Biomechanical property of limbal niche maintains stemness through YAP

Abstract

Stem cells (SCs) decision to self-renew or differentiate largely depends on the extracellular environment and elasticity of their niche. A well-described mediator of the mechanotransduction pathway is the co-transcriptional activator Yes-associated protein (YAP), known to shuttle into the nucleus of cells grown on stiff matrices. YAP is also known to be essential for stemness, but confusingly, SCs often reside in soft niches. Furthermore, the role of matrix rigidity in niche formation and SC function in vivo is poorly understood. Here we report that the post-natal development of the murine corneal epithelium involves matrix stiffening and loss of YAP activity that is associated with the formation of differentiation compartment. Importantly, manipulating the matrix crosslinking enzyme, Lox, perturbed SC mark expression and resulted in loss of corneal transparency. In agreement, we found that YAP and mechanotransduction pathways are essential for stemness in the soft niche compartment, wound healing response, and dedifferentiation of committed cells into SCs following SC depletion. In vitro experiments revealed that stiffer substrates induced cytoplasmic YAP localization through activation of LATS1/2, facilitating SMAD2/3-mediated cell differentiation. Taken together, we propose that the soft environment of the corneal SC niche maintains YAP activity to support SC regulation during morphogenesis, adult homeostasis and regeneration by the niche.

The Hippo/YAP Pathway Mediates the De-differentiation of Corneal Epithelial Cells into Functional Limbal Epithelial Stem CellsIn Vivo

“…During the submission of our manuscript, Bhattacharya et al reported that the activity of YAP played significant roles in maintaining LESCs via the mechanotransduction pathway, and the inhibition of YAP by VTP hindered the de-differentiation of CECs in vivo (48). However, we observed rare nuclear YAP in LESCs during normal homeostasis.…”

“…As for the opposing effects of VTP on the de-differentiation of CECs, we surmise that might result from these different markers used to identify LESCs. Bhattacharya et al used CK15-GFP, CD63 and IFITM3 to mark LESCs (48). However, we found that CD63 and IFITM3 were also expressed by basal cells of peripheral and central epithelium.…”

“…Instead, we tested various markers and ultimately selected ApoE + /Cx43 low /CK12to define LESCs. Interestingly, CK15-GFP was a useful indicator of aLESCs in previous reports (11,48), while ApoE was mainly expressed in qLESCs as shown in single cell RNA sequencing (48). Thus, we wonder whether the opposing effects of VTP on the de-differentiation of CECs may reflect the identification of different sub-populations of LESCs (aLESCs and qLESCs).…”

Measuring competitive exclusion in non–small cell lung cancer

“…For example, clinical tumors are highly heterogeneous. Extending this work to include three ( 56 ) or more types will allow us to better model more clinically relevant resistance evolution. Last, our results suggest that ecological effects are an important consideration in competition experiments, and continuing to show this empirically remains a priority going forward.…”