Squamous differentiation requires G2/mitosis slippage to avoid apoptosis

Abstract

The cellular mechanisms controlling cell fate in self-renewal tissues remain unclear. Cell cycle failure often leads to an apoptosis anti-oncogenic response. We have inactivated Cdk1 or Polo-like-1 kinases, essential targets of the mitotic checkpoints, in the epithelia of skin and oral mucosa. Here, we show that inactivation of the mitotic kinases leading to polyploidy in vivo, produces a fully differentiated epithelium. Cells within the basal layer aberrantly differentiate and contain large or various nuclei. Freshly isolated KO cells were also differentiated and polyploid. However, sustained metaphase arrest downstream of the spindle anaphase checkpoint (SAC) due to abrogation of CDC20 (essential cofactor of anaphase-promoting complex), impaired squamous differentiation and resulted in apoptosis. Therefore, upon prolonged arrest keratinocytes need to slip beyond G2 or mitosis in order to initiate differentiation. The results altogether demonstrate that mitotic checkpoints drive squamous cell fate towards differentiation or apoptosis in response to genetic damage.

The DNA damage response links human squamous proliferation with differentiation

“…Keratinocytes are resistant to apoptosis unless they undergo Sunburn (Bell and Megeney, 2017;Sanz-Gómez et al, 2020a). Consistently, no apoptotic sub-G1 cells were detected in the stratifying cultures (Fig.…”

“…Interestingly, we found that mushroom cells accumulate mitotic markers such as cyclin A or cyclin B (Zanet et al, 2010), further suggesting a natural link between mitosis arrest and differentiation. It is also noteworthy that lack of essential mitotic kinases Aurora B kinase or Polo-like kinase 1 in vivo produces a fully differentiated squamous epithelia (Sanz-Gómez et al, 2020a). The frequent presence of 53BP1 NBs in differentiating cells in vitro and in situ supports the notion that irreparable damage leads to differentiation.…”

CDC20 in and out of mitosis: a prognostic factor and therapeutic target in hematological malignancies

“…Pathway analysis of CDC20 interacting proteins suggested additional roles of CDC20 outside cell cycle regulation, with a significant enrichment of specific cellular processes, including protein modification, localization and degradation, telomeres regulation, transcription, and other signaling pathways, as Hippo, TGF-β, β-catenin, MAPK (Table S 1 ). Accordingly, it has been recently shown that CDC20 exerts a pivotal role in different cell type-specific biological processes, as ciliary disassembly [ 87 , 88 ], brain development [ 89 , 90 ], necrosis suppression in neural stem cells under catastrophic cellular stresses [ 91 ], tissue homeostasis and cell fate in human keratinocytes [ 92 , 93 ], genomic stability [ 94 , 95 ], aging [ 96 ] and autophagy [ 97 , 98 ] (Fig. 3 A-D).…”

Beta-Genus Human Papillomavirus 8 E6 Destabilizes the Host Genome by Promoting p300 Degradation

“…If the danger is not mitigated, permanent growth arrest assures that cells containing a mutated genome do not propagate. Additionally, differentiation was recently identified as a mechanism by which polyploidy epithelial cells are prevented from growth [ 78 ]. Despite the benefits to the cell, pauses to cellular growth run counter to the requirements for β-HPV replication.…”