Protocadherin gamma C3:a new player in regulating vascular barrier function

Defects in the endothelial cell barrier accompany diverse malfunctions of the central nervous system such as neurodegenerative diseases,stroke,traumatic brain injury,and systemic diseases such as sepsis,viral and bacterial infections,and cancer.Compromised endothelial sealing leads to leaking blood vessels,followed by vasogenic edema.Brain edema as the most common complication caused by stroke and traumatic brain injury is the leading cause of death.Brain microvascular endothelial cells,together with astrocytes,pericytes,microglia,and neurons form a selective barrier,the so-called blood-brain barrier,which regulates the movement of molecules inside and outside of the brain.Mechanisms that regulate blood-brain barrier permeability in health and disease are complex and not fully understood.Several newly discovered molecules that are involved in the regulation of cellular processes in brain microvascular endothelial cells have been described in the literature in recent years.One of these molecules that are highly expressed in brain microvascular endothelial cells is protocadherin gamma C3.In this review,we discuss recent evidence that protocadherin gamma C3 is a newly identified key player involved in the regulation of vascular barrier function.

The protocadherin alpha cluster is required for axon extension and myelination in the developing central nervous system

In adult mammals, axon regeneration after central nervous system injury is very poor, resulting in persistent functional loss. Enhancing the ability of axonal outgrowth may be a potential treatment strategy because mature neurons of the adult central nervous system may retain the intrinsic ability to regrow axons after injury. The protocadherin （Pcdh） clusters are thought to function in neuronal morphogenesis and in the assembly of neural circuitry in the brain. We cultured primary hippocampal neurons from E17.5 Pcdhα deletion （del-α） mouse embryos. After culture for 1 day, axon length was obviously shorter in del-α neurons compared with wild-type neurons. RNA sequencing of hippocampal E17.5 RNA showed that expression levels of BDNF, Fmod, Nrp2, OGN, and Sema3d, which are associated with axon extension, were significantly down-regulated in the absence of the Pcdhα gene cluster. Using transmission electron microscopy, the ratio of myelinated nerve fibers in the axons of del-α hippocampal neurons was significantly decreased; myelin sheaths of P21 Pcdhα-del mice showed lamellar disorder, discrete appearance, and vacuoles. These results indicate that the Pcdhα cluster can promote the growth and myelination of axons in the neurodevelopmental stage.

Methylation of the PCDH8 (Protocadherin-8) gene in gastric cancer

Objective: To investigate the methylation status of the PCDH8 (Protocadherin-8) gene in gastric cancer tissues and find out the relationship between methylation status of the PCDH8 and clinicopathological features in gastric cancer patients. Methods: We first investigated the methylation status of the PCDH8 (Protocadherin-8) gene in 65 gastric cancer and detected aberrant promoter methylation in gastric cancers; and then analyzed he relationship between methylation status of the PCDH8 and clinicopathological status with SPSS 13.0 software. Results: We first investigated the methylation status of the PCDH8 (Protocadherin-8) gene in 65 gastric cancer and detected aberrant promoter methylation in 36 of 65 (55.4%) gastric cancers. There was no significant difference in the distribution of patients with methylation or unmethylation of PCDH8 in terms of age, sex, tumor size, distant metastasis, or TNM stage. Methylation of PCDH8 was significantly correlated to negative pathological lymph node metastasis (P=0.038) and tumor differentiation (P=0.01). These two factors were proved to be of prognostic importance. Conclusion: Methylated PCDH8 seems to have a trend for worse prognosis in gastric cancer. However, a further large series of tumor samples and a longer follow-up period are required to elucidate its potential role.

New antigens involved in membranous nephropathy beyond phospholipase A2 receptor

When the physiopathology of membranous nephropathy was first described,almost 30%of cases were recognized to be secondary to well-known diseases such as autoimmune diseases,tumors or infections.The remaining 70%cases were called primary membranous nephropathy as the exact mechanism or pathogenic factor involved was unknown.The discovery of the M type phospholipase A2 receptor and thrombospondin type 1 domain containing 7A as causative antigens in these“so called”primary membranous nephropathies provided new insights into the effective causes of a large proportion of these cases.Novel techniques such as laser microdissection and tandem mass spectrometry as well as immunochemistry with antibodies directed against novel proteins allowed the confirmation of new involved antigens.Finally,using confocal microscopy to localize these new antigens and immunoglobulin G and Western blot analysis of serum samples,these new antigens were detected on the glomerular membrane,and the related antibodies were detected in serum samples.The same antigens have been recognized in some cases of secondary membranous disease due to autoimmune diseases,tumors and infections.This has allowed examination of the relationship between antigens in primary membranous nephropathy and their presence in some secondary nephropathies.The aim of this study is to describe the characteristics of the new antigens discovered and their association with other diseases.

Effect of PCDH10 on infiltrative growth and epithelial-mesenchymal transition of cancer cells in gastric cancer

Objective:To study the effect of protocadherin 10 (PCDH10) on infiltrative growth and epithelial-mesenchymal transition of cancer cells in gastric cancer.Methods: The patients with gastric cancer who underwent surgical resection in Panzhihua Central Hospital were selected as the research subjects, and the gastric cancer lesions and adjacent lesions were collected after surgical resection to determine the mRNA expression of PCDH10 gene and epithelial-mesenchymal transition genes as well as the protein levels of proteases and their inhibitory molecules.Results: PCDH10, TIMP1, TIMP2, RASAL2 and E-cadherin mRNA expression levels in gastric cancer lesions were significantly lower than those in adjacent lesions whereas Vav2, Vav3, CatB, MMP9, ZEB1, Twist1 and Vimentin contents were significantly higher than those in adjacent lesions;Vav2, Vav3, CatB, MMP9, ZEB1, Twist1 and Vimentin contents in gastric caner lesions with lower PCDH10 expression were significantly higher than those in gastric caner lesions with higher PCDH10 expression whereas TIMP1, TIMP2, RASAL2 and E-cadherin contents were significantly lower than those in gastric caner lesions with higher PCDH10 expression.Conclusion: The low expression of PCDH10 in gastric cancer can promote the infiltrative growth and epithelial-mesenchymal transition of cancer cells.

Wiring the Brain by Clustered Protocadherin Neural Codes

There are more than a thousand trillion specific synaptic connections in the human brain and over a million new specific connections are formed every second during the early years of life. The assembly of these staggeringly complex neuronal circuits requires specific cell-surface molecular tags to endow each neuron with a unique identity code to discriminate self from non-self. The clustered protocadherin(Pcdh) genes, which encode a tremendous diversity of cell-surface assemblies, are candidates for neuronal identity tags. We describe the adaptive evolution,genomic structure, and regulation of expression of the clustered Pcdhs. We specifically focus on the emerging3-D architectural and biophysical mechanisms that generate an enormous number of diverse cell-surface Pcdhs as neural codes in the brain.

Three-dimensional genome architectural CCCTC-binding factor makes choice in duplicated enhancers at Pcdhα locus

During development, gene expression is spatiotemporally regulated by long-distance chromatin interactions between distal enhancers and target promoters. However, how specificity of the interactions between enhancers and promoters is achieved remains largely unknown. As there are far more enhancers than promoters in mammalian genomes, the complexities of enhancer choice during gene regulation remain obscure. CTCF, the CCCTC-binding factor that directionally binds to a vast range of genomic sites known as CBSs(CTCF-binding sites), mediates oriented chromatin looping between a substantial set of distal enhancers and target promoters. To investigate mechanisms by which CTCF engages in enhancer choice, we used CRISPR/Cas9-based DNA-fragment editing to duplicate CBS-containing enhancers and promoters in the native genomic locus of the clustered Pcdhα genes. We found that the promoter is regulated by the proximal one among duplicated enhancers and that this choice is dependent on CTCF-mediated directional enhancer-promoter looping. In addition, gene expression is unaltered upon the switch of enhancers. Moreover, after promoter duplication, only the proximal promoter is chosen by CTCF-mediated directional chromatin looping to contact with the distal enhancer. Finally, we demonstrated that both enhancer activation and chromatin looping with the promoter are essential for gene expression. These findings have important implications regarding the role of CTCF in specific interactions between enhancers and promoters as well as developmental regulation of gene expression by enhancer switching.

Pyk2 suppresses contextual fear memory in an autophosphorylation-independent manner

Clustered protocadherins(Pcdhs)are a large family of cadherin-like cell adhesion proteins that are central for neurite selfavoidance and neuronal connectivity in the brain.Their downstream nonreceptor tyrosine kinase Pyk2(proline-rich tyrosine kinase 2,also known as Ptk2b,Cakb,Raftk,Fak2,and Cadtk)is predominantly expressed in the hippocampus.We constructed Pyk2-null mouse lines and found that these mutant mice showed enhancement in contextual fear memory,without significant change in auditory-cued and spatial-referenced learning and memory.In addition,by preparing Y402F mutant mice,we observed that Pyk2 suppressed contextual fear memory in an autophosphorylation-independent manner.Moreover,using high-throughput RNA sequencing,we found that immediate early genes,such as Npas4,cFos,Zif268/Egr1,Arc,and Nr4a1,were enhanced in Pyk2-null mice.We further showed that Pyk2 disruption affected pyramidal neuronal complexity and spine dynamics.Thus,we demonstrated that Pyk2 is a novel fear memory suppressor molecule and Pyk2-null mice provide a model for understanding fearrelated disorders.These findings have interesting implications regarding dysregulation of the Pcdh–Pyk2 axis in neuropsychiatric disorders.