The role of ESRG in human pluripotency

Human pluripotent stem cells (PSCs) express human endogenous retroviruses type-H (HERV-Hs), which exist more than a thousand copies on the human genome and frequently produce chimeric transcripts as long-non-coding RNAs (lncRNAs) fused with downstream neighbor genes. Previous studies showed that HERV-H expression is required for the maintenance of PSC identity, and the aberrant HERV-H expression attenuated neural differentiation potentials, but little is known what their roles are. In this study, therefore, we focused on ESRG, which is known as a PSC-related HERV-H-driven lncRNA. The global transcriptome data of various tissues and cell lines and quantitative expression analysis showed that ESRG expression is much higher than other HERV-Hs and tightly silenced after differentiation, letting us hypothesize its crucial role in human pluripotency. However, the loss of function by the complete excision of the entire ESRG gene body using a CRISPR/Cas9 platform revealed that ESRG is dispensable for the maintenance of primed and naïve pluripotent states. The loss of ESRG hardly affects the global gene expression of PSCs and differentiation potentials toward trilineage. Differentiated cells derived from ESRG knockout PSCs retained the potential to be reprogrammed into induced PSC (iPSC) by the forced expression of OCT3/4, SOX2, and KLF4. In conclusion, ESRG is dispensable for the maintenance and the recapturing of human pluripotency. Human pluripotent stem cell line in primed condition, N=6 Human pluripotent stem cell line in naive condition, N=6 Human pluripotent stem cell-derived embryoid body, N=12