Biology subjects

Pawlak, R.

Publications and source records attributed to Pawlak, R..

4 recordsLinked to original sources

bioRxiv2026

Perineuronal nets in the bed nucleus of stria terminalis mediate stress-induced anxiety behaviour in adult male mice

Anxiety disorders affect an estimated 301.4 million people globally. However, they remain among the most challenging conditions to treat, with only around half of patients reporting a 50% or greater reduction in their symptoms. The discovery of novel and more effective treatments therefore requires a better understanding of the underlying mechanisms of anxiety at both the circuit and cellular levels. Stress induces aberrant changes in neuronal plasticity across brain regions within the anxiety circuitry including the bed nucleus of the stria terminalis (BNST). One mechanism through which synaptic plasticity is regulated is the organisation of perineuronal nets (PNNs), specialised extracellular matrix structures that are highly sensitive to stress. In rodent models, stress is associated with a reduction in PNN number and/or decreased Wisteria floribunda Agglutinin (WFA) labelling in limbic areas. However, the development of PNNs within the BNST and their role in the stress responsiveness remain largely unknown. In the current study we investigated the spatiotemporal development of PNNs within the BNST of male mice, where they first appear at P30 and continue to mature into adulthood, reaching their highest expression at P210 and specifically within the anteromedial BNST. We further showed that stress-induced anxiety is associated with a reduction in PNN number and significant changes to PNN fine structure including increased leakiness in the anteromedial BNST. Most importantly, enzymatic removal of PNNs by chondroitinase ABC in the mouse anteromedial BNST exacerbated behavioural responses to acute stress as demonstrated by increased anxiety-like behaviour. Collectively, these results highlight an indispensable role for PNNs within the anteromedial BNST in mediating a healthy emotional response to psychosocial stress.

neuroscience↗

bioRxiv2025

Lcn2 deficiency leads to social impairments independent of maternal immune activation.

Maternal infection during pregnancy is a well-established risk factor for neurodevelopmental disorders (NDDs), yet the underlying molecular mechanisms remain poorly understood. Lipocalin-2 (Lcn2), an innate immune protein that is highly upregulated during infection, also affects neuronal and glial function. This study investigates the role of Lcn2 in shaping brain development, particularly after maternal immune activation (MIA). To mimic maternal infection, pregnant mice received intraperitoneal injections of either lipopolysaccharide (LPS) or saline on embryonic days 16 to 18 to model infection during the second trimester of pregnancy in humans. We first showed that Lcn2 mRNA is expressed in the fetal brain and that MIA significantly upregulates Lcn2 mRNA and protein in the hippocampus and neocortex of both sexes. To assess functional relevance, we employed Lcn2 heterozygous females to generate wild-type and Lcn2 KO offspring from the MIA and control groups. Both female and male offspring underwent a battery of behavioral assays. Lcn2 deletion and MIA independently induced deficits in social behavior and increased repetitive behavior phenotypes relevant to NDDs in adult animals. However, their combination did not exacerbate these effects, suggesting an occlusion effect. Interestingly, no deficits were observed in the learning and memory task. To investigate potential shared molecular mechanisms, we performed RNA sequencing of the fetal forebrain 4 hours after the final LPS injection. This analysis revealed an overlapping group of differentially expressed genes in the Lcn2 KO and MIA groups, indicating convergence on similar transcriptional pathways that may underlie the observed behavioral phenotypes. These results suggest that while Lcn2 may not mediate the pathological effects of prenatal immune challenge, it plays a critical role in normal brain development.

neuroscience↗

bioRxiv2021

The sodium leak channel NALCN encodes the major background sodium ion conductance in murine anterior pituitary cells

The pituitary gland produces and secretes a variety of hormones that are essential to life, such as for the regulation of growth and development, metabolism, reproduction, and the stress response. This is achieved through an intricate signalling interplay between the brain and peripheral feedback signals that shapes pituitary cell excitability by regulating ion channel properties of these cells. In addition, endocrine anterior pituitary cells fire action potentials spontaneously to regulate intracellular calcium ([Ca2+]i) level, an essential signalling conduit for hormonal secretion. To this end, pituitary cells have to critically regulate their resting membrane potential (RMP) close to firing threshold, but the molecular identity of the ionic mechanisms involved remains largely unknown. Here, we revealed that the sodium leak channel NALCN, known to modulate neuronal excitability elsewhere in the brain, acts to regulate excitability in the mouse anterior endocrine pituitary cells. Using viral transduction combined with powerful electrophysiology methods and calcium imaging, we show that NALCN forms the major Na+ leak conductance in these cells, appropriately tuning cellular RMP for sustaining spontaneous firing activity. Genetic interruption of NALCN channel activity drastically hyperpolarised the cells, suppressing firing and ([Ca2+]i) oscillations. Remarkably, we uncover that NALCN conductance formed a very small fraction of the total cell conductance, but yet had a profound impact on pituitary cell excitability. Our results also provide a possible mechanism through which hypothalamic and hormone feedback signals can powerfully affect pituitary activity to influence hormonal function.

physiology↗

bioRxiv2021

Plasmin-mediated cleavage of EphA4 at central amygdala inhibitory synapses controls anxiety

Severe stress can trigger complex behavioural changes such as high anxiety (1). Inhibitory GABA-ergic interneurons in the lateral division of the central amygdala (CEl) control anxiety through feedforward inhibition of their target cells in the medial division (CEm) (2, 3). In particular, PKC{delta}-positive (PKC{delta}+) interneurons in CEl are critical elements of the neuronal circuitry of fear and anxiety (3-5), but the molecular mechanisms they employ are poorly understood. Here, we show that, during stress, GABA-ergic synapses of amygdala PKC{delta}+ interneurons are regulated by a serine protease plasmin. On stress, plasmin cleaves the extracellular portion of the tyrosine kinase receptor EphA4 triggering its dissociation from gephyrin, a postsynaptic GABA-receptor anchoring protein. Dynamic EphA4/gephyrin interaction leads to modification of dendritic spine morphology and synaptic GABA-receptor expression profile. Consistent with the critical role for the plasmin/EphA4/gephyrin signalling axis in anxiogenesis, viral delivery of plasmin-resistant (prEphA4) form of EphA4 into the central amygdala prevents the development of stress-induced anxiety in mice, while the delivery of plasmin-truncated EphA4 (tEphA4) dramatically enhances this effect. Thus, our studies identify a novel, critical molecular cascade regulating GABA-ergic signalling in the central amygdala synapses that allows bidirectional switching of animal behaviour from high to low anxiety states.

neuroscience↗