Spine plasticity of dentate gyrus parvalbumin-positive interneurons is regulated by experience.

Experience-driven alterations in neuronal activity are followed by structural-functional modifications allowing cells to adapt to these activity changes. Structural plasticity has been observed for cortical principal cells. However, how GABAergic interneurons respond to experience-dependent network activity changes is not well understood. We show that parvalbumin-expressing interneurons (PVIs) of the dentate gyrus (DG) possess dendritic spines, which undergo behaviorally induced structural dynamics. Glutamatergic inputs at PVI spines evoke signals with high spatial compartmentalization defined by neck length. Mice experiencing novel contexts form more PVI spines with elongated necks and exhibit enhanced network and PVI activity and cFOS expression. Enhanced green fluorescent protein reconstitution across synaptic partner-mediated synapse labeling shows that experience-driven PVI spine growth boosts targeting of PVI spines over shafts by glutamatergic synapses. Our findings propose a role for PVI spine dynamics in regulating PVI excitation by their inputs, which may allow PVIs to dynamically adjust their functional integration in the DG microcircuitry in relation to network computational demands.

TMEM87a/Elkin1, a component of a novel mechanoelectrical transduction pathway, modulates melanoma adhesion and migration.

Mechanoelectrical transduction is a cellular signalling pathway where physical stimuli are converted into electro-chemical signals by mechanically activated ion channels. We describe here the presence of mechanically activated currents in melanoma cells that are dependent on TMEM87a, which we have renamed Elkin1. Heterologous expression of this protein in PIEZO1-deficient cells, that exhibit no baseline mechanosensitivity, is sufficient to reconstitute mechanically activated currents. Melanoma cells lacking functional Elkin1 exhibit defective mechanoelectrical transduction, decreased motility and increased dissociation from organotypic spheroids. By analysing cell adhesion properties, we demonstrate that Elkin1 deletion is associated with increased cell-substrate adhesion and decreased homotypic cell-cell adhesion strength. We therefore conclude that Elkin1 supports a PIEZO1-independent mechanoelectrical transduction pathway and modulates cellular adhesions and regulates melanoma cell migration and cell-cell interactions.

When cells receive signals about their surrounding environment, this initiates a chain of signals which generate a response. Some of these signalling pathways allow cells to sense physical and mechanical forces via a process called mechanotransduction. There are different types of mechanotransduction. In one pathway, mechanical forces open up specialized channels on the cell surface which allow charged particles to move across the membrane and create an electrical current. Mechanoelectrical transduction plays an important role in the spread of cancer: as cancer cells move away from a tumour they use these signalling pathways to find their way between cells and move into other parts of the body. Understanding these pathways could reveal ways to stop cancer from spreading, making it easier to treat. However, it remains unclear which molecules regulate mechanoelectrical transduction in cancer cells. Now, Patkunarajah, Stear et al. have studied whether mechanoelectrical transduction is involved in the migration of skin cancer cells. To study mechanoelectrical transduction, a fine mechanical input was applied to the skin cancer cells whilst measuring the flow of charged molecules moving across the membrane. This experiment revealed that a previously unknown protein named Elkin1 is required to convert mechanical forces into electrical currents. Deleting this newly found protein caused skin cancer cells to move more slowly and dissociate more easily from tumour-like clusters of cells. These findings suggest that Elkin1 is part of a newly identified mechanotransduction pathway that allows cells to sense mechanical forces from their surrounding environment. More work is needed to determine what role Elkin1 plays in mechanoelectrical transduction and whether other proteins are also involved. This could lead to new approaches that prevent cancer cells from dissociating from tumours and spreading to other body parts.

Newly Generated Cells in the Dentate Gyrus Differentially Respond to Brief Spatial Exploration and Forced Swim in Adult Female Balb/C Mice.

Neurogenesis in the hippocampus is influenced by several factors including external stimuli. In addition to their involvement in learning and memory processes, newborn neurons of the dentate gyrus (DG) buffer against the effects of stress. Although the response of these cells to environmental stimuli has been shown, the age of the cells that respond to a brief spatial exploration or a stressful situation produced by forced-swim stress in adult female Balb/C mice is still unknown. Here, we investigated the activation of newborn neurons after three (IdU) or six weeks (CldU) postlabelling with the expression of Arc in the same mice but exposed to different environmental stimuli. Mice housed in standard conditions showed an increase in the activation of CldU-labelled cells after two exposures to a brief spatial exploration but no increase in the activation of IdU-labelled cells compared with the control group. Additionally, we analysed neuronal activation in the DG of mice housed in standard conditions and further exposed to forced-swim stress. We found a decreased activation of IdU-labelled cells in mice exposed to forced-swim stress with increase number of CldU-labelled cells. Our results suggest that based on their time postlabelling, newly generated hippocampal neurons show a different response to several environmental stimuli.

Las zonas neurogénicas en el adulto y su relación con las enfermedades neuropsiquiátricas / Neurogenic regions in the adult: Relationship with the neuropsychiatric disorders

Neuropsychiatric diseases (NPD) are characterized by changes in brain plasticity involving alterations in the morphology and functionality of neurons. However, affectations of the neuronal development (neurogenesis) in the adult brain are also shown. The neurogenic process is widely regulated by different factors such as genes, microenvironment, hormones, neurotransmitters, environmental cues and, also, nutrition. Thus, alterations in these factors negatively impact the neuronal development. Several studies performed in humans have revealed alterations of neurogenesis in NPD. However, most of the knowledge derives from studies done in animal models of NPD. The evidences from animal models are controversial, thus the use of human-induced pluripotent stem cells as a model of NPD has marked a way to study alterations in the neuronal development. Recently, the use of another cellular model for studying NPD has been proposed. Multipotent stem cells derived from olfactory epithelium (MOESCs) are a good candidate. However, evidences are scarce and deeper studies are necessary to know if there is or not a correlation of alterations in neuronal development in the OE with the changes observed in the brain; or if the MOESCs can mimic alterations shown in NPD that could let to get more knowledge about the factors promoting these diseases. Thus, in this review we discuss basic information about adult neurogenesis under physiological and non-physiological conditions in the hippocampus, olfactory bulb and olfactory epithelium.

Las enfermedades neuropsiquiátricas (ENP) se caracterizan por cambios en la plasticidad cerebral que incluyen la pérdida neuronal en regiones específicas en el encéfalo, cambios en la transmisión sináptica originada por alteraciones en los contactos sinápticos y también por la expresión de genes. Además, otro proceso que forma parte de la plasticidad cerebral y que también se encuentra afectado en las ENP es la generación de nuevas neuronas (neurogénesis). El proceso neurogénico en el adulto es regulado de manera fina por diversos factores como los aspectos genéticos, celulares, el microambiente, los elementos neuroquímicos, los ambientales y los nutricionales. Las alteraciones de estos factores impactan en el desarrollo y en la función de las nuevas neuronas. Algunos estudios realizados en humanos han revelado las alteraciones en la neurogénesis en algunos ENP. Sin embargo los mayores avances logrados han utilizado modelos animales de ENP. En algunos casos estas evidencias son controvertidas y recientemente se han tratado de aclarar utilizando cultivos de células madre pluripotenciales-inducibles humanas como modelos de ENP. Otro modelo que se ha propuesto para estudiar las alteraciones en el desarrollo neuronal en las ENP son las células madre multipotenciales del epitelio olfatorio (CMPEO). Sin embargo las evidencias obtenidas con las CMPEO son escasas y resulta necesario demostrar si existe o no un correlato con las alteraciones que ocurren en el desarrollo neuronal a nivel central en las ENP, o bien si las CMPEO pueden mostrar las alteraciones observadas en las ENP que permitan obtener información acerca de los factores que promueven estas enfermedades. Por lo tanto en esta revisión se incluyen aspectos básicos de la neurogénesis e información relevante de las alteraciones de este proceso en las tres regiones neurogénicas en el adulto: el hipocampo, el bulbo olfatorio y el epitelio olfatorio.