Background: Increased protein N-glycosylation and aberrant Wnt signaling are features of oral cancer. Results: Overexpression of pro-migratory protein CTHRC1 is due to hyperglycosylation and transcriptional activation by canonical Wnt. Conclusion: N-Glycosylation collaborates with canonical Wnt to induce CTHRC1 and drive OSCC cell migration. Significance: Elucidating how N-glycosylation impacts tumor-promoting proteins is critical to understand cancer development and progression.

IntroductionInduced pluripotent stem cells (iPSCs) are a potent cell source for neurogenesis. Previously we have generated iPSCs from human dental stem cells carrying transgene vectors. These exogenous transgenes may affect iPSC behaviors and limit their clinical applications. The purpose of this study was to establish transgene-free iPSCs (TF-iPSCs) reprogrammed from human stem cells of apical papilla (SCAP) and determine their neurogenic potential.MethodsA single lentiviral 'stem cell cassette' flanked by the loxP site (hSTEMCCA-loxP), encoding four human reprogramming factors, OCT4, SOX2, KLF4, and c-MYC, was used to reprogram human SCAP into iPSCs. Generated iPSCs were transfected with plasmid pHAGE2-EF1α-Cre-IRES-PuroR and selected with puromycin for the TF-iPSC subclones. PCR was performed to confirm the excision of hSTEMCCA. TF-iPSC clones did not resist to puromycin treatment indicating no pHAGE2-EF1α-Cre-IRES-PuroR integration into the genome. In vitro and in vivo analyses of their pluripotency were performed. Embryoid body-mediated neural differentiation was undertaken to verify their neurogenic potential.ResultsTF-SCAP iPSCs were generated via a hSTEMCCA-loxP/Cre system. PCR of genomic DNA confirmed transgene excision and puromycin treatment verified the lack of pHAGE2-EF1α-Cre-IRES-PuroR integration. Transplantation of the TF-iPSCs into immunodeficient mice gave rise to teratomas containing tissues representing the three germ layers -- ectoderm (neural rosettes), mesoderm (cartilage and bone tissues) and endoderm (glandular epithelial tissues). Embryonic stem cell-associated markers TRA-1-60, TRA-2-49 and OCT4 remained positive after transgene excision. After neurogenic differentiation, cells showed neural-like morphology expressing neural markers nestin, βIII-tubulin, NFM, NSE, NeuN, GRM1, NR1 and CNPase.ConclusionsTF-SCAP iPSCs reprogrammed from SCAP can be generated and they may be a good cell source for neurogenesis.

SummaryThe metabolic pathway of protein N-glycosylation influences intercellular adhesion by affecting the composition and cytoskeletal association of E-cadherin protein complexes, or adherens junctions (AJs). In sparse cells, E-cadherin is modified extensively with complex N-glycans and forms nascent AJs, while in dense cultures, hypoglycosylated E-cadherin drives the assembly of mature AJs with increased levels of c-and a-catenins. N-glycosylation of E-cadherin is controlled by the DPAGT1 gene, a key regulator of the Nglycosylation pathway. DPAGT1 is a target of the canonical Wnt signaling pathway, with both b-and c-catenins binding to Tcf at its promoter. We now report that DPAGT1 senses cell density through canonical Wnt signaling. In dense cells, depletion of b-catenin from the DPAGT1 promoter correlated with downregulation of its cellular abundance, while loss of nuclear c-catenin reflected its greater recruitment to AJs. DPAGT1 itself affected canonical Wnt signaling, with forced changes in its expression resulting in corresponding changes in transcriptionally active b-catenin and canonical Wnt activity. Remarkably, a 2.4-fold increase in the DPAGT1 mRNA level resulted in increased N-glycosylation and reduced membrane localization of E-cadherin, coincident with dramatic changes in cell morphology. Lastly, we present evidence that N-glycosylation status of E-cadherin controls its antagonism of canonical Wnt signaling. Transfection of hypoglycosylated E-cadherin mutant, V13, but not fully N-glycosylated E-cadherin, into sparse cells inhibited canonical Wnt activity by depleting nuclear b-and c-catenins. Collectively, our studies show that cells coordinate DPAGT1 expression and protein N-glycosylation with canonical Wnt signaling and E-cadherin adhesion via positive and negative feedback mechanisms.