Fas-Activated Mitochondrial Apoptosis Culls Stalled Embryonic Stem Cells to Promote Differentiation

Abstract

SUMMARY The intrinsic (mitochondrial) apoptotic pathway is a conserved cell death program crucial for eliminating superfluous, damaged, or incorrectly specified cells [1], and the multi-domain pro-death BCL-2 family proteins BAX and BAK are required for its activation [2, 3]. In response to internal damage or developmental signals, BAX and/or BAK permeabilize the mitochondrial outer membrane [4, 5], resulting in cytochrome c release and activation of effector caspases such as Caspase-3 (Casp3) [6]. While the mitochondrial apoptotic pathway plays a critical role during late embryonic development in mammals [3], its role during early development remains controversial [7, 8]. Here, we show that Bax−/−Bak−/− murine embryonic stem cells (ESCs) display defects during the exit from pluripotency, both in culture and during teratoma formation. Specifically, we find that when ESCs are stimulated to differentiate, a subpopulation fails to do so and instead upregulates FAS in a p53-dependent manner to trigger Bax/Bak-dependent apoptosis. Blocking this apoptotic pathway prevents the removal of these poorly-differentiated cells, resulting in the retention of cells that have not exited pluripotency. Taken together, our results provide further evidence for heterogeneity in the potential of ESCs to successfully differentiate, and reveal a novel role for apoptosis in promoting efficient ESC differentiation by culling cells that are slow to exit pluripotency.

BAK/BAX-Mediated Apoptosis Is a Myc-Induced Roadblock to Reprogramming

“…To further assess the pluripotency of colonies generated from Bak −/− ; Bax −/− MEFs, we cultured them over at least five passages to confirm their self-renewal capacity, during which time they maintained a shiny, rounded morphology and expression of the pluripotency markers SSEA1, NANOG, and OCT4 ( Figure 1 C). These observations are consistent with those reported for embryonic stem cells deficient in BAK and BAX ( Wang et al., 2015 ).…”

“…Furthermore, using low pass whole genome sequencing, we observed no significant difference in the number of CNAs in iPSC clones derived from Bak −/– ; Bax −/– MEFs compared with those derived from WT MEFs ( Figures 4 C, 4D, S3 A, and S3B). Although this method is not sensitive enough to detect single-nucleotide aberrations that may occur during reprogramming, these results are consistent with reports that the process of reprogramming is not inherently mutagenic ( Young et al., 2012 ) and that embryonic stem cells lacking BAK and BAX maintain a normal karyotype ( Wang et al., 2015 ). In contrast, iPSC clones derived from p53 -deficient MEFs exhibited a significantly higher number of CNAs compared with the Bak −/– ; Bax −/– and WT groups ( Figures 4 C, 4D, and S3 C).…”

Investigating core genetic-and-epigenetic cell cycle networks for stemness and carcinogenic mechanisms, and cancer drug design using big database mining and genome-wide next-generation sequencing data

“… 73 Furthermore, it has recently been suggested that ESC differentiation is efficiently maintained by eliminating those cells that are slow to exit pluripotency, implicating a novel role for the apoptotic signaling pathway. 81 Therefore, we propose that the functions of the principal GECN in ESCs should play a significant role in determining the ESCs mechanisms of stemness.…”

Probing into the Mechanism of Alkaline Citrus Extract Promoted Apoptosis in Pulmonary Fibroblasts of Bleomycin‐Induced Pulmonary Fibrosis Mice

“…Fas binds to FasL to form a death-induced compound. This compound activates Caspase 8 that induces Caspase 3 production and activates death receptor apoptosis pathway [ 8 ]. At present, it is believed that COX-2 plays an important role in regulating the expression of Fas receptor in pulmonary fibroblasts [ 9 ].…”