{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T11:02:07Z","timestamp":1790420527679,"version":"4.1.0"},"posted":{"date-parts":[[2026,9,23]]},"group-title":"Neuroscience","reference-count":51,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.biorxiv.org\/about\/FAQ#license"}],"funder":[{"name":"National Institute of Mental Health","award":["R21MH135128"],"award-info":[{"award-number":["R21MH135128"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,9,23]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>Microglia, the tissue resident immune cells of the central nervous system, are critical regulators of postnatal neural circuit refinement. Innate immune receptors on microglia such as toll-like receptor 4 (TLR4) are best characterized in the context of inflammation, however, endogenous TLR4 ligands are generated during typical developmental processes. Here, we investigated whether TLR4 signaling in CX3CR1-expressing myeloid cells contributes to microglial morphology, synaptic engulfment, and behavioral development in mice under basal conditions. TLR4 conditional knockout altered maternal separation-induced ultrasonic vocalizations without impacting social preference or anxiety-like behaviors. Conditional TLR4 knockout in CX3CR1-expressing myeloid cells markedly increased microglial ramification and cell volume within the paraventricular nucleus (PVN) of the hypothalamus. TLR4 conditional knockout also reduced microglial engulfment of vGlut2-positive presynaptic material, while overall excitatory synapse numbers remained unchanged. Together, these findings demonstrate that TLR4 signaling in CX3CR1-expressing myeloid cells contributes to microglial morphology, presynaptic engulfment, and neonatal communicative behavior under basal conditions.<\/jats:p>","DOI":"10.64898\/2026.09.17.752150","type":"posted-content","created":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T21:05:37Z","timestamp":1790197537000},"source":"Crossref","is-referenced-by-count":0,"title":["<i>Cx3cr1<\/i>\n                  -BAC-CRE-mediated knockout of toll-like receptor 4 alters mouse communicative behaviors, microglial morphology, and engulfment of synaptic material"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2269-8476","authenticated-orcid":false,"given":"Izabella M","family":"Bankowski","sequence":"first","affiliation":[{"name":"Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, MA, USA"},{"name":"Lurie Center for Autism, Massachusetts General Hospital, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1535-1220","authenticated-orcid":false,"given":"Indra R","family":"Bishnoi","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, MA, USA"},{"name":"Lurie Center for Autism, Massachusetts General Hospital, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-6781-4334","authenticated-orcid":false,"given":"Eva E","family":"Shin","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, MA, USA"},{"name":"Lurie Center for Autism, Massachusetts General Hospital, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mia J","family":"Cashin","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, MA, USA"},{"name":"Lurie Center for Autism, Massachusetts General Hospital, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-5969-553X","authenticated-orcid":false,"given":"Dorit","family":"M\u00f6hrle","sequence":"additional","affiliation":[{"name":"Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5319-924X","authenticated-orcid":false,"given":"Haley A","family":"Norris","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, MA, USA"},{"name":"Lurie Center for Autism, Massachusetts General Hospital, MA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-2024-3619","authenticated-orcid":false,"given":"Drew T","family":"Barry","sequence":"additional","affiliation":[{"name":"Department of 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