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Microglia are a heterogeneous population whose identity and function are dictated by signals from their microenvironment. Kana et al. show CSF-1 signaling is critical for cerebellar microglial transcriptional identity and homeostasis, and that altering the CSF-1–CSF-1R axis leads to motor and behavioral defects., Microglia, the brain resident macrophages, critically shape forebrain neuronal circuits. However, their precise function in the cerebellum is unknown. Here we show that human and mouse cerebellar microglia express a unique molecular program distinct from forebrain microglia. Cerebellar microglial identity was driven by the CSF-1R ligand CSF-1, independently of the alternate CSF-1R ligand, IL-34. Accordingly, CSF-1 depletion from Nestin+ cells led to severe depletion and transcriptional alterations of cerebellar microglia, while microglia in the forebrain remained intact. Strikingly, CSF-1 deficiency and alteration of cerebellar microglia were associated with reduced Purkinje cells, altered neuronal function, and defects in motor learning and social novelty interactions. These findings reveal a novel CSF-1–CSF-1R signaling-mediated mechanism that contributes to motor function and social behavior.

Background: The intensive care unit (ICU) is a technical environment where patients’ lives are at risk. The COVID-19 pandemic has led to for visitors of patients hospitalised in ICUs. Methods: A qualitative study including 10 semi-directive interviews with caregivers working in an ICU. Results: The COVID-19 crisis disrupted the inclusion of patients’ relatives in the ICU. Their inclusion had been established by various means before the crisis: 24-hour visits, participation in mortuary toilets, pets’ visits, logbooks, family lounges, and volunteer visits. These options led to better inclusion in the ICU, even if there were still difficulties: involving the patients’ loved ones during the acute phase, communicating with the visitors, waiting for care, choosing a healthcare proxy, and coping with restricted visiting hours. The COVID-19 crisis added barriers: the initial closure of all the wards in which the interviewed caregivers worked, followed by their partial reopening; a fear of the virus; equipment related constraints; exacerbated communication difficulties; and an extreme lack of medical time. The caregivers tried to implement new means of including relatives in this context: videoconferencing, virtual logbooks, and regular telephone interviews. However, the global context of the pandemic made it difficult for hospital professionals to accommodate the patients’ loved ones, thus deteriorating caregivers’ relationships with relatives, resulting in negative experiences for both relatives and caregivers. Conclusion: The COVID-19 crisis has made it challenging for caregivers to accommodate the relatives of hospitalised patients. Despite the means implemented to maintain a link between caregivers and family members, face-to-face relationships are necessary for humane patient care. Funding: None to declare. Declaration of Interest: None to declare. Ethical Approval: This study was approved by an IRB. It did not request any further approval according to French law