Biology subjects

Mätlik, K.

Publications and source records attributed to Mätlik, K..

12 recordsLinked to original sources

bioRxiv2026

Long-term maintenance of H3K27me3 in postmitotic neurons is dispensable for gene expression regulation

Neuronal maturation is associated with extensive changes in gene expression and chromatin organization. However, the molecular mechanisms that control the epigenetic landscape in terminally differentiated neurons remain poorly understood. Here, we show that maturing cerebellar granule cells undergo a striking and specific increase in the levels of the repressive histone modification H3K27me3 across different genomic regions, including individual genes, broad intergenic regions, and gene clusters. The accumulation of H3K27me3 coincides with a developmental switch from EZH2 to EZH1 and colocalizes with H3K36me2 and DNA non-CpG methylation. Using mice with a conditional deletion in the catalytic domain of EZH1, we demonstrate that the maintenance of H3K27me3 in mature neurons depends on EZH1. Unexpectedly, an almost complete loss of H3K27me3 in postmitotic GCs induces minimal changes in gene expression and chromatin accessibility at 7 months of age. Using single-nucleus RNA sequencing (snRNAseq) from the mouse neocortex, we show that, similarly to GCs, the loss of EZH1-mediated H3K27me3 also has a minimal impact on cortical neuron gene expression. The amino acid composition of EZH1 suggests reduced sensitivity to H3K36 methylation, providing a potential basis for its activity in chromatin contexts that are not permissive for EZH2. Together, our results show that a postmitotic switch from EZH2 to EZH1 establishes novel chromatin domains in neurons with a minimal role in transcriptional maintenance.

molecular biology↗

bioRxiv2026

GPCRs as Targets for Human Brain Modulation: A Multi-omic Atlas of Cell-Type Specific Expression

G Protein coupled receptors (GPCRs) are the largest class of clinically validated drug targets with nearly 35% of all approved therapeutic agents acting on these receptors. To further explore the potential of this class of receptors for the development of circuit-specific and mechanism-based therapeutic strategies for neurological disorders, we focused on GPCRs with no known endogenous ligand, orphan GPCRs (oGPCRs), because knowledge of their functions in the human brain remains rudimentary. Here, we utilized fluorescence activated nuclear sorting and sequencing (FANSseq) to generate deep molecular profiles of cell type specific nuclei isolated from post-mortem brains to generate an atlas of oGPCR expression across multiple regions of the human brain. We identified 22 oGPCRs that displayed selective cell-type enrichment both in RNA transcript expression and chromatin accessibility. We further validated each of these targets for cell-type specific expression in human brains and developed an open-source web atlas of all oGPCR expression in the human brain to serve as a neuro-resource for the broader scientific community. These studies reveal novel cell-type specific expression patterns of several oGPCRs, suggest potential endogenous roles for these receptors, and identify validated candidates for cell-type specific neuromodulation of the human brain. One Sentence SummaryThis study presents an atlas of orphan GPCR expression across the human brain for translational targeting.

neuroscience↗

bioRxiv2026

Loss of interruption in the HTT CAG repeat is associated with increased somatic expansion and loss of medium spiny neurons in HD

Synonymous loss of interruption variants in the expanded CAG repeat sequence of Huntingtin (HTT) accelerate the clinical onset and progression of Huntington disease (HD). Medium spiny neurons (MSNs) are gradually lost in HD and undergo selective somatic CAG expansion, but it is unclear how CAG expansion in MSNs relates to HD pathology. Here, we show that MSNs with large (111-150 CAG) and very large (>150 CAG) somatic expansions are rare in early manifest HD, but accumulate in proportion with duration of disease and inherited CAG repeat length. In patients with the deleterious CAG-CCG loss-of-interruption (CAG-CCG LOI) modifier, the proportion of MSNs with large and very large expansions is increased [~]5-fold despite reduced small somatic expansions in blood, and direct caudate MSN counts are reduced. Our findings suggest that increased somatic CAG expansion contributes to accelerated striatal MSN pathology and hastened onset of HD, but that MSNs with very large genomic CAG expansions can persist among surviving neurons of the HD brain.

neuroscience↗

bioRxiv2025

Epigenetic mechanisms governing cell type specific somatic expansion and toxicity in Huntington's disease

Huntingtons disease (HD) is characterized by neuronal dysfunction and degeneration that varies markedly by brain region and cell type. Using high-resolution epigenetic profiling of postmortem human cell types we identify a pathogenic cascade linking cell type specific enhancer activity to somatic CAG expansion, and toxicity to epigenetic dysregulation. Enhancers regulating mismatch-repair (MMR) gene expression explain the specificity of expansion. In the second, toxic phase of HD we identify two distinct epigenetic mechanisms that disrupt regulation of hundreds of genes in the majority of HD MSNs, including several that cause haploinsufficient neurological disorders. Together, these data unify enhancer function, impaired DNA demethylation, and transcriptional dysregulation into a single model highlighting therapeutic opportunities that combine inhibition of somatic CAG expansion with restoration of neuronal DNA demethylation.

neuroscience↗

bioRxiv2024

Serotonin system development and adult function are regulated by GDNF

Cognitive functions, neuropsychiatric disorders and behaviors from feeding to mood relate to the serotonin (5-hydroxytryptamine; 5-HT) system. We report that expression of glial cell line-derived neurotrophic factor (GDNF), a known potent stimulator of the brain dopamine system, correlates with serotonergic markers in humans, and increased GDNF defines a subset of psychiatric patients with a characteristic 5-HT-related gene expression pattern. A similar [~]1.5- to 2-fold upregulation of endogenous GDNF expression in mice increases brain 5-HT levels and function, both developmentally and during adulthood, and modulates response to fluoxetine. Notably, increasing GDNF more than approximately 2-fold does not increase 5-HT further and instead produces an inverted U-shaped curve of 5-HT levels, suggesting why the GDNF/5-HT correlation has remained controversial. Collectively, our data indicate that GDNF levels fine-tune 5-HT system development and adult function while excess GDNF exclusively associates with neuropsychiatric illness, making it an important target for future research.

neuroscience↗

bioRxiv2024

Mice lacking Astn2 have ASD-like behaviors and altered cerebellar circuit properties

Astrotactin 2 (ASTN2) is a transmembrane neuronal protein highly expressed in the cerebellum that functions in receptor trafficking and modulates cerebellar Purkinje cell (PC) synaptic activity. We recently reported a family with a paternally inherited intragenic ASTN2 duplication with a range of neurodevelopmental disorders, including autism spectrum disorder (ASD), learning difficulties, and speech and language delay. To provide a genetic model for the role of the cerebellum in ASD-related behaviors and study the role of ASTN2 in cerebellar circuit function, we generated global and PC-specific conditional Astn2 knockout (KO and cKO, respectively) mouse lines. Astn2 KO mice exhibit strong ASD-related behavioral phenotypes, including a marked decrease in separation-induced pup ultrasonic vocalization calls, hyperactivity and repetitive behaviors, altered social behaviors, and impaired cerebellar-dependent eyeblink conditioning. Hyperactivity and repetitive behaviors were also prominent in Astn2 cKO animals. By Golgi staining, Astn2 KO PCs have region-specific changes in dendritic spine density and filopodia numbers. Proteomic analysis of Astn2 KO cerebellum reveals a marked upregulation of ASTN2 family member, ASTN1, a neuron-glial adhesion protein. Immunohistochemistry and electron microscopy demonstrates a significant increase in Bergmann glia volume in the molecular layer of Astn2 KO animals. Electrophysiological experiments indicate a reduced frequency of spontaneous excitatory postsynaptic currents (EPSCs), as well as increased amplitudes of both spontaneous EPSCs and inhibitory postsynaptic currents (IPSCs) in the Astn2 KO animals, suggesting that pre- and postsynaptic components of synaptic transmission are altered. Thus, ASTN2 regulates ASD-like behaviors and cerebellar circuit properties.

neuroscience↗

bioRxiv2023

Cell Type Specific CAG Repeat Expansion and Toxicity of Mutant Huntingtin in Human Striatal and Cerebellar Cell Types

Brain region-specific degeneration and somatic expansions of the mutant Huntingtin (mHTT) CAG tract are key features of Huntingtons disease (HD). However, the relationships between CAG expansions, death of specific cell types, and molecular events associated with these processes are not established. Here we employed fluorescence-activated nuclear sorting (FANS) and deep molecular profiling to gain insight into the properties of cell types of the human striatum and cerebellum in HD and control donors. CAG expansions arise in striatal medium spiny neurons (MSNs) and cholinergic interneurons, in cerebellar Purkinje neurons, and at mATXN3 in MSNs from SCA3 donors. CAG expansions in MSNs are associated with higher levels of MSH2 and MSH3 (forming MutS{beta}), which can inhibit nucleolytic excision of CAG slip-outs by FAN1 in a concentration-dependent manner. Our data indicate that ongoing CAG expansions are not sufficient for cell death, and identify transcriptional changes associated with somatic CAG expansions and striatal toxicity.

neuroscience↗

bioRxiv2023

Layer 5a Corticostriatal Projection Neurons are Selectively Vulnerable in Huntington's Disease

The properties of the cell types that are selectively vulnerable in Huntingtons disease (HD) cortex, the nature of somatic CAG expansions of mHTT in these cells, and their importance in CNS circuitry have not been delineated. Here we employed serial fluorescence activated nuclear sorting (sFANS), deep molecular profiling, and single nucleus RNA sequencing (snRNAseq) to demonstrate that layer 5a pyramidal neurons are vulnerable in primary motor cortex and other cortical areas of HD donors. Extensive mHTT-CAG expansions occur in vulnerable layer 5a pyramidal cells, and in Betz cells, layer 6a, layer 6b neurons that are resilient in HD. Retrograde tracing experiments in macaque brains identify the vulnerable layer 5a neurons as corticostriatal pyramidal cells. We propose that enhanced somatic mHTT-CAG expansion and altered synaptic function act together to cause corticostriatal disconnection and selective neuronal vulnerability in the HD cerebral cortex.

neuroscience↗

bioRxiv2023

Histone bivalency regulates the timing of cerebellar granule cell development

Developing neurons undergo a progression of morphological and gene expression changes as they transition from neuronal progenitors to mature, multipolar neurons. Here we use RNA-seq and H3K4me3 and H3K27me3 ChIP-seq to analyze how chromatin modifications control gene expression in a specific type of CNS neuron, the mouse cerebellar granule cell (GC). We find that in proliferating GC progenitors (GCPs), H3K4me3/H3K27me3 bivalency is common at neuronal genes and undergoes dynamic changes that correlate with gene expression during migration and circuit formation. Expressing a fluorescent sensor for bivalent H3K4me3 and H3K27me3 domains revealed subnuclear bivalent foci in proliferating GCPs. Inhibiting H3K27 methyltransferases EZH1 and EZH2 in vitro and in organotypic cerebellar slices dramatically altered the expression of bivalent genes and induced the downregulation of migration-related genes and upregulation of synaptic genes, inhibited glial-guided migration, and accelerated terminal differentiation. Thus, histone bivalency is required to regulate the timing of the progression from progenitor cells to mature neurons.

neuroscience↗

bioRxiv2021

Nicotinamide riboside alleviates Parkinson's disease symptoms but downregulates dopamine metabolism upon lactacystin-induced proteostasis failure

Activation of mitochondrial metabolism and proteostasis with the NAD+ precursor nicotinamide riboside (NR) has emerged as a potential therapeutic approach for neurodegenerative disorders including Parkinsons disease (PD). However, despite recently started clinical trials, studies on NR in animal models of PD are scarce. In this study, we investigated the effect of NR in multiple models of PD. In transgenic C. elegans overexpressing -synuclein, a protein of which aggregation is believed to promote PD, NR rescued PD-like phenotypes including mitochondrial dysfunction and motility defects, decreased oxidative stress, and age-related dopamine (DA) neuron loss. We found that NR eased symptoms of disease by activating the mitochondrial unfolded protein response (UPRmt) via the transcription factor atfs-1. Similarly, in a proteasome inhibitor, lactacystin, -induced mouse model of PD, NR rescued mitochondrial dysfunction and behavioural deficits caused by lactacystin lesion. However, long-term NR supplementation, in conjunction with proteasome inhibition, resulted in decreased DA levels in both the lesioned and unlesioned sides of the substantia nigra with concomitant downregulation of key genes in DA metabolism. Our results suggest specific endpoints that should be monitored in ongoing NR clinical trials.

neuroscience↗

bioRxiv2020

Tumor-free elongation of mammalian nephrogenesis by excess fetal GDNF

Due to poor regenerative capacity of adult kidneys, nephron endowment defined by the nephrogenic program during the fetal period dictates renal and related cardiovascular health throughout life. We show that the neurotropic factor GDNF, which is in clinical trials for Parkinsons disease, is capable of prolonging the nephrogenic program beyond its normal cessation without increasing the risk of kidney tumors. Our data demonstrates that excess GDNF expands the nephrogenic program by maintaining nephron progenitors and nephrogenesis in postnatal mouse kidneys. GDNF, through its transcriptional targets excreted from the adjacent epithelium, has a major effect on nephron progenitor self-renewal and maintenance; abnormally high GDNF inhibits nephron progenitor proliferation, but lowering its level normalizes the nephrogenic program to that permissive for nephron progenitor self-renewal and differentiation. Based on our results, we propose that the lifespan of nephron progenitors is determined by mechanisms related to perception of GDNF and other signaling levels.

developmental biology↗

bioRxiv2019

Gene Knock Up via 3’UTR editing to study gene function in vivo

Currently available genetic tools do not allow researchers to upregulate ( Knock Up) the levels of a given protein while retaining its cell-type-specific regulation. As a result, we have limited ability to develop overexpression-related disease models, to study the contribution of single genes in diseases caused by copy number variations and to identify disease pathways for drug targets. Here we develop two approaches for endogenous gene upregulation: conditional Knock Up (cKU) utilizing the Cre/lox system, and CRISPR-Cas9 mediated gene Knock Up (KU) in wild-type mouse embryos and human cells. Using glial cell line derived neurotrophic factor (GDNF) as a proof of concept, we show that both approaches resulted in upregulation of endogenous GDNF levels without disturbing Gdnfs expression pattern. Furthermore, CNS-specific GDNF cKU resulted in dopaminergic abnormalities and schizophrenia-like phenotypes. Our results suggest that gene Knock Up can reveal unknown gene functions and provide novel entry points for studying neurological disease.

neuroscience↗