Trisomy 21 Dosage Compensation Map (T21DoCoMap)

225951) of the NIGMS genetic cell repository, to enable analysis of whole-chromosomal and individual gene dosage imbalance in the context of in vitro models of DS development. Virtual karyotyping (by Infinium CytoSNP-850k), and phased genotyping (by linked-read whole-genome sequencing) of the resulting iPSC lines provide a deeply-characterized genomic platform for dissection of HSA21 gene dosage. We apply this highly unique resource to allelic analysis of mRNA sequencing of iPSCs and differentiated neural lineages, and demonstrate its utility in the context of inducible HSA21 dosage compensation. To this end, we equipped one distinct HSA21 copy with a doxycycline-inducible XIST transgene, which endogenously silences one X in 46,XX females. Standard and allele-specific RNA-seq analysis confirms mono-allelic T21 silencing to be virtually complete and irreversible, further supported by DNA methylation data (Infinium methylEPIC). This full-length HSA21 map of phased single-nucleotide and insertion/deletion variants enables allele-specific applications for gene-level dissection T21 dosage effects. Because our XIST remains inducible in post-mitotic T21 neurons and astrocytes, we perform single-nuclei RNA-seq to demonstrate XIST efficiently represses genes even after terminal differentiation.]]>