Probes for CP

The choroid plexus (CP) is one of the key gateways regulating the entry of peripheral immune cells into the CNS. However, the neuromodulatory mechanisms of maintaining its gateway activity are not fully understood. Here, we identified adenosine A2A receptor (A2AR) activity as a regulatory signal for the activity of CP gateway under physiological conditions. In association with a tightly closed CP gateway, we found that A2AR was present at low density in the CP. The RNA-seq analysis revealed that the A2AR antagonist KW6002 affected the expression of the cell adhesion molecules' (CAMs) pathway and cell response to IFN-γ in the CP. Furthermore, blocking or activating A2AR signaling in the CP resulted in a decreased and an increased, respectively, expression of lymphocyte trafficking determinants and disruption of the tight junctions (TJs). Furthermore, A2AR signaling regulates the CP permeability. Thus, A2AR activity in the CP may serve as a therapeutic target for remodeling the immune homeostasis in the CNS with implications for the treatment of neuroimmunological disorders.

The choroid plexus (CP) is an extensively vascularized neuroepithelial tissue that projects into the brain ventricles. The restriction of transepithelial transport across the CP establishes the blood-cerebrospinal fluid (CSF) barrier that is fundamental to the homeostatic regulation of the central nervous system microenvironment. However, the molecular mechanisms that control this process remain elusive. Here we show that the genetic ablation of Sox9 in the hindbrain CP results in a hyperpermeable blood-CSF barrier that ultimately upsets the CSF electrolyte balance and alters CSF protein composition. Mechanistically, SOX9 is required for the transcriptional up-regulation of Col9a3 in the CP epithelium. The reduction of Col9a3 expression dramatically recapitulates the blood-CSF barrier defects of Sox9 mutants. Loss of collagen IX severely disrupts the structural integrity of the epithelial basement membrane in the CP, leading to progressive loss of extracellular matrix components. Consequently, this perturbs the polarized microtubule dynamics required for correct orientation of apicobasal polarity and thereby impedes tight junction assembly in the CP epithelium. Our findings reveal a pivotal cascade of SOX9-dependent molecular events that is critical for construction of the blood-CSF barrier.

Introduction: The transcription factor δNp63 drives an aggressive basal-like molecular subtype of pancreatic ductal adenocarcinoma (PDAC). In many healthy epithelia, this protein is expressed in basal cells with stem cell capacity that can be at origin of tumours. In the pancreas, basal cells have not been identified. Aims: We aimed to characterize the expression of δNp63 in the healthy pancreas, in PDAC and in chronic pancreatitis (CP), a condition with increased risk for PDAC development. Next we aimed at determining the phenotype of δNp63+ cells. Materials and Methods: We assessed the expression of δNp63 in tissue sections from human and mouse pancreas, CP and PDAC. The identified cell niches were further investigated using immunohistochemical stainings and RNAscope. Resulting (whole slide) images were quantified using HALO software. Data were analysed with Graphpad Prism. Results: δNp63 is expressed in a subset of PDAC tumours. In normal human pancreas, rare δNp63+ cells exist in the ductal lining and increase in number in CP. They express KRT19 and canonical basal cell markers (KRT5, KRT14 and S100A2), but lack markers of differentiated duct cells such as CA19.9, HNF1β and SOX9. In addition, δNp63+ cells pertain to a niche of cells expressing gastrointestinal stem cell markers. In mice, δNp63 expression could not be found in normal adult pancreas nor in in vivo models of CP or PDAC. Conclusion: We discovered a novel cell population in normal human pancreas similar to basal cells in other tissues. Their expansion in CP and their presence in a subset of PDAC suggest a developmental relationship.