LRRK2-G2019S impairs astrocyte differentiation and triggers a senescence-like phenotype in Parkinson’s disease models

Multi-omics characterization of IDH-mutant astrocytoma-derived cell lines reveals NOTCH-regulated plastic quiescent astrocyte-like state and insights into progression.

Diffuse IDH-mutant astrocytomas are brain tumors typically diagnosed as low-grade but capable of progressing to higher grades. They exhibit three cellular states resembling astrocytes, oligodendrocytes, and neural progenitor (NPC) cells. Understanding their biology has been limited by the scarcity of relevant in vitro models. Here, we established and extensively characterized four astrocytoma cell lines (LGG275, LGG336, LGG85, LGG349) derived from IDH-mutant astrocytomas of different grades and analyzed them using multi-omics approaches. These lines display growth rates in vitro and in vivo consistent with tumor grade and recapitulate some key molecular alterations observed in patient tumors, including IDH1, ATRX, and TP53 mutations, ALT (alternative lengthening of telomeres) activation and, in more aggressive lines, MET and PDGFRA alterations. Single-cell RNA sequencing revealed three major transcriptional states (astrocyte-like, oligodendrocyte-like, and NPC-like), consistent with those described in patient tumors. A hallmark of higher-grade-derived lines (LGG85, LGG349) is the persistence of NPC-like populations without growth factors possibly reflecting tumor progression. The LGG275 line most accurately mirrors slow-growing astrocytomas. Using CD44 and GLAST, we isolated astrocyte-like (CD44⁺/GLAST⁺) cells from LGG275 that preferentially adopt a quiescent state yet retain remarkable plasticity, generating oligodendrocyte-like cells (CD44⁻/GLAST⁻). Transcriptomic and proteomic analyses revealed that astrocyte-like and oligodendrocyte-like cells populations resemble, respectively, quiescent and activated neural stem (NSC) cells from the adult subventricular zone (SVZ). Finally, we provide evidence that NOTCH signaling contributes to the regulation of cell state balance, promoting transitions toward an astrocyte-like transcriptional program while DLL3, an anti-Notch protein, expressed by oligodendrocyte-like cells, modulates both proliferation and phenotype. These cell lines represent valuable resources for dissecting lineage dynamics, heterogeneity, and progression mechanisms in IDH-mutant astrocytomas.

Single-nucleus transcriptomics reveals cell type-specific remodeling and epilepsy-associated microglia

Summary Temporal lobe epilepsy (TLE) is the most common acquired epilepsy, causing refractory seizures and cognitive deficits. We performed single-nucleus RNA sequencing on hippocampal tissue from mice 3 and 6 weeks following pilocarpine-induced status epilepticus, a robust model of TLE. Epilepsy samples showed reductions in Cck and Lamp5-Lhx6 interneuron subclusters, alongside increases in Cajal-Retzius cells, dentate granule (DG) cell precursors, and a mature DG cell subcluster. Among glia, an astrocyte subcluster and a markedly expanded microglia sublcuster were increased. We term this microglia population epilepsy-associated microglia (EAM). The transcriptomic profile of EAM overlaps with microglia described in models of Alzheimer’s disease and traumatic brain injury, including enrichment of Myo1e and Igf1. EAM display amoeboid morphology, can be found in clumps around pyramidal and granule cell body layers, and exhibit enlarged vesicles and mitochondria. Cell-cell interaction analysis predicts DG cells as their primary interaction partners. This dataset defines transcriptomic programs underlying key cellular alterations in TLE, enabling mechanistic dissection of epileptogenesis.

The lncRNA Gm16685/MITA1 modulates inflammatory astrocyte reactivity through PCBP2 associated regulation of IKKβ signaling

Senescence Markers and Associated Transcriptomic Changes Are Expressed at Early Stages of Alzheimer’s Neuropathology but Are Not Independently Related to Dementia

Cellular senescence may affect the post-mitotic cells of the brain. We examined the expression of senescence markers, including p16, p21, γH2Ax and H3K9me3, in the frontal cortex of brain donations from the Cognitive Function and Ageing Study to assess their relationship to Alzheimer’s disease neuropathological change (ADNC) and dementia. p21, γH2Ax and H3K9me3 were expressed in pyramidal neurons and glia, whilst p16 was confined to glial cells. p21 and γH2Ax were correlated in neurons, and with p16 in glia. They did not increase with ADNC, tending to be higher at early Braak neurofibrillary tangle stages. Transcriptomic profiling of pyramidal neuron-enriched samples at low Braak stages showed that higher neuronal p21 expression was associated with altered pathways for neuronal function, neurodegeneration, protein homeostasis, mitochondrial dysfunction and synaptic signalling. In conclusion, the different expression profile of senescence markers in neurons and glia suggest possible differences in senescence-related mechanisms. Expression at lower ADNC stages suggests senescence may be important at earlier stages of Alzheimer’s pathogenesis, whilst transcriptomic changes suggest an impact on neuronal function. The lack of association of senescence markers with dementia status indicates that more work is needed to determine the value of senescence as a therapeutic target for dementia.

Senescent microglia with shortened telomeres secrete soluble DLK1 to induce aging-associated hypomyelination and neuronal dysfunction.

Aging is the major risk factor for neurodegenerative disease, yet the mechanisms linking physiological aging to brain dysfunction remain unclear. We investigated the brains of telomere-shortened mice and observed lipofuscinosis, hypomyelination, microglial atrophy, and cognitive deficits. Single-nucleus RNA sequencing (snRNA-seq) revealed accelerated glial aging and elevated microglial senescence pathways. In a senescence model of human induced pluripotent stem cell (iPSC)-derived microglia, delta-like non-canonical Notch ligand 1 (DLK1) was identified as a novel senescence-associated ligand. Soluble DLK1 (sDLK1) was increased in the cerebrospinal fluid of telomere-shortened and naturally aged mice, and this increase was eliminated by microglial depletion. In vivo elevation of sDLK1 caused hypomyelination and blocked oligodendrocyte lineage progression, and these effects demonstrate the detrimental nature of excessive sDLK1. In human iPSC systems, sDLK1 impaired oligodendrocyte maturation and altered calcium signaling in excitatory neurons. These findings identify microglial senescence as a core consequence of telomere shortening and reveal sDLK1 as a microglia-derived senescence ligand that drives oligodendrocyte and neuronal dysfunction in aging.

Delayed astrocyte development impairs Sema6a-Plxna2/4-mediated astrocyte-neuron crosstalk and causes depressive-like behavior

It is demonstrated that Egfr knockout during the critical period of neuronal maturation results in a transient absence of astrocytes, with recovery observed in adult mice, and developmental disruption of EGFR signaling leads to transient astrocyte loss and impaired astrocyte–neuron crosstalk.