Project description:The immune cells of the central nervous system (CNS) comprise parenchymal microglia and at the CNS border regions meningeal, perivascular and choroid plexus macrophages (summarized as CNS-associated macrophages, CAMs). Previous work has uncovered that microglial properties are strongly dependent on environmental signals from the commensal microbiota while its effect on CAMs remained unknown. By combining several microbiota manipulation approaches, genetic mouse models and single-cell RNA-sequencing, we comprehensively characterized CNS myeloid cell composition and function. Under steady-state, the transcriptional profile and numbers of choroid plexus macrophages were found to be tightly steered by complex microbiota. Divergently, perivascular and meningeal macrophages were affected to a lesser extent. An acute perturbation through viral infection evoked an attenuated immune response of all CAMs in germ-free mice. Additionally, we assessed CAMs in a more chronic pathological state in 5xFAD mice as a model for Alzheimer’s disease whereby exclusively perivascular macrophages displayed enhanced amyloid beta uptake in GF 5xFAD mice. Our results provide novel insights for understanding distinct microbiota-CNS macrophage interactions during health and perturbation that could potentially be targeted therapeutically.
Project description:The transcriptional responses of cryptococcus during human infection are dynamic and highly dependent on the immediate signals from the environment. We examined the RNA-Seq profiles of Cryptococcus isoalted from human CSF and in comparison with to the same isolate's response to the stresses of artificial CSF and within the rabbit subarachnoid space as well as growth in nutritious media with little or no stress. By comparing these transcriptomes, we have identified regulated genes and categorized them by networks and functional classifications to identify candidate genes essential for yeast survival and as well as those uniformly expressed in CSF across diverse isolates that may be markers for the human disease state.
Project description:During central nervous system (CNS) development, proper and timely induction of axon elongation is critical for generating functional, mature neurons and neuronal networks. Despite the wealth of information on the action of extracellular cues, little is known about the intrinsic gene regulatory factors that control this developmental decision. Here we report the identification of Prox1, a homeobox transcription factor, as a key player in inhibiting axon elongation. Although Prox1 promotes acquisition of early neuronal identity and is expressed in nascent post-mitotic neurons, it is heavily down-regulated in the majority of terminally differentiated neurons, indicating a regulatory role in delaying axon outgrowth in newly formed neurons. Consistently, we show that Prox1 is sufficient to inhibit neurite extension in neuroblastoma cell lines. Furthermore, shRNA-mediated knock-down of Prox1 in Neuro2A cells induces the extension of neurites. More importantly, Prox1 overexpression suppresses axon elongation in primary neuronal cultures as well as in the developing mouse brain, while Prox1 knock-down promotes axon outgrowth. Mechanistically, RNA-Seq analysis reveals that Prox1 affects critical pathways for neuronal maturation and neurite extension. Interestingly, Prox1 strongly inhibits many components of Ca2+ signaling pathway, an important mediator of axon extension and neuronal maturation. In accordance, Prox1 represses Ca2+ entry upon KCl-mediated depolarization and reduce CREB phosphorylation. These observations suggest that Prox1 acts as a potent suppressor of axon elongation by inhibiting Ca2+ signaling pathway. This action may provide the appropriate time window for nascent neurons to find the correct position in the CNS prior to initiation of axon elongation.