Telomere-Dependent and Telomere-Independent Roles of RAP1 in Regulating Human Stem Cell Homeostasis

RAP1 is well known as a telomere-binding protein; yet its functions in human stem cells remain unclear. Here we generated RAP1-deficient human embryonic stem cells (hESCs) by CRISPR/Cas9 and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via directed differentiation. In both hMSCs and hNSCs, RAP1 negatively regulated telomere length. In addition, RAP1 acted as a transcriptional regulator of RLEN by tuning the methylation status of its promoter region. Phenotypically, RAP1 deficiency resulted in enhanced self-renewal and delayed senescence in hMSCs rather than in hNSCs, suggesting a complex role of RAP1 in regulating lineage specific stem cell homeostasis. Altogether, these results indicate that RAP1 plays both telomeric and non-telomeric roles in regulating the homeostasis of human stem cells. Transcriptomic and WGS analyses of WT and Rap1 deficiency mesenchymal stem cell or neural stem cells.