ATF6 safeguards organelle homeostasis and cellular aging in human mesenchymal stem cells

Loss of organelle homeostasis is a hallmark of aging. However, it remains elusive how this occurs at transcriptional levels. Here, we report that human mesenchymal stem cell (hMSC) aging is associated with dysfunction of double-membrane organelles and downregulation of transcription factor ATF6. CRISPR/Cas9-mediated inactivation of ATF6 in hMSCs, not in human embryonic stem cells (hESCs), resulted in premature cellular aging, characteristic of loss of endomembrane homeostasis. Comparative transcriptomic analyses in hMSCs identify 145 constitutive and 112 tunicamycin-induced ATF6-regulated genes implicated in different layers of cellular homeostasis regulation. Notably, FOS was identified as one of the constitutive ATF6 responsive genes, downregulation of which contributes to accelerated hMSC senescence. Our study identifies a novel transcriptional program related to homeostatic regulation of membrane organelles, and provides mechanistic insights into aging-associated attrition of human stem cells. RNA Seq and ChIP-Seq