Neuroligin3 splice isoforms shape inhibitory synaptic function in the mouse hippocampus.

Synapse formation is a dynamic process essential for the development and maturation of the neuronal circuitry in the brain. At the synaptic cleft, trans-synaptic protein-protein interactions are major biological determinants of proper synapse efficacy. The balance of excitatory and inhibitory synaptic transmission (E-I balance) stabilizes synaptic activity, and dysregulation of the E-I balance has been implicated in neurodevelopmental disorders, including autism spectrum disorders. However, the molecular mechanisms underlying the E-I balance remain to be elucidated. Here, using single-cell transcriptomics, immunohistochemistry, and electrophysiology approaches to murine CA1 pyramidal neurons obtained from organotypic hippocampal slice cultures, we investigate neuroligin (Nlgn) genes that encode a family of postsynaptic adhesion molecules known to shape excitatory and inhibitory synaptic function. We demonstrate that the NLGN3 protein differentially regulates inhibitory synaptic transmission in a splice isoform-dependent manner at hippocampal CA1 synapses. We also found that distinct subcellular localizations of the NLGN3 isoforms contribute to the functional differences observed among these isoforms. Finally, results from single-cell RNA-Seq analyses revealed that Nlgn1 and Nlgn3 are the major murine Nlgn genes and that the expression levels of the Nlgn splice isoforms are highly diverse in CA1 pyramidal neurons. Our results delineate isoform-specific effects of Nlgn genes on the E-I balance in the murine hippocampus.

NADPH oxidase controls neutrophilic response to sterile inflammation in mice by regulating the IL-1α/G-CSF axis.

The leukocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase generates reactive oxygen species essential in microbial killing and regulation of inflammation. Inactivating mutations in this enzyme lead to chronic granulomatous disease (CGD), associated with increased susceptibility to both pyogenic infections and to inflammatory disorders. The role of the NADPH oxidase in regulating inflammation driven by nonmicrobial stimuli is poorly understood. Here, we show that NADPH oxidase deficiency enhances the early local release of interleukin-1α (IL-1α) in response to damaged cells, promoting an excessive granulocyte colony-stimulating factor (G-CSF)-regulated neutrophilic response and prolonged inflammation. In peritoneal inflammation elicited by tissue injury, X-linked Cybb-null (X-CGD) mice exhibited increased release of IL-1α and IL-1 receptor -mediated G-CSF production. In turn, higher levels of systemic G-CSF increased peripheral neutrophilia, which amplified neutrophilic peritoneal inflammation in X-CGD mice. Dampening early neutrophil recruitment by neutralization of IL-1α, G-CSF, or neutrophil depletion itself promoted resolution of otherwise prolonged inflammation in X-CGD. IL-1ß played little role. Thus, we identified an excessive IL-1α/G-CSF response as a major driver of enhanced sterile inflammation in CGD in the response to damaged cells. More broadly, these results provide new insights into the regulation of sterile inflammation, and identify the NADPH oxidase in regulating the amplitude of the early neutrophilic response.

A neurogenic signature involving monoamine Oxidase-A controls human thermogenic adipose tissue development.

Mechanisms that control 'beige/brite' thermogenic adipose tissue development may be harnessed to improve human metabolic health. To define these mechanisms, we developed a species-hybrid model in which human mesenchymal progenitor cells were used to develop white or thermogenic/beige adipose tissue in mice. The hybrid adipose tissue developed distinctive features of human adipose tissue, such as larger adipocyte size, despite its neurovascular architecture being entirely of murine origin. Thermogenic adipose tissue recruited a denser, qualitatively distinct vascular network, differing in genes mapping to circadian rhythm pathways, and denser sympathetic innervation. The enhanced thermogenic neurovascular network was associated with human adipocyte expression of THBS4, TNC, NTRK3, and SPARCL1, which enhance neurogenesis, and decreased expression of MAOA and ACHE, which control neurotransmitter tone. Systemic inhibition of MAOA, which is present in human but absent in mouse adipocytes, induced browning of human but not mouse adipose tissue, revealing the physiological relevance of this pathway. Our results reveal species-specific cell type dependencies controlling the development of thermogenic adipose tissue and point to human adipocyte MAOA as a potential target for metabolic disease therapy.

PI(3)P-p40phox binding regulates NADPH oxidase activation in mouse macrophages and magnitude of inflammatory responses in vivo.

Mutations in the leukocyte NADPH oxidase that abrogate superoxide production result in chronic granulomatous disease (CGD), an inherited immunodeficiency associated with recurrent infections and inflammatory complications. The cytosolic regulatory subunit p40phox plays a specialized role in stimulating NADPH oxidase activity on intracellular membranes via its phosphatidylinositol 3-phosphate [PI(3)P]-binding domain, as revealed by studies largely focused on neutrophils. Whether PI(3)P-p40phox-regulated superoxide production contributes to regulating inflammatory responses is not well understood. Here, we report that mice expressing p40phox R58A, which lacks PI(3)P binding, had impaired macrophage NADPH oxidase activity and increased sterile inflammation. p40phoxR58A/R58A macrophages exhibited diminished phagosome reactive oxygen species (ROS) in response to certain particulate and soluble ligands, including IgG-opsonized particles and a TLR2 agonist, along with unexpected defects in plasma membrane oxidase activity. Compared with wild-type (WT) mice, p40phoxR58A/R58A mice had elevated numbers of newly recruited neutrophils and monocytes in peritoneal inflammation elicited by zymosan, monosodium urate (MSU) crystals, or sodium periodate. At later time points, higher numbers of inflammatory macrophages in p40phoxR58A/R58A mice were consistent with delayed resolution. Our studies demonstrate a critical role of PI(3)P-p40phox binding for optimal activation of the NADPH oxidase in macrophages. Furthermore, selective loss of PI(3)P-regulated NADPH oxidase activity was sufficient to enhance significantly responses to inflammation and delay resolution.