Hematopoiesis in the Ts65Dn Mouse Model of Down Syndrome (DS) Recapitulates Many Features of Human DS.

Abstract Down syndrome-associated acute megakaryocytic leukemia (DS-AMKL) is a complex malignancy that evolves in hematopoietic progenitors with trisomy 21 that acquire a somatic mutation in the blood transcription factor GATA1. The mechanistic relationship between these two genetic factors that leads to leukemia is poorly understood. In order to study the interplay between trisomy 21 and GATA1 mutations, we are developing a mouse model of this malignancy. The Ts65Dn mouse, which contains a segmental trisomy for mouse chromosome 16, homologous to human 21, has been reported to display several of the cognitive and craniofacial phenotypes seen in humans with DS, but the hematopoietic system has not been assessed as a model for blood development in humans with DS. We have evaluated adult hematopoiesis in the Ts65Dn strain by comparing monthly complete blood counts (CBC) of peripheral blood from 14 trisomic and 20 disomic littermates. Similar to humans with DS, Ts65Dn trisomic mice display persistent erythrocyte macrocytosis, with values at the high end of the normal range. Trisomic mice also harbor decreased numbers of red blood cells, mildly elevated platelet counts, a higher percentage of monocytes and a lower hemoglobin concentration. Interestingly infants with DS frequently display thrombocytosis. In addition, we have characterized fetal liver hematopoiesis in the Ts65Dn strain by FACS analysis of hematopoietic precursors and by performing colony assays. In general, we did not detect any significant differences in erythroid, myeloid, or megakaryocytic colony formation between trisomic or disomic fetuses. Likewise flow cytometry for CD34, TER119, and CD41 demonstrated overall similar numbers of cells in these compartments for Ts65Dn mice and disomic littermates. However, one of seven trisomic embryos displayed a significant increase in the proportion of CD34+ cells with concomitant decrease in both Ter119+ and CD41+ populations. In addition, cells from this fetal liver gave rise to seven-fold and three-fold increases in BFU-E and CFU-Mk colonies respectively, with no change in the CFU-GM. Although the sample size is small, these findings suggest that a subset of Ts65Dn trisomic fetuses exhibit aberrant hematopoiesis. Taken together, our study indicates that the Ts65Dn trisomic mouse may be an excellent model to study human DS hematopoiesis.

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Trisomy 21 Expands the Megakaryocyte-Erythroid Progenitor Compartment in Human Fetal Liver-Implications for Down Syndrome AMKL.

Blood ◽

10.1182/blood.v108.11.563.563 ◽

2006 ◽

Vol 108 (11) ◽

pp. 563-563 ◽

Cited By ~ 3

Author(s):

Oliver Tunstall-Pedoe ◽

Josu de la Fuente ◽

Phillip R. Bennett ◽

Nicholas M. Fisk ◽

Paresh Vyas ◽

...

Keyword(s):

Bone Marrow ◽

Down Syndrome ◽

Trisomy 21 ◽

Fetal Liver ◽

Fetal Blood ◽

Fetal Bone ◽

Cd34 Cells ◽

Progenitor Compartment ◽

Gata1 Mutation

Abstract Children with Down syndrome (DS) have a uniquely high frequency of acute megakaryoblastic leukemia (AMKL)- ~500-fold increased compared to children without trisomy 21 (T21). At least two genetic events are required but are not sufficient for DS-AMKL: T21 and N-terminal truncating mutations in the key megakaryocytic transcription factor GATA1. This tight association of T21 with GATA1 mutations and the development of AMKL in a narrow temporal window (fetal life-5yrs) makes DS-AMKL a highly informative model of multi-hit leukemogenesis in which the first steps occur in utero. However, the individual contributions of T21 and mutant GATA1 in the leukemogenesis are unclear. To specifically investigate the role of T21 in DS-AMKL and why leukemia-initiation is confined to fetal (or early post-natal) life we have studied fetal hemopoiesis in DS during the second and third trimester in 16 fetuses (gestational age 15–37 weeks) where an antenatal diagnosis of DS with T21 was made by amniotic fluid fetal cell karyotyping. Samples of fetal blood (n=13), fetal liver (n=9) and fetal bone marrow (n=8) were screened for mutations in the GATA1 gene genomic DNA by DHPLC or direct sequencing (sensitivity of detecting a GATA1 mutation is 1–5% by DHPLC). No GATA1 mutations were detected. This allowed us to study the impact of T21 independent of GATA1 mutation on fetal hemopoiesis. DS fetuses showed marked qualitative and quantitative abnormalities in hemopoiesis. While the total number of CD34+ cells in DS and normal fetal liver were comparable, DS fetuses had a striking increase in bi-potential megakaryocyte-erythroid progenitors (MEP; CD34+CD38+FcgloCD45RA+− 74.4% vs 27.0% of fetal liver CD34+/CD38+ cells. Peripheral blood from all DS fetuses studied compared to normal fetal blood samples showed dysmegakaryopoiesis (abnormally shaped and/or giant platelets and MK fragments), dyserythropoiesis (macrocytes, poikilocytes, basophilic stippling), increased numbers of blast cells and also had an increased percentage of MEPs − 40.3% vs 26.9%. By contrast, there was no difference in the number of MEP nor erythroid or MK lineage morphology in DS fetal bone marrow compared to normal fetal bone marrow. CD34+ cells from DS fetal liver and fetal blood expressed both fl GATA1 and GATA1s mRNA indicating that dysmegakaryopoiesis and erythropoiesis were not due to lack of expression of fl GATA1. These data indicate, for the first time, that T21 by itself profoundly disturbs megakaryopoiesis and erythropoiesis and leads to an increased of frequency of MEP. This has important implications since it provides a testable hypothesis for the role of T21 in the initiating step of AMKL, namely that T21 expands a fetal liver-derived progenitor compartment which forms a substrate upon which GATA1 mutations then confer a further selective advantage.

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Hematopoietic defects in the Ts1Cje mouse model of Down syndrome

Blood ◽

10.1182/blood-2008-06-161422 ◽

2009 ◽

Vol 113 (9) ◽

pp. 1929-1937 ◽

Cited By ~ 36

Author(s):

Catherine L. Carmichael ◽

Ian J. Majewski ◽

Warren S. Alexander ◽

Donald Metcalf ◽

Douglas J. Hilton ◽

...

Keyword(s):

Down Syndrome ◽

Mouse Model ◽

Cell Function ◽

Fetal Liver ◽

Partial Trisomy ◽

Chromosome 21 ◽

Loss Of Function ◽

Premalignant Disease ◽

Acute Megakaryocytic Leukemia ◽

Insight Into

Down syndrome (DS) persons are born with various hematopoietic abnormalities, ranging from relatively benign, such as neutrophilia and macrocytosis, to a more severe transient myeloproliferative disorder (TMD). In most cases, these abnormalities resolve in the first few months to years of life. However, sometimes the TMD represents a premalignant disease that develops into acute megakaryocytic leukemia (AMKL), usually in association with acquired GATA1 mutations. To gain insight into the mechanisms responsible for these abnormalities, we analyzed the hematopoietic development of the Ts1Cje mouse model of DS. Our analyses identified defects in mature blood cells, including macrocytosis and anemia, as well as abnormalities in fetal liver and bone marrow stem and progenitor cell function. Despite these defects, the Ts1Cje mice do not develop disease resembling either TMD or AMKL, and this was not altered by a loss of function allele of Gata1. Thus, loss of Gata1 and partial trisomy of chromosome 21 orthologs, when combined, do not appear to be sufficient to induce TMD or AMKL-like phenotypes in mice.

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Trisomy of Erg is required for myeloproliferation in a mouse model of Down syndrome

Blood ◽

10.1182/blood-2009-09-242107 ◽

2010 ◽

Vol 115 (19) ◽

pp. 3966-3969 ◽

Cited By ~ 45

Author(s):

Ashley P. Ng ◽

Craig D. Hyland ◽

Donald Metcalf ◽

Catherine L. Carmichael ◽

Stephen J. Loughran ◽

...

Keyword(s):

Down Syndrome ◽

Mouse Model ◽

Trisomy 21 ◽

Progenitor Cell ◽

Gene Dosage ◽

Myeloproliferative Disorder ◽

Chromosome 21 ◽

Loss Of Function ◽

Hematologic Disorders ◽

Acute Megakaryocytic Leukemia

Abstract Down syndrome is characterized by multiple phenotypic manifestations associated with trisomy of chromosome 21. The transient myeloproliferative disorder and acute megakaryocytic leukemia associated with Down syndrome are uniquely associated with mutations in the transcription factor GATA1; however, the identity of trisomic genes on chromosome 21 that predispose to these hematologic disorders remains unknown. Using a loss-of-function allele, we show that specific reduction to functional disomy of the Erg gene corrects the pathologic and hematologic features of myeloproliferation in the Ts(1716)65Dn mouse model of Down syndrome, including megakaryocytosis and progenitor cell expansion. Our data provide genetic evidence establishing the need for Erg trisomy for myeloproliferation in Ts(1716)65Dn mice and imply that increased ERG gene dosage may be a key consequence of trisomy 21 that can predispose to malignant hematologic disorders in Down syndrome.

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Signalling pathways contributing to learning and memory deficits in the Ts65Dn mouse model of Down Syndrome

Neuronal Signaling ◽

10.1042/ns20200011 ◽

2021 ◽

Author(s):

Aimée Freeburn ◽

Robert Gordon Keith Munn

Keyword(s):

Down Syndrome ◽

Mouse Model ◽

Learning And Memory ◽

Memory Deficits ◽

Signalling Pathways ◽

Chromosome 16 ◽

Ts65dn Mouse ◽

Electrophysiological Studies

Down syndrome is a genetic trisomic disorder that produces life-long changes in physiology and cognition. Many of the changes in learning and memory seen in Down Syndrome (DS) are reminiscent of disorders involving the hippocampal/entorhinal circuit. Mouse models of DS typically involve trisomy of murine chromosome 16 is homologous for many of the genes triplicated in human trisomy 21, and provide us with good models of changes in, and potential pharmacotherapy for, human DS. Recent careful dissection of the Ts65Dn mouse model of DS has revealed differences in key signalling pathways from the basal forebrain to the hippocampus and associated rhinal cortices, as well as changes in the microstructure of the hippocampus itself. In vivo behavioural and electrophysiological studies have shown that Ts65Dn animals have difficulties in spatial memory that mirror hippocampal deficits, and have changes in hippocampal electrophysiological phenomenology that may explain these differences, and align with expectations generated from in vitro exploration of this model. Finally, given the existing data, we will examine the possibility for pharmacotherapy for DS, and outline the work that remains to be done to fully understand this system.

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