IL‐35Ig–expressing dendritic cells induce tolerance via Arginase 1

The cytokine interleukin IL‐35 is known to exert strong immunosuppressive functions. Indoleamine 2,3‐dioxygenase 1 (IDO1) and Arginase 1 (Arg1) are metabolic enzymes that, expressed by dendritic cells (DCs), contribute to immunoregulation. Here, we explored any possible link between IL‐35 and the activity of those enzymes. We transfected a single chain IL‐35Ig gene construct in murine splenic DCs (DC₃₅) and assessed any IDO1 and Arg1 activities as resulting from ectopic IL‐35Ig expression, both in vitro and in vivo. Unlike Ido1, Arg1 expression was induced in vitro in DC₃₅, and it conferred an immunosuppressive phenotype on those cells, as revealed by a delayed‐type hypersensitivity assay. Moreover, the in vivo onset of a tolerogenic phenotype in DC₃₅ was associated with the detection of CD25⁺CD39⁺, rather than Foxp3⁺, regulatory T cells. Therefore, Arg1, but not Ido1, expression in DC₃₅ appears to be an early event in IL‐35Ig–mediated immunosuppression.     

Phosphoinositide 3-kinase regulates the role of retromer in transcytosis of the polymeric immunoglobulin receptor

Retromer is a multimeric protein complex that mediates intracellular receptor sorting. One of the roles of retromer is to promote transcytosis of the polymeric immunoglobulin receptor (pIgR) and its ligand polymeric immunoglobulin A (pIgA) in polarized epithelial cells. In Madin-Darby Canine Kidney (MDCK) cells, overexpression of Vps35, the retromer subunit key for cargo recognition, restores transcytosis to a pIgR mutant that is normally degraded. Here we show that pIgA transcytosis was not restored in these cells when treated with the specific phosphoinositide 3-kinase (PI3K) inhibitor LY294002. Likewise, the decrease in pIgA transcytosis by wild-type pIgR seen upon PI3K inhibition was not reverted by Vps35 overexpression. PI3K inhibition reduced membrane association of sorting-nexins (SNX) 1 and 2, which constitute the retromer subcomplex involved in membrane deformation, while association of the Vps35-Vps26-Vps29 subcomplex, involved in cargo recognition, remained virtually unaffected. Colocalization between the two retromer subcomplexes was reduced upon the treatment. Whereas the interaction among the subunits of the Vps35-Vps26-Vps29 subcomplex remained unchanged, less Vps35 was found associated with pIgR upon PI3K inhibition. In addition, colocalization of internalized pIgA with subunits of both retromer subcomplexes throughout the transcytotic pathway was substantially reduced by LY294002 treatment. These data implicate PI3K in controlling retromer's role in pIgR-pIgA transcytosis.     

The Role of Cytoplasmic Serine Residues of the Cell Adhesion Molecule L1 in Neurite Outgrowth,Endocytosis, and Cell Migration

Summary 1. The cell adhesion molecule L1 has been implicated in adhesion and migration of cells, in axon growth, guidance, and fasciculation, in myelination and synaptic plasticity. The cytoplasmic domain of neuronal L1 is highly conserved between species and has been shown to be phosphorylated at serine and tyrosine residues. 2. To investigate the significance of L1 serine phosphorylation, mutants of L1 were generated in which ser-1152, ser-1181, ser-1204, and ser-1248 were exchanged for leucine and rat B35 neuroblastoma cells were stably transfected with the L1-cDNA constructs. 3. Neurite outgrowth on poly-l-lysine (PLL) as substrate was determined either with or without differentiation into a neuronal phenotype with dbcAMP. In addition, antibody-induced endocytosis and cell migration were examined. 4. Our observations indicate that phosphorylation of single serine residues of the cytoplasmic domain of L1 contributes to neurite outgrowth through different mechanisms. Neurite growth is increased when ser-1152 or ser-1181 is replaced by a non-phosphorylatable leucine and decreased when ser-1204 or ser-1248 is mutated to leucine. Furthermore, mutation of ser-1181 to leucine results in strongly enhanced antibody-induced endocytosis of L1 and also in enhanced cell migration.     

Travelling-wave behaviour in a multiphase model of a population of cells in an artificial scaffold

This paper analyses travelling-wave behaviour in a recently-formulated multiphase model for the growth of biological tissue that comprises motile cells and water inside a porous scaffold. The model arises in the context of tissue engineering, and its purpose is to study how cells migrate and proliferate inside porous biomaterials. In suitable limits, tissue growth in the model is shown to occur in the form of travelling waves that can propagate either forwards or backwards, depending on the values of the parameters. In the case where the drag force between the scaffold and the cells is non-zero, the growth of the aggregate can be analysed in terms of the propagation of a constant-speed wavefront in a semi-infinite domain. A numerical (shooting) method is described for calculating the wave speed, and detailed results for how the speed varies with respect to the parameters are given. In the case where the drag force is zero, the size of the aggregate is shown either to grow or to shrink exponentially with time. These results may be of importance in determining the experimental factors that control tissue invasiveness in scaffolds thereby allowing greater control over engineered tissue growth.     

炎性肠病易感基因GPR35在肠炎发生发展中的功能研究

炎性肠病在全球范围内发生极其普遍,具有反复发作、难以治愈的特点,也是诱发结直肠癌的高风险因素之一。肠炎的发生与遗传因素密切相关,有报道发现位于GPR35基因座上的多个单核苷酸多态性(single nucleotidepolymorphism,SNP)位点rs4676410、rs3749171和rs3749172与肠炎敏感性高度相关,但是GPR35基因在肠炎的发生发展进程中的功能及相关机制尚没有明确结论。为了研究GPR35在肠炎中的作用,首先通过CRISPR/Cas9技术构建Gpr35敲除小鼠,随后利用DSS诱导的肠炎模型评价Gpr35在肠炎发生中的作用,发现敲除小鼠在体重变化、DAI评分、肠上皮损伤以及炎性细胞浸润等肠炎相关指标显著低于野生型小鼠。为了研究肠炎相关SNP突变对GPR35活性的影响,首先根据rs3749171和rs3749172SNP位点突变信息构建GPR35-T108M和GPR35-S294R两种突变型受体,其次通过多种GPR35下游信号通路活性测试,发现两种突变均能够增强GPR35受体活性。最后通过Westernblotting分析发现相较于野生型小鼠,Gpr35敲除小鼠肠上皮Erk1/2磷酸化水平增加,表明Gpr35敲除后可能通过上调Erk1/2信号通路的方式抑制肠炎的发生发展。综上所述,本研究发现人类肠炎易感的rs3749171和rs3749172位点可能通过激活GPR35及下游信号通路的方式促进肠炎的发生发展,为炎性肠病的治疗提供了潜在的药物作用靶点。     

Siblings with opposite chromosome constitutions,dup(2q)/del(7q) and del(2q)/dup(7q)

Chromosome 7q36 microdeletion syndrome is a rare genomic disorder characterized by underdevelopment of the brain, microcephaly, anomalies of the sex organs, and language problems. Developmental delay, intellectual disability, autistic spectrum disorders, BDMR syndrome, and unusual facial morphology are the key features of the chromosome 2q37 microdeletion syndrome. A genetic screening for two brothers with global developmental delay using high-resolution chromosomal analysis and subtelomeric multiplex ligation-dependent probe amplification revealed subtelomeric rearrangements on the same sites of 2q37.2 and 7q35, with reversed deletion and duplication. Both of them showed dysmorphic facial features, severe disability of physical and intellectual development, and abnormal genitalia with differential abnormalities in their phenotypes. The family did not have abnormal genetic phenotypes. According to the genetic analysis of their parents, adjacent-1 segregation from their mother's was suggested as a mechanism of their gene mutation. By comparing the phenotypes of our patients with previous reports on similar patients, we tried to obtain the information of related genes and their chromosomal locations.     

Molecular aspects of hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is a clinically and genetically heterogeneous group of neurodegenerative disorders characterized by progressive lower limbs spasticity and weakness. What was first thought to be a small group of rare Mendelian disorder has now become a large group that includes many complex syndromes. While large families with defined modes of inheritance were used for the initial HSP gene discovery, new sequencing technologies have recently allowed the study of small families, with the identification of many new disease causative genes. These discoveries are slowly leading to a better understanding of the molecular mechanisms underlying HSP with the identification of precise disease pathways. These insights may lead to new therapeutic strategies for what is a group of largely untreatable diseases. This review looks at the key players involved in HSP and where they act in their specific pathways.     

Light-dependent phosphorylation of the gamma subunit of cGMP-phophodiesterase (PDE6γ) at residue threonine 22 in intact photoreceptor neurons

The γ subunit of rod-specific cGMP phosphodiesterase 6 (PDE6γ), an effector of the G-protein GNAT1, is a key regulator of phototransduction. The results of several in vitro biochemical reconstitution experiments conducted to examine the effects of phosphorylation of PDE6γ on its ability to regulate the PDE6 catalytic core have been inconsistent, showing that phosphorylation of PDE6γ may increase or decrease the ability of PDE6γ to deactivate phototransduction. To resolve role of phosphorylation of PDE6γ in living photoreceptors, we generated transgenic mice in which either one or both Threonine (T) sites in PDE6γ (T22 and T35), which are candidates for putative regulatory phosphorylation, were substituted with alanine (A). Phosphorylation of these sites was examined as a function of light exposure. We found that phosphorylation of T22 increases with light exposure in intact mouse rods while constitutive phosphorylation of T35 is unaffected by light in intact mouse rods and cones. Phosphorylation of the cone isoform of PDE6γ, PDE6H, is constitutively phosphorylated at the T20 residue. Light-induced T22 phosphorylation was lost in T35A transgenic rods, and T35 phosphorylation was extinguished in T22A transgenic rods. The interdependency of phosphorylation of T22 and T35 suggests that light-induced, post-translational modification of PDE6γ is essential for the regulation of G-protein signaling.     

Early embryonic requirement for nucleoporin Nup35/NPP-19 in nuclear assembly

Nuclear pore complexes (NPCs) are gateways for transport between the nucleus and cytoplasm of eukaryotic cells and play crucial roles in regulation of gene expression. NPCs are composed of multiple copies of ∼ 30 different nucleoporins (nups) that display both ubiquitous and cell type specific functions during development. Vertebrate Nup35 (also known as Nup53) was previously described to interact with Nup93, Nup155 and Nup205 and to be required for nuclear envelope (NE) assembly in vitro. Here, we report the first in vivo characterization of a Nup35 mutation, npp-19(tm2886), and its temperature-dependent effects on Caenorhabditis elegans embryogenesis. At restrictive temperature, npp-19(tm2886) embryos exhibit chromosome missegregation, nuclear morphology defects and die around mid-gastrulation. Depletion of Nup35/NPP-19 inhibits NE localization of Nup155/NPP-8, NPC assembly and nuclear lamina formation. Consequently, nuclear envelope function, including nucleo-cytoplasmic transport, is impaired. In contrast, recruitment of Nup107/NPP-5, LEM-2 and nuclear membranes to the chromatin surface is Nup35/NPP-19-independent, suggesting an uncoupling of nuclear membrane targeting and NPC assembly in the absence of Nup35/NPP-19. We propose that Nup35/NPP-19 has an evolutionary conserved role in NE formation and function, and that this role is particularly critical during the rapid cell divisions of early embryogenesis.