Biology subjects

Farkas, I.

Publications and source records attributed to Farkas, I..

8 recordsLinked to original sources

bioRxiv2026

Age-related loss of brain demyelinating and remyelinating potential is overcome by microglia renewal

Multiple sclerosis (MS) is an immune-mediated demyelinating disease, with progressive neurodegeneration that is refractory to current therapies. Here, we identify microglia aging as a major factor responsible for age-related loss of beneficial demyelinating and remyelinating brain functions. Brain transcriptomics and in situ spatial gene transcription analysis revealed significant oligodendrocyte loss in both young and aged mice during cuprizone-induced experimental demyelination, but impaired microglial activation in aged mice. Age-related defects in microglial activation were associated with reduced clearance of dead myelin and accumulation of lipid droplets, and impaired remyelination, implying exhaustion of microglial function in the aged mouse brain. Transcriptomic analysis of human brain samples from MS donors with matched disease course and severity and with chronic active and inactive lesions, validated that microglial activation is strongly reduced with increasing age. To investigate microglial responses after repeated demyelinating insults and their direct impact on myelin integrity, we established an experimental model of repeated demyelinating episodes in young and aged mice to recapitulate MS features. Notably, aged mice developed a progressive neuroinflammatory response following sequential demyelinating episodes, in contrast to the alternating cycles of demyelination and remyelination reminiscent of relapsing-remitting MS that were observed in young mice. Microglia depletion and repopulation using a CSF1R antagonist recovered demyelination-remyelination capacity in aged mice. The results indicate that microglia aging is a major determinant in the pathogenesis of progressive MS, and that microglia replacement represents a promising therapeutic approach.

immunology↗

bioRxiv2023

Estrogen-dependent development and transcriptome regulation of the lateral septal kisspeptin system

While hypothalamic kisspeptin (KP) neurons play well-established roles in the estrogen-dependent regulation of reproduction, little is known about extrahypothalamic KP-producing (KPLS) neurons of the lateral septum. Our studies on Kiss1-Cre/ZsGreen transgenic mice revealed that KP expression in the LS is linked to puberty and estrogen receptor signaling and neurons reach higher numbers in females. Viral tracing uncovered that KPLS axons abundantly innervate gonadotropin-releasing hormone neurons, the hypothalamic supramammillary nucleus and various limbic structures. RNA-Seq analysis of laser-microdissected KPLS neurons revealed a unique transcriptome profile containing markers of GABAergic and peptidergic (Penk, Cartpt, Vgf) cotransmission and 571 estrogen-dependent transcripts. Immunohistochemical evidence for homologous neurons in the post mortem human brain indicate that the KPLS neurons may contribute to evolutionarily conserved regulatory mechanisms. The KPLS system now emerges as a novel player in the estrogen-dependent control of gonadotropin-releasing hormone neurons and currently unknown hypothalamic and limbic functions requiring clarification.

neuroscience↗

bioRxiv2023

Central cholinergic regulation of the GnRH system: involvement of ACh/GABA co-transmission

Gonadotropin-releasing hormone (GnRH)-synthesizing neurons orchestrate reproduction centrally. Early studies have proposed the contribution of acetylcholine (ACh) to hypothalamic control of reproduction, although the causal mechanisms have not been clarified. Here, we report that in vivo pharmacogenetic activation of the cholinergic system increased the secretion of luteinizing hormone (LH) in orchidectomized mice. 3DISCO immunocytochemistry and electron microscopy revealed the innervation of GnRH neurons by cholinergic axons. Retrograde viral labeling initiated from GnRH-Cre neurons identified the medial septum and the diagonal band of Broca as exclusive sites of origin for cholinergic afferents of GnRH neurons. In acute brain slices, ACh and the ACh receptor (AChR) agonist carbachol evoked a biphasic effect on the firing rate in GnRH neurons, first increasing and then diminishing it. In the presence of tetrodotoxin, carbachol induced an inward current, followed by a decline in the frequency of mPSCs, indicating a direct influence on GnRH cells. RT-PCR and whole-cell patch-clamp studies revealed that GnRH neurons expressed both nicotinic (4{beta}2, 3{beta}4, and 7) and muscarinic (M1-M5) ACh receptors. The nicotinic AChRs contributed to the nicotine-elicited inward current and the rise in firing rate. Muscarine via M1 and M3 receptors increased, while via M2 and M4 reduced the frequency of both miniature postsynaptic currents (mPSCs) and firing. Optogenetic activation of channelrhodopsin-2-tagged cholinergic axons modified GnRH neuronal activity and evoked co-transmission of ACh and GABA from a subpopulation of boutons. These findings confirm that the central cholinergic system immensely regulates GnRH neurons and activates the HPG-axis via ACh and ACh/GABA neurotransmissions. Significance statementCholinergic drugs influence reproduction centrally, although the exact neuronal targets and regulatory mechanisms remain unsettled. We found that pharmacogenetic activation of the cholinergic system in vivo evoked an augmented LH release. The study also identified cholinergic cell groups in the mouse forebrain that innervate gonadotropin-releasing hormone (GnRH) neurons, the main hypothalamic regulators of reproduction. We also determined the subtypes of nicotinic and muscarinic receptors involved in neuronal information transmission and explored how their ligands affect the electrophysiological activity of GnRH neurons. A subset of cholinergic neurons was found to co-transmit GABA, which excites GnRH cells via GABA-A receptors. The findings suggest a novel, cholinergic regulation of the adult GnRH system in male mice that activates the pituitary-gonadal axis.

physiology↗

bioRxiv2023

Development of a versatile LCM-Seq method for spatial transcriptomics of fluorescently-tagged cholinergic neuron populations

Single-cell transcriptomics are powerful tools to define neuronal cell types based on co-expressed gene clusters. Limited RNA input in these technologies necessarily compromises transcriptome coverage and accuracy of differential expression analysis. We propose that bulk RNA-sequencing of neuronal pools defined by spatial position offers an alternative strategy to overcome these technical limitations. We report an LCM-Seq method which allows deep transcriptome profiling of fluorescently-tagged neuron populations isolated with laser-capture microdissection (LCM) from histological sections of transgenic mice. Mild formaldehyde-fixation of ZsGreen marker protein, LCM sampling of [~]300 pooled neurons, followed by RNA isolation, library preparation and RNA-sequencing with methods optimized for nanogramm amounts of moderately degraded RNA enabled us to detect [~]15,000 different transcripts in fluorescently-labeled cholinergic neuron populations. The versatile LCM-Seq method showed excellent accuracy in quantitative studies, with 2,891 transcripts expressed differentially between the spatially defined and clinically relevant cholinergic neuron populations of the caudate-putamen and medial septum.

neuroscience↗

bioRxiv2022

Common signatures of differential microRNA expression in Parkinson's and Alzheimer's disease brains

BackgroundDysregulation of microRNA (miRNA)-mediated gene expression has been implicated in the pathogenesis and course of many neurodegenerative diseases including Parkinsons disease (PD). However, the functionally relevant miRNAs remain largely unknown. Previous meta-analyses on differential miRNA expression data in post-mortem PD brains have highlighted several miRNAs showing consistent and statistically significant effects. However, these meta-analyses were based on exceedingly small sample sizes. MethodsIn this study, we quantified the expression of the four most compelling PD candidate miRNAs from these meta-analyses in the superior temporal gyrus (STG) of one of the largest case-control post-mortem brain datasets available (261 samples), thereby quadruplicating previously investigated sample sizes. Furthermore, we probed for common differential miRNA expression signatures with Alzheimers disease (AD) by also analyzing these miRNAs in post-mortem STG of 190 AD patients and controls and by testing six top AD miRNAs in the PD brains. ResultsOf all ten analyzed miRNAs, PD candidate miRNA homo sapiens (hsa-) miR-132-3p showed evidence for differential expression in both PD (p=4.89E-06) and AD (p=3.20E-24), and AD miRNAs hsa-miR-132-5p (p=4.52E-06) and hsa-miR-129-5p (p=0.0379) showed evidence for differential expression in PD. Combining these novel data with previously published data substantially improved the statistical support (=3.85E-03 using Bonferroni correction) of the corresponding meta-analyses clearly and compellingly implicating these miRNAs in both PD and AD. Furthermore, hsa-miR-132-3p/-5p (but not hsa-miR-129-5p) showed association with neuropathological Braak PD staging (p=3.51E-03/p=0.0117), suggesting that these miRNAs may play a role in -synuclein aggregation beyond the early disease phase. ConclusionsOur study represents the largest independent assessment of recently highlighted candidate brain miRNAs in PD and AD post-mortem brain samples, to date. Our results implicate hsa-miR-132-3p/-5p and hsa-miR-129-5p to be differentially expressed in both PD and AD brains, potentially pinpointing shared pathogenic mechanisms across these neurodegenerative diseases.

neuroscience↗

bioRxiv2022

A thalamo-preoptic pathway promoting social touch

Social touch is an important form of communication, it is still unknown how it is processed. Here, we discovered a functional role for a neuronal pathway projecting from the posterior intralaminar thalamic nucleus (PIL) to the medial preoptic area (MPOA) in controlling social contact. Neurons in the PIL and the MPOA were activated by physical contact between female rodents and also by chemogenetic stimulation of PIL neurons. Chemogenetic stimulation of PIL neurons tagged by social contact experience increased direct physical interactions between familiar female rats without affecting other forms of social behavior. Furthermore, selective stimulation of the PIL-MPOA pathway, and the local activation of PIL terminals within the MPOA, elevated direct social contact between the animals suggesting the role of pathway-specific activated cell assemblies. Neurons projecting from the PIL to the MPOA contain the neuropeptide parathyroid hormone 2 (PTH2). The expression of the peptide was induced by social housing, the presence of PTH2 receptor was identified in MPOA neurons, and local injection of PTH2 increased the firing rate of identified preoptic area GABAergic neurons via the PTH2 receptor suggesting that PTH2 acts as a neurotransmitter in the PIL-MPOA pathway. We also found a homologous PIL to MPOA neuronal pathway in the human brain. Altogether, we discovered a direct thalamo-preoptic pathway, which bypasses the cerebral cortex and controls social touch. This pathway originates in neurons expressing PTH2, a neuropeptide recently shown in fish to respond to the social environment. These observations provide evidence for common evolutionary-conserved PTH2-containing social-touch specific engram circuits.

neuroscience↗

bioRxiv2021

The cryptic gonadotropin-releasing hormone neuronal system of human basal ganglia

Human reproduction is controlled by [~]2,000 hypothalamic gonadotropin-releasing hormone (GnRH) neurons. Here we report the discovery and characterization of additional 150-200,000 GnRH-synthesizing cells in the human basal ganglia and basal forebrain. Extrahypothalamic GnRH neurons were cholinergic. Though undetectable in adult rodents, the GnRH-GFP transgene was expressed transiently by caudate-putamen cholinergic interneurons in newborn transgenic mice. In slice electrophysiological studies, GnRH inhibited these interneurons via GnRHR1 autoreceptors. Whole-transcriptome analysis of cholinergic interneurons and medium spiny projection neurons laser-microdissected from the human putamen confirmed selective expression of GNRH1 and GNRHR1 autoreceptors in cholinergic cells and uncovered the detailed transcriptome profile and molecular connectome of these two cell types. Higher- order non-reproductive functions regulated by GnRH under physiological conditions in the human basal ganglia and basal forebrain require clarification. GnRH/GnRHR1 signaling as a potential therapeutic target in the treatment of neurodegenerative disorders affecting cholinergic neurocircuitries, including Parkinsons and Alzheimers diseases, needs to be explored.

cell biology↗

bioRxiv2020

Somatostatin neurons of the bed nucleus of stria terminalis enhance associative fear memory consolidation in mice

Excessive fear learning and extinction-resistant fear memories are core symptoms of anxiety and trauma-related disorders. Despite significant evidence from clinical studies reporting hyperactivity of the bed nucleus of stria terminalis (BNST) under these conditions, the role of BNST in fear learning and expression is still not clarified. Here, we tested how BNST modulates fear learning in mice using a chemogenetic approach. Activation of GABAergic neurons of BNST during fear acquisition, more specifically the consolidation phase, resulted in enhanced cued fear recall. Importantly, BNST activation had no acute impact on fear expression during conditioning or recalls, but it enhanced cued fear recall subsequently, potentially via altered activity of downstream regions as indicated by c-Fos. Enhanced fear memory consolidation could be replicated by selectively activating somatostatin neurons (but not corticotropin releasing factor neurons), suggesting significant modulation of fear memory strength by specific circuits of BNST.

neuroscience↗