hematological malignancies. We also review the key clinical, morphologic, and molecular features, that should initiate screening for these entities.

Transcription factor genetics and biology in predisposition to bone marrow failure and hematological malignancy

Transcription factors (TFs) play a critical role as key mediators of a multitude of developmental pathways, with highly regulated and tightly organized networks crucial for determining both the timing and pattern of tissue development. TFs can act as master regulators of both primitive and definitive hematopoiesis, tightly controlling the behavior of hematopoietic stem and progenitor cells (HSPCs). These networks control the functional regulation of HSPCs including self-renewal, proliferation, and differentiation dynamics, which are essential to normal hematopoiesis. Defining the key players and dynamics of these hematopoietic transcriptional networks is essential to understanding both normal hematopoiesis and how genetic aberrations in TFs and their networks can predispose to hematopoietic disease including bone marrow failure (BMF) and hematological malignancy (HM). Despite their multifaceted and complex involvement in hematological development, advances in genetic screening along with elegant multi-omics and model system studies are shedding light on how hematopoietic TFs interact and network to achieve normal cell fates and their role in disease etiology. This review focuses on TFs which predispose to BMF and HM, identifies potential novel candidate predisposing TF genes, and examines putative biological mechanisms leading to these phenotypes. A better understanding of the genetics and molecular biology of hematopoietic TFs, as well as identifying novel genes and genetic variants predisposing to BMF and HM, will accelerate the development of preventative strategies, improve clinical management and counseling, and help define targeted treatments for these diseases.

Hereditary platelet disorders associated with germ line variants in RUNX1, ETV6, and ANKRD26

Hereditary platelet disorders (HPDs) are a group of blood disorders with variable severity and clinical impact. Although phenotypically there is much overlap, known genetic causes are many, prompting the curation of multigene panels for clinical use, which are being deployed in increasingly large-scale populations to uncover missing heritability more efficiently. For some of these disorders, in particular RUNX1, ETV6, and ANKRD26, pathogenic germ line variants in these genes also come with a risk of developing hematological malignancy (HM). Although they may initially present as similarly mild-moderate thrombocytopenia, each of these 3 disorders have distinct penetrance of HM and a different range of somatic alterations associated with malignancy development. As our ability to diagnose HPDs has improved, we are now faced with the challenges of integrating these advances into routine clinical practice for patients and how to optimize management and surveillance of patients and carriers who have not developed malignancy. The volume of genetic information now being generated has created new challenges in how to accurately assess and report identified variants. The answers to all these questions involve international initiatives on rare diseases to better understand the biology of these disorders and design appropriate models and therapies for preclinical testing and clinical trials. Partnered with this are continued technological developments, including the rapid sharing of genetic variant information and automated integration with variant classification relevant data, such as high-throughput functional data. Collective progress in this area will drive timely diagnosis and, in time, leukemia preventive therapeutic interventions.

Novel ANKRD26 and PDGFRB gene mutations in pediatric case of non-Langerhans cell histiocytosis: Case report and literature review

Cutaneous non-Langerhans cell histiocytosis (NLCH) is a rare and biologically benign entity that can be broadly classified into two categories: xanthogranuloma and non-xanthogranuloma. The xanthogranuloma family is characterized by a proliferation of histiocytes with both macrophage and dendritic cell differentiation, negative BRAF mutation, and rare Touton-type giant cells. Molecular studies have reported that mutations involved in the MAPK signaling pathways are implicated in the pathophysiology of histiocytoses. While LCH is associated with the somatic mutation of BRAF v600e, however, mutations and gene fusions in NLCH cases are undefined. We hereby present a 19-month-old female with recalcitrant nodular rashes diagnosed as NLCH with associated novel genetic mutation involving ANKRD26 and PDGFRB genes, as well as PDGFRB::CD74 fusion mRNA. Immunohistochemical staining showed strong and diffuse CD68 and CD163 positivity, and negative CD1a, CD207, ALK D5F3, S100 protein, and BRAF V600E (VE1). Albeit unknown significance, this case of an ANKRD26 and PDGFRB gene mutation in cutaneous NLCH has not been reported prior in the literature. Our case highlights the advantage of pathology and genetic studies in cutaneous NLCH to increase the understanding of this heterogeneous enigmatic disorder and identify further options in management.