Abstract
We previously demonstrated that an integrated XIST transgene can broadly repress one chromosome 21 in Down syndrome (DS) pluripotent cells. Here we address whether trisomy-silencing can normalize cell function and development sufficiently to correct cell pathogenesis, tested in an in vitro model of human fetal hematopoiesis, for which DS cellular phenotypes are best known. XIST induction in four transgenic clones reproducibly corrected over-production of megakaryocytes and erythrocytes, key to DS myeloproliferative disorder and leukemia. A contrasting increase in neural stem and iPS cells shows cell-type specificity, supporting this approach successfully rebalances the hematopoietic developmental program. Given this, we next used this system to extend knowledge of hematopoietic pathogenesis on multiple points. Results demonstrate trisomy 21 expression promotes over-production of CD43+ but not earlier CD34+/CD43−progenitors and indicates this is associated with increased IGF signaling. This study demonstrates proof-of-principle for this epigenetic-based strategy to investigate, and potentially mitigate, DS developmental pathologies.
Highlights
We previously demonstrated that an integrated XIST transgene can broadly repress one chromosome 21 in Down syndrome (DS) pluripotent cells
This prior study focused on showing that a full-length cDNA could be targeted into chromosome 21 and the XIST RNA properly localized to induce transcriptional silencing across that chromosome in cis, shown in undifferentiated induced pluripotent stem cells (iPSCs)
We investigate whether trisomy silencing can normalize hematopoietic cell phenotypes using a previously characterized all-isogenic panel of DS iPSC subclones, including four independent XIST-transgenic clones, the non-transgenic parental trisomic line, and an isogenic disomic subclone
Summary
We previously demonstrated that an integrated XIST transgene can broadly repress one chromosome 21 in Down syndrome (DS) pluripotent cells. We address the critical question: can trisomy silencing (epigenetic repression of one extra chromosome) effectively normalize or mitigate defects in cell function and pathogenesis, which underlie DS phenotypes? Direct determination of this is important for any future prospect of chromosome therapy, or for the utility of this experimental approach (inducible trisomy silencing) to investigate trisomy 21 effects on developmental pathogenesis, for any cell type. We test this in an in vitro model of human fetal hematopoiesis, for which DS cellular phenotypes are best characterized[9,10,11,12]. Trisomy silencing may normalize overproduction of these blood cell types, indicating successful correction of a specific defect by normalizing the hematopoietic developmental program
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