Mitochondrial Morphogenesis, Dendrite Development, and Synapse Formation in Cerebellum Require both Bcl-w and the Glutamate Receptor δ2

Bcl-w belongs to the prosurvival group of the Bcl-2 family, while the glutamate receptor δ2 (Grid2) is an excitatory receptor that is specifically expressed in Purkinje cells, and required for Purkinje cell synapse formation. A recently published result as well as our own findings have shown that Bcl-w can physically interact with an autophagy protein, Beclin1, which in turn has been shown previously to form a protein complex with the intracellular domain of Grid2 and an adaptor protein, nPIST. This suggests that Bcl-w and Grid2 might interact genetically to regulate mitochondria, autophagy, and neuronal function. In this study, we investigated this genetic interaction of Bcl-w and Grid2 through analysis of single and double mutant mice of these two proteins using a combination of histological and behavior tests. It was found that Bcl-w does not control the cell number in mouse brain, but promotes what is likely to be the mitochondrial fission in Purkinje cell dendrites, and is required for synapse formation and motor learning in cerebellum, and that Grid2 has similar phenotypes. Mice carrying the double mutations of these two genes had synergistic effects including extremely long mitochondria in Purkinje cell dendrites, and strongly aberrant Purkinje cell dendrites, spines, and synapses, and severely ataxic behavior. Bcl-w and Grid2 mutations were not found to influence the basal autophagy that is required for Purkinje cell survival, thus resulting in these phenotypes. Our results demonstrate that Bcl-w and Grid2 are two critical proteins acting in distinct pathways to regulate mitochondrial morphogenesis and control Purkinje cell dendrite development and synapse formation. We propose that the mitochondrial fission occurring during neuronal growth might be critically important for dendrite development and synapse formation, and that it can be regulated coordinately by multiple pathways including Bcl-2 and glutamate receptor family members

Enhancement of Both Long-Term Depression Induction and Optokinetic Response Adaptation in Mice Lacking Delphilin

In the cerebellum, Delphilin is expressed selectively in Purkinje cells (PCs) and is localized exclusively at parallel fiber (PF) synapses, where it interacts with glutamate receptor (GluR) δ2 that is essential for long-term depression (LTD), motor learning and cerebellar wiring. Delphilin ablation exerted little effect on the synaptic localization of GluRδ2. There were no detectable abnormalities in cerebellar histology, PC cytology and PC synapse formation in contrast to GluRδ2 mutant mice. However, LTD induction was facilitated at PF-PC synapses in Delphilin mutant mice. Intracellular Ca2+ required for the induction of LTD appeared to be reduced in the mutant mice, while Ca2+ influx through voltage-gated Ca2+ channels and metabotropic GluR1-mediated slow synaptic response were similar between wild-type and mutant mice. We further showed that the gain-increase adaptation of the optokinetic response (OKR) was enhanced in the mutant mice. These findings are compatible with the idea that LTD induction at PF-PC synapses is a crucial rate-limiting step in OKR gain-increase adaptation, a simple form of motor learning. As exemplified in this study, enhancing synaptic plasticity at a specific synaptic site of a neural network is a useful approach to understanding the roles of multiple plasticity mechanisms at various cerebellar synapses in motor control and learning

GluRδ2 Expression in the Mature Cerebellum of Hotfoot Mice Promotes Parallel Fiber Synaptogenesis and Axonal Competition

Glutamate receptor delta 2 (GluRdelta2) is selectively expressed in the cerebellum, exclusively in the spines of the Purkinje cells (PCs) that are in contact with parallel fibers (PFs). Although its structure is similar to ionotropic glutamate receptors, it has no channel function and its ligand is unknown. The GluRdelta2-null mice, such as knockout and hotfoot have profoundly altered cerebellar circuitry, which causes ataxia and impaired motor learning. Notably, GluRdelta2 in PC-PF synapses regulates their maturation and strengthening and induces long term depression (LTD). In addition, GluRdelta2 participates in the highly territorial competition between the two excitatory inputs to the PC; the climbing fiber (CF), which innervates the proximal dendritic compartment, and the PF, which is connected to spiny distal branchlets. Recently, studies have suggested that GluRdelta2 acts as an adhesion molecule in PF synaptogenesis. Here, we provide in vivo and in vitro evidence that supports this hypothesis. Through lentiviral rescue in hotfoot mice, we noted a recovery of PC-PF contacts in the distal dendritic domain. In the proximal domain, we observed the formation of new spines that were innervated by PFs and a reduction in contact with the CF; ie, the pattern of innervation in the PC shifted to favor the PF input. Moreover, ectopic expression of GluRdelta2 in HEK293 cells that were cocultured with granule cells or in cerebellar Golgi cells in the mature brain induced the formation of new PF contacts. Collectively, our observations show that GluRdelta2 is an adhesion molecule that induces the formation of PF contacts independently of its cellular localization and promotes heterosynaptic competition in the PC proximal dendritic domain

Deletion of Glutamate Delta-1 Receptor in Mouse Leads to Aberrant Emotional and Social Behaviors

The delta family of ionotropic glutamate receptors consists of glutamate δ1 (GluD1) and glutamate δ2 (GluD2) receptors. While the role of GluD2 in the regulation of cerebellar physiology is well understood, the function of GluD1 in the central nervous system remains elusive. We demonstrate for the first time that deletion of GluD1 leads to abnormal emotional and social behaviors. We found that GluD1 knockout mice (GluD1 KO) were hyperactive, manifested lower anxiety-like behavior, depression-like behavior in a forced swim test and robust aggression in the resident-intruder test. Chronic lithium rescued the depression-like behavior in GluD1 KO. GluD1 KO mice also manifested deficits in social interaction. In the sociability test, GluD1 KO mice spent more time interacting with an inanimate object compared to a conspecific mouse. D-Cycloserine (DCS) administration was able to rescue social interaction deficits observed in GluD1 KO mice. At a molecular level synaptoneurosome preparations revealed lower GluA1 and GluA2 subunit expression in the prefrontal cortex and higher GluA1, GluK2 and PSD95 expression in the amygdala of GluD1 KO. Moreover, DCS normalized the lower GluA1 expression in prefrontal cortex of GluD1 KO. We propose that deletion of GluD1 leads to aberrant circuitry in prefrontal cortex and amygdala owing to its potential role in presynaptic differentiation and synapse formation. Furthermore, these findings are in agreement with the human genetic studies suggesting a strong association of GRID1 gene with several neuropsychiatric disorders including schizophrenia, bipolar disorder, autism spectrum disorders and major depressive disorder

Trans-synaptic interaction of GluRdelta2 and Neurexin through Cbln1 mediates synapse formation in the cerebellum

SummaryElucidation of molecular mechanisms that regulate synapse formation is required for the understanding of neural wiring, higher brain functions, and mental disorders. Despite the wealth of in vitro information, fundamental questions about how glutamatergic synapses are formed in the mammalian brain remain unanswered. Glutamate receptor (GluR) δ2 is essential for cerebellar synapse formation in vivo. Here, we show that the N-terminal domain (NTD) of GluRδ2 interacts with presynaptic neurexins (NRXNs) through cerebellin 1 precursor protein (Cbln1). The synaptogenic activity of GluRδ2 is abolished in cerebellar primary cultures from Cbln1 knockout mice and is restored by recombinant Cbln1. Knockdown of NRXNs in cerebellar granule cells also hinders the synaptogenic activity of GluRδ2. Both the NTD of GluRδ2 and the extracellular domain of NRXN1β suppressed the synaptogenic activity of Cbln1 in cerebellar primary cultures and in vivo. These results suggest that GluRδ2 mediates cerebellar synapse formation by interacting with presynaptic NRXNs through Cbln1

The impact of providing business training to microfinance clients: empirical evidence from Tanzania

This master thesis studies the impact of providing business training to microfinance clients in Tanzania. Based on data collected six months after the programme ended, we cannot confirm positive treatment effects from business training on the micro entrepreneurs’ profits. However, treated entrepreneurs have higher likelihood of operating multiple businesses; increased their engagement within commerce and reduced their engagement within manufacturing. Based on the market situation at the time, these changes all represent advancement towards business structures associated with higher profitability. Moreover, findings of low profitability in new establishments can serve as an explanation to the small effect from business training on profits, and imply that treatment effects will be manifested in higher future profits of the entrepreneurs

Congenital Aniridia: Exploring Visual Disabling Manifestations in the Ocular Surface and Ocular Fundus through Clinical and Translational Approaches

Congenital aniridia is primarily characterized by hypoplasia of the iris and the retinal fovea. Foveal hypoplasia is the main cause of congenital reduced vision. Keratopathy is common in aniridia, leading to considerable visual impairment. We hypothesized that keratopathy is related to dry eye disease, and that patients with aniridia have more severe dry eye than healthy individuals. Finally, we proposed that autofluorescence imaging could be used to evaluate foveal hypoplasia. First, we studied 35 patients with aniridia and 21 healthy controls. An extensive examination of dry eye disease was undertaken. Next, 14 aniridia patients and 14 matched controls underwent autofluorescence imaging. We detected more severe dry eye disease in aniridia patients than in healthy individuals. Dry eye disease was related to keratopathy. Aniridia patients had increased levels of pro-inflammatory cytokines in the tear fluid. We also found that autofluorescence imaging could be useful in evaluation of foveal hypoplasia. In conclusion, the thesis brings together two main causes of visual disability in aniridia. The results may help improve treatment and follow-up of aniridia patients in the future

Role kybernetických operací v íránské politice vůči Spojeným státům: Kvalitativní perspektiva

This study examines the role and utility of low-severity cyber operations in one state's policy toward another within the context of a long-term hostile feud. This study has fulfilled this task through an explanatory qualitative analysis with cyber operations as an embedded unit of study. The subject of research is the policy of the Islamic Republic of Iran toward the United States in the time spanning from the historic agreement of the Joint Comprehensive Plan of Action (JCPOA), also known as the Nuclear Deal, in July 2015 through 2020. The role of the cyber operations in Iran's policy is examined by juxtaposing the pattern of escalations and de- escalations occurring in the context, and in the political and military domains conducted by the Islamic Republic with their deployment of cyber operations. Through this pattern matching, this study identified a visible relative restraint in the cyber domain during the first years following the conclusion of the JCPOA, as the Islamic Republic had obtained its top strategic goal, defined as eliminating all sanctions burdening its economy. Iran's cyber operations towards the United States re-emerged when Washington exited the Nuclear Deal in 2018 and began re-instating sanctions, and the operations were intensified when Tehran began steadily escalating in...Katedra bezpečnostních studiíDepartment of Security StudiesFaculty of Social SciencesFakulta sociálních vě

The role of cyber operations in Iran's policy toward the United States: A qualitative perspective

This study examines the role and utility of low-severity cyber operations in one state's policy toward another within the context of a long-term hostile feud. This study has fulfilled this task through an explanatory qualitative analysis with cyber operations as an embedded unit of study. The subject of research is the policy of the Islamic Republic of Iran toward the United States in the time spanning from the historic agreement of the Joint Comprehensive Plan of Action (JCPOA), also known as the Nuclear Deal, in July 2015 through 2020. The role of the cyber operations in Iran's policy is examined by juxtaposing the pattern of escalations and de- escalations occurring in the context, and in the political and military domains conducted by the Islamic Republic with their deployment of cyber operations. Through this pattern matching, this study identified a visible relative restraint in the cyber domain during the first years following the conclusion of the JCPOA, as the Islamic Republic had obtained its top strategic goal, defined as eliminating all sanctions burdening its economy. Iran's cyber operations towards the United States re-emerged when Washington exited the Nuclear Deal in 2018 and began re-instating sanctions, and the operations were intensified when Tehran began steadily escalating in..