Abstract
Purpose :
Many studies have focused on the embryonic development of the lacrimal gland, but relatively little is known about the maturation and homeostasis of the lacrimal gland during the postnatal stage. We showed that an epithelial specific knockout of Csk did not affect branching morphogenesis during embryogenesis, but the lacrimal gland degenerated postnatally with dilated lumens lacking acinar cells. In this study, we have investigated the mechanism of Csk in regulating postnatal lacrimal gland development.
Methods :
The lacrimal gland specific knockout mutants are analyzed by histology, RNA in situ hybridization and immunohistochemistry. Single-cell RNAseq analysis was carried out to examine the cell differentiation trajectory. Cell culture and western blot were used to study protein function.
Results :
Through single cell analysis and genetic lineage tracing, we show that the pan-epithelial ablation of c-terminal Src kinase (Csk) in the lacrimal gland unleashes broad Src signaling but causes extrusion and apoptosis of only acinar progenitors. Csk mutants can be phenocopied by constitutively active Yap and rescued by genetic ablation of Yap or Taz, indicating remarkable functional equivalence between Src and Yap signaling. Although Csk inactivation induces tyrosine phosphorylation of Yap, mutating these tyrosine residues in both Yap and Taz fails to alleviate the Csk lacrimal gland phenotype. In contrast, Yap loses Hippo signaling-dependent serine phosphorylation and translocates into the nucleus in Csk mutants. Chemical genetics studies further demonstrate that acute inhibition of Csk enhances Crk/CrkL phosphorylation and Rac1 activity, whereas the deletion of either Crk/CrkL or Rac1/Rap1 rescues the Csk mutant phenotype.
Conclusions :
Our study shows that Csk controls Hippo-Yap signaling through the Crk/CrkL-Rac/Rap axis to regulate cell competition. It illuminated the molecular mechanism by which Src-regulated mechanosignaling induces cell competition by Yap/Taz-mediated transcriptomic reprogramming.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.