Golgi satellites are essential for polysialylation of NCAM and expression of LTP at distal synapses.

The complex cytoarchitecture of neurons poses significant challenges for the maturation of synaptic membrane proteins. It is currently unclear whether locally secreted synaptic proteins bypass the Golgi or whether they traffic through Golgi satellites (GSs). Here, we create a transgenic GS reporter mouse line and show that GSs are widely distributed along dendrites and are capable of mature glycosylation, in particular sialylation. We find that polysialylation of locally secreted NCAM takes place at GSs. Accordingly, in mice lacking a component of trans-Golgi network-to-plasma membrane trafficking, we find fewer GSs and significantly reduced PSA-NCAM levels in distal dendrites of CA1 neurons that receive input from the temporoammonic pathway. Induction of long-term potentiation at those, but not more proximal, synapses is severely impaired. We conclude that GSs serve the need for local mature glycosylation of synaptic membrane proteins in distal dendrites and thereby contribute to rapid changes in synaptic strength.

Disruption of tubulin-alpha4a polyglutamylation prevents aggregation of hyper-phosphorylated tau and microglia activation in mice.

Dissociation of hyper-phosphorylated Tau from neuronal microtubules and its pathological aggregates, are hallmarks in the etiology of tauopathies. The Tau-microtubule interface is subject to polyglutamylation, a reversible posttranslational modification, increasing negative charge at tubulin C-terminal tails. Here, we asked whether tubulin polyglutamylation may contribute to Tau pathology in vivo. Since polyglutamylases modify various proteins other than tubulin, we generated a knock-in mouse carrying gene mutations to abolish Tuba4a polyglutamylation in a substrate-specific manner. We found that Tuba4a lacking C-terminal polyglutamylation prevents the binding of Tau and GSK3 kinase to neuronal microtubules, thereby strongly reducing phospho-Tau levels. Notably, crossbreeding of the Tuba4a knock-in mouse with the hTau tauopathy model, expressing a human Tau transgene, reversed hyper-phosphorylation and oligomerization of Tau and normalized microglia activation in brain. Our data highlight tubulin polyglutamylation as a potential therapeutic strategy in fighting tauopathies.

Converging roles of PSENEN/PEN2 and CLN3 in the autophagy-lysosome system.

PSENEN/PEN2 is the smallest subunit of the γ-secretase complex, an intramembrane protease that cleaves proteins within their transmembrane domains. Mutations in components of the γ-secretase underlie familial Alzheimer disease. In addition to its proteolytic activity, supplementary, γ-secretase independent, functions in the macroautophagy/autophagy-lysosome system have been proposed. Here, we screened for PSENEN-interacting proteins and identified CLN3. Mutations in CLN3 are causative for juvenile neuronal ceroid lipofuscinosis, a rare lysosomal storage disorder considered the most common neurodegenerative disease in children. As mutations in the PSENEN and CLN3 genes cause different neurodegenerative diseases, understanding shared cellular functions of both proteins might be pertinent for understanding general cellular mechanisms underlying neurodegeneration. We hypothesized that CLN3 modulates γ-secretase activity and that PSENEN and CLN3 play associated roles in the autophagy-lysosome system. We applied CRISPR gene-editing and obtained independent isogenic HeLa knockout cell lines for PSENEN and CLN3. Following previous studies, we demonstrate that PSENEN is essential for forming a functional γ-secretase complex and is indispensable for γ-secretase activity. In contrast, CLN3 does not modulate γ-secretase activity to a significant degree. We observed in PSENEN- and CLN3-knockout cells corresponding alterations in the autophagy-lysosome system. These include reduced activity of lysosomal enzymes and lysosome number, an increased number of autophagosomes, increased lysosome-autophagosome fusion, and elevated levels of TFEB (transcription factor EB). Our study strongly suggests converging roles of PSENEN and CLN3 in the autophagy-lysosome system in a γ-secretase activity-independent manner, supporting the idea of common cytopathological processes underlying different neurodegenerative diseases.Abbreviations: Aß, amyloid-beta; AD, Alzheimer disease; APP, amyloid precursor protein; ATP5MC, ATP synthase membrane subunit c; DQ-BSA, dye-quenched bovine serum albumin; ER, endoplasmic reticulum; GFP, green fluorescent protein; ICC, immunocytochemistry; ICD, intracellular domain; JNCL, juvenile neuronal ceroid lipofuscinosis; KO, knockout; LC3, microtubule associated protein 1 light chain 3; NCL, neuronal ceroid lipofuscinoses; PSEN, presenilin; PSENEN/PEN2: presenilin enhancer, gamma-secretase subunit; TAP, tandem affinity purification; TEV, tobacco etch virus; TF, transferrin; WB, Western blot; WT, wild type.

Competitive and Clonal Dominance Behavior: Raising Awareness of Their Role in Shape Generation.

Gene regulatory networks, which are crucial for the proper development of organisms, are extensively studied. From these investigations, coordinative mechanisms are shown to be instructive for further development. Competitive mechanisms as well as environmental and metabolic influences, however, are widely ignored so far but appear to be important for the emergence of shape.

The Microtubule Severing Protein Katanin Regulates Proliferation of Neuronal Progenitors in Embryonic and Adult Neurogenesis.

Microtubule severing regulates cytoskeletal rearrangement underlying various cellular functions. Katanin, a heterodimer, consisting of catalytic (p60) and regulatory (p80) subunits severs dynamic microtubules to modulate several stages of cell division. The role of p60 katanin in the mammalian brain with respect to embryonic and adult neurogenesis is poorly understood. Here, we generated a Katna1 knockout mouse and found that consistent with a critical role of katanin in mitosis, constitutive homozygous Katna1 depletion is lethal. Katanin p60 haploinsufficiency induced an accumulation of neuronal progenitors in the subventricular zone during corticogenesis, and impaired their proliferation in the adult hippocampus dentate gyrus (DG) subgranular zone. This did not compromise DG plasticity or spatial and contextual learning and memory tasks employed in our study, consistent with the interpretation that adult neurogenesis may be associated with selective forms of hippocampal-dependent cognitive processes. Our data identify a critical role for the microtubule-severing protein katanin p60 in regulating neuronal progenitor proliferation in vivo during embryonic development and adult neurogenesis.

Amyloidosis causes downregulation of SorLA, SorCS1 and SorCS3 expression in mice.

Accumulation of ß-amyloid peptide (Aß) is regarded as a primary cause of Alzheimer's disease (AD). Aß is derived by sequential cleavage of the amyloid precursor protein (APP). Alterations in the subcellular targeting of APP are thought to affect the degree of Aß production. Sorting receptors, such as SorLA, convey subcellular targeting of APP. Dysfunction of SorLA, and likely of the related receptors SorCS1 and SorCS3, cause AD. Nevertheless, disease progression could also provoke altered expression of the receptors. Here, we assessed if Aß plaque formation promotes altered expression of SorLA, SorCS1 and SorCS3. We analyzed transcript levels during aging and after amyloidosis in brain areas characterized by early amyloid plaque formation in an AD mouse model (APPPS1) and wild types. We observed stable expression levels during aging (1-12 months). After plaque formation, SorCS1 and SorLA expression were markedly reduced in the frontal cerebral cortex and to a minor extent in the hippocampus, whereas SorCS3 expression was solely reduced in the frontal cerebral cortex. Our results indicate that disease progression, associated with Aß accumulation, can negatively regulate expression of the receptors.

TCR bias and HLA cross-restriction are strategies of human brain-infiltrating JC virus-specific CD4+ T cells during viral infection.

Virus-specific CD4(+) T cells play a central role in control of viral pathogens including JC polyoma virus (JCV) infection. JCV is a ubiquitous small DNA virus that leads to persistent infection of humans with no clinical consequences. However, under circumstances of immunocompromise, it is able to cause an opportunistic and often fatal infection of the brain called progressive multifocal leukoencephalopathy (PML). PML has emerged as a serious adverse event in multiple sclerosis patients treated with the anti-VLA-4 mAb natalizumab, which selectively inhibits cell migration across the blood-brain barrier and the gut's vascular endothelium thus compromising immune surveillance in the CNS and gut. In a multiple sclerosis patient who developed PML under natalizumab treatment and a vigorous immune response against JCV after Ab washout, we had the unique opportunity to characterize in detail JCV-specific CD4(+) T cell clones from the infected tissue during acute viral infection. The in-depth analysis of 14 brain-infiltrating, JCV-specific CD4(+) T cell clones demonstrated that these cells use an unexpectedly broad spectrum of different strategies to mount an efficient JCV-specific immune response including TCR bias, HLA cross-restriction that increases avidity and influences in vivo expansion, and a combination of Th1 and Th1-2 functional phenotypes. The level of combinatorial diversity in TCR- and HLA-peptide interactions used by brain-infiltrating, JCV-specific CD4(+) T cells has not, to our knowledge, been reported before in humans for other viral infections and confirms the exceptional plasticity that characterizes virus-specific immune responses.

The orphan G-protein-coupled receptor GPR19 is expressed predominantly in neuronal cells during mouse embryogenesis.

G-protein-coupled receptors (GPCRs) are characterized by seven transmembrane domains and constitute the largest and structurally best-conserved family of signaling molecules. They are present in a diversity of organs and tissues and are involved in virtually all physiological processes. Here we report the expression of GPR19, an orphan GPCR, during mouse embryonic development and in the adult brain. Transcripts of GPR19 were detected early in embryonic development and were prominent in tissues of neuroectodermal origin. With ongoing differentiation, the localization of GPR19 transcripts became restricted to distinct regions of the developing brain, and the overall signal intensity declined in parallel. In the adult mouse, GPR19 showed high levels of transcription in several regions of the brain, including the olfactory bulb, the hippocampus, hypothalamic nuclei, and the cerebellum, and in testis. Lower levels of GPR19 expression were detected in heart, liver, and kidney. These data suggest that, amongst several other functions in the adult organism, GPR19 probably exerts its most characteristic effects during the early development of the nervous system.

Isolation of a putative peroxidase, a target for factors controlling foot-formation in the coelenterate hydra.

In hydra, differentiated ectodermal cells of the foot region contain a peroxidase activity that can be used as a marker for foot-specific differentiation processes. Because the expression of the gene coding for the peroxidase must be tightly regulated during foot-specific differentiation, characterization of the protein and cloning of the corresponding gene should provide valuable tools for getting deeper insights into the regulation of foot-specific differentiation. In this paper we characterize the foot-specific peroxidase by biochemical, histochemical, and molecular biological methods. We show that it is localized in granules, and that it consists of a single component, the molecular mass of which is in the range of 43-45 kDa. Purification of the protein and subsequent cloning of its complementary DNA yielded two closely related clones, ppod1 and ppod2. Transcripts of ppod2 are abundant in the whole animal with the exception of the hypostome, the tentacles, and the foot; the expression of ppod1 matches exactly the localization of the foot-specific peroxidase.