Biology subjects

Weisz, F.

Publications and source records attributed to Weisz, F..

5 recordsLinked to original sources

bioRxiv2024

Synaptic communication within the microcircuits of pyramidal neurons and basket cells in the mouse prefrontal cortex

Basket cells are inhibitory interneurons in cortical structures with the potential to efficiently control the activity of their postsynaptic partners. Although their contribution to higher order cognitive functions associated with the medial prefrontal cortex (mPFC) relies on the characteristics of their synaptic connections, the way they are embedded into local circuits is still not fully uncovered. Here, we determined the synaptic properties of excitatory and inhibitory connections between pyramidal neurons (PNs), cholecystokinin-containing basket cells (CCKBCs) and parvalbumin-containing basket cells (PVBCs) in the mouse mPFC. By performing paired recordings, we revealed that PVBCs receive larger unitary excitatory postsynaptic currents from PNs with shorter latency and faster kinetic properties compared to events evoked in CCKBCs. Also, unitary inhibitory postsynaptic currents in PNs were more reliably evoked by PVBCs than by CCKBCs yet the former connections showed profound short-term depression. Moreover, we demonstrated that CCKBCs and PVBCs in the mPFC are mutually interconnected with each other. As alterations in PVBC function have been linked to neurological and psychiatric conditions like Alzheimers disease and schizophrenia and CCKBC vulnerability might play a role in mood disorders, a deeper understanding of the general features of basket cell synapses could serve as a reference point for future investigations with therapeutic objectives.

neuroscience↗

bioRxiv2024

Imaging Giardia intestinalis cellular organisation using expansion microscopy revealed atypical centrin localisation.

Advanced imaging of microorganisms, including protists, is challenging due to their small size. Specimen expansion prior to imaging is thus beneficial to increase resolution and cellular details. Here, we present a sample preparation workflow for improved observations of the single-celled eukaryotic pathogen Giardia intestinalis (Excavata, Metamonada). The binucleated trophozoites colonize the small intestine of humans and animals and cause a diarrhoeal disease. Their remarkable morphology includes two nuclei and a pronounced microtubular cytoskeleton enabling cell motility, attachment and proliferation. By use of expansion and confocal microscopy, we resolved in a great detail subcellular structures and organelles of the parasite cell. The acquired spatial resolution of 43 nm enabled novel observations of centrin localisation at Giardia basal bodies. Interestingly, non-luminal centrin localization between the Giardia basal bodies was observed, which is an atypical eukaryotic arrangement. Our protocol includes antibody staining and can be used for the localisation of epitope-tagged proteins, as well as for differential organelle labelling by amino reactive esters. This fast and simple protocol is suitable for routine use without a superresolution microscopy equipment.

microbiology↗

bioRxiv2023

Diversity and connectivity of principal neurons in the lateral and basal nuclei of the mouse amygdala

The basolateral amygdala is a non-layered cortical structure playing a role in various cognitive processes. Despite many studies focusing on local information processing within the circuits of the basolateral amygdala, the characteristics of excitatory principal neurons (PNs) are still not fully revealed. Here, we combined neuroanatomical, electrophysiological, and tracing techniques to determine the single-cell features, dendritic and axonal projections of PNs within the lateral (LA) and basal amygdala (BA). Using a mouse reporter line, we found that cholecystokinin (CCK) expression defines two spatially and functionally segregated groups of PNs both in the LA and BA. PNs in CCK-positive (CCK+) areas of the LA (LAa) had small somata and short dendrites which matched their single-cell electrophysiological properties. PNs in CCK-negative (CCK-) areas of the LA (LAp) and all BA had similarly ramified dendrites and single-cell features with some differences. Importantly, the dendritic arbors of PNs were restricted to the subnuclei defined by CCK expression, which corresponded to various extra-amygdalar afferents indicating specific inputs on distinct PN groups. Axonal arborization patterns of PNs within the basolateral amygdala and surrounding areas showed consistency to their soma location. For instance, BA PNs that projected to the medial prefrontal cortex but not to the lateral nucleus of the central amygdala were present in CCK+ areas. In contrast, those BA PNs that projected to the lateral part of the central nucleus were found in the subnucleus lacking CCK. Our study revealed that the basolateral amygdala is composed of functionally different subnuclei with specific inputs and outputs. This structural arrangement may empower the LA and BA to flexibly channel processed information toward their downstream regions, which can be a key requirement for diverse amygdala functions in cognitive operation.

neuroscience↗

bioRxiv2023

Structural organisation of perisomatic inhibition in the mouse medial prefrontal cortex

Perisomatic inhibition profoundly controls neural function. However, the structural organisation of inhibitory circuits giving rise to the perisomatic inhibition in the higher-order cortices is not completely known. Here, we performed a comprehensive analysis of those GABAergic cells in the medial prefrontal cortex (mPFC) that provide inputs onto the somata and proximal dendrites of pyramidal neurons. Our results show that most GABAergic axonal varicosities contacting the perisomatic region of superficial (layer 2/3) and deep (layer 5) pyramidal cells express parvalbumin (PV) or cannabinoid receptor type 1 (CB1). Further, we found that the ratio of PV/CB1 GABAergic inputs is larger on the somatic membrane surface of pyramidal tract neurons in comparison to those projecting to the contralateral hemisphere. Our morphological analysis of in vitro labelled PV+ basket cells (PVBC) and CCK/CB1+ basket cells (CCKBC) revealed differences in many features. PVBC dendrites and axons arborized preferentially within the layer where their soma was located. In contrast, the axons of CCKBCs expanded throughout layers, though their dendrites were found preferentially either in superficial or deep layers. Finally, using anterograde trans-synaptic tracing we observed that PVBCs are preferentially innervated by thalamic and basal amygdala afferents in layer 5a and 5b, respectively. Thus, our results suggest that PVBCs can control the local circuit operation in a layer-specific manner via their characteristic arborization, while CCKBCs rather provide cross-layer inhibition in the mPFC. Significance StatementInhibitory cells in cortical circuits are crucial for the precise control of local network activity. Nevertheless, in higher-order cortical areas that are involved in cognitive functions like decision making, working memory and cognitive flexibility, the structural organisation of inhibitory cell circuits is not completely understood. In this study we show that perisomatic inhibitory control of excitatory cells in the medial prefrontal cortex is performed by two types of basket cells endowed with different morphological properties that provide inhibitory inputs with distinct layer specificity on cells projecting to disparate areas. Revealing this difference in innervation strategy of the two basket cell types is a key step towards understanding how they fulfil their distinct roles in cortical network operations.

neuroscience↗

bioRxiv2021

Cas9-mediated genome editing in Giardia intestinalis

CRISPR/Cas9 system is an extremely powerful technique that is extensively used for various genome modifications in different organisms including parasitic protists. Giardia intestinalis, a protist parasite infecting about 280 million people around the world each year, has been eluding the routine use of CRISPR/Cas9 for generating knock-out cell lines due to the presence of four copies of each gene in its two nuclei. Apart from single exception employing rather laborious Cre/loxP system, no full knock-out cell line has been established yet. In this work, we show the ability of in-vitro assembled CRISPR/Cas9 components to successfully edit the genome of G. intestinalis. We further established a cell line stably expressing Cas9 in both G. intestinalis nuclei. Subsequent introduction of a template for homologous recombination containing the transcription units for the resistance marker and gRNA resulted in the removal of all gene copies at once for three independent experimental genes, mem, cwp1 and mlf1. The method was also applicable for the incomplete disruption of an essential gene, as documented by markedly decreased expression of tom40. Finally, testing the efficiency of Cas9-induced recombination revealed that homologous arms as short as 150 bp can be sufficient to establish a full knock-out cell line in G. intestinalis.

cell biology↗