Trisomy silencing by XIST normalizes Down syndrome cell pathogenesis demonstrated for hematopoietic defects in vitro

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.

Gain of chromosome 21 in hematological malignancies: lessons from studying leukemia in children with Down syndrome

“…Through the establishment of DS-derived induced pluripotent stem cells (iPSCs), independent studies have shown that trisomy 21 alone significantly accelerates the early stages of hematopoiesis [82][83][84][85]. Regardless of whether primitive (yolk-sac type) or definitive (fetal liver type) hematopoiesis was induced, all groups reported an increase in the clonogenic potential of erythroid progenitors and enhanced erythroid differentiation.…”

An isogenic cell line panel identifies major regulators of aberrant astrocyte proliferation in Down syndrome

“…Tet-regulated XIST was stably expressed after Dox treatment in both iPSCs and differentiated cells in previous studies 19,20,21 . Nevertheless, XIST RNA was not detected in our differentiated XIST-Tri21 NPCs, likely due to silencing of the rtTA inserted in the AAVS1 locus.…”

“…In one such cell line, XIST was inserted into a copy of chromosome 21 in trisomy 21 iPSCs (Tri21 iPSCs), and a long noncoding RNA induced a series of chromatin modi cations that stably silenced gene transcription across the whole chromosome in cis. Chromosome silencing occurred even in differentiated cells, and various pathologies observed in DS (including proliferative defects, impaired neural differentiation, and haematopoietic abnormalities) were successfully reversed by the transcriptional inactivation of the supernumerary chromosome 20,21 . Using this genome-silencing technology, where XIST RNA expression is regulated by the tetracycline-inducible system, enables researchers to investigate the correlation between gene-expression changes and cellular phenotypes in DS, without limitations caused by transcriptional heterogeneity and differences among cell lines.…”

Applications of Genome Editing Technology in Research on Chromosome Aneuploidy Disorders

“…In this review, we have provided an overview of the deletion or silencing of an extra chromosome copy using genome editing technology, cell-autonomous correction of ring chromosomes, and TCLs during the reprogramming process in constitutional aneuploidy disorders. However, most of these approaches still have low efficacy [94,105].…”

“…Recently, it was reported that trisomy 21 upregulates insulin-like growth factor (IGF) signaling to enhance the GATA1 expression aberrantly, thereby causing leukemia in DS. The XIST-mediated trisomy 21 silencing in DS patient-derived iPSCs restored the proper hematopoietic differentiation in vitro [94]. For clinical applications of this method, further improvements are required for the complete silencing of targeted chromosome 21.…”