Transient Abnormal Myelopoiesis Research Articles

Single-cell transcriptomics reveal individual and synergistic effects of Trisomy 21 and GATA1s on hematopoiesis.

Trisomy 21 (T21), or Down syndrome (DS), is associated with baseline macrocytic erythrocytosis, thrombocytopenia, and neutrophilia, as well as transient abnormal myelopoiesis (TAM) and myeloid leukemia of DS (ML-DS). TAM and ML-DS blasts both arise from an aberrant megakaryocyte-erythroid progenitor and exclusively express GATA1s, the truncated isoform of GATA1 , while germline GATA1s mutations in a non-T21 context lead to congenital cytopenia(s) without a leukemic predisposition. This suggests that T21 and GATA1s both perturb hematopoiesis in multipotent progenitors, but studying their individual effects is challenging due to limited access to relevant human progenitor populations. To dissect individual developmental impacts, we used single-cell RNA-sequencing to interrogate hematopoietic progenitor cells (HPCs) from isogenic human induced pluripotent stem cells differing only by chromosome 21 and/or GATA1 status. The transcriptomes of these HPCs revealed significant heterogeneity and lineage skew dictated by T21 and/or GATA1s. T21 and GATA1s each disrupted temporal regulation of lineage-specific transcriptional programs and specifically perturbed cell cycle genes. Trajectory inference revealed that GATA1s nearly eliminated erythropoiesis, slowed MK maturation, and promoted myelopoiesis in the euploid context, while in T21 cells, GATA1s competed with the enhanced erythropoiesis and impaired megakaryopoiesis driven by T21 to promote production of immature erythrocytes, MKs, and myeloid cells. The use of isogenic cells revealed distinct transcriptional programs that can be attributed specifically to T21 and GATA1s, and how they independently and synergistically result in HPC proliferation at the expense of maturation, consistent with a pro-leukemic phenotype.

Prenatal Manifestation of Transient Abnormal Myelopoiesis: Case Report and Review of the Literature.

Background: Congenital malignancies are unusual fetal conditions, and therefore, the data on their prenatal manifestation are limited. Transient abnormal myelopoiesis (TAM) is a hematologic disorder characteristic for babies with trisomy 21 and based on the transient appearance of blast cells in peripheral blood. Methods: This paper presents prenatal manifestation of congenital TAM in a newborn with normal karyotype and reviews the literature on prenatal manifestation of this disorder. Results: A pregnant woman in her third pregnancy referred herself to the hospital for reduced fetal movements at 30 weeks of gestation. Admission's ultrasound scan showed an increased middle cerebral artery peak systolic velocity together with hepatomegaly. The patient was admitted to the labor ward for cardiotocography monitoring which showed acute fetal distress with repeated unprovoked decelerations. An emergency cesarean section was conducted and a phenotypically normal female newborn with low Apgar score was delivered. Further examination of the peripheral blood revealed anemia and leukocytosis with high blast proportion. A bone marrow aspirate revealed 70.2% of blasts in a sample with an abnormal karyotype of 47 XX+21. Cytogenetic analysis of the blasts with later microarray comparative genomic hybridization confirmed the presence of GATA1 mutation. However, the buccal smear showed a normal karyotype in the infant. The disease was classified as TAM. Conclusions: Our study demonstrates a rare case of prenatal manifestation of TAM in a neonate with a normal karyotype. Obstetricians should pay attention to symptoms like high MCA PSV and hepatosplenomegaly as possible causes of fetal hematological disorders and differentiate it with infection or isoimmunization.

Transient Abnormal Myelopoiesis in Down Syndrome Patients

Neonates with Down Syndrome (DS) have a propensity to develop the unique myeloproliferative disorder, Transient Abnormal Myelopoiesis (TAM). Transient abnormal myelopoiesis usually resolves spontaneously in < 3 months, but approximately 10% of patients with TAM die from hepatic or multi-organ failure. After remission, 20% of patients with TAM progress into acute myeloid leukemia associated with down syndrome (ML-DS). The patient was a full-term 2-day-old baby girl with a birth weight of 3300 gr. Physical examination revealed dysmorphic facial features, hypertelorism, macroglossia, and low set ears, which is a characteristic sign of DS face, skin rash, and there was no anus. On examination of peripheral blood smears and bone marrow aspiration, hematological abnormalities, and circulating blast cells were found. Early diagnosis of low-lying anorectal malformation (MAR) without fistula and down syndrome. In treating patients with TAM, it is first necessary to know whether they have trisomy 21 syndrome, then trace the existing hematological disorders to find the GATA 1 genetic mutation. The most crucial hematological problem in patients with DS is leukemia. Mutations in the GATA 1 gene and the presence of DS can result in abnormal proliferation of megakaryocytes and erythroid progenitors in the fetus and hematological abnormalities in TAM. Transient abnormal myelopoiesis can be fatal in up to 10% of patients and resolves spontaneously. Therefore, laboratory examinations are very significant, including blood tests, peripheral blood smears, supporting examinations such as bone marrow aspiration, monitoring of clinical symptoms, and close monitoring of comorbidities. Examination repeat or follow-up bone marrow aspiration is required within six months of patient follow-up to reduce the risk of further complications. In this case, a follow-up examination is highly recommended because if there are no changes, the further examination must be carried out.

Cytokine profiling in 128 patients with transient abnormal myelopoiesis: a report from the JPLSG TAM-10 trial

AbstractTransient abnormal myelopoiesis (TAM) occurs in 10% of neonates with Down syndrome (DS). Although most patients show spontaneous resolution of TAM, early death occurs in ∼20% of cases. Therefore, new biomarkers are needed to predict early death and determine therapeutic interventions. This study aimed to determine the association between clinical characteristics and cytokine levels in patients with TAM. A total of 128 patients with DS with TAM enrolled in the TAM-10 study conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group were included in this study. Five cytokine levels (interleukin-1b [IL-1b], IL-1 receptor agonist, IL-6, IL-8, and IL-13) were significantly higher in patients with early death than in those with nonearly death. Cumulative incidence rates (CIRs) of early death were significantly associated with high levels of the 5 cytokines. Based on unsupervised consensus clustering, patients were classified into 3 cytokine groups: hot-1 (n = 37), hot-2 (n = 42), and cold (n = 49). The CIR of early death was significantly different between the cytokine groups (hot-1/2, n = 79; cold, n = 49; hot-1/2 CIR, 16.5% [95% confidence interval (CI), 7.9-24.2]; cold CIR, 2.0% [95% CI, 0.0-5.9]; P = .013). Furthermore, cytokine groups (hot-1/2 vs cold) were independent poor prognostic factors in the multivariable analysis for early death (hazard ratio, 15.53; 95% CI, 1.434-168.3; P = .024). These results provide valuable information that cytokine level measurement was useful in predicting early death in patients with TAM and might help to determine the need for therapeutic interventions. This trial was registered at UMIN Clinical Trials Registry as #UMIN000005418.

Fetal Anemia in Northern Thailand: Etiologies and Outcomes

OBJECTIVE In Southeast Asia, hemoglobin (Hb) Bart’s disease is the primary cause of fetal anemia, although other causes are increasingly being identified. This study aimed to characterize the etiologies and outcomes of fetal anemia in northern Thailand. METHODS A retrospective chart review was conducted, involving pregnant women who attended antenatal care at Chiang Mai University Hospital between 2014 and 2021 and had a diagnosis by ultrasound findings of fetal anemia, or a fetal diagnosis of Hb Bart’s disease or other known hereditary anemias. RESULTS Among 71 fetuses from 64 pregnancies, 45 (63.4%) had Hb Bart’s disease. Twelve cases (16.9%) of fetal anemia were from other causes, including three cases of homozygous Hb Constant Spring, three cases of hereditary pyropoikilocytosis, one case of suspected red cell membrane disorder, one case each of Rh(D) alloimmunization, Hb H/Hb Pakse disease, transient abnormal myelopoiesis, syphilis infection, and one of unknown cause. All of the seven sets of twins (19.7%) had twin-to-twin transfusion syndrome (TTTS). Intrauterine transfusion was given in four cases of fetal hemolytic anemia which rendered good outcomes. Overall, 12 cases (16.9%) survived beyond the neonatal period. CONCLUSIONS Hb Bart’s disease remains the leading cause of fetal anemia in northern Thailand. Increasingly, frequently diagnosed causes include hemoglobinopathies and red cell membrane disorders.

Transient abnormal myelopoiesis requiring advanced neonatal intensive care treatment.

Five to thirty percent of neonates with trisomy 21 develop transient abnormal myelopoiesis (TAM) with a high mortality rate. The aim of the study was to identify contributing factors that determine mortality and need for chemotherapy in this patient group. Six-year, single-centre, retrospective study of neonatal TAM cases requiring admission to intensive care. Data were collected from electronic patient records, laboratory and genetic results. The odds ratio was calculated to assess the likelihood of neonates with certain clinical characteristics having short-term mortality and needing chemotherapy. Twenty-one neonates were studied with a mortality rate of 28%. Neonates requiring inotropic support (OR 19, 95% CI: 0.9-399, p = 0.05) and inhaled nitric oxide (iNO) (OR 13, 95% CI: 1.4-124.3, p = 0.03) were less likely to survive to discharge. Neonates needing mechanical ventilation (OR 14, 95% CI: 1.1-185.5, p = 0.04), or a white cell count >50 × 109/L (OR 27, 95% CI: 1.2-605.7, p = 0.04) were more likely to receive chemotherapy. A high mortality rate was identified in TAM neonates with symptomatic pulmonary hypertension (PH) needing active treatment strategies, such as inotropes and iNO. The presence of PH should be considered in the clinical management, prognosis and parental counselling.

MiR-1202 acts as anti-oncomiR in myeloid leukaemia by down-modulating GATA-1S expression.

Transient abnormal myelopoiesis (TAM) is a Down syndrome-related pre-leukaemic condition characterized by somatic mutations in the haematopoietic transcription factor GATA-1 that result in exclusive production of its shorter isoform (GATA-1S). Given the common hallmark of altered miRNA expression profiles in haematological malignancies and the pro-leukaemic role of GATA-1S, we aimed to search for miRNAs potentially able to modulate the expression of GATA-1 isoforms. Starting from an in silico prediction of miRNA binding sites in the GATA-1 transcript, miR-1202 came into our sight as potential regulator of GATA-1 expression. Expression studies in K562 cells revealed that miR-1202 directly targets GATA-1, negatively regulates its expression, impairs GATA-1S production, reduces cell proliferation, and increases apoptosis sensitivity. Furthermore, data from TAM and myeloid leukaemia patients provided substantial support to our study by showing that miR-1202 down-modulation is accompanied by increased GATA-1 levels, with more marked effects on GATA-1S. These findings indicate that miR-1202 acts as an anti-oncomiR in myeloid cells and may impact leukaemogenesis at least in part by down-modulating GATA-1S levels.

Inherent genome instability underlies trisomy 21-associated myeloid malignancies.

Constitutional trisomy 21 (T21) is a state of aneuploidy associated with high incidence of childhood acute myeloid leukemia (AML). T21-associated AML is preceded by transient abnormal myelopoiesis (TAM), which is triggered by truncating mutations in GATA1 generating a short GATA1 isoform (GATA1s). T21-associated AML emerges due to secondary mutations in hematopoietic clones bearing GATA1s. Since aneuploidy generally impairs cellular fitness, the paradoxically elevated risk of myeloid malignancy in T21 is not fully understood. We hypothesized that individuals with T21 bear inherent genome instability in hematopoietic lineages that promotes leukemogenic mutations driving the genesis of TAM and AML. We found that individuals with T21 show increased chromosomal copy number variations (CNVs) compared to euploid individuals, suggesting that genome instability could be underlying predisposition to TAM and AML. Acquisition of GATA1s enforces myeloid skewing and maintenance of the hematopoietic progenitor state independently of T21; however, GATA1s in T21 hematopoietic progenitor cells (HPCs) further augments genome instability. Increased dosage of the chromosome 21 (chr21) gene DYRK1A impairs homology-directed DNA repair as a mechanism of elevated mutagenesis. These results posit a model wherein inherent genome instability in T21 drives myeloid malignancy in concert with GATA1s mutations.

GATA1 in Normal and Pathologic Megakaryopoiesis and Platelet Development.

GATA1 is a highly conserved hematopoietic transcription factor (TF), essential for normal erythropoiesis and megakaryopoiesis, that encodes a full-length, predominant isoform and an amino (N)terminus-truncated isoform GATA1s. It is consistently expressed throughout megakaryocyte development and interacts with its target genes either independently or in association with binding partners such as FOG1(friend of GATA1). While the N-terminus and zinc finger have classically been demonstrated to be necessary for the normal regulation of platelet-specific genes, murine models, cell-line studies, and human case reports indicate that the carboxy-terminal activation domain and zinc finger also play key roles in precisely controlling megakaryocyte growth, proliferation, and maturation. Murine models have shown that disruptions to GATA1 increase the proliferation of immature megakaryocytes with abnormal architecture and impaired terminal differentiation into platelets. In humans, germline GATA1 mutations result in variable cytopenias, including macrothrombocytopenia with abnormal platelet aggregation and excessive bleeding tendencies, while acquired GATA1s mutations in individuals with trisomy 21 (T21) result in transient abnormal myelopoiesis (TAM) and myeloid leukemia of Down syndrome (ML-DS) arising from a megakaryocyte-erythroid progenitor(MEP). Taken together, GATA1 plays a key role in regulating megakaryocyte differentiation, maturation, and proliferative capacity. As sequencing and proteomic technologies expand, additional GATA1 mutations and regulatory mechanisms contributing to human diseases of megakaryocytes and platelets are likely to be revealed.

Down syndrome-associated leukaemias: current evidence and challenges.

Children with Down syndrome (DS) are at increased risk of developing haematological malignancies, in particular acute megakaryoblastic leukaemia and acute lymphoblastic leukaemia. The microenvironment established by abnormal haematopoiesis driven by trisomy 21 is compounded by additional genetic and epigenetic changes that can drive leukaemogenesis in patients with DS. GATA-binding protein 1 (GATA1) somatic mutations are implicated in the development of transient abnormal myelopoiesis and the progression to myeloid leukaemia of DS (ML-DS) and provide a model of the multi-step process of leukaemogenesis in DS. This review summarises key genetic drivers for the development of leukaemia in patients with DS, the biology and treatment of ML-DS and DS-associated acute lymphoblastic leukaemia, late effects of treatments for DS-leukaemias and the focus for future targeted therapy.

Hypoechoic liver in a fetus with trisomy 21 but without transient abnormal myelopoiesis at birth

Hypoechoic liver in a fetus with trisomy 21 but without transient abnormal myelopoiesis at birth

Too many white cells-TAM, JMML, or something else?

Leukocytosis is a common finding in pediatric patients, and the differential diagnosis can be broad, including benign reactive leukocytosis and malignant myeloproliferative disorders. Transient abnormal myelopoiesis is a myeloproliferative disorder that occurs in young infants with constitutional trisomy 21 and somatic GATA1 mutations. Most patients are observed, but outcomes span the spectrum from spontaneous resolution to life-threatening complications. Juvenile myelomonocytic leukemia is a highly aggressive myeloproliferative disorder associated with altered RAS-pathway signaling that occurs in infants and young children. Treatment typically involves hematopoietic stem cell transplantation, but certain patients can be observed. Early recognition of these and other myeloproliferative disorders is important and requires a clinician to be aware of these diagnoses and have a clear understanding of their presentations. This paper discusses the presentation and evaluation of leukocytosis when myeloproliferative disorders are part of the differential and reviews different concepts regarding treatment strategies.

GATA1 Target Gene CSF2RB Is Functionally Coupled to MPL and Marks a TPO-Dependent Preleukemic TAM Cell Population Sustained By the Fetal Liver but Not Bone Marrow

Paediatric cancers differ from adult cancers on the basis of their genetics and biology. Understanding these differences can identify factors important in oncogenesis during development. One exemplar are the genetically linked myeloid pre-leukemic and leukemic disorders in newborns and children with Trisomy 21 (T21) or Down syndrome (DS). DS children have a 400-fold increased risk of developing myeloid leukemia (ML-DS) in early life. ML-DS is preceded by a fetal/neonatal pre-leukemic phase known as transient abnormal myelopoiesis (TAM), when T21 hemopoietic cells acquire mutations in the GATA1 gene. These mutations produce an N-terminal truncated GATA1 protein (GATA1s). Remarkably, the proliferative effect exerted by T21 and GATA1s is developmentally restricted. As hemopoiesis shifts from fetal liver to new-born bone marrow, TAM usually spontaneously regresses. The biological basis for the requirement of a fetal liver environment for TAM cells and their failure to thrive in the bone marrow is unknown. However, a clue is that TAM cells can proliferate in bone marrow if they acquire oncogenic mutations, typically in genes of the JAK-STAT signalling pathway. These mutations transform the TAM clone to an ML-DS clone. To address the question of why TAM cells survive only in a fetal liver environment, we performed scRNA sequencing, coupled with genotyping from 3 primary TAM samples. 4 T21 and 3 disomic cord blood samples were used as controls (Fig1A). We identified a marked expansion of mutant TAM GATA1s cells, compared to controls, at the earliest GATA1-expressing progenitor stages (Fig1A). TAM GATA1s cells displayed transcriptional upregulation of the PI3K/AKT/mTOR, TNFA/NFκB and JAK/STAT pathways and enhanced STAT3 regulon activity when compared to controls (Fig1A). We hypothesized that aberrant cytokine receptor activation leading to increased STAT3 activity is essential for GATA1s cell proliferation. Differential gene expression between TAM GATA1s cells and disomic cells, pointed to CSF2RB, a cytokine receptor that directly activates the JAK-STAT signalling pathway (Fig1A). Next, we demonstrated that CSF2RB is overexpressed at the protein level in TAM and marks 80% of CD34 + cells compared to 5% CD34+ control cells. Using CUT&TAG we confirmed binding of GATA1s and GATA2 at two GATA sites in the CSF2RB locus in CMK cells (Fig 1A). CRISPR-Cas9 disruption of either GATA2, or the -12kb GATA motif led to downregulation of CSF2RB protein (Fig1A). We are testing if GATA1 represses CSF2RB and whether GATA1s fails to repress CSF2RB, allowing sustained abnormal CSF2RB expression in TAM. CSF2RB gene knockout in GATA1s cells leads to cell death. Taken together, CSF2RB is a direct GATA target gene and abnormal sustained, CSF2RB expression in TAM cells is required for GATA1s cell survival. Classically, CSF2RB partners with the α-chain of either IL3, IL5 or GMCSF receptors. Interestingly, none of the α-chains are expressed at the protein or RNA level in TAM CSF2RB+ cells, suggesting that CSF2RB might partner with another cytokine receptor. We nominated MPL, the thrombopoietin (TPO) receptor as a new candidate binding partner of CSF2RB for the following reasons: (i) we documented co-expression of MPL with CSF2RB at the RNA and protein level in TAM cells. (ii) we confirmed functional coupling between CSF2RB and MPL in Ba/F3 and TF-1 cells, where at equivalent MPL levels, TPO signalling via the JAK-STAT pathway is enhanced by CSF2RB. This effect is stronger at high TPO levels. (iii) A mutation in CSFR2RB (A455D) that we described in ML-DSrequires interaction with human MPL to induce autonomous growth of cytokine-dependent hematopoietic cells. Notably, direct interaction between MPL and CSF2RB A455D is detected by BRET assays. We hypothesize that high levels of fetal liver derived TPO sustain TAM proliferation because of the functional coupling between MPL and CSF2RB (Fig1B). This proliferation signal is lost as cells migrate to the low TPO bone marrow environment. Further work will assess TPO concentration in DS fetal liver and whether TAM cells display increased proliferation in response to varying TPO doses. In summary, we propose a model whereby reduced TPO levels experienced by TAM cells as they migrate from fetal liver to bone marrow creates selective pressure for acquisition of secondary mutations that permit TAM cells to proliferate independently of the high TPO environment of the fetal liver (Fig1B).

Single-Cell Transcriptomics Reveal Altered Hematopoietic Mechanisms Driven By T21 and GATA1s

Introduction Trisomy 21 (T21) is associated with baseline erythrocytosis and thrombocytopenia and risk of transient abnormal myelopoiesis (TAM) and acute megakaryoblastic leukemia of Down syndrome (ML-DS). TAM and ML-DS are characterized by mutations in the transcription factor GATA1, resulting in the truncated isoform GATA1s (G1S). We previously found that T21 increases erythropoiesis, while G1S severely impairs erythroid development but enhances megakaryocyte (MK) proliferation (Byrska-Bishop et al, JCI 2015). To better understand how T21 and G1S each impact hematopoiesis, we performed single-cell RNA sequencing (scRNA-seq) of multipotent and late hematopoietic progenitor cells (HPCs) differing only by chromosome 21 and/or G1S status. Methods Four isogenic human induced pluripotent stem cell (iPSC) lines differing only by chromosome 21 (euploid vs. T21) and/or GATA1 (WT vs. G1S) status underwent hematopoietic differentiation by embryoid body formation. Cells were collected at 3 timepoints: on day 7 (D7), CD41 +235 + multipotent HPCs were purified by flow cytometry and on days 9 (D9) and 11 (D11), late HPCs biased to a single lineage were collected. Cells were sequenced by scRNA-seq and underwent quality control followed by clustering and analysis using Seurat. Clusters were manually annotated based on expression of 141 key hematopoietic genes, including aggregated expression of lineage markers. Early vs. committed lineage clusters were determined based on the relative expression of lineage-specific markers. Within each lineage, differentially expressed genes (DEGs) associated with a genetic background were assessed using the Wilcoxon rank-sum test. The χ² test was used to compare categorical data. A 2-tailed p or adjusted p <0.05 was considered statistically significant. Results Cluster annotation revealed HPC, early and committed erythroid and MK, and myeloid cells (Figure 1). D7 T21/G1S HPCs surprisingly showed an erythroid bias, with upregulation of genes such as GYPA and AHSP, while euploid/G1S HPCs showed a MK bias, with upregulation of genes including PF4V1 and PF4. With wtGATA1, neither euploid nor T21 D7 HPCs showed a significant lineage skew. On D9 and D11, the euploid/WT, T21/WT, and T21/G1S cells developed subpopulations committing to the erythroid lineage, while the euploid/G1S cells demonstrated minimal erythroid potential (Figure 1). Across all 3 timepoints, early and committed erythrocytes from T21 and euploid cells with G1S had a greater number of combined DEGs than their wtGATA1 counterparts (G1S vs. WT, T21: 692 vs. 378; euploid: 1235 vs. 599). On D9, T21 was associated with a greater erythroid skew (38.6% of T21/WT and 32.2% of T21/G1S cells vs. 27.8% of euploid/WT cells; p <0.00001). By D11, this erythroid drive was no longer apparent, and the T21/G1S erythrocytes were significantly less mature (Table 1; p <0.00001). These data suggest that T21 initially enhances erythropoietic drive, while G1S results in a near-complete erythroid block in euploid cells but an incomplete developmental block with T21. All 4 genotypes yielded MK subpopulations on D9 and D11 (Figure 1). With wtGATA1, euploid and T21 MKs were predominantly early MKs by D11 (Table 1). Interestingly, G1S was associated with enhanced MK commitment and maturation in the euploid context but arrest at the early stage with T21 (Table 1; p <0.00001). G1S was again associated with increased DEGs compared to wtGATA1 (G1S vs. WT, T21: 594 vs. 454; euploid: 1689 vs. 1310). These data suggest that G1S in a euploid background promotes MK differentiation, but T21 and G1S cooperate to generate immature, abnormal MKs. Conclusions Although the hematopoietic abnormalities and leukemic risk of T21 have been well-described, the underlying developmental events remain unclear. This scRNA-seq timecourse of HPCs differentiated from isogenic iPSCs reveals the individual and synergistic effects of T21 and G1S. Overall, T21 enhances erythropoietic drive while G1S alone suppresses erythropoiesis. G1S in euploid cells enhances megakaryopoiesis, but with T21, megakaryopoietic commitment and maturation are uncoupled with a strong bias to early MKs. Together, the competing effects of T21 and G1S appear to result in abnormal, immature erythrocytes and MKs with impaired lineage commitment, consistent with a pro-leukemic phenotype.

The Challenge of Treating Relapsed Myeloid Leukemia in Children with Down Syndrome - a Targeted Analysis Using Patient-Derived Xenograft Models

Background. Myeloid leukemia occurs with a 150-fold increased incidence in children with Down syndrome (ML-DS) and is characterized by distinct disease mechanism and response to treatment. In the context of trisomy 21, somatic GATA1 mutations first initiate preleukemic transient abnormal myelopoiesis, a disorder of fetal liver hematopoiesis. Co-operating events, which target cohesin complex components, epigenetic modifiers or signal transducers including RAS pathway genes (Yoshida 2013, Labuhn M 2019), then drive transformation to ML-DS in 20% of infants with TAM, typically by age 4 years. Abnormal sonic hedgehog signaling was recently associated with trisomy 21 (Galati 2019). Its role in the development of ML-DS is unknown. Hypersensitivity of ML-DS blasts to chemotherapy with cytarabine and other agents accounts at least in part for the more favorable response of ML-DS compared to acute myeloid leukemia of children without DS. Contemporary treatment protocols for ML-DS achieve event-free and overall survival of approx. 89% and 90% at 5 years (Taub 2017). In marked contrast, patients who develop a relapse of ML-DS face a significantly lower probability of survival (EFS 20.9% and OS 22% at 3 years, Raghuram 2023), compared to children with relapsed AML who do not have DS, and appear to be resistant against conventional chemotherapy. Since the few survivors with a relapsed ML-DS are almost exclusively found among patients who first achieve a second remission and then undergo hematopoietic stem cell transplantation, successful identification of agents with efficacy against the blasts of relapsed ML-DS is essential for survival. We tested if blasts of relapsed ML-DS had lost their sensitivity to cytarabine and whether new drugs could be identified that target pathways active in the blasts of ML-DS. Patients, Materials and Methods . We used patient-derived xenografts (PDX) of human ML-DS and relapsed ML-DS blasts in immunodeficient mice (NSG and NSG-W41) to determine in vivo responses to standard chemotherapeutic agents (cytarabine, vincristine) and novel approaches such as demethylating agents (azacytidine), inhibition of histone deacetylation (panobinostat), mTOR (rapamycin), PARP (olaparib), and sonic hedgehog signaling (glasdegib) alone or in combination (glasdegib + cytarabine; panobinostast + azacytidine). Injection of leukemic cells was performed intrafemorally. Endpoint was inhibition of leukemic engraftment compared to control recipients receiving vehicle only. Results.Responses of primary and relapsed ML-DS samples to drugs tested in PDX models showed marked heterogeneity. While some ML-DS samples showed resistance to cytarabine at the time of relapse this was not the universal cause of failure of primary treatment of ML-DS and some blasts of relapsed ML-DS retained sensitivity to cytarabine. Some primary and relapsed ML-DS blasts showed unexpected sensitivity to vincristine, a drug more commonly used to treat acute lymphoblastic leukemia. Despite intriguing rationales we observed no responses of primary and relapsed ML-DS blasts to the PARP inhibitor olaparib, mTOR inhibition by rapamycin and sonic hedgehog inhibition by glasdegib. Conclusions. Loss of hypersensitivity to cytarabine was not universal at the time of ML-DS relapse. Some agents not typically used to treat AML, such as vincristine, showed unexpected efficacy whereas others lacked responses despite a plausible mechanistic rationale. Patient-specific molecular mechanisms underlying relapsed ML-DS are likely to have an impact on drug sensitivity. They should be determined for all patients with relapsed ML-DS to assist identification of targets and selection of drugs in order to establish urgently needed but currently still lacking efficacious treatment for relapsed ML-DS.

Death of children with Down syndrome by gestational age and cause.

We often encounter preterm infants with Down syndrome (DS) who die in the neonatal intensive care unit (NICU). In this study, we examined survival until NICU discharge and assessed the developmental prognosis of preterm infants with DS. We retrospectively reviewed 416 infants with DS hospitalized during the past 27 years at our NICU. Death occurred in 8/20 (40%) infants at <32 weeks' gestation, 11/23 (48%) at 32-33 weeks, 9/99 (9%) at 34-36 weeks, and 9/274 (3%) at >36 weeks. In total, 84% of infants who died and 25% of those who survived had a non-reassuring fetal status (p < 0.001). Sex, small-for-gestational-age status, and postnatal transport were not associated with death. The main causes of death were bronchopulmonary dysplasia in 4/8 (50%) infants at <32 weeks' gestation, transient abnormal myelopoiesis in 11/20 (55%) and lymphatic dysplasia in 6/20 (30%) at 32-36 weeks, and varied causes at >36 weeks. Among survivors born at <34 weeks' gestation, 6/19 (32%) aged >2 years had moderate or severe cerebral palsy. These data on the high mortality and morbidity of preterm infants with DS may be useful for patient treatment and parent counseling in NICUs treating critically ill infants. Most infants with Down syndrome born at <34 weeks' gestation are born by cesarean section because of the non-reassuring fetal status. The mortality rate before discharge for infants with Down syndrome born at <34 weeks' gestation was 40%, and 30% of survivors developed moderate or severe cerebral palsy. The risk of death due to bronchopulmonary dysplasia and pulmonary hypertension was high in very preterm infants with Down syndrome despite the absence of chorioamnionitis. Infants with Down syndrome were born 1-2 weeks earlier than unaffected controls.

Prenatal diagnosis of Down syndrome combined with transient abnormal myelopoiesis in foetuses with a GATA1 gene variant: two case reports

BackgroundDown syndrome myeloid hyperplasia includes transient abnormal myelopoiesis (TAM) and the myeloid leukemia associated with Down syndrome (ML-DS). The mutation of GATA1 gene is essential in the development of Down syndrome combined with TAM or ML-DS. Some patients with TAM are asymptomatic and may also present with severe manifestations such as hepatosplenomegaly and hydrops.Case presentationWe report two cases of prenatally diagnosed TAM. One case was a rare placental low percentage 21 trisomy mosiacism, resulting in the occurrence of a false negative NIPT. The final diagnosis was made at 36 weeks of gestation when ultrasound revealed significant enlargement of the foetal liver and spleen and an enlarged heart; the foetus eventually died in utero. We detected a placenta with a low percentage (5–8%) of trisomy 21 mosiacism by Copy Number Variation Sequencing (CNV-seq) and Fluorescence in situ hybridization (FISH). In another case, foetal oedema was detected by ultrasound at 31 weeks of gestation. Two foetuses were diagnosed with Down syndrome by chromosomal microarray analysis via umbilical vein puncture and had significantly elevated cord blood leucocyte counts with large numbers of blasts. The GATA1 Sanger sequencing results suggested the presence of a [NM_002049.4(GATA1):c.220G > A (p. Val74Ile)] hemizygous variant and a [NM_002049.4(GATA1):c.49dupC(p. Gln17ProfsTer23)] hemizygous variant of the GATA1 gene in two cases.ConclusionIt seems highly likely that these two identified mutations are the genetic cause of prenatal TAM in foetuses with Down syndrome.

Hematologic Neoplasms Associated with Down Syndrome: Cellular and Molecular Heterogeneity of the Diseases.

The molecular basis of Down syndrome (DS) predisposition to leukemia is not fully understood but involves various factors such as chromosomal abnormalities, oncogenic mutations, epigenetic alterations, and changes in selection dynamics. Myeloid leukemia associated with DS (ML-DS) is preceded by a preleukemic phase called transient abnormal myelopoiesis driven by GATA1 gene mutations and progresses to ML-DS via additional mutations in cohesin genes, CTCF, RAS, or JAK/STAT pathway genes. DS-related ALL (ALL-DS) differs from non-DS ALL in terms of cytogenetic subgroups and genetic driver events, and the aberrant expression of CRLF2, JAK2 mutations, and RAS pathway-activating mutations are frequent in ALL-DS. Recent advancements in single-cell multi-omics technologies have provided unprecedented insights into the cellular and molecular heterogeneity of DS-associated hematologic neoplasms. Single-cell RNA sequencing and digital spatial profiling enable the identification of rare cell subpopulations, characterization of clonal evolution dynamics, and exploration of the tumor microenvironment's role. These approaches may help identify new druggable targets and tailor therapeutic interventions based on distinct molecular profiles, ultimately improving patient outcomes with the potential to guide personalized medicine approaches and the development of targeted therapies.

Myeloid Leukemia of Down Syndrome.

Myeloid leukemia of Down syndrome (ML-DS) is characterized by a distinct natural history and is classified by the World Health Organization (WHO) as an independent entity, occurring with unique clinical and molecular features. The presence of a long preleukemic, myelodysplastic phase, called transient abnormal myelopoiesis (TAM), precedes the initiation of ML-DS and is defined by unusual chromosomal findings. Individuals with constitutional trisomy 21 have a profound dosage imbalance in the hematopoiesis-governing genes located on chromosome 21 and thus are subject to impaired fetal as well as to neonatal erythro-megakaryopoiesis. Almost all neonates with DS develop quantitative and morphological hematological abnormalities, yet still only 5-10% of them present with one of the preleukemic or leukemic conditions of DS. The acquired mutations in the key hematopoietic transcription factor gene GATA1, found solely in cells trisomic for chromosome 21, are considered to be the essential step for the selective growth advantage of leukemic cells. While the majority of cases of TAM remain clinically 'silent' or undergo spontaneous remission, the remaining 20% to 30% of them progress into ML-DS until the age of 4 years. The hypersensitivity of ML-DS blasts to chemotherapeutic agents, including but not limited to cytarabine, and drugs' increased infectious and cardiac toxicity have necessitated the development of risk-adapted treatment protocols for children with ML-DS. Recent advances in cytogenetics and specific molecular mechanisms involved in the evolution of TAM and ML-DS are reviewed here, as well as their integration in the improvement of risk stratification and targeted management of ML-DS.

Role of Morphology in the Diagnosis of Acute Leukemias: Systematic Review

AbstractThe role of hematopathologists in the diagnosis of acute leukemia (AL) starts with the morphological examination of either peripheral blood smear or bone marrow. The morphological hallmark for the myeloblast includes “Auer rods” and “Phi bodies.” The addition of cytochemical stains such as myeloperoxidase, Sudan Black B, periodic acid-Schiff stain, nonspecific esterase, and Perls' stain acts as an important adjunct to the morphological classification in the resource-constrained settings. The recent World Health Organization classification still endorses the utility of morphology which requires the presence of either ≥ 20% lymphoblasts or myeloblasts/or its equivalents (monoblasts, promonocytes, or megakaryoblasts) and integrates it with the clinical features, immunophenotyping (IP), and molecular genetics for making the diagnosis of AL. Morphology can give clue to the specific diagnosis of acute myeloid leukemia (AML) with t(8:21), t(15:17), t(16:16), or inv(16) and this diagnosis can be made irrespective of blasts count if such translocations are demonstrated by molecular tests. There are some interesting findings such as blasts with “hand-mirror” morphology, nuclear cleavage, prominent cytoplasmic vacuoles, pseudo-Chediak-Higashi granules, cup-like nucleus, and other dysplastic features helping in differentiating lymphoid and myeloid leukemias. Transient abnormal myelopoiesis in Down syndrome and hypoplastic AL can be picked up on morphological examination. Bone marrow biopsy would be greatly beneficial and complementary to aspirate smears and is required for diagnosing exact cellularity, topography of cells, dyspoiesis, myelonecrosis, gelatinous marrow transformation, myelofibrosis, and IP can be performed using immunohistochemistry. Morphological examination in AL is not only helpful for diagnosis but also useful for predicting the prognosis in posttherapy cases, AML with myelodysplasia-related changes, therapy-related myeloid neoplasms, and mixed phenotype AL. Hematogones, blastoid mantle cell lymphoma, high grade B cell lymphoid with blastoid morphology, Burkitt leukemia, prolymphocytes in prolymphocytic leukemia, hairy cell leukemia variant, plasmablasts especially in plasmablastic leukemia, or plasma cell leukemia can mimic AL and IP is useful in these situations. Hence, morphology should be considered as a kind of “gold-standard” starting point for the analysis of AL cases. Morphological examination cannot be replaced and advanced tests cannot be used as surrogate for morphology.