Banda, E. C. | Search bioRxiv

bioRxiv2022

A dynamic in vitro model of Down Syndrome neurogenesis with Trisomy 21 gene dosage correction

ABSTRACT/SUMMARYExcess gene dosage from human chromosome 21 (chr21) causes Down syndrome (DS), spanning developmental as well as acute phenotypes in terminal cell types. Which phenotypes remain amenable to intervention after development is unknown. To address this question in a model of DS neurogenesis, we generated trisomy 21 (T21) human induced pluripotent stem cells (hiPSCs) alongside otherwise isogenic euploid controls from mosaic DS fibroblasts, and integrated an inducible XIST transgene on one chr21 copy. Monoallelic chr21 silencing by XIST was near-complete and irreversible in hiPSCs. Differential expression reveals T21 neural lineages and T21 hiPSCs suppress similar translation and mitochondrial pathways, and activate cellular stress responses. When XIST is induced before the neural progenitor stage, T21 dosage correction mitigates a pronounced skew towards astrogenesis in differentiation. Because our transgene remained inducible in post-mitotic T21 neurons and astrocytes, we demonstrate XIST efficiently represses genes even after terminal differentiation, which will empower exploration of cell type-specific T21 phenotypes that remain responsive to chr21 dosage.

developmental biology↗

bioRxiv2021

Monosomy X in isogenic human iPSC-derived trophoblast model impacts expression modules preserved in human placenta

SUMMARY/ABSTRACTMammalian sex chromosomes encode homologous X/Y gene pairs that were retained on the male Y and escape X chromosome inactivation (XCI) in females. Inferred to reflect X/Y-pair dosage sensitivity, monosomy X is a leading cause of miscarriage in humans with near full penetrance. This phenotype is shared with many other mammals but not the mouse, which offers sophisticated genetic tools to generate sex chromosomal aneuploidy but also tolerates its developmental impact. To address this critical gap, we generated X-monosomic human induced pluripotent stem cells (hiPSCs) alongside otherwise isogenic euploid controls from male and female mosaic samples. Phased genomic variants of these hiPSC panels enable systematic investigation of X/Y dosage-sensitive features using in vitro models of human development. Here, we demonstrate the utility of these validated hiPSC lines to test how X/Y-linked gene dosage impacts a widely-used model for the human syncytiotrophoblast. While these isogenic panels trigger a GATA2/3 and TFAP2A/C -driven trophoblast gene circuit irrespective of karyotype, differential expression implicates monosomy X in altered levels of placental genes, and in secretion of placental growth factor (PlGF) and human chorionic gonadotropin (hCG). Remarkably, weighted gene co-expression network modules that significantly reflect these changes are also preserved in first-trimester chorionic villi and term placenta. Our results suggest monosomy X may skew trophoblast cell type composition, and that the pseudoautosomal region likely plays a key role in these changes, which may facilitate prioritization of haploinsufficient drivers of 45,X extra-embryonic phenotypes.

developmental biology↗