Biology subjects

Lombroso, S. I.

Publications and source records attributed to Lombroso, S. I..

3 recordsLinked to original sources

bioRxiv2026

Synaptic activity controls local exposure of an 'eat-me' signal via ANO3-ITPR1 signaling

Neuronal synapses are eliminated during brain development and disease through pruning by glial cells. Individual synapses are marked for engulfment by eat-me signals, which include externalized phosphatidylserine. In apoptotic cells, phosphatidylserine externalization is driven by caspase-dependent activation of Xkr scramblases1 and inactivation of specific flippases2. Localized caspase activation at neuronal synapses can mediate spatially-restricted synaptic phosphatidylserine exposure leading to synapse pruning by glial cells during development and neurodegeneration3-6. It is unknown which caspase-regulated flippases and scramblases promote synaptic phosphatidylserine exposure and whether there are any caspase-independent mechanisms of phosphatidylserine exposure relevant for synapse elimination. To address this question, we here develop a scalable CRISPR screening approach, COMPASS-seq (compartment-anchored sgRNA screen sequencing), to uncover the genetic underpinnings of subcellular phenotypes. COMPASS-seq is compatible with in vitro and in vivo systems and a wide range of subcellular compartments; we here apply it to the neuronal synapse. We discover that inhibition of the caspase-independent, calcium-activated anoctamin ANO3 (TMEM16C) is sufficient to increase synapse numbers in vivo. ANO3 co-localizes with IP3 receptor 1 (ITPR1), a calcium channel in the endoplasmic reticulum, to form a postsynaptic signaling platform that drives spatially restricted phosphatidylserine exposure at synapses. Activation of the ITPR1 calcium channel activity is sufficient to drive synaptic phosphatidylserine exposure via an ANO3-dependent but caspase-independent mechanism. Our results suggest a mechanism for integrating synaptic activity information to control synaptic pruning. The role of ANO3 in regulating synapses could shed light on the mechanisms underlying its numerous associations with both dementia7 and other neurological diseases8,9.

neuroscience↗

bioRxiv2024

Microglia replacement by ER-Hoxb8 conditionally immortalized macrophages provides insight into Aicardi-Goutieres Syndrome neuropathology

Microglia, the brains resident macrophages, can be reconstituted by surrogate cells - a process termed "microglia replacement." To expand the microglia replacement toolkit, we here introduce estrogen-regulated (ER) homeobox B8 (Hoxb8) conditionally immortalized macrophages, a cell model for generation of immune cells from murine bone marrow, as a versatile model for microglia replacement. We find that ER-Hoxb8 macrophages are highly comparable to primary bone marrow-derived (BMD) macrophages in vitro, and, when transplanted into a microglia-free brain, engraft the parenchyma and differentiate into microglia-like cells. Furthermore, ER-Hoxb8 progenitors are readily transducible by virus and easily stored as stable, genetically manipulated cell lines. As a demonstration of this systems power for studying the effects of disease mutations on microglia in vivo, we created stable, Adar1-mutated ER-Hoxb8 lines using CRISPR-Cas9 to study the intrinsic contribution of macrophages to Aicardi-Goutieres Syndrome (AGS), an inherited interferonopathy that primarily affects the brain and immune system. We find that Adar1 knockout elicited interferon secretion and impaired macrophage production in vitro, while preventing brain macrophage engraftment in vivo - phenotypes that can be rescued with concurrent mutation of Ifih1 (MDA5) in vitro, but not in vivo. Lastly, we extended these findings by generating ER-Hoxb8 progenitors from mice harboring a patient-specific Adar1 mutation (D1113H). We demonstrated the ability of microglia-specific D1113H mutation to drive interferon production in vivo, suggesting microglia drive AGS neuropathology. In sum, we introduce the ER-Hoxb8 approach to model microglia replacement and use it to clarify macrophage contributions to AGS.

neuroscience↗

bioRxiv2019

Set2-mediated alternative splicing of Srsf11 regulates cocaine reward behavior

Alternative splicing is a key mechanism for neuronal gene regulation, and is grossly altered in mouse brain reward regions following investigator-administered cocaine. It is well established that cocaine epigenetically regulates transcription, yet mechanism(s) by which cocaine-induced epigenetic modifications regulate alternative splicing is largely unexplored. Our group and others have previously identified the histone modification, H3K36me3, as a putative splicing regulator. However, it has not yet been possible to establish the direct causal relevance of this modification to alternative splicing in brain or any other context. We found that mouse cocaine self-administration caused widespread alternative splicing, concomitant with enrichment of H3K36me3 at splice junctions. Differentially spliced genes were enriched in the motif for splice factor, Srsf11, which was both differentially spliced and enriched in H3K36me3. Epigenetic editing led us to conclude that H3K36me3 functions directly in alternative splicing of Srsf11, and that Set2 mediated H3K36me3 bidirectionally regulates cocaine intake.

neuroscience↗