GATA1 Mutations Research Articles

Valproic Acid Induced Thrombocytopenia and Dysmegakaryopoiesis in a Pediatric Patient

Abstract Introduction/Objective Valproic acid is a branched short chain fatty acid derivative that is used primarily to treat epilepsy as well as mood disorders, certain types of headaches, and neuropathic pain. It is commonly prescribed in the pediatric population and has shown to be effective for refractory epilepsy with adequate seizure control. Serious side effects may be prominent if the medication is not kept at the therapeutic range. A wide variety of known hematologic problems can be encountered including but not limited to anemia, thrombocytopenia, and leukopenia. Methods/Case Report We present a case of a pediatric patient with a past medical history significant for history of seizure disorder and who presented to Jackson Memorial Hospital for intermittent fevers and multiple unexplained bruises for 3 weeks as well as fatigue and weakness.The patient was recently started on valproic acid. Complete blood count (CBC) was obtained and showed a platelet count of 23 x10(3)/mcL with WBC of 3.5 x10(3)/mcL and hemoglobin of 9.7 g/dL.Serum valproate concentration was critically high (154 mg/L). Trephine biopsy showed a normocellular marrow (60%) showing maturing trilineage hematopoiesis and scattered atypical megakaryopoiesis characterized by small forms that are seen in relatively loose interstitial clusters (Figure 1). The marrow aspirate smears were characterized by cellular spicules with dysmegakaryopoiesis including numerous small hypolobated forms with frequent forms showing separated nuclei (Figure 2, 3, and 4). Blasts did not appear increased, comprising overall 1% of marrow cellularity. Karyotype studies revealed a normal female karyotype, 46, XX. FISH studies using probes commonly detected in MDS were negative. Next generation sequencing was negative for AML specific mutations including GATA1 and GATA2 mutations. Results (if a Case Study enter NA) N/A Conclusion This case report highlights the significant hematologic adverse effects of valproic acid, specifically pancytopenia with dysmegakaryopoiesis, raising the clinical suspicion of potential myelodysplastic syndrome. Critically high level of valproic acid (154 mg/L) and normalization of CBC after the stoppage of the medication strongly suggests that valproic acid can cause severe bone marrow suppression and specific morphologic atypia in the megakaryocytic lineage thus introducing a potential diagnostic pitfall. Because the CBC returned to normal, bone marrow biopsy was not repeated.

Molecular blood group screening in Omani blood donors.

Blood group genotyping has been used in different populations. This study aims at evaluating the genotypes of common blood group antigens in the Omani blood donors and to assess the concordance rate with obtained phenotypes. Blood samples from 180 Omani donors were evaluated. Samples were typed by serological methods for the five blood group systems MNS, RH (RHD/RHCE), KEL, FY and JK. Samples were genotyped using RBC-FluoGene vERYfy eXtend kit (inno-train©). Predicted phenotypic variants for 70 red blood cell antigens among the MNS, RH (RHD/RHCE), KEL, FY, JK, DO, LU, YT, DI, VEL, CO and KN blood group systems were assessed. Simultaneous phenotype and genotype results were available in 130 subjects. Concordance rate was >95% in all blood group systems with exception of Fy(b+) (87%). Homozygous GATA-1 mutation leading to erythroid silencing FY*02N.01 (resulting in the Fy(b-)ES phenotype) was detected in 81/112 (72%) of genotyped samples. In addition, discrepant Fyb phenotype/genotype result was obtained in 14/112 samples; 13 of which has a heterozygous GATA-1 mutation and one sample with a wild GATA genotype. D and partial e c.733C>G variants expressing the V+VS+ phenotype were found in 22/121 (18.2%) and 14/120 (11.7%) of the samples, respectively. Di(a-b+), Js(a-b+), Yt(a+b-) and Kn(a+b-) genotype frequencies were 99.4%, 95.8%, 91.9% and 97.7%, respectively. In conclusion, we report a high frequency of FY*02N.01 allele due to homozygous c.-67T>C GATA-1 single-nucleotide variation. This is the first study reporting the detailed distribution of common and rare red cell genotypes in Omani blood donors.

Clinical evolution, genetic landscape and trajectories of clonal hematopoiesis in SAMD9/SAMD9L syndromes.

Germline SAMD9 and SAMD9L mutations (SAMD9/9Lmut) predispose to myelodysplastic syndromes (MDS) with propensity for somatic rescue. In this study, we investigated a clinically annotated pediatric MDS cohort (n = 669) to define the prevalence, genetic landscape, phenotype, therapy outcome and clonal architecture of SAMD9/9L syndromes. In consecutively diagnosed MDS, germline SAMD9/9Lmut accounted for 8% and were mutually exclusive with GATA2 mutations present in 7% of the cohort. Among SAMD9/9Lmut cases, refractory cytopenia was the most prevalent MDS subtype (90%); acquired monosomy 7 was present in 38%; constitutional abnormalities were noted in 57%; and immune dysfunction was present in 28%. The clinical outcome was independent of germline mutations. In total, 67 patients had 58 distinct germline SAMD9/9Lmut clustering to protein middle regions. Despite inconclusive in silico prediction, 94% of SAMD9/9Lmut suppressed HEK293 cell growth, and mutations expressed in CD34+ cells induced overt cell death. Furthermore, we found that 61% of SAMD9/9Lmut patients underwent somatic genetic rescue (SGR) resulting in clonal hematopoiesis, of which 95% was maladaptive (monosomy 7 ± cancer mutations), and 51% had adaptive nature (revertant UPD7q, somatic SAMD9/9Lmut). Finally, bone marrow single-cell DNA sequencing revealed multiple competing SGR events in individual patients. Our findings demonstrate that SGR is common in SAMD9/9Lmut MDS and exemplify the exceptional plasticity of hematopoiesis in children.

The megakaryocytic transcription factor ARID3A suppresses leukemia pathogenesis

AbstractGiven the plasticity of hematopoietic stem and progenitor cells, multiple routes of differentiation must be blocked in the the pathogenesis of acute myeloid leukemia, the molecular basis of which is incompletely understood. We report that posttranscriptional repression of the transcription factor ARID3A by miR-125b is a key event in the pathogenesis of acute megakaryoblastic leukemia (AMKL). AMKL is frequently associated with trisomy 21 and GATA1 mutations (GATA1s), and children with Down syndrome are at a high risk of developing the disease. The results of our study showed that chromosome 21–encoded miR-125b synergizes with Gata1s to drive leukemogenesis in this context. Leveraging forward and reverse genetics, we uncovered Arid3a as the main miR-125b target behind this synergy. We demonstrated that, during normal hematopoiesis, this transcription factor promotes megakaryocytic differentiation in concert with GATA1 and mediates TGFβ-induced apoptosis and cell cycle arrest in complex with SMAD2/3. Although Gata1s mutations perturb erythroid differentiation and induce hyperproliferation of megakaryocytic progenitors, intact ARID3A expression assures their megakaryocytic differentiation and growth restriction. Upon knockdown, these tumor suppressive functions are revoked, causing a blockade of dual megakaryocytic/erythroid differentiation and subsequently of AMKL. Inversely, restoring ARID3A expression relieves the arrest of megakaryocytic differentiation in AMKL patient-derived xenografts. This work illustrates how mutations in lineage-determining transcription factors and perturbation of posttranscriptional gene regulation can interact to block multiple routes of hematopoietic differentiation and cause leukemia. In AMKL, surmounting this differentiation blockade through restoration of the tumor suppressor ARID3A represents a promising strategy for treating this lethal pediatric disease.

Donor source and post-transplantation cyclophosphamide influence outcome in allogeneic stem cell transplantation for GATA2 deficiency.

GATA2 deficiency was described in 2011, and shortly thereafter allogeneic hematopoietic stem cell transplantation (HSCT) was shown to reverse the hematologic disease phenotype. However, there remain major unanswered questions regarding the type of conditioning regimen, type of donors, and graft-versus-host disease (GVHD) prophylaxis. We report 59 patients with GATA2 mutations undergoing HSCT at National Institutes of Health between 2013 and 2020. Primary endpoints were engraftment, reverse of the clinical phenotype, secondary endpoints were overall survival (OS), event-free survival (EFS), and the incidence of acute and chronic GVHD. The OS and EFS at 4 years were 85·1% and 82·1% respectively. Ninety-six percent of surviving patients had reversal of the hematologic disease phenotype by one-year post-transplant. Incidence of grade III-IV aGVHD in matched related donor (MRD) and matched unrelated donor recipients (URD) patients receiving Tacrolimus/Methotrexate for GVHD prophylaxis was 32%. In contrast, in the MRD and URD who received post-transplant cyclophosphamide (PT/Cy), no patient developed grade III-IV aGVHD. Six percent of haploidentical related donor (HRD) recipients developed grade III-IV aGVHD. In summary, a busulfan-based HSCT regimen in GATA2 deficiency reverses the hematologic disease phenotype, and the use of PT/Cy reduced the risk of both aGVHD and cGVHD.

ASXL1 and STAG2 are common mutations in GATA2 deficiency patients with bone marrow disease and myelodysplastic syndrome

AbstractPatients with GATA2 deficiencyharbor de novo or inherited germline mutations in the GATA2 transcription factor gene, predisposing them to myeloid malignancies. There is considerable variation in disease progression, even among family members with the same mutation in GATA2. We investigated somatic mutations in 106 patients with GATA2 deficiency to identify acquired mutations that are associated with myeloid malignancies. Myelodysplastic syndrome (MDS) was the most common diagnosis (∼44%), followed by GATA2 bone marrow immunodeficiency disorder (G2BMID; ∼37%). Thirteen percent of the cohort had GATA2 mutations but displayed no disease manifestations. There were no correlations between age or sex with disease progression or survival. Cytogenetic analyses showed a high incidence of abnormalities (∼43%), notably trisomy 8 (∼23%) and monosomy 7 (∼12%), but the changes did not correlate with lower survival. Somatic mutations in ASXL1 and STAG2 were detected in ∼25% of patients, although the mutations were rarely concomitant. Mutations in DNMT3A were found in ∼10% of patients. These somatic mutations were found similarly in G2BMID and MDS, suggesting clonal hematopoiesis in early stages of disease, before the onset of MDS. ASXL1 mutations conferred a lower survival probability and were more prevalent in female patients. STAG2 mutations also conferred a lower survival probability, but did not show a statistically significant sex bias. There was a conspicuous absence of many commonly mutated genes associated with myeloid malignancies, including TET2, IDH1/2, and the splicing factor genes. Notably, somatic mutations in chromatin-related genes and cohesin genes characterized disease progression in GATA2 deficiency.

Impairment of the Hypothalamus-Pituitary-Thyroid Axis Caused by Naturally Occurring GATA2 Mutations In Vitro.

The transcription factor GATA2 regulates gene expression in several cells and tissues, including hematopoietic tissues and the central nervous system. Recent studies revealed that loss-of-function mutations in GATA2 are associated with hematological disorders. Our earlier in vitro studies showed that GATA2 plays an essential role in the hypothalamus–pituitary–thyroid axis (HPT axis) by regulating the genes encoding prepro-thyrotropin-releasing hormone (preproTRH) and thyroid-stimulating hormone β (TSHβ). However, the effect of GATA2 mutants on the transcriptional activity of their promoters remains unelucidated. In this study, we created five human GATA2 mutations (R308P, T354M, R396Q, R398W, and S447R) that were reported to be associated with hematological disorders and analyzed their functional properties, including transactivation potential and DNA-binding capacity toward the preproTRH and the TSHβ promoters. Three mutations (T354M, R396Q, and R398W) within the C-terminal zinc-finger domain reduced the basal GATA2 transcriptional activity on both the preproTRH and the TSHβ promoters with a significant loss of DNA binding affinity. Interestingly, only the R398W mutation reduced the GATA2 protein expression. Subsequent analysis demonstrated that the R398W mutation possibly facilitated the GATA2 degradation process. R308P and S447R mutants exhibited decreased transcriptional activity under protein kinase C compared to the wild-type protein. In conclusion, we demonstrated that naturally occurring GATA2 mutations impair the HPT axis through differential functional mechanisms in vitro.

Clinical and biological aspects of myeloid leukemia in Down syndrome.

Children with Down syndrome are at an elevated risk of leukemia, especially myeloid leukemia (ML-DS). This malignancy is frequently preceded by transient abnormal myelopoiesis (TAM), which is self-limited expansion of fetal liver-derived megakaryocyte progenitors. An array of international studies has led to consensus in treating ML-DS with reduced-intensity chemotherapy, leading to excellent outcomes. In addition, studies performed in the past 20 years have revealed many of the genetic and epigenetic features of the tumors, including GATA1 mutations that are arguably associated with all cases of both TAM and ML-DS. Despite these advances in understanding the clinical and biological aspects of ML-DS, little is known about the mechanisms of relapse. Upon relapse, patients face a poor outcome, and there is no consensus on treatment. Future studies need to be focused on this challenging aspect of leukemia in children with DS.

The Mutational Landscape of Myeloid Leukaemia in Down Syndrome

Simple SummaryLeukaemia occurs when specific mutations promote aberrant transcriptional and proliferation programs, which drive uncontrolled cell division and inhibit the cell’s capacity to differentiate. In this review, we summarize the most frequent genetic lesions found in myeloid leukaemia of Down syndrome, a rare paediatric leukaemia specific to individuals with trisomy 21. The evolution of this disease follows a well-defined sequence of events and represents a unique model to understand how the ordered acquisition of mutations drives malignancy.Children with Down syndrome (DS) are particularly prone to haematopoietic disorders. Paediatric myeloid malignancies in DS occur at an unusually high frequency and generally follow a well-defined stepwise clinical evolution. First, the acquisition of mutations in the GATA1 transcription factor gives rise to a transient myeloproliferative disorder (TMD) in DS newborns. While this condition spontaneously resolves in most cases, some clones can acquire additional mutations, which trigger myeloid leukaemia of Down syndrome (ML-DS). These secondary mutations are predominantly found in chromatin and epigenetic regulators—such as cohesin, CTCF or EZH2—and in signalling mediators of the JAK/STAT and RAS pathways. Most of them are also found in non-DS myeloid malignancies, albeit at extremely different frequencies. Intriguingly, mutations in proteins involved in the three-dimensional organization of the genome are found in nearly 50% of cases. How the resulting mutant proteins cooperate with trisomy 21 and mutant GATA1 to promote ML-DS is not fully understood. In this review, we summarize and discuss current knowledge about the sequential acquisition of genomic alterations in ML-DS.

CEBPA mutations in 4708 patients with acute myeloid leukemia: differential impact of bZIP and TAD mutations on outcome

AbstractBiallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis; however, the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adults with acute myeloid leukemia (AML) who had been recruited into the Study Alliance Leukemia trials, to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%): 131 CEBPAbi and 109 CEBPAsm (60 affecting the N-terminal transactivation domains [CEBPAsmTAD] and 49 the C-terminal DNA-binding or basic leucine zipper region [CEBPAsmbZIP]). Interestingly, patients carrying CEBPAbi or CEBPAsmbZIP shared several clinical factors: they were significantly younger (median, 46 and 50 years, respectively) and had higher white blood cell (WBC) counts at diagnosis (median, 23.7 × 109/L and 35.7 × 109/L) than patients with CEBPAsmTAD (median age, 63 years, median WBC 13.1 × 109/L; P < .001). Co-mutations were similar in both groups: GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs 6.7% CEBPAsmTAD; P < .001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs 38.3% CEBPAsmTAD; P < .001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (OS; median 103 and 63 vs 13 months) and event-free survival (EFS; median, 20.7 and 17.1 months vs 5.7 months), in univariate and multivariable analyses. Additional analyses revealed that the clinical and molecular features as well as the favorable survival were confined to patients with in-frame mutations in bZIP (CEBPAbZIP-inf). When patients were classified according to CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and non-CEBPAbZIP-inf), only patients bearing CEBPAbZIP-inf showed superior complete remission rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutation.

High-dose AraC is essential for the treatment of ML-DS independent of postinduction MRD: results of the COG AAML1531 trial

AbstractMyeloid leukemia in children with Down syndrome (ML-DS) is associated with young age and somatic GATA1 mutations. Because of high event-free survival (EFS) and hypersensitivity of the leukemic blasts to chemotherapy, the prior Children's Oncology Group protocol ML-DS protocol (AAML0431) reduced overall treatment intensity but lacking risk stratification, retained the high-dose cytarabine course (HD-AraC), which was highly associated with infectious morbidity. Despite high EFS of ML-DS, survival for those who relapse is rare. AAML1531 introduced therapeutic risk stratification based on the previously identified prognostic factor, measurable residual disease (MRD) at the end of the first induction course. Standard risk (SR) patients were identified by negative MRD using flow cytometry (<0.05%) and did not receive the historically administered HD-AraC course. Interim analysis of 114 SR patients revealed a 2-year EFS of 85.6% (95% confidence interval [CI], 75.7-95.5), which was significantly lower than for MRD− patients treated with HD-AraC on AAML0431 (P = .0002). Overall survival at 2 years was 91.0% (95% CI, 83.8-95.0). Twelve SR patients relapsed, mostly within 1 year from study entry and had a 1-year OS of 16.7% (95% CI, 2.7-41.3). Complex karyotypes were more frequent in SR patients who relapsed compared with those who did not (36% vs 9%; P = .0248). MRD by error-corrected sequencing of GATA1 mutations was piloted in 18 SR patients and detectable in 60% who relapsed vs 23% who did not (P = .2682). Patients with SR ML-DS had worse outcomes without HD-AraC after risk classification based on flow cytometric MRD.

Clinical utility of targeted next-generation sequencing for the diagnosis of myeloid neoplasms with germline predisposition.

Myeloid neoplasms (MN) with germline predisposition (MNGP) are likely to be more common than currently appreciated. Many of the genes involved in MNGP are also recurrently mutated in sporadic MN. Therefore, routine analysis of gene panels by next‐generation sequencing provides an effective approach to detect germline variants with clinical significance in patients with hematological malignancies. Gene panel sequencing was performed in 88 consecutive and five nonconsecutive patients with MN diagnosis. Disease‐causing germline mutations in CEBPα, ASXL1, TP53, MPL, GATA2, DDX41, and ETV6 genes were identified in nine patients. Six out of the nine patients with germline variants had a strong family history. These patients presented great heterogeneity in the age of diagnosis and phenotypic characteristics. In our study, there were families in which all the affected members presented the same subtype of disease, whereas members of other families presented various disease phenotypes. This intrafamiliar heterogeneity suggests that the acquisition of particular somatic variants may drive the evolution of the disease. This approach enabled high‐throughput detection of MNGP in patients with MN diagnosis, which is of great relevance for both the patients themselves and the asymptomatic mutation carriers within the family. It is crucial to make a proper diagnosis of these patients to provide them with the most suitable treatment, follow‐up, and genetic counseling.

Hematopoietic stem cell transplantation in children and adolescents with GATA2-related myelodysplastic syndrome

GATA2 deficiency is a heterogeneous multi-system disorder characterized by a high risk of developing myelodysplastic syndrome (MDS) and myeloid leukemia. We analyzed the outcome of 65 patients reported to the registry of the European Working Group (EWOG) of MDS in childhood carrying a germline GATA2 mutation (GATA2mut) who had undergone hematopoietic stem cell transplantation (HSCT). At 5 years the probability of overall survival and disease-free survival (DFS) was 75% and 70%, respectively. Non-relapse mortality and relapse equally contributed to treatment failure. There was no evidence of increased incidence of graft-versus-host-disease or excessive rates of infections or organ toxicities. Advanced disease and monosomy 7 (−7) were associated with worse outcome. Patients with refractory cytopenia of childhood (RCC) and normal karyotype showed an excellent outcome (DFS 90%) compared to RCC and −7 (DFS 67%). Comparing outcome of GATA2mut with GATA2wt patients, there was no difference in DFS in patients with RCC and normal karyotype. The same was true for patients with −7 across morphological subtypes. We demonstrate that HSCT outcome is independent of GATA2 germline mutations in pediatric MDS suggesting the application of standard MDS algorithms and protocols. Our data support considering HSCT early in the course of GATA2 deficiency in young individuals.

Germline GATA2 variant disrupting endothelial eNOS function and angiogenesis can be restored by c-Jun/AP-1 upregulation.

GATA2 is a transcription factor with key roles in hematopoiesis. Germline GATA2 gene variants have been associated with several inherited and acquired hematologic disorders, including myelodysplastic syndromes. Among the spectrum of GATA2 deficiency- associated manifestations thrombosis has been reported in 25% of patients, but the mechanisms are unknown. GATA2 was shown to be involved in endothelial nitric oxide synthase (eNOS) regulation and vascular development. We assessed eNOS expression and angiogenesis in patients with GATA2 deficiency. Platelets and blood outgrowth endothelial cells (BOEC) from GATA2 variant carriers showed impaired NO production and reduction of eNOS mRNA and protein expression and of eNOS activity. GATA2 binding to the eNOS gene was impaired in BOEC from GATA2-deficient patients, differently from control BOEC. GATA2 deficiency BOEC showed also defective angiogenesis, which was completely restored by treatment with the NO-donor Snitroso- N-acetylpenicillamine (SNAP). Atorvastatin, but not resveratrol, largely restored eNOS expression, NO biosynthesis and neoangiogenesis in GATA2-deficient BOEC by a mechanism involving increased expression of the eNOS transcription factor AP-1/c-JUN, replacing GATA2 when the latter is inactive. Our results unravel a possible thrombogenic mechanism of GATA2 mutations, definitely establish the regulation of eNOS by GATA2 in endothelial cells and show that endothelial angiogenesis is strictly dependent on the eNOS/NO axis. Given the ability of atorvastatin to restore NO production and angiogenesis by GATA2-deficient endothelial cells, the preventive effect of atorvastatin on thrombotic events and possibly on other clinical manifestations of the syndrome related to deranged angiogenesis should be explored in patients with GATA2 deficiency in an ad hoc designed clinical trial.

Laboratory evaluation and prognostication among adults and children with CEBPA-mutant acute myeloid leukemia.

CEBPA-mutant acute myeloid leukemia (AML) encompasses clinically and biologically distinct subtypes of AML in both adults and children. CEBPA-mutant AML may occur with monoallelic (moCEBPA) or biallelic (biCEBPA) mutations, which can be somatic or germline, with each entity impacting prognosis in unique ways. BiCEBPA AML is broadly associated with a favorable prognosis, but differences in the type and location of CEBPA mutations as well as the presence of additional leukemogenic mutations can lead to heterogeneity in survival. Concurrent FLT3-ITD mutations have a well-documented negative effect on survival in adult biCEBPA AML, whereas support for a negative prognostic effect of mutations in TET2, DNMT3A, WT1, CSF3R, ASXL1, and KIT is mixed. NPM1 and GATA2 mutations may have a positive prognostic impact. MoCEBPA AML has similar survival outcomes compared to AML with wild-type CEBPA, and risk stratification is determined by other cytogenetic and molecular findings. Germline CEBPA mutations may lead to familial biCEBPA AML after acquisition of second somatic CEBPA mutation, with variable penetrance and age. BiCEBPA AML in children is likely a favorable-risk diagnosis as it is in adults, but the role of a single CEBPA mutation and the impact of concurrent leukemogenic mutations are not clear in this population. Laboratory evaluation of the CEBPA gene includes PCR-based fragment-length analysis, Sanger sequencing, and next-generation sequencing. Phenotypic analysis using multiparameter flow cytometry can also provide additional data in evaluating CEBPA, helping to assess for the likelihood of mutation presence.

Genomic and Transcriptomic Analyses of Breast Cancer Primaries and Matched Metastases in AURORA, the Breast International Group (BIG) Molecular Screening Initiative.

AURORA aims to study the processes of relapse in metastatic breast cancer (MBC) by performing multi-omics profiling on paired primary tumors and early-course metastases. Among 381 patients (primary tumor and metastasis pairs: 252 targeted gene sequencing, 152 RNA sequencing, 67 single nucleotide polymorphism arrays), we found a driver role for GATA1 and MEN1 somatic mutations. Metastases were enriched in ESR1, PTEN, CDH1, PIK3CA, and RB1 mutations; MDM4 and MYC amplifications; and ARID1A deletions. An increase in clonality was observed in driver genes such as ERBB2 and RB1. Intrinsic subtype switching occurred in 36% of cases. Luminal A/B to HER2-enriched switching was associated with TP53 and/or PIK3CA mutations. Metastases had lower immune score and increased immune-permissive cells. High tumor mutational burden correlated to shorter time to relapse in HR+/HER2- cancers. ESCAT tier I/II alterations were detected in 51% of patients and matched therapy was used in 7%. Integration of multi-omics analyses in clinical practice could affect treatment strategies in MBC. SIGNIFICANCE: The AURORA program, through the genomic and transcriptomic analyses of matched primary and metastatic samples from 381 patients with breast cancer, coupled with prospectively collected clinical data, identified genomic alterations enriched in metastases and prognostic biomarkers. ESCAT tier I/II alterations were detected in more than half of the patients.This article is highlighted in the In This Issue feature, p. 2659.

Generation of two heterozygous GATA2 CRISPR/Cas9-edited iPSC lines, R398W and R396Q, for modeling GATA2 deficiency

Germline heterozygous GATA2 mutations underlie a complex disorder characterized by bone marrow failure, immunodeficiency and high risk to develop myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Our understanding about GATA2 deficiency is limited due to the lack of relevant disease models. Here we generated high quality human induced pluripotent stem cell (iPSC) lines carrying two of the most recurrent germline GATA2 mutations (R389W and R396Q) associated with MDS, using CRISPR/Cas9. These hiPSCs represent an in vitro model to study the molecular and cellular mechanisms underlying GATA2 deficiency, when differentiated into blood progenitors.

Single-cell ATAC-seq reveals GATA2-dependent priming defect in myeloid and a maturation bottleneck in lymphoid lineages

AbstractGermline heterozygous mutations in GATA2 are associated with a syndrome characterized by cytopenias, atypical infections, and increased risk of hematologic malignancies. Here, we generated a zebrafish mutant of gata2b that recapitulated the myelomonocytopenia and B-cell lymphopenia of GATA2 deficiency syndrome. Using single-cell assay for transposase accessible chromatin with sequencing of marrow cells, we showed that loss of gata2b led to contrasting alterations in chromosome accessibility in early myeloid and lymphoid progenitors, associated with defects in gene expression. Within the myeloid lineage in gata2b mutant zebrafish, we identified an attenuated myeloid differentiation with reduced transcriptional priming and skewing away from the monocytic program. In contrast, in early lymphoid progenitors, gata2b loss led to accumulation of B-lymphoid transcription factor accessibility coupled with increased expression of the B-cell lineage-specification program. However, gata2b mutant zebrafish had incomplete B-cell lymphopoiesis with loss of lineage-specific transcription factor accessibility in differentiating B cells, in the context of aberrantly reduced oxidative metabolic pathways. Our results establish that transcriptional events in early progenitors driven by Gata2 are required to complete normal differentiation.

Mature Analysis of the Prospective Oxford Down Syndrome (DS) Cohort Study: Timing and Clinical Impact of Preleukemic GATA1 Mutations and Lessons for Management of Newborns with DS

Children with Down syndrome (DS) have a high risk of developing a unique form of AML known as myeloid leukaemia of DS (ML-DS) defined by the presence of one or more acquired N-terminal truncating mutations in the hematopoietic transcription factor gene GATA1 . ML-DS is confined to children <4 y of age and preceded by a neonatal preleukemic syndrome, Transient Abnormal Myelopoiesis (TAM). Although the same GATA1 mutations are present in ML-DS and TAM, indicating they are clonally-linked disorders, chemotherapy is essential to cure ML-DS whereas most cases of TAM spontaneously resolve without treatment.To determine the natural history of GATA1 mutations in DS and the true risk of subsequent leukemia conferred by GATA1 mutations we established the Oxford DS Cohort Study that prospectively analyses serial clinical, hematological and GATA1 mutational data from children with DS from birth to age 4y. All children had serial blood counts and smears and mutation analysis of exon 2/3 of GATA1 by next-generation-sequencing (NGS). A diagnosis of TAM was made if peripheral blood (PB) blasts were >10% and a GATA1 mutation was detected. DS neonates with PB blasts <10% and a GATA1 mutation were designated Silent TAM as our previous data on 18/80 DS neonates with blasts <10% showed that small mutant GATA1 clones were clinically and hematologically undetectable [Roberts et al, Blood 2013].We have now studied 471 neonates (gestational age [GA] at birth 29-42 wks) with karyotypically-confirmed DS. 130/471 (27.6%) had >1 GATA1 mutation confirming the high frequency of GATA1 mutations in DS neonates. Multiple GATA1 clones (2-7) were detected in 19% of TAM and 21% of Silent TAM (p=ns). A diagnosis of TAM was made in 55/471 (11.7%). 75/471 (15.9%) had Silent TAM and 341/471 had no GATA1 mutations. Typical clinical findings of TAM (hepatomegaly, splenomegaly, skin rash and effusions) were uncommon in Silent TAM, affecting 7%, 1.3%, 1.3% and 3% neonates respectively compared to 40%, 29%, 17% and 10% of neonates with TAM (p<0.0001). There were no specific hematological abnormalities in Silent TAM: median WBC and blasts were not increased: 13.1x109/L v 14.5x109/L and 4% v 4% (Silent TAM v no GATA1 mutation) and no neonates with Silent TAM had leucocytosis (WBC >35x109/L) or anemia. There was a strong correlation (r=0.753; p<0.0001) between PB blast% and mutant GATA1 clone size (assessed by VAF) with a greater mutant clone size in TAM v Silent TAM (median VAF 17.1% v 1.2%; p<0.0001).Unexpectedly, clone size was inversely proportional to GA (r=-0.2569; p=0.004). Despite similar median GA at delivery for all 3 groups, no GATA1 mutations were detected before 31 wks GA and no cases of TAM before 33 wks; the highest frequency of GATA1 mutations was seen at 34-35 wks GA (40%) reducing to 7% at >40 wks. This suggests GATA1 mutations are likely to be acquired and expand during a narrow time window early in the 3rd trimester of fetal life. Consistent with this, GATA1 mutations were not detected in 16 DS fetal liver samples (GA 8-19 wks) analysed over the same period. Similarly, in a case of TAM presenting in utero with fetal pericardial effusion and 96% PB blasts at 27 wks GA, the blast% and mutant GATA1 VAF spontaneously fell progressively (blasts 19%; VAF 23% at birth at 34 wks GA; undetectable at 4 wks postnatal age).Outcome: 7 neonates developed ML-DS: 6/52 survivors with TAM; 1/71 survivors with Silent TAM and 0/328 survivors without neonatal GATA1 mutations; 2/451 survivors developed ALL (1 Silent TAM, 1 no GATA1 mutation). 5 yr overall survival was the same in all 3 groups (95.1%, 95.8%, 95.1% for TAM, Silent TAM and no GATA1 mutations; Plog-rank 0.8994) while 5 yr event-free survival was lower in TAM (89.2%, 92.8%, 95.1% in TAM, Silent TAM and neonates with no GATA1 mutations; Plog-rank=0.0262). ML-DS was diagnosed at a median age of 14 m (range 3-18 m) preceded in all cases by a fall in platelet count. No single risk factor at birth specifically predicted for ML-DS although all 6 neonates with TAM who developed ML-DS had a mutant GATA1 VAF of >15% and blasts >20% at birth. The DS neonate with Silent TAM had a VAF of 2.5% and 4% blasts; this neonate was the only one of the cohort with a partial trisomy 21. Conclusion: Acquired N-terminal mutations in GATA1 are very frequent in neonates with DS and most probably occur or expand in the 3rd trimester; in the majority of cases mutant GATA1 clones are very small, clinically silent, resolve spontaneously and confer an extremely low risk of ML-DS. DisclosuresVyas:Jazz Pharmaceuticals: Speakers Bureau; Celgene Corporation: Speakers Bureau.

Targeted Deep Sequencing of GATA1 more Sensitively Identifies Transient Myeloproliferative Disorder in Neonates with Down Syndrome

Down syndrome (DS) is caused by a constitutional trisomy 21 and up to 10% of neonates with DS develop a temporary accumulation of leukemic blasts in the peripheral blood, called transient myeloproliferative disorder (TMD). In most cases, TMD is a self-limiting disorder, however 20% of children develop serious symptoms and treatment with low dose cytarabine is then necessary. TMD is caused by a mutation in the GATA1 gene, occurring in cells with trisomy 21. Around 20% of children with TMD will develop a myeloid leukemia (ML) before the age of 4 years. It is a megakaryoblastic leukemia characterized by a GATA1 mutation identical to the mutation these children had in their TMD blast cells. The primary aim of this study was to define a population based frequency of TMD in DS neonates.In this nation-wide study we prospectively screened 368 peripheral blood (PB) samples from DS neonates (< 4 weeks old) in the Netherlands between January 1st 2008 and January 1st 2013 for TMD using morphology and immunophenotyping (IPT) (Dutch Trial Registry number NTR1667). TMD was defined as >5% myeloblasts in the PB. Patients with less than 5% of cells in the PB consistent with TMD using IPT were also included. PB samples of TMD positive patients were tested for GATA1 exon 2 mutations using Sanger sequencing. Patients with TMD were followed at least until the age of 4 years. TMD positive patients without a GATA1 exon 2 mutation using Sanger sequencing and TMD negative patients were retrospectively screened for GATA1 exon 2 and 3 mutations using targeted deep sequencing. Using this technique we could detect mutations with a frequency of 0.1%.In the prospective part of the study, TMD was diagnosed in 45 of the 368 cases screened (12.2%). In 41 of 45 neonates with TMD, GATA1 mutation analysis was performed. In 4 cases no GATA1 PCR was performed. In 28 cases a GATA1 exon 2 mutation was detected (28/41=68%), while in 13 cases no GATA1 mutation was detected.It was recently shown that there is a subgroup of DS neonates who do not have TMD by conventional criteria, but when more sensitively screened do harbour a GATA1 mutation (Roberts et al, Blood 2013). Therefore using targeted deep sequencing we retrospectively screened the 13 TMD cases without a GATA1 mutation by Sanger sequencing and 2 of the 4 cases that were not screened at TMD diagnosis. No GATA1 exon 3 mutations were detected. In 9 out of 15 patients a GATA1 mutation was detected using targeted deep sequencing. Both cases not prospectively Sanger sequenced were positive. 7 of 13 TMD samples tested negative using Sanger sequencing, using targeted deep sequencing were positive for a GATA1 mutation (median mutational frequency 6,8%). Overall, 43 TMD patient samples were screened using Sanger sequencing and/or targeted deep sequencing and 38 of these tested GATA1 positive (88%).In addition, we retrospectively screened 319 of the 323 peripheral blood samples of the TMD negative DS neonates for GATA1 using targeted deep sequencing. No GATA1 exon 3 mutations were detected. In 11 out of 319 TMD negative cases we detected a GATA1 exon 2 mutation with a median mutational frequency of 0,8%.14 children with DS born in the Netherlands between 1-1-2008 and 31-12-2013 were diagnosed with ML DS (follow-up until 31st of dec 2016). Of these 14 children, 7 were screened neonatally and in 6 cases TMD was diagnosed. Therefore 6 out of 45 TMD patients identified using conventional screening developed ML DS (13.3%). Out of the 11 ‘subclinical’ TMD cases only detected by targeted deep sequencing GATA1 screening, one patient was later diagnosed with ML DS (1/11=9.1%). The patient's neonatal blood sample harboured two different GATA1 exon 2 mutations (14 base pair (bp) insertion in 0,24% of cells and a 1 bp insertion in 2,6% of cells). In the ML DS cells of this patient the identical 1 bp exon 2 insertion in GATA1 was detected.In conclusion, conventional screening for TMD using immunophenotyping en morphology identified TMD in 12% of the screened DS neonates. An additional 3.4% can be detected using targeted deep sequencing. This is clinically relevant as these children are at risk of developing ML DS. Therefore, for future clinical studies we are developing targeted deep sequencing methods screening for GATA 1 in neonatal DS PB samples. DisclosuresKaspers:Janssen-Cilag: Research Funding.