Investigation of the role of the extracellular matrix molecule Tenascin-C in the regulation of structural and functional plasticity of the cerebellum and in shaping of the behavior of the mouse after exposure to enriched environment conditions

Tenascin-C (TnC) je glikoprotein prisutan u vanćelijskom matriksu (VĆM) različitih tkiva kičmenjaka tokom razvića, gde je uključen u regulaciju ćelijskog rasta, migracije i adhezije preko aktivacije različitih unutarćelijskih signalnih puteva. Ekspresija TnC je značajno smanjenja u adultnom organizmu, međutim ostaje prisutna samo u određenim perifernim tkivima, kao i u delovima centralnog nervnog sistema koji zadržavaju visok nivo plastičnosti, kao što je mali mozak, gde je uočena njegova uloga u modulaciji sinaptičkih funkcija. Obogaćena sredina (OS) oblikuje mnoge aspekte ponašanja i stoga može da posluži kao pristup za proučavanje neuronalne plastičnosti u adultnom organizmu. Izlaganje OS dovodi do brojnih promena na molekularnom i ćelijskom nivou u različitim regionima mozga uključujući mali mozak. Cilj ove studije je bio da se ispita uloga TnC u modulaciji strukturne plastičnosti malog mozga indukovane OS praćenjem distribucije perineuronalnih mreža (PNM), promene u veličini i gustini ekscitatornih i inhibitornih presinaptičkih završetaka, kao i aktivnosti glavnih enzima koji vrše razgradnju VĆM, MMP-2 i MMP-9. Takođe, ova studija je imala za cilj da ispita kako nedostatak TnC interaguje sa spoljašnjom sredinom u oblikovanju različitih domena ponašanja povezanih sa funkcijom malog mozga. U te svrhe, miševi sa nedostatkom TnC (TnC-/-) ili MMP-9 (MMP-9-/-) i odgovarajući kontrolni miševi starosti 3 nedelje su izlagani standardnim uslovima gajenja (SS) ili OS 4 ili 8 nedelja. Ova studija je pokazala da izlaganje OS u toku 8 nedelja dovodi do smanjenja intenziteta bojenja na PNM, kao i smanjenja u veličini GABAergičkih i povećanja broja i veličine glutamatergičkih sinaptičkih završetaka u kontrolnim miševima. Nasuprot tome, TnC-/- miševi su pokazali smanjen intenzitet bojenja na PNM u poređenju sa kontrolnim životinjama gajenim u SS, dok njihovo izlaganje OS nije dovelo da smanjenja, već do blagog povećanja intenziteta PNM...Tenascin-C (TnC) is a glycoprotein present in the extracellular matrix (ECM) of a variety of vertebrate tissues during development, where it plays multiple roles in cell growth, migration and adhesion by activating diverse intracellular signaling pathways. Expression of TnC is markedly downregulated in the adulthood, persisting in a few peripheral structures and in central nervous system areas known to retain high degree of plasticity, such as the cerebellum, where it is involved in the modulation of synaptic functions. Enriched environment (EE) shapes many aspects of behavior and may, therefore, serve as a paradigm to study neuronal plasticity in the adult. Exposure to EE leads to numerous changes at the molecular and cellular levels, which target various brain regions including the cerebellum. The aim of present study was to examine the role of TnC in the modulation of cerebellar structural plasticity induced by the exposure to EE by following the appearance of perineuronal nets (PNN), changes in size and density of excitatory and inhibitory synaptic terminals, and the activity of major ECM degrading enzymes, MMP-2 and MMP-9. Furthermore, the present study aimed to examine how TnC deficiency interacts with the environment in shaping different behavioral domains associated with the cerebellum. To this end, 3-week-old mice lacking TnC (TnC-/-) or MMP-9 (MMP-9-/-) and corresponding wild-type mice were exposed to standard conditions (SC) or an enriched environment (EE) for 4 or 8 weeks. The present study shows that 8 weeks of exposure to EE leads to reduced staining of PNN, reduction in the size of GABAergic and increase in the number and size of glutamatergic synaptic terminals in wild-type mice. Conversely, TnC-/- mice showed reduced staining of PNNs compared to wild-type mice maintained under standard conditions, while exposure to EE did not further reduce, but even slightly increased PNN staining..

Effect of enriched environment on serotonin and RNA editing of serotonin 2C receptor is specific for brain regions and mouse strains

Serotonin neurotransmission is sensitive to environmental stimuli. Serotonin receptor 2C (HTR2C) undergoes dynamic A-to-I editing that fine-tunes cell response to serotonin and is altered in depressed suicide victims and by pharmacological treatments. We aimed to explore a mediating role of Htr2c mRNA editing in response to enriched environment and factors involved in this response. Three-week-old BALB/c and C57BL/6 male mice were housed in enriched and standard conditions for four weeks. Htr2c mRNA editing pattern and expression, serotonin level and expression of Adar and Adarb1 mRNAs (coding enzymes catalyzing A-to-I editing) and Snord115 RNA (regulating Htr2c mRNA alternative splicing and editing) were measured in prefrontal cortex (PFC) and hippocampus (HC), brain regions implicated in suicidal behavior. BALB/c mice, a “stress-sensitive” strain due to genetically determined lower serotonin level, responded to enriched conditions by adapting the Htr2c editing pattern to a slight serotonin decrease in PFC and a significant increase in HC. C57BL/6 mice, a “stress-resilient” strain, responded to enriched environment by increasing the serotonin level and changing Adar and Adarb1 mRNAs expression in HC, and without changes in PFC. Our findings suggest that the enriched environment effect on the serotonin level and a mediating role of Htr2c mRNA editing in PFC depend on the genetic background and its interactions with the environment. On the other hand, changes in HC are primarily driven by enriched environment. Our results imply usefulness of enriched environment paradigm for understanding interactions of genetic and environmental factors underlying suicidal behavior, which might improve psychological treatments.BOOK OF ABSTRACTS: 8th CONGRESS OF SERBIAN NEUROSCIENCE SOCIETY with international participation 31 May – 2 June 2023. Belgrade, Serbi

Structural and Functional Modulation of Perineuronal Nets: In Search of Important Players with Highlight on Tenascins

The extracellular matrix (ECM) of the brain plays a crucial role in providing optimal conditions for neuronal function. Interactions between neurons and a specialized form of ECM, perineuronal nets (PNN), are considered a key mechanism for the regulation of brain plasticity. Such an assembly of interconnected structural and regulatory molecules has a prominent role in the control of synaptic plasticity. In this review, we discuss novel ways of studying the interplay between PNN and its regulatory components, particularly tenascins, in the processes of synaptic plasticity, mechanotransduction, and neurogenesis. Since enhanced neuronal activity promotes PNN degradation, it is possible to study PNN remodeling as a dynamical change in the expression and organization of its constituents that is reflected in its ultrastructure. The discovery of these subtle modifications is enabled by the development of super-resolution microscopy and advanced methods of image analysis

Fatigue Life Estimation of Notched Structural Components

This work considers the analytical/numerical methods and procedures for obtaining the stress intensity factors and for predicting the fatigue crack growth life of notched structural components. Many efforts have been made during the past two decades to evaluate the stress intensity factor for corner cracks and for through cracks emanating from fastener holes. A variety of methods have been used to estimate the stress intensity factor (SIF), values, such as approximate analytical methods, finite element method (FEM), finite element alternating, weight function, photo elasticity and fatigue tests. In this paper the analytic/numerical methods and procedures were used to obtain SIF, and predict the fatigue crack growth life for cracks at attachment lugs. Single through crack in the attachment lug analysis is considered. For this purpose analytic expressions are evaluated for SIF of cracked lug structures. For validation of the analytic stress intensity factors of cracked lugs, FEM with singular finite elements is used. Good agreement between computation and experimental results for fatigue life of aircraft cracked lugs was obtained. To determine crack trajectory of cracked structural components under mixed modes conventional singular finite elements and X-FEM are used

Chorological and Ecological Differentiation of the Commonest Leech Species from the Suborder Erpobdelliformes (Arhynchobdellida, Hirudinea) on the Balkan Peninsula

This study is the result of extensive investigations of leeches on the Balkan Peninsula. Our aim was to detect actual and potential (modeled) distributions of common Erpobdellidae species, and to identify their ecological differentiation with respect to the altitudinal and waterbody type gradient. Although widespread, these species rarely live together. Intense competition is avoided by preferences for different types of habitats. This was confirmed by Pearson correlation analyses that yielded negative results. Differentiation of these species was clarified by the results of logistic Gaussian regression analyses. While Erpobdella octoculata and Dina lineata have a similar distribution along the altitudinal gradient, they prefer different waterbody types. Erpobdella vilnensis prefers higher altitudes than the other two species. Its preferred habitats are smaller rivers and streams located at altitudes from 400 to 1000 m a.s.l. Although present in all waterbody types, large lowland rivers and standing waterbodies are the preferred habitats of E. octoculata. Fast-flowing springs and streams are mostly inhabited by D. lineata. While the distribution of the species overlaps to a large degree, the ecological preferences of species differ significantly and thus they can be used as confident typological descriptors and indicators of ecological status