MerTK is a mediator of alpha-synuclein fibril uptake by human microglia

ADNP is essential for sex-dependent hippocampal neurogenesis, through male unfolded protein response and female mitochondrial gene regulation

Essential for brain formation and protective against tauopathy, activity-dependent neuroprotective protein (ADNP) is critical for neurogenesis and cognitive functions, while regulating steroid hormone biogenesis. As such, de novo mutations in ADNP lead to syndromic autism and somatic ADNP mutations parallel Alzheimer's disease progression. Furthermore, clinical trials with the ADNP fragment NAP (the investigational drug davunetide) showed efficacy in women suffering from the tauopathy progressive supranuclear palsy and differentially boosted memory in men (spatial) and women (verbal), exhibiting prodromal Alzheimer's disease. While autism is more prevalent in boys and Alzheimer's disease in women, both involve impaired neurogenesis. Here, we asked whether ADNP sex-dependently regulates neurogenesis. Using bromodeoxyuridine (BrdU) as a marker of neurogenesis, we identified two-fold higher labeling in the hippocampal sub-ventricular zone of ADNP-intact male versus female mice. Adnp haplo-insufficient (Adnp+/-) mice or mice CRSIPR/Cas9-edited to present the most prevalent neurodevelopmental ADNP syndrome mutation, p.Tyr718* (Tyr) showed dramatic reductions in male BrdU incorporation, resulting in mutated females presenting higher labeling than males. Treatment with NAP compensated for the male reduction of BrdU labeling. Mechanistically, hippocampal RNAseq revealed male-specific Tyr down-regulation of endoplasmic reticulum unfolded protein response genes critical for sex-dependent organogenesis. Newly discovered mitochondrial accessibility of ADNP was inhibited by the Tyr718* mutation further revealing female-specific Tyr downregulation of mitochondrial ATP6. NAP moderated much of the differential expression caused by p.Tyr718*, accompanied by the down-regulation of neurotoxic, pro-inflammatory and pro-apoptotic genes. Thus, ADNP is a key regulator of sex-dependent neurogenesis that acts by controlling canonical pathways, with NAP compensating for fundamental ADNP deficiencies, striding toward clinical development targeting the ADNP syndrome and related neurodevelopmental/neurodegenerative diseases.

Irisin suppressed the progression of TBI via modulating AMPK/MerTK/autophagy and SYK/ROS/inflammatory signaling

Irisin is a hormone-like peptide secreted by muscle tissues and generated by hydrolysis of type III fibronectin domain-containing protein 5 by proteolytic hydrolases. Whether Irisin has a potential protective role in traumatic brain injury (TBI). In this study, we will investigate the relevant research progress of Irisin's protective role in traumatic brain injury (TBI) in recent years in terms of attenuating oxidative stress, inhibiting pyroptosis, suppressing inflammatory response, and improving autophagy, with the aim of providing valuable references for the diagnosis and treatment of traumatic brain injury (TBI). Utilize bioinformatics analysis to study the interactions between genes in TBI (Traumatic Brain Injury). Construct a TBI mouse model to observe the effects of Irisin on TBI. The Morris water maze test is used to assess the learning and spatial memory abilities of mice, TUNEL fluorescence is used to detect cell apoptosis, Nissl staining is employed to observe the survival of hippocampal neurons in mice, and HE staining is used to observe the extent of brain injury in mice. Western blot is used to detect protein expression in both in vivo and in vitro experiments. Q-PCR is employed to detect the levels of proteins related to autophagy/pyroptosis/inflammation. Irisin promotes MerTK overexpression by enhancing AMPK activation. Irisin can increase the expression of LC3I and Beclin-1 proteins, indicating the promotion of autophagic response. Additionally, Irisin reduces ROS levels and decreases SYK expression, thereby inhibiting the inflammatory response. Irisin improves the learning and spatial memory abilities of TBI mice and reduces cell apoptosis, as well as decreases hippocampal neuron death. HE staining shows that the brain injury in mice treated with Irisin is significantly alleviated. Irisin can enhance the expression of phosphorylated AMPK and phosphorylated MerTK proteins, promote autophagic response, and inhibit pyroptosis/inflammatory response. Correction experiments confirmed that after stimulation with an AMPK agonist, the expression of phosphorylated MerTK protein is significantly increased, autophagic response is enhanced, and pyroptosis/inflammatory response is weakened. When treated with a MerTK inhibitor during AMPK agonist stimulation, the autophagic response is weakened while pyroptosis/inflammatory response is enhanced. Irisin can inhibit the progression of traumatic brain injury by regulating AMPK/MerTK/autophagy and SYK/ROS/inflammatory signaling.

Plasma proteomic profiling reveals Parkinson's disease-associated proteins: A UK Biobank study

INTRODUCTION

The rapid advancement of proteomics has provided new insights into early detection and prediction of Parkinson's disease (PD), particularly in identifying risk factors for PD. This study aims to develop a proteomics-based model to predict the risk of PD in patients.

METHODS

We analyzed data from the UK Biobank cohort, including 52,851 PD-free participants at baseline, with a median follow-up of 15.3 years and 811 newly diagnosed PD cases. A prospective proteomic analysis was conducted to assess the predictive value of 2,923 plasma proteins, and LightGBM models were used to calculate protein importance, followed by an evaluation of the proteins' predictive performance.

RESULTS

The study found that higher levels of NEFL and MERTK were significantly associated with future PD events, while lower levels of ITGAV, BAG3, CLEC10A, ITGAM, HNMT, and TPK1 were identified as potential risk factors for PD. Notably, the axonal injury marker NEFL and the thiamine metabolism-related protein TPK1 ranked higher than other proteins in terms of importance. The combination of NEFL and TPK1 significantly enhanced the predictive accuracy of conventional clinical models, increasing the Area Under the Curve (AUC) of the full-cohort prediction model from 0.784 to 0.842 and the 5-year prediction model from 0.780 to 0.908.

CONCLUSIONS

This study provides a novel insight for screening high-risk PD populations and underscores the significant role of nutritional metabolism in PD development, offering valuable insights for precision prevention strategies.

The Influence of Changes in Microglia Development on the Plasticity of the Developing Visual Cortex Circuit in Juvenile Mice

Purpose

To investigate the role of microglial subtypes in mouse visual cortex development, focusing on ocular dominance plasticity and interactions with GABAergic neurons and the extracellular matrix.

Methods

Immunofluorescence and single-nucleus RNA-sequencing (snRNA-seq) were used to study microglia in the binocular primary visual cortex (V1) from postnatal day (P) 11 to P42. Gene ontology (GO) analysis assessed synapse organization, and the impact of microglial disruption on ocular dominance plasticity was examined. Visual evoked potentials and miniature postsynaptic current recordings are used to monitor functional changes in V1.

Results

Microglia underwent a marked expansion between P11 and P21 and stabilized after P35, coinciding with notable changes in gene expression that aligned with synaptic remodeling. GO analysis at P14 and P28 revealed significant enrichment in synaptic organization linked to microglia. Single-nucleus RNA sequencing identified six distinct microglial clusters, among which two functionally relevant subpopulations were closely linked to cortical synaptic plasticity. One cluster, enriched in inflammatory responses and endocytosis, peaked at P21, whereas another cluster, associated with synapse organization and signaling, exhibited dynamic changes after eye opening and during the critical period, significantly influencing cortical synaptic plasticity. In parallel, perineuronal nets (PNNs) and PV(+) interneuron populations increased and reached steady levels by P42, suggesting that microglia help coordinate the timing of inhibitory circuit maturation. Disrupting microglial function during the critical period impaired ocular dominance plasticity, but this effect was reversed after treatment cessation. Mechanistically, microglial depletion enhanced PV(+) interneuron numbers, elevated PNN expression, and altered synapse development.

Conclusions

Our findings highlight specific microglial subtypes as key regulators of cortical synapse development and plasticity through their interactions with PV(+) interneurons and PNNs. These insights advance our understanding of microglial contributions to visual cortex development and provide potential avenues for targeting microglial function to modulate cortical plasticity.

Haploinsufficiency of ITSN1 is associated with a substantial increased risk of Parkinson's disease

Despite its significant heritability, the genetic basis of Parkinson's disease (PD) remains incompletely understood. Here, in analyzing whole-genome sequence data from 3,809 PD cases and 247,101 controls in the UK Biobank, we discover that protein-truncating variants in ITSN1 confer a substantially increased risk of PD (p = 6.1 × 10-7; odds ratio [95% confidence interval] = 10.5 [5.2, 21.3]). We replicate this association in three independent datasets totaling 8,407 cases and 413,432 controls (combined p = 4.5 × 10-12). Notably, ITSN1 haploinsufficiency has also been associated with autism spectrum disorder, suggesting variable penetrance/expressivity. In Drosophila, we find that loss of the ITSN1 ortholog Dap160 exacerbates α-synuclein-induced neuronal toxicity and motor deficits, and in vitro assays further suggest a physical interaction between ITSN1 and α-synuclein. These results firmly establish ITSN1 as a PD risk gene with an effect size exceeding previously established loci, implicate vesicular trafficking dysfunction in PD pathogenesis, and potentially open new avenues for therapeutic development.

The night's watch: Exploring how sleep protects against neurodegeneration

Sleep loss is often regarded as an early manifestation of neurodegenerative diseases given its common occurrence and link to cognitive dysfunction. However, the precise mechanisms by which sleep disturbances contribute to neurodegeneration are not fully understood, nor is it clear why some individuals are more susceptible to these effects than others. This review addresses critical unanswered questions in the field, including whether sleep disturbances precede or result from neurodegenerative diseases, the functional significance of sleep changes during the preclinical disease phase, and the potential role of sleep homeostasis as an adaptive mechanism enhancing resilience against cognitive decline and neurodegeneration.

Neuronal FAM171A2 mediates α-synuclein fibril uptake and drives Parkinson's disease

Neuronal accumulation and spread of pathological α-synuclein (α-syn) fibrils are key events in Parkinson's disease (PD) pathophysiology. However, the neuronal mechanisms underlying the uptake of α-syn fibrils remain unclear. In this work, we identified FAM171A2 as a PD risk gene that affects α-syn aggregation. Overexpressing FAM171A2 promotes α-syn fibril endocytosis and exacerbates the spread and neurotoxicity of α-syn pathology. Neuronal-specific knockdown of FAM171A2 expression shows protective effects. Mechanistically, the FAM171A2 extracellular domain 1 interacts with the α-syn C terminus through electrostatic forces, with >1000 times more selective for fibrils. Furthermore, we identified bemcentinib as an effective blocker of FAM171A2-α-syn fibril interaction with an in vitro binding assay, in cellular models, and in mice. Our findings identified FAM171A2 as a potential receptor for the neuronal uptake of α-syn fibrils and, thus, as a therapeutic target against PD.

A Disintegrin and Metalloproteinase 17 Disrupts Bovine Macrophage MER Proto-Oncogene Tyrosine Kinase Integrity to Impede Apoptotic Cell Clearance and Promote Inflammation in Clinical Mastitis

In clinical mastitis of dairy cows, the abnormal accumulation of apoptotic cells (ACs) and subsequent secondary necrosis and inflammation pose significant concerns, with macrophage-mediated efferocytosis, crucial for ACs clearance, remaining unexplored in this context. In nonruminants, MER proto-oncogene tyrosine kinase (MERTK) receptors are essential for efferocytosis and A Disintegrin and Metalloproteinase 17 (ADAM17) is thought to play a role in regulating MERTK integrity. This study aimed to delineate the in situ role of efferocytosis in clinical mastitis, with a particular focus on the interaction between MERTK and ADAM17 in bovine macrophages. In mastitic mammary tissue, a significant accumulation of ACs was observed, along with active macrophage efferocytosis. Western blotting analysis revealed elevated expressions of MERTK and ADAM17, and immunofluorescence confirmed that MERTK is predominantly localized within CD163+ macrophages. Additionally, elevated levels of soluble MERTK (sol-MER) in serum indicated impaired integrity and functionality of MERTK. In vitro experiments with the bovine macrophage cell line Bo-mac cells selectively phagocytosed apoptotic MAC-T cells, a process associated with increased MERTK phosphorylation and an anti-inflammatory phenotype. The activation of ADAM17 by Phorbol 12-myristate 13-acetate (PMA) induced sol-Mer release and impaired efferocytosis, with these effects reversed by the ADAM17 inhibitor TAPI-1. Bo-mac efferocytosis was influenced by the presence and activation of MERTK. Silencing MERTK interrupted efferocytosis, a phenomenon also observed with the inhibition of MERTK phosphorylation by UNC2025, which concurrently suppressed anti-inflammatory cytokine production. These findings suggest that targeting the MERTK-ADAM17 axis could enhance inflammatory resolution, providing a novel therapeutic strategy for dairy cattle health management.

⍺-Synuclein levels in Parkinson's disease - Cell types and forms that contribute to pathogenesis

Parkinson's disease (PD) has two main pathological hallmarks, the loss of nigral dopamine neurons and the proteinaceous aggregations of ⍺-synuclein (⍺Syn) in neuronal Lewy pathology. These two co-existing features suggest a causative association between ⍺Syn aggregation and the underpinning mechanism of neuronal degeneration in PD. Both increased levels and post-translational modifications of ⍺Syn can contribute to the formation of pathological aggregations of ⍺Syn in neurons. Recent studies have shown that the protein is also expressed by multiple types of non-neuronal cells in the brain and peripheral tissues, suggesting additional roles of the protein and potential diversity in non-neuronal pathogenic triggers. It is important to determine (1) the threshold levels triggering ⍺Syn to convert from a biological to a pathologic form in different brain cells in PD; (2) the dominant form of pathologic ⍺Syn and the associated post-translational modification of the protein in each cell type involved in PD; and (3) the cell type associated biological processes impacted by pathologic ⍺Syn in PD. This review integrates these aspects and speculates on potential pathological mechanisms and their impact on neuronal and non-neuronal ⍺Syn in the brains of patients with PD.

An adapted protocol to derive microglia from stem cells and its application in the study of CSF1R-related disorders

BACKGROUND

Induced pluripotent stem cell-derived microglia (iMGL) represent an excellent tool in studying microglial function in health and disease. Yet, since differentiation and survival of iMGL are highly reliant on colony-stimulating factor 1 receptor (CSF1R) signaling, it is difficult to use iMGL to study microglial dysfunction associated with pathogenic defects in CSF1R.

METHODS

Serial modifications to an existing iMGL protocol were made, including but not limited to changes in growth factor combination to drive microglial differentiation, until successful derivation of microglia-like cells from an adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) patient carrying a c.2350G > A (p.V784M) CSF1R variant. Using healthy control lines, the quality of the new iMGL protocol was validated through cell yield assessment, measurement of microglia marker expression, transcriptomic comparison to primary microglia, and evaluation of inflammatory and phagocytic activities. Similarly, molecular and functional characterization of the ALSP patient-derived iMGL was carried out in comparison to healthy control iMGL.

RESULTS

The newly devised protocol allowed the generation of iMGL with enhanced transcriptomic similarity to cultured primary human microglia and with higher scavenging and inflammatory competence at ~ threefold greater yield compared to the original protocol. Using this protocol, decreased CSF1R autophosphorylation and cell surface expression was observed in iMGL derived from the ALSP patient compared to those derived from healthy controls. Additionally, ALSP patient-derived iMGL presented a migratory defect accompanying a temporal reduction in purinergic receptor P2Y12 (P2RY12) expression, a heightened capacity to internalize myelin, as well as heightened inflammatory response to Pam3CSK4. Poor P2RY12 expression was confirmed to be a consequence of CSF1R haploinsufficiency, as this feature was also observed following CSF1R knockdown or inhibition in mature control iMGL, and in CSF1RWT/KO and CSF1RWT/E633K iMGL compared to their respective isogenic controls.

CONCLUSIONS

We optimized a pre-existing iMGL protocol, generating a powerful tool to study microglial involvement in human neurological diseases. Using the optimized protocol, we have generated for the first time iMGL from an ALSP patient carrying a pathogenic CSF1R variant, with preliminary characterization pointing toward functional alterations in migratory, phagocytic and inflammatory activities.