Trisomy 21 enhances human fetal erythro-megakaryocytic development

Abstract

IntroductionTransient myeloproliferative disorder (TMD) occurs in 10% to 20% of newborns with Down syndrome (DS) and usually resolves after birth. However, approximately 30% of TMD patients develop acute megakaryoblastic leukemia (AMKL) within 4 years, suggesting that TMD is a premalignant disorder and that both diseases originate in the fetus. 1-4 DS TMD and AMKL blasts harbor somatic mutations of GATA1, which encodes an essential hematopoietic transcription factor. 5-7 These mutations occur in exon 2 and result in exclusive expression of an amino-truncated protein, termed GATA-1 short (GATA-1s).Presumably, GATA-1s cooperates with trisomy 21 (T21) to induce a preleukemic state that progresses to frank malignancy through additional mutations. TMD and AMKL blasts exhibit erythro-megakaryocytic features 8-10 and GATA-1 regulates the maturation, survival, and proliferation of these lineages. 11 In contrast, little is known about how T21 itself alters hematopoiesis, particularly in the fetus, where TMD/AMKL-initiating events occur. We analyzed fetal liver hematopoiesis in T21 and control abortuses. In vitro and in vivo transplantation studies show that T21 is associated with enhanced erythroid and megakaryocytic precursor expansion, independent of GATA1 mutations. These findings provide insight into the hematopoietic abnormalities of DS and indicate how T21 might synergize with GATA-1s to promote TMD and AMKL. MethodsFetal livers were obtained from pathology specimens of week 13 to 23 abortuses. Institutional Review Board-approval was obtained from The Children's Hospital of Philadelphia and The University of Pennsylvania. Informed consent was obtained in accordance with the Declaration of Helsinki. T21 was confirmed by karyotype analysis of fetal tissue. DNA sequencing, hematopoietic assays, and gene expression analysis were performed using standard methods described in Document S1 (available on the Blood website; see the Supplemental Materials link at the top of the online article). Approval from the Institutional Animal Care and Use Committee at the University of Pennsylvania was obtained for mouse studies. Results and discussionDS-associated TMD and AMKL initiate in utero, as evidenced clinically 1,3 and by GATA1 mutational analysis. 7,12,13 We analyzed fetal liver specimens from DS and control abortuses at 13 to 23 weeks' gestation. Histologically, T21 fetal livers were indistinguishable from controls (not shown). We isolated fetal liver hematopoietic mononuclear cells (MNCs), amplified GATA1 exon 2 by polymerase chain reaction (PCR), and subcloned the fragments. No mutations in 31 T21 or 10 control fetal liver MNC samples were detected by direct sequencing of the PCR product and 24 independent clones from each fetal liver, consistent with the relatively low incidence of GATA1 mutations (3.8%) identified by screening 585 DS newborns. 13 The absence of GATA1 mutations in our specimens allowed us to study the hematopoietic effects of T21 in isolation.We analyzed T21 and control fetal liver MNCs in methylcellulose...

Pluripotent stem cells reveal erythroid-specific activities of the GATA1 N-terminus

“…While the current study focuses on the role of GATA1s mutations in erythropoiesis, our findings also provide insights into how these mutations interact with T21. Previous work has shown that T21 augments erythropoiesis in primary fetal cells (61)(62)(63) and iPSCs (18,64). Here, we confirm these findings in T21/WT GATA1 iPSCs and demonstrate that GATA1s overrides the erythropoietic effects of T21 in isogenic double-mutant T21/GATA1s iPSCs derived from 2 different patients with TMD.…”

Aneuploidy impairs hematopoietic stem cell fitness and is selected against in regenerating tissues in vivo

“…Particular aneuploidies in conjunction with other specific genomic alterations could also facilitate the development of specific cancers. For example, analyses of individuals with DS demonstrate that trisomy 21 is sufficient to bias differentiation in the human fetal liver, leading to a relative expansion of myeloid cells (Chou et al 2008;TunstallPedoe et al 2008). This bias can progress to a transient myeloproliferative disorder (TMD) (Gamis and Smith 2012) and eventually AML if a cooperating GATA1 mutation is also present (Hitzler 2003;Mundschau et al 2003).…”

Unique Myeloid Leukemias in Young Children with Down Syndrome: Cell Origin, Association with Hematopoietic Microenvironment and Leukemogenesis

“…However, none of these mouse strains develop TL and AMKL, indicating that additional genetic abnormalities are required to cause leukemia. In humans as well, trisomy 21 itself has been shown to disturb fetal liver, but not bone marrow, hematopoiesis, enhance production of megakaryocyte/erythroid progenitors (MEPs), which may be susceptible to acquisition of other genetic abnormalities, and predispose these cells to DS-related leukemias (Chou et al, 2008;De Vita et al, 2008;Tunstall-Pedoe et al, 2008). These data support the model that the genes on chromosome 21 play essential roles in the development of these disorders and trisomy 21 is the first step of myeloid leukemogenesis in DS.…”