Patients with Systemic Lupus Erythematosus (SLE) display a complex blood transcriptome whose cellular origin is poorly resolved. Using single-cell RNA-seq, we profiled ~276,000 PBMCs from 33 children with SLE (cSLE) with different degrees of disease activity (DA) and 11 matched controls. Increased expression of interferon-stimulated genes (ISGs) distinguished cSLE from healthy control cells. The high-ISG expression signature (ISG hi ) derived from a small number of transcriptionally defined subpopulations within major cell types, including monocytes, CD4 + and CD8 + T cells, natural killer cells, conventional dendritic cells (cDCs), plasmacytoid DCs (pDCs), B cells and especially plasma cells. Expansion of unique subpopulations enriched in ISGs and/or in monogenic lupus-associated genes classified patients with the highest DA. Profiling of ~82,000 single peripheral blood mononuclear cells (PBMCs) from adult SLE patients confirmed the expansion of similar subpopulations in patients with the highest DA. This study lays the groundwork for resolving the origin of the SLE transcriptional signatures and the disease heterogeneity towards precision medicine applications.

The present study demonstrates that perikaryal ␦-opioid receptors (␦ORs) in rat dorsal root ganglion (DRG) neurons bind and internalize opioid ligands circulating in the CSF. Using confocal and electron microscopy, we found that prolonged morphine treatment increased the cell surface density of these perikaryal ␦ORs and, by way of consequence, receptor-mediated internalization of the fluorescent deltorphin (DLT) analog -Bodipy 576/589 deltorphin-I 5-aminopentylamide (Fluo-DLT) in all three types of DRG neurons (small, medium, and large). In contrast, chronic inflammatory pain induced by the injection of complete Freund's adjuvant (CFA) into one hindpaw selectively increased Fluo-DLT internalization in small and medium-sized DRG neurons ipsilateral to the inflammation. Based on our previous studies in the spinal cord of -opioid receptor (OR) knock-out mice, it may be assumed that the enhanced membrane recruitment of ␦ORs observed after sustained morphine is attributable to stimulation of ORs. However, the selectivity of the effect induced by inflammatory pain suggests that it involves a different mechanism, namely a modality-specific and pain-related activation of C and A␦ fibers. Indeed, stimulation by capsaicin of transient receptor potential vanilloid 1 receptors, which are selectively expressed by small diameter (Ͻ 600 m 2 ) DRG neurons, increased Fluo-DLT internalization exclusively in this cell population. The present results, therefore, demonstrate that DRG neurons express perikaryal ␦ORs accessible to CSF-circulating ligands and that the density and, hence, presumably also the responsiveness, of these receptors may be modulated by both pain-related stimuli and sustained exposure to OR agonists.

CNS synapse assembly typically follows after stable contacts between "appropriate" axonal and dendritic membranes are made. We show that presynaptic boutons selectively form de novo following neuronal fiber adhesion to beads coated with poly-D-lysine (PDL), an artificial cationic polypeptide. As demonstrated by atomic force and live confocal microscopy, functional presynaptic boutons self-assemble as rapidly as 1 h after bead contact, and are found to contain a variety of proteins characteristic of presynaptic endings. Interestingly, presynaptic compartment assembly does not depend on the presence of a biological postsynaptic membrane surface. Rather, heparan sulfate proteoglycans, including syndecan-2, as well as others possibly adsorbed onto the bead matrix or expressed on the axon surface, are required for assembly to proceed by a mechanism dependent on the dynamic reorganization of F-actin. Our results indicate that certain (but not all) nonspecific cationic molecules like PDL, with presumably electrostatically mediated adhesive properties, can effectively bypass cognate and natural postsynaptic ligands to trigger presynaptic assembly in the absence of specific target recognition. In contrast, we find that postsynaptic compartment assembly depends on the prior presence of a mature presynaptic ending.

The formation of functional synapses on artificial substrates is a very important step in the development of engineered in vitro neural networks. Spherical supported bilayer lipid membranes (SS-BLMs) are used here as a novel substrate to demonstrate presynaptic vesicle accumulation at an in vitro synaptic junction. Confocal fluorescence microscopy, cryo-transmission electron microscopy (cryo-TEM), and fluorescence recovery after photobleaching (FRAP) experiments have been used to characterize the SS-BLMs. Conventional immunocytochemistry combined with confocal fluorescence microscopy was used to observe the formation of presynaptic vesicles at the neuron-SS-BLM contacts. These results indicate that lipid phases may play a role in the observed phenomenon, in addition to the chemical and electrostatic interactions between the neurons and SS-BLMs. The biocompatibility of lipid bilayers along with their membrane tunability makes the suggested approach a useful "toolkit" for many neuroengineering applications including artificial synapse formation and synaptogenesis in vivo.