PARP1 UFMylation ensures the stability of stalled replication forks.

The S-phase checkpoint involving CHK1 is essential for fork stability in response to fork stalling. PARP1 acts as a sensor of replication stress and is required for CHK1 activation. However, it is unclear how the activity of PARP1 is regulated. Here, we found that UFMylation is required for the efficient activation of CHK1 by UFMylating PARP1 at K548 during replication stress. Inactivation of UFL1, the E3 enzyme essential for UFMylation, delayed CHK1 activation and inhibits nascent DNA degradation during replication blockage as seen in PARP1-deficient cells. An in vitro study indicated that PARP1 is UFMylated at K548, which enhances its catalytic activity. Correspondingly, a PARP1 UFMylation-deficient mutant (K548R) and pathogenic mutant (F553L) compromised CHK1 activation, the restart of stalled replication forks following replication blockage, and chromosome stability. Defective PARP1 UFMylation also resulted in excessive nascent DNA degradation at stalled replication forks. Finally, we observed that PARP1 UFMylation-deficient knock-in mice exhibited increased sensitivity to replication stress caused by anticancer treatments. Thus, we demonstrate that PARP1 UFMylation promotes CHK1 activation and replication fork stability during replication stress, thus safeguarding genome integrity.

ASPM promotes ATR-CHK1 activation and stabilizes stalled replication forks in response to replication stress.

ASPM is a protein encoded by primary microcephaly 5 (MCPH5) and is responsible for ensuring spindle position during mitosis and the symmetrical division of neural stem cells. We recently reported that ASPM promotes homologous recombination (HR) repair of DNA double strand breaks. However, its potential role in DNA replication and replication stress response remains elusive. Interestingly, we found that ASPM is dispensable for DNA replication under unperturbed conditions. However, ASPM is enriched at stalled replication forks in a RAD17-dependent manner in response to replication stress and promotes RAD9 and TopBP1 loading onto chromatin, facilitating ATR-CHK1 activation. ASPM depletion results in failed fork restart and nuclease MRE11-mediated nascent DNA degradation at the stalled replication fork. The overall consequence is chromosome instability and the sensitization of cancer cells to replication stressors. These data support a role for ASPM in loading RAD17-RAD9/TopBP1 onto chromatin to activate the ATR-CHK1 checkpoint and ultimately ensure genome stability.

Repopulated microglia after pharmacological depletion decrease dendritic spine density in adult mouse brain.

Microglia are innate immune cells in the brain and show exceptional heterogeneity. They are key players in brain physiological development regulating synaptic plasticity and shaping neuronal networks. In pathological disease states, microglia-induced synaptic pruning mediates synaptic loss and targeting microglia was proposed as a promising therapeutic strategy. However, the effect of microglia depletion and subsequent repopulation on dendritic spine density and neuronal function in the adult brain is largely unknown. In this study, we investigated whether pharmacological microglia depletion affects dendritic spine density after long-term permanent microglia depletion and after short-term microglia depletion with subsequent repopulation. Long-term microglia depletion using colony-stimulating-factor-1 receptor (CSF1-R) inhibitor PLX5622 resulted in increased overall spine density, especially of mushroom spines, and increased excitatory postsynaptic current amplitudes. Short-term PLX5622 treatment with subsequent repopulation of microglia had an opposite effect resulting in activated microglia with increased synaptic phagocytosis and consequently decreased spine density and reduced excitatory neurotransmission, while Barnes maze and elevated plus maze testing was unaffected. Moreover, RNA sequencing data of isolated repopulated microglia showed an activated and proinflammatory phenotype. Long-term microglia depletion might be a promising therapeutic strategy in neurological diseases with pathological microglial activation, synaptic pruning, and synapse loss. However, repopulation after depletion induces activated microglia and results in a decrease of dendritic spines possibly limiting the therapeutic application of microglia depletion. Instead, persistent modulation of pathological microglia activity might be beneficial in controlling synaptic damage.

JADE1 is dispensable for the brain development in mice.

In mammalian brain development, WNT signaling balances proliferation and differentiation of neural progenitor cells, and is essential for the maintenance of regular brain development. JADE1 is a candidate transcription co-factor essential for DNA replication, cell division, and cell cycle regulation. In 293T cells, JADE1 is stabilized by von Hippel-Lindau protein pVHL, promotes the ß-catenin ubiquitination and thus blunts canonical WNT signaling. Furthermore, JADE1 inhibits ß-catenin-induced ectopic axis formation in Xenopus embryos. However, JADE1's role in mammalian brain development remains unknown. Here, we generated a new Jade1 knockout mouse line using CRISPR-Cas9 technology. We found that JADE1 null resulted in decreased survival rate, reduced body weight and brain weight in mice. However, histological analysis revealed a normal brain development. Furthermore, Jade1 null neural progenitor cells proliferated normally in vivo and in vitro. RNA-seq analysis further showed that JADE1 loss did not affect the cerebral cortex gene expression. Our findings indicate that JADE1 is dispensable for developing the cerebral cortex in mice.

Mre11 Is Essential for the Removal of Lethal Topoisomerase 2 Covalent Cleavage Complexes.

The Mre11/Rad50/Nbs1 complex initiates double-strand break repair by homologous recombination (HR). Loss of Mre11 or its nuclease activity in mouse cells is known to cause genome aberrations and cellular senescence, although the molecular basis for this phenotype is not clear. To identify the origin of these defects, we characterized Mre11-deficient (MRE11-/-) and nuclease-deficient Mre11 (MRE11-/H129N) chicken DT40 and human lymphoblast cell lines. These cells exhibit increased spontaneous chromosomal DSBs and extreme sensitivity to topoisomerase 2 poisons. The defects in Mre11 compromise the repair of etoposide-induced Top2-DNA covalent complexes, and MRE11-/- and MRE11-/H129N cells accumulate high levels of Top2 covalent conjugates even in the absence of exogenous damage. We demonstrate that both the genome instability and mortality of MRE11-/- and MRE11-/H129N cells are significantly reversed by overexpression of Tdp2, an enzyme that eliminates covalent Top2 conjugates; thus, the essential role of Mre11 nuclease activity is likely to remove these lesions.

Ab initio determination of melting and sound velocity of neon up to the deep interior of the Earth.

The thermophysical properties and elemental abundances of the noble gases in terrestrial materials can provide unique insights into the Earth's evolution and mantle dynamics. Here, we perform extensive ab initio molecular dynamics simulations to determine the melting temperature and sound velocity of neon up to 370 GPa and 7500 K to constrain its physical state and storage capacity, together with to reveal its implications for the deep interior of the Earth. It is found that solid neon can exist stably under the lower mantle and inner core conditions, and the abnormal melting of neon is not observed under the entire temperature (T) and pressure (P) region inside the Earth owing to its peculiar electronic structure, which is substantially distinct from other heavier noble gases. An inspection of the reduction for sound velocity along the Earth's geotherm evidences that neon can be used as a light element to account for the low-velocity anomaly and density deficit in the deep Earth. A comparison of the pair distribution functions and mean square displacements of MgSiO3-Ne and Fe-Ne alloys further reveals that MgSiO3 has a larger neon storage capacity than the liquid iron under the deep Earth condition, indicating that the lower mantle may be a natural deep noble gas storage reservoir. Our results provide valuable information for studying the fundamental behavior and phase transition of neon in a higher T-P regime, and further enhance our understanding for the interior structure and evolution processes inside the Earth.

Microcephaly Gene Mcph1 Deficiency Induces p19ARF-Dependent Cell Cycle Arrest and Senescence.

MCPH1 has been identified as the causal gene for primary microcephaly type 1, a neurodevelopmental disorder characterized by reduced brain size and delayed growth. As a multifunction protein, MCPH1 has been reported to repress the expression of TERT and interact with transcriptional regulator E2F1. However, it remains unclear whether MCPH1 regulates brain development through its transcriptional regulation function. This study showed that the knockout of Mcph1 in mice leads to delayed growth as early as the embryo stage E11.5. Transcriptome analysis (RNA-seq) revealed that the deletion of Mcph1 resulted in changes in the expression levels of a limited number of genes. Although the expression of some of E2F1 targets, such as Satb2 and Cdkn1c, was affected, the differentially expressed genes (DEGs) were not significantly enriched as E2F1 target genes. Further investigations showed that primary and immortalized Mcph1 knockout mouse embryonic fibroblasts (MEFs) exhibited cell cycle arrest and cellular senescence phenotype. Interestingly, the upregulation of p19ARF was detected in Mcph1 knockout MEFs, and silencing p19Arf restored the cell cycle and growth arrest to wild-type levels. Our findings suggested it is unlikely that MCPH1 regulates neurodevelopment through E2F1-mediated transcriptional regulation, and p19ARF-dependent cell cycle arrest and cellular senescence may contribute to the developmental abnormalities observed in primary microcephaly.

Bi-allelic HPDL Variants Cause a Neurodegenerative Disease Ranging from Neonatal Encephalopathy to Adolescent-Onset Spastic Paraplegia.

We report bi-allelic pathogenic HPDL variants as a cause of a progressive, pediatric-onset spastic movement disorder with variable clinical presentation. The single-exon gene HPDL encodes a protein of unknown function with sequence similarity to 4-hydroxyphenylpyruvate dioxygenase. Exome sequencing studies in 13 families revealed bi-allelic HPDL variants in each of the 17 individuals affected with this clinically heterogeneous autosomal-recessive neurological disorder. HPDL levels were significantly reduced in fibroblast cell lines derived from more severely affected individuals, indicating the identified HPDL variants resulted in the loss of HPDL protein. Clinical presentation ranged from severe, neonatal-onset neurodevelopmental delay with neuroimaging findings resembling mitochondrial encephalopathy to milder manifestation of adolescent-onset, isolated hereditary spastic paraplegia. All affected individuals developed spasticity predominantly of the lower limbs over the course of the disease. We demonstrated through bioinformatic and cellular studies that HPDL has a mitochondrial localization signal and consequently localizes to mitochondria suggesting a putative role in mitochondrial metabolism. Taken together, these genetic, bioinformatic, and functional studies demonstrate HPDL is a mitochondrial protein, the loss of which causes a clinically variable form of pediatric-onset spastic movement disorder.

Simultaneous Nbs1 and p53 inactivation in neural progenitors triggers high-grade gliomas.

AIMS: Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder caused by hypomorphic mutations of NBS1. NBS1 is a member of the MRE11-RAD50-NBS1 (MRN) complex that binds to DNA double-strand breaks and activates the DNA damage response (DDR). Nbs1 inactivation in neural progenitor cells leads to microcephaly and premature death. Interestingly, p53 homozygous deletion rescues the NBS1-deficient phenotype allowing long-term survival. The objective of this work was to determine whether simultaneous inactivation of Nbs1 and p53 in neural progenitors triggered brain tumorigenesis and if so in which category this tumour could be classified. METHODS: We generated a mouse model with simultaneous genetic inactivation of Nbs1 and p53 in embryonic neural stem cells and analysed the arising tumours with in-depth molecular analyses including immunohistochemistry, array comparative genomic hybridisation (aCGH), whole exome-sequencing and RNA-sequencing. RESULTS: NBS1/P53-deficient mice develop high-grade gliomas (HGG) arising in the olfactory bulbs and in the cortex along the rostral migratory stream. In-depth molecular analyses using immunohistochemistry, aCGH, whole exome-sequencing and RNA-sequencing revealed striking similarities to paediatric human HGG with shared features with radiation-induced gliomas (RIGs). CONCLUSIONS: Our findings show that concomitant inactivation of Nbs1 and p53 in mice promotes HGG with RIG features. This model could be useful for preclinical studies to improve the prognosis of these deadly tumours, but it also highlights the singularity of NBS1 among the other DNA damage response proteins in the aetiology of brain tumours.

Janus 2H-MXTe (M = Zr, Hf; X = S, Se) monolayers with outstanding thermoelectric properties and low lattice thermal conductivities.

Two-dimensional (2D) materials have been one of the most popular objects in the research field of thermoelectric (TE) materials and have attracted substantial attention in recent years. Inspired by the synthesized 2H-MoSSe and numerous theoretical studies, we systematically investigated the electronic, thermal, and TE properties of Janus 2H-MXTe (M = Zr and Hf; X = S and Se) monolayers by using first-principles calculations. The phonon dispersion curves and AIMD simulations confirm the thermodynamic stabilities. Moreover, Janus 2H-MXTe were evaluated as indirect band-gap semiconductors with band gaps ranging from 0.56 to 0.90 eV using the HSE06 + SOC method. To evaluate the TE performance, firstly, we calculated the temperature-dependent carrier relaxation time with acoustic phonon scattering τac, impurity scattering τimp, and polarized scattering τpol. Secondly, the calculation of lattice thermal conductivity (κl) shows that these monolayers possess relatively poor κl with values of 3.4-5.4 W mK-1 at 300 K, which is caused by the low phonon lifetime and group velocity. After computing the electronic transport properties, we found that the n-type doped Janus 2H-MXTe monolayers exhibit a high Seebeck coefficient exceeding 200 µV K-1 at 300 K, resulting in a high TE power factor. Eventually, combining the electrical and thermal conductivities, the optimal dimensionless figure of merit (zT) at 300 K (900 K) can be obtained, which is 0.94 (3.63), 0.51 (2.57), 0.64 (2.72), and 0.50 (1.98) for n-type doping of ZrSeTe, HfSeTe, ZeSTe, and HfSTe monolayers. Particularly, the ZrSeTe monolayer shows the best TE performance with the maximal zT value. These results indicate the excellent application potential of Janus 2H-MXTe (M = Zr and Hf; X = S and Se) monolayers in TE materials.

Two-dimensional Janus pentagonal MSeTe (M = Ni, Pd, Pt): promising water-splitting photocatalysts and optoelectronic materials.

Inspired by the interesting and novel properties exhibited by Janus transition metal dichalcogenides (TMDs) and two-dimensional pentagonal structures, we here investigated the structural stability, mechanical, electronic, photocatalytic, and optical properties for a class of two-dimensional (2D) pentagonal Janus TMDs, namely penta-MSeTe (M = Ni, Pd, Pt) monolayers, by using density functional theory (DFT) combined with Hubbard's correction (U). Our results showed that these monolayers exhibit good structural stability, appropriate band structures for photocatalysts, high visible light absorption, and good photocatalytic applicability. The calculated electronic properties reveal that the penta-MSeTe are semiconductors with a bandgap range of 2.06-2.39 eV, and their band edge positions meet the requirements for water-splitting photocatalysts in various environments (pH = 0-13). We used stress engineering to seek higher solar-to-hydrogen (STH) efficiency in acidic (pH = 0), neutral (pH = 7) and alkaline (pH = 13) environments for penta-MSeTe from 0% to +8% biaxial and uniaxial strains. Our results showed that penta-PdSeTe stretched 8% along the y direction and demonstrates an STH efficiency of up to 29.71% when pH = 0, which breaks the theoretical limit of the conventional photocatalytic model. We also calculated the optical properties and found that they exhibit high absorption (13.11%) in the visible light range and possess a diverse range of hyperbolic regions. Hence, it is anticipated that penta-MSeTe materials hold great promise for applications in photocatalytic water splitting and optoelectronic devices.

XRCC1 mutation is associated with PARP1 hyperactivation and cerebellar ataxia.

XRCC1 is a molecular scaffold protein that assembles multi-protein complexes involved in DNA single-strand break repair. Here we show that biallelic mutations in the human XRCC1 gene are associated with ocular motor apraxia, axonal neuropathy, and progressive cerebellar ataxia. Cells from a patient with mutations in XRCC1 exhibited not only reduced rates of single-strand break repair but also elevated levels of protein ADP-ribosylation. This latter phenotype is recapitulated in a related syndrome caused by mutations in the XRCC1 partner protein PNKP and implicates hyperactivation of poly(ADP-ribose) polymerase/s as a cause of cerebellar ataxia. Indeed, remarkably, genetic deletion of Parp1 rescued normal cerebellar ADP-ribose levels and reduced the loss of cerebellar neurons and ataxia in Xrcc1-defective mice, identifying a molecular mechanism by which endogenous single-strand breaks trigger neuropathology. Collectively, these data establish the importance of XRCC1 protein complexes for normal neurological function and identify PARP1 as a therapeutic target in DNA strand break repair-defective disease.

Tuberous sclerosis complex is required for tumor maintenance in MYC-driven Burkitt's lymphoma.

The tuberous sclerosis complex (TSC) 1/2 is a negative regulator of the nutrient-sensing kinase mechanistic target of rapamycin complex (mTORC1), and its function is generally associated with tumor suppression. Nevertheless, biallelic loss of function of TSC1 or TSC2 is rarely found in malignant tumors. Here, we show that TSC1/2 is highly expressed in Burkitt's lymphoma cell lines and patient samples of human Burkitt's lymphoma, a prototypical MYC-driven cancer. Mechanistically, we show that MYC induces TSC1 expression by transcriptional activation of the TSC1 promoter and repression of miR-15a. TSC1 knockdown results in elevated mTORC1-dependent mitochondrial respiration enhanced ROS production and apoptosis. Moreover, TSC1 deficiency attenuates tumor growth in a xenograft mouse model. Our study reveals a novel role for TSC1 in securing homeostasis between MYC and mTORC1 that is required for cell survival and tumor maintenance in Burkitt's lymphoma. The study identifies TSC1/2 inhibition and/or mTORC1 hyperactivation as a novel therapeutic strategy for MYC-driven cancers.

A gene dosage-dependent effect unveils NBS1 as both a haploinsufficient tumour suppressor and an essential gene for SHH-medulloblastoma.

AIMS: Inherited or somatic mutations in the MRE11, RAD50 and NBN genes increase the incidence of tumours, including medulloblastoma (MB). On the other hand, MRE11, RAD50 and NBS1 protein components of the MRN complex are often overexpressed and sometimes essential in cancer. In order to solve the apparent conundrum about the oncosuppressive or oncopromoting role of the MRN complex, we explored the functions of NBS1 in an MB-prone animal model. MATERIALS AND METHODS: We generated and analysed the monoallelic or biallelic deletion of the Nbn gene in the context of the SmoA1 transgenic mouse, a Sonic Hedgehog (SHH)-dependent MB-prone animal model. We used normal and tumour tissues from these animal models, primary granule cell progenitors (GCPs) from genetically modified animals and NBS1-depleted primary MB cells, to uncover the effects of NBS1 depletion by RNA-Seq, by biochemical characterisation of the SHH pathway and the DNA damage response (DDR) as well as on the growth and clonogenic properties of GCPs. RESULTS: We found that monoallelic Nbn deletion increases SmoA1-dependent MB incidence. In addition to a defective DDR, Nbn+/- GCPs show increased clonogenicity compared to Nbn+/+ GCPs, dependent on an enhanced Notch signalling. In contrast, full NbnKO impairs MB development both in SmoA1 mice and in an SHH-driven tumour allograft. CONCLUSIONS: Our study indicates that Nbn is haploinsufficient for SHH-MB development whereas full NbnKO is epistatic on SHH-driven MB development, thus revealing a gene dosage-dependent effect of Nbn inactivation on SHH-MB development.

Consistency and synchronization of AMPK-glycogen in endometrial epithelial cells are critical to the embryo implantation.

Uterine receptivity to the embryo is crucial for successful implantation. The establishment of uterine receptivity requires a large amount of energy, and abnormal energy regulation causes implantation failure. Glucose metabolism in the endometrium is tissue specific. Glucose is largely stored in the form of glycogen, which is the main energy source for the endometrium. AMP-activated protein kinase (AMPK), an important energy-sensing molecule, is a key player in the regulation of glucose metabolism and its regulation is also tissue specific. However, the mechanism of energy regulation in the endometrium for the establishment of uterine receptivity remains to be elucidated. In this study, we aimed to investigate the energy regulation mechanism of mouse uterine receptivity and its significance in embryo implantation. The results showed that the AMPK, p-AMPK, glycogen synthase 1, and glycogen phosphorylase M levels and the glycogen content in mouse endometrial epithelium varied in a periodic manner under regulation by the ovarian hormone. Specifically, progesterone significantly activated AMPK, promoted glycogenolysis, and upregulated glycogen phosphorylase M expression. AMPK regulated glycogen phosphorylase M expression and promoted glycogenolysis. AMPK was also found to be activated by changes in the energy or glycogen of the endometrial epithelial cells. The inhibition of AMPK activity or glycogenolysis altered the uterine receptivity markers during the window of implantation and ultimately interfered with implantation. In summary, consistency and synchronization of AMPK and glycogen metabolism constitute the core regulatory mechanism in mouse endometrial epithelial cells involved in the establishment of uterine receptivity.

NBS1 interacts with Notch signaling in neuronal homeostasis.

NBS1 is a critical component of the MRN (MRE11/RAD50/NBS1) complex, which regulates ATM- and ATR-mediated DNA damage response (DDR) pathways. Mutations in NBS1 cause the human genomic instability syndrome Nijmegen Breakage Syndrome (NBS), of which neuronal deficits, including microcephaly and intellectual disability, are classical hallmarks. Given its function in the DDR to ensure proper proliferation and prevent death of replicating cells, NBS1 is essential for life. Here we show that, unexpectedly, Nbs1 deletion is dispensable for postmitotic neurons, but compromises their arborization and migration due to dysregulated Notch signaling. We find that Nbs1 interacts with NICD-RBPJ, the effector of Notch signaling, and inhibits Notch activity. Genetic ablation or pharmaceutical inhibition of Notch signaling rescues the maturation and migration defects of Nbs1-deficient neurons in vitro and in vivo. Upregulation of Notch by Nbs1 deletion is independent of the key DDR downstream effector p53 and inactivation of each MRN component produces a different pattern of Notch activity and distinct neuronal defects. These data indicate that neuronal defects and aberrant Notch activity in Nbs1-deficient cells are unlikely to be a direct consequence of loss of MRN-mediated DDR function. This study discloses a novel function of NBS1 in crosstalk with the Notch pathway in neuron development.

The E3 ubiquitin ligase APC/CCdh1 degrades MCPH1 after MCPH1-ßTrCP2-Cdc25A-mediated mitotic entry to ensure neurogenesis.

Mutations of microcephalin (MCPH1) can cause the neurodevelopmental disorder primary microcephaly type 1. We previously showed that MCPH1 deletion in neural stem cells results in early mitotic entry that distracts cell division mode, leading to exhaustion of the progenitor pool. Here, we show that MCPH1 interacts with and promotes the E3 ligase ßTrCP2 to degrade Cdc25A independent of DNA damage. Overexpression of ßTrCP2 or the knockdown of Cdc25A remedies the high mitotic index and rescues the premature differentiation of Mcph1-deficient neuroprogenitors in vivo MCPH1 itself is degraded by APC/CCdh1, but not APC/CCdc20, in late mitosis and G1 phase. Forced MCPH1 expression causes cell death, underlining the importance of MCPH1 turnover after mitosis. Ectopic expression of Cdh1 leads to premature differentiation of neuroprogenitors, mimicking differentiation defects of Mcph1-knockout neuroprogenitors. The homeostasis of MCPH1 in association with the ubiquitin-proteasome system ensures mitotic entry independent of cell cycle checkpoint. This study provides a mechanistic understanding of how MCPH1 controls neural stem cell fate and brain development.

Multishock to Quasi-Isentropic Compression of Dense Gaseous Deuterium-Helium Mixtures up to 120 GPa: Probing the Sound Velocities Relevant to Planetary Interiors.

Shock reverberation compression experiments on dense gaseous deuterium-helium mixtures are carried out to provide thermodynamic parameters relevant to the conditions in planetary interiors. The multishock pressures are determined up to 120 GPa and reshock temperatures to 7400 K. Furthermore, the unique compression path from shock-adiabatic to quasi-isentropic compressions enables a direct estimation of the high-pressure sound velocities in the unexplored range of 50-120 GPa. The equation of state and sound velocity provide particular dual perspectives to validate the theoretical models. Our experimental data are found to agree with several equation of state models widely used in astrophysics within the probed pressure range. The current data improve the experimental constraints on sound velocities in the Jovian insulating-to-metallic transition layer.

Beyond HAT Adaptor: TRRAP Liaisons with Sp1-Mediated Transcription.

The members of the phosphatidylinositol 3-kinase-related kinase (PIKK) family play vital roles in multiple biological processes, including DNA damage response, metabolism, cell growth, mRNA decay, and transcription. TRRAP, as the only member lacking the enzymatic activity in this family, is an adaptor protein for several histone acetyltransferase (HAT) complexes and a scaffold protein for multiple transcription factors. TRRAP has been demonstrated to regulate various cellular functions in cell cycle progression, cell stemness maintenance and differentiation, as well as neural homeostasis. TRRAP is known to be an important orchestrator of many molecular machineries in gene transcription by modulating the activity of some key transcription factors, including E2F1, c-Myc, p53, and recently, Sp1. This review summarizes the biological and biochemical studies on the action mode of TRRAP together with the transcription factors, focusing on how TRRAP-HAT mediates the transactivation of Sp1-governing biological processes, including neurodegeneration.

The Role of the Pathogen Dose and PI3Kγ in Immunometabolic Reprogramming of Microglia for Innate Immune Memory.

Microglia, the innate immune cells of the CNS, exhibit long-term response changes indicative of innate immune memory (IIM). Our previous studies revealed IIM patterns of microglia with opposing immune phenotypes: trained immunity after a low dose and immune tolerance after a high dose challenge with pathogen-associated molecular patterns (PAMP). Compelling evidence shows that innate immune cells adopt features of IIM via immunometabolic control. However, immunometabolic reprogramming involved in the regulation of IIM in microglia has not been fully addressed. Here, we evaluated the impact of dose-dependent microglial priming with ultra-low (ULP, 1 fg/mL) and high (HP, 100 ng/mL) lipopolysaccharide (LPS) doses on immunometabolic rewiring. Furthermore, we addressed the role of PI3Kγ on immunometabolic control using naïve primary microglia derived from newborn wild-type mice, PI3Kγ-deficient mice and mice carrying a targeted mutation causing loss of lipid kinase activity. We found that ULP-induced IIM triggered an enhancement of oxygen consumption and ATP production. In contrast, HP was followed by suppressed oxygen consumption and glycolytic activity indicative of immune tolerance. PI3Kγ inhibited glycolysis due to modulation of cAMP-dependent pathways. However, no impact of specific PI3Kγ signaling on immunometabolic rewiring due to dose-dependent LPS priming was detected. In conclusion, immunometabolic reprogramming of microglia is involved in IIM in a dose-dependent manner via the glycolytic pathway, oxygen consumption and ATP production: ULP (ultra-low-dose priming) increases it, while HP reduces it.