Genome-wide comparison of trisomy 21 iPSCs and derived isogenic disomy 21 iPSCs.

Human trisomies can alter cellular phenotypes and produce congenital abnormalities such as Down Syndrome (DS). Here we have generated induced pluripotent stem cells (iPSCs) from DS fibroblasts, and introduced a TKNEO transgene into one copy of chromosome 21 by gene targeting. When selecting against TKNEO, spontaneous chromosome loss was the most common cause for survival, with a frequency of ~10-4, while point mutations, epigenetic silencing, and TKNEO deletions occurred at lower frequencies in this unbiased comparison of inactivating mutations. Mitotic recombination events resulting in extended loss of heterozygosity were not observed in DS iPSCs. The disomic cells that we derived proliferated faster and produced more endothelia in vivo than their otherwise isogenic trisomic counterparts, but hematopoietic differentiation, pluripotency and survival were statistically unchanged. Our study describes the first targeted removal of a human trisomy, which could prove useful in both clinical and research applications. RNA samples were from two trisomic iPSC clone (C2-4, C3-5) and four derived disomic subclones (C2-4-3, C2-4-4 and C3-5-11, C3-5-13). Duplicate RNA samples from human embyonic stem cells (H1) were included as control.