Combining Double Fluorescence In Situ Hybridization with Immunolabelling for Detection of the Expression of Three Genes in Mouse Brain Sections

Increasing Aspartoacylase in the Central Amygdala: The Common Mechanism of Gastroprotective Effects of Monoamine-Based Antidepressants Against Stress

Monoamine-based antidepressants can prophylactically protect against stress-induced gastric ulcers. Although the central nucleus of amygdala (CeA) has been shown to modulate the severity of stress ulcers, little is known about the molecular mechanisms underlying the gastroprotective effect of this kind of drugs. Here, we first used proton magnetic resonance spectroscopy, a non-invasive tool, to explore the change of neurometabolites of the CeA of rats pretreated with the duloxetine of selective serotonin-norepinephrine reuptake inhibitors during 6 h of water-immersion restraint stress (WIRS). Duloxetine decreased N-acetyl-aspartate/creatine ratio (NAA/creatine) in CeA after WIRS, which was paralleled by the amelioration of gastric lesions. Meanwhile, the gastric ulcer index was negatively correlated with reduced NAA/creatine. Furthermore, the intra-CeA infusion of NAA aggravated WIRS-induced gastric mucosa damage, which suggested the crucial role of reduced NAA. Western blotting was performed to identify the specific enzymes responsible for the change of the contents of NAA at 0.5 h/3 h/6 h after WIRS, considering the preventative gastric protection of duloxetine. The NAA-catabolizing enzyme aspartoacylase (ASPA) was the only enzyme downregulated by 0.5 h WIRS and upregulated by duloxetine. Moreover, overexpressing ASPA in CeA alleviated stress ulcers. Additionally, all of the other three monoamine-based antidepressants, the fluoxetine of selective serotonin reuptake inhibitors, the amitriptyline of tricyclic agents, and the moclobemide of MAOs, increased ASPA expression in CeA. Together, these results indicate that increasing ASPA to hydrolyze NAA in CeA is a common mechanism of gastroprotective effects against stress exerted by monoamine-based antidepressants, and ASPA is a shared target more than monoamine regulation for this kind of drugs.

A versatile toolbox for semi-automatic cell-by-cell object-based colocalization analysis

Differential fluorescence labeling and multi-fluorescence imaging followed by colocalization analysis is commonly used to investigate cellular heterogeneity in situ. This is particularly important when investigating the biology of tissues with diverse cell types. Object-based colocalization analysis (OBCA) tools can employ automatic approaches, which are sensitive to errors in cell segmentation, or manual approaches, which can be impractical and tedious. Here, we present a novel set of tools for OBCA using a semi-automatic approach, consisting of two ImageJ plugins, a Microsoft Excel macro, and a MATLAB script. One ImageJ plugin enables customizable processing of multichannel 3D images for enhanced visualization of features relevant to OBCA, and another enables semi-automatic colocalization quantification. The Excel macro and the MATLAB script enable data organization and 3D visualization of object data across image series. The tools are well suited for experiments involving complex and large image data sets, and can be used in combination or as individual components, allowing flexible, efficient and accurate OBCA. Here we demonstrate their utility in immunohistochemical analyses of the developing central nervous system, which is characterized by complexity in the number and distribution of cell types, and by high cell packing densities, which can both create challenging situations for OBCA.

How to distinguish between different cell lineages sharing common markers using combinations of double in-situ-hybridization and immunostaining in avian embryos: CXCR4-positive mesodermal and neural crest-derived cells

Cell migration plays a crucial role in early embryonic development. The chemokine receptor CXCR4 has been reported to guide migration of neural crest cells (NCCs) to form the dorsal root ganglia (DRG) and sympathetic ganglia (SG). CXCR4 also plays an important part during the formation of limb and cloacal muscles. NCCs migration and muscle formation during embryonic development are usually considered separately, although both cell lineages migrate in close neighbourhood and have markers in common. In this study, we present a new method for the simultaneous detection of CXCR4, mesodermal markers and NCCs markers during chicken embryo developmental stages HH18–HH25 by combining double whole-mount in situ hybridization (ISH) and immunostaining on floating vibratome sections. The simultaneous detection of CXCR4 and markers for the mesodermal and neural crest cells in multiple labelling allowed us to compare complex gene expression patterns and it could be easily used for a wide range of gene expression pattern analyses of other chicken embryonic tissues. All steps of the procedure, including the preparation of probes and embryos, prehybridization, hybridization, visualization of the double labelled transcripts and immunostaining, are described in detail.

ADAMTS4 is upregulated in colorectal cancer and could be a useful prognostic indicator of colorectal cancer

OBJECTIVE

ADAMTS4 is a member of the ADAMTS4 family, which secretes proteinases. The mechanism of tumor metastasis may be correlated to its promotion of angiogenesis. It was determined whether ADAMTS4 participates in colorectal cancer progression.

METHODS

The expression in clinical samples and CRC cell lines was investigated. Using immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and RT-PCR, the expression of ADAMTS4 was determined in colorectal tumors of different cancer stages and anatomic sites, and in three cell lines of different aggressiveness.

RESULTS

The overexpression of ADAMTS4 was observed in tissue samples by IHC, and this was mainly located in the cytoplasm, as detected by FISH. The qRT-PCR and western blot analyses further supported the clinical sample findings.

CONCLUSION

The present data support the notion that the overexpression of ADAMTS4 in CRC might be useful as a non-invasive biomarker for detecting CRC in patients.

G protein-coupled receptor 37-like 1 modulates astrocyte glutamate transporters and neuronal NMDA receptors and is neuroprotective in ischemia

We show that the G protein‐coupled receptor GPR37‐like 1 (GPR37L1) is expressed in most astrocytes and some oligodendrocyte precursors in the mouse central nervous system. This contrasts with GPR37, which is mainly in mature oligodendrocytes. Comparison of wild type and Gpr37l1^–/– mice showed that loss of GPR37L1 did not affect the input resistance or resting potential of astrocytes or neurons in the hippocampus. However, GPR37L1‐mediated signalling inhibited astrocyte glutamate transporters and – surprisingly, given its lack of expression in neurons – reduced neuronal NMDA receptor (NMDAR) activity during prolonged activation of the receptors as occurs in ischemia. This effect on NMDAR signalling was not mediated by a change in the release of D‐serine or TNF‐α, two astrocyte‐derived agents known to modulate NMDAR function. After middle cerebral artery occlusion, Gpr37l1 expression was increased around the lesion. Neuronal death was increased by ∼40% in Gpr37l1^–/– brain compared to wild type in an in vitro model of ischemia. Thus, GPR37L1 protects neurons during ischemia, presumably by modulating extracellular glutamate concentration and NMDAR activation.

Suppressing N-Acetyl-l-Aspartate Synthesis Prevents Loss of Neurons in a Murine Model of Canavan Leukodystrophy

Canavan disease is a leukodystrophy caused by aspartoacylase (ASPA) deficiency. The lack of functional ASPA, an enzyme enriched in oligodendroglia that cleaves N-acetyl-l-aspartate (NAA) to acetate and l-aspartic acid, elevates brain NAA and causes "spongiform" vacuolation of superficial brain white matter and neighboring gray matter. In children with Canavan disease, neuroimaging shows early-onset dysmyelination and progressive brain atrophy. Neuron loss has been documented at autopsy in some cases. Prior studies have shown that mice homozygous for the Aspa nonsense mutation Nur7 also develop brain vacuolation. We now report that numbers of cerebral cortical and cerebellar neurons are decreased and that cerebral cortex progressively thins in Aspa^Nur7/Nur7 mice. This neuronal pathology is prevented by constitutive disruption of Nat8l, which encodes the neuronal NAA-synthetic enzyme N-acetyltransferase-8-like.

SIGNIFICANCE STATEMENT

This is the first demonstration of cortical and cerebellar neuron depletion and progressive cerebral cortical thinning in an animal model of Canavan disease. Genetic suppression of N-acetyl-l-aspartate (NAA) synthesis, previously shown to block brain vacuolation in aspartoacylase-deficient mice, also prevents neuron loss and cerebral cortical atrophy in these mice. These results suggest that lowering the concentration of NAA in the brains of children with Canavan disease would prevent or slow progression of neurological deficits.

Resolving in vivo gene expression during collective cell migration using an integrated RNAscope, immunohistochemistry and tissue clearing method

During collective cell migration individual cells display diverse behaviors that complicate our understanding of group cell decisions of direction and cohesion. In vivo gene and protein expression analyses would shed light on the underlying molecular choreography. However, this information has been limited due to difficulties to integrate single cell detection methods and the simultaneous readout of multiple signals deep within the embryo. Here, we optimize and integrate multiplex fluorescence in situ hybridization by RNAscope, immunohistochemistry, and tissue clearing to visualize transcript and protein localization within single cells deep within intact chick embryos. Using standard confocal microscopy, we visualize the mRNA expression of up to 3 genes simultaneously within protein labeled HNK1-positive migrating cranial neural crest cells within 2day old cleared chick embryos. Gene expression differences measured between adjacent cells or within subregions are quantified using spot counting and polyline kymograph methods, respectively. This optimization and integration of methods provide an improved 3D in vivo molecular interrogation of collective cell migration and foundation to broaden into a wider range of embryo and adult model systems.

Signalling through AMPA receptors on oligodendrocyte precursors promotes myelination by enhancing oligodendrocyte survival

Myelin, made by oligodendrocytes, is essential for rapid information transfer in the central nervous system. Oligodendrocyte precursors (OPs) receive glutamatergic synaptic input from axons but how this affects their development is unclear. Murine OPs in white matter express AMPA receptor (AMPAR) subunits GluA2, GluA3 and GluA4. We generated mice in which OPs lack both GluA2 and GluA3, or all three subunits GluA2/3/4, which respectively reduced or abolished AMPAR-mediated input to OPs. In both double- and triple-knockouts OP proliferation and number were unchanged but ~25% fewer oligodendrocytes survived in the subcortical white matter during development. In triple knockouts, this shortfall persisted into adulthood. The oligodendrocyte deficit resulted in ~20% fewer myelin sheaths but the average length, number and thickness of myelin internodes made by individual oligodendrocytes appeared normal. Thus, AMPAR-mediated signalling from active axons stimulates myelin production in developing white matter by enhancing oligodendrocyte survival, without influencing myelin synthesis per se.

DOI:http://dx.doi.org/10.7554/eLife.28080.001

Endocannabinoid signaling in hypothalamic circuits regulates arousal from general anesthesia in mice

Consciousness can be defined by two major attributes: awareness of environment and self, and arousal, which reflects the level of awareness. The return of arousal after general anesthesia presents an experimental tool for probing the neural mechanisms that control consciousness. Here we have identified that systemic or intracerebral injection of the cannabinoid CB1 receptor (CB1R) antagonist AM281 into the dorsomedial nucleus of the hypothalamus (DMH) - but not the adjacent perifornical area (Pef) or the ventrolateral preoptic nucleus of the hypothalamus (VLPO) - accelerates arousal in mice recovering from general anesthesia. Anesthetics selectively activated endocannabinoid (eCB) signaling at DMH glutamatergic but not GABAergic synapses, leading to suppression of both glutamatergic DMH-Pef and GABAergic DMH-VLPO projections. Deletion of CB1R from widespread cerebral cortical or prefrontal cortical (PFC) glutamatergic neurons, including those innervating the DMH, mimicked the arousal-accelerating effects of AM281. In contrast, CB1R deletion from brain GABAergic neurons or hypothalamic glutamatergic neurons did not affect recovery time from anesthesia. Inactivation of PFC-DMH, DMH-VLPO, or DMH-Pef projections blocked AM281-accelerated arousal, whereas activation of these projections mimicked the effects of AM281. We propose that decreased eCB signaling at glutamatergic terminals of the PFC-DMH projection accelerates arousal from general anesthesia through enhancement of the excitatory DMH-Pef projection, the inhibitory DMH-VLPO projection, or both.

Rapid production of new oligodendrocytes is required in the earliest stages of motor-skill learning

We identified a novel marker of newly-forming oligodendrocytes – the ecto-enzyme Enpp6 – and used this to track oligodendrocyte differentiation in adult mice as they learned a motor skill (running on a wheel with unevenly spaced rungs). Production of Enpp6 - expressing immature oligodendrocytes was accelerated within just 2.5 hours exposure to the complex wheel in subcortical white matter and within 4 hours in motor cortex. Conditional deletion of Myelin regulatory factor (Myrf) in oligodendrocyte precursors blocked formation of new Enpp6⁺ oligodendrocytes and impaired learning within the same ~2-3 hour time frame. This very early requirement for oligodendrocytes suggests a direct and active role in learning, closely linked to synaptic strengthening. Running performance of normal mice continued to improve over the following week accompanied by secondary waves of oligodendrocyte precursor proliferation and differentiation. We conclude that new oligodendrocytes contribute to both early and late stages of motor skill learning.