Biology subjects

Pervolaraki, E.

Publications and source records attributed to Pervolaraki, E..

3 recordsLinked to original sources

bioRxiv2020

A super-resolution protocol to correlate structural underpinnings of fast second-messenger signalling in primary cell types

Nanometre-scale cellular information obtained through super-resolution microscopies are often unaccompanied by functional information, particularly transient and diffusible signals through which life is orchestrated in the nano-micrometre spatial scale. We describe a correlative imaging protocol which allows the ubiquitous intracellular second messenger, calcium (Ca2+), to be directly visualised against nanoscale patterns of the ryanodine receptor (RyR) Ca2+ channels which give rise to these Ca2+ signals in wildtype primary cells. This was achieved by combining total internal reflection fluorescence (TIRF) imaging of the elementary Ca2+ signals, with the subsequent DNA-PAINT imaging of the RyRs. We report a straightforward image analysis protocol of feature extraction and image alignment between correlative datasets and demonstrate how such data can be used to visually identify the ensembles of Ca2+ channels that are locally activated during the genesis of cytoplasmic Ca2+ signals.

biophysics↗

bioRxiv2018

Insoluble Aβ overexpression in an App knock-in mouse model alters microstructure and gamma oscillations in the prefrontal cortex, and social and anxiety-related behaviours

We studied two new App knock-in mice models of Alzheimers disease (AppNL-F and AppNL-G-F), which generate elevated levels of A{beta}40 and A{beta}42 without the confounds associated with APP overexpression. This enabled us to assess changes in anxiety-related and social behaviours, and neural alterations potentially underlying such changes, driven specifically by A{beta} accumulation. AppNL-G-F knock-in mice exhibited subtle deficits in tasks assessing social memory, but not in social motivation tasks. In anxiety-assessing tasks, AppNL-G-F knock-in mice exhibited: 1) increased thigmotaxis in the Open Field (OF), yet; 2) reduced closed-arm, and increased open-arm, time in the Elevated Plus Maze (EPM). Their ostensibly-anxiogenic OF profile, yet ostensibly-anxiolytic EPM profile, could hint at altered cortical mechanisms affecting decision-making (e.g. disinhibition), rather than simple core deficits in emotional motivation. Consistent with this possibility, alterations in microstructure, glutamatergic-dependent gamma oscillations, and glutamatergic gene expression were all observed in the prefrontal cortex, but not the amygdala, of AppNL-G-F knock-in mice. Thus, insoluble A{beta} overexpression drives prefrontal cortical alterations, potentially underlying changes in social and anxiety-related behavioural tasks.\n\nHighlightsO_LIAppNL-G-F KI mice displayed differing anxiety behaviours in two tests of anxiety.\nC_LIO_LIPrefrontal gamma was no longer NMDA-receptor dependent in AppNL-G-F KI mice.\nC_LIO_LIPrefrontal expression of Grin2b was reduced in AppNL-G-F KI mice.\nC_LIO_LIDTI found structural alterations in the hippocampus and prefrontal cortex in AppNL-G-F KI mice.\nC_LI

neuroscience↗

bioRxiv2018

Within-subject combination of diffusion tensor MRI and CLARITY reveals alterations in the social brain network resulting from α-neurexin II deletion

BackgroundOf the many genetic mutations known to increase the risk of autism spectrum disorder, a large proportion cluster upon synaptic proteins. One such family of presynaptic proteins are the neurexins (NRXN), and recent genetic and mouse evidence has suggested a causative role for NRXN2 in generating altered social behaviours. Autism has been conceptualised as a disorder of atypical connectivity, yet how single-gene mutations affect such connectivity remains under-explored. To attempt to address this, we have developed a quantitative analysis of microstructure and structural connectivity leveraging diffusion tensor MRI (DTI) with high-resolution 3D imaging in optically cleared (CLARITY) brain tissue in the same mouse, applied here to the Nrxn2 knockout (KO) model. MethodsFixed brains of Nrxn2 KO mice underwent DTI using 9.4T MRI, and diffusion properties of socially-relevant brain regions were quantified. The same tissue was then subjected to CLARITY to immunolabel axons and cell bodies, which were also quantified. ResultsDTI revealed decreases in fractional anisotropy and increases in apparent diffusion coefficient in the amygdala (including the basolateral nuclei), the anterior cingulate cortex, the orbitofrontal cortex and the hippocampus. Radial diffusivity of the anterior cingulate cortex and orbitofrontal cortex was significantly increased in Nrxn2 KO mice, as were tracts between the amygdala and the orbitofrontal cortex. Using CLARITY, we find significantly altered axonal orientation in the amygdala, orbitofrontal cortex and the anterior cingulate cortex, which was unrelated to cell density. ConclusionsOur findings demonstrate that deleting a single neurexin gene (Nrxn2) induces atypical structural connectivity within socially-relevant brain regions. More generally, our combined within-subject DTI and CLARITY approach presents a new, more sensitive method of revealing hitherto undetectable differences in the autistic brain.

neuroscience↗