Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) resets the epigenetic landscapes that mark the aging clock, and consequently cells differentiated from iPSCs resemble fetal cells rather than adult or aged cells. The lack of proper cellular aging in cells differentiated from iPSCs presents a unique challenge in iPSC-based modeling of age-associated diseases such as neurodegeneration. To address this challenge, we seek to introduce cellular senescence, a hallmark of aging, into iPSC-based models in a robust and temporally controlled manner. An inducible CRISPR interference (CRISPRi) is used to suppress the expression of TERF2, a key component of the telomere protecting Shelterin complex. We demonstrate that suppression of TERF2 robustly activates the DNA damage response, p53/p21 signaling, and cellular senescence in iPSCs in a highly homogeneous and synchronous manner. Applying this inducible CRISPRi-TERF2 system to differentiation of iPSCs to neural progenitor cells (NPCs), we show efficient activation of senescence-associated phenotypes in NPCs. This inducible cell model allows isogenic comparisons of the same cell populations over the course of differentiation with or without the activation of cellular senescence in a synchronous and homogeneous manner, and has broad applications in investigating the role of cellular senescence in the progression of age-related diseases.
Keywords: aging; cellular senescence; disease modeling; neurodegeneration; telomere dysfunction.
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