An Integrated Method for Crafting Flexible and Convenient Electrophysiological Optrodes for Multi-Region In Vivo Recording

Epilepsy is a neurological disorder characterized by synchronized abnormal discharges involving multiple brain regions. Focal lesions facilitate the ...

Fudan University

Mitochondrial nucleases play important roles in accurate maintenance and correct metabolism of mtDNA, the own genetic materials of mitochondria that are passed exclusively from mother to child. MGME1 is a highly conserved DNase that was discovered recently. Mutations in MGME1-coding gene lead to severe mitochondrial syndromes characterized by external ophthalmoplegia, emaciation, and respiratory failure in humans. Unlike many other nucleases that are distributed in multiple cellular organelles, human MGME1 is a mitochondria-specific nuclease; therefore, it can serve as an ideal target for treating related syndromes. Here, we report one HsMGME1-Mn2+ complex and three different HsMGME1-DNA complex structures. In combination with in vitro cleavage assays, our structures reveal the detailed molecular basis for substrate DNA binding and/or unwinding by HsMGME1. Besides the conserved two-cation-assisted catalytic mechanism, structural analysis of HsMGME1 and comparison with homologous proteins also clarified substrate binding and cleavage directionalities of the DNA double-strand break repair complexes RecBCD and AddAB.

Structural insights into DNA degradation by human mitochondrial nuclease MGME1.

Pain perception involves multiple brain regions and networks. Understanding how these brain networks work together is fundamental for appreciating network-wise changes reported in patients with chronic pain disorders. Parcellating pain related networks and understanding their causal relationships is the first step to understand how painful information is processed, integrated, and modulated, and it requires direct manipulation of specific brain regions. Nonhuman primates (NHP) offer an ideal model system to achieve these goals because cortical and subcortical regions in the NHP brain are established based on a variety of different types of data collected in a way that is not feasible or, at least, extremely difficult in humans (i.e., histology data, tract-tracing, intracerebral recordings). In addition, different methodological techniques can also help characterize and further understand these brain cortical and subcortical regions over the course of development. Here we used a heat nociceptive stimulation that is proven to elicit activity of nociceptive neurons in the cortex to refine and parcellate the whole brain nociceptive functional networks, to identify key network hubs, and to characterize network-wise temporal dynamic signatures using high-resolution fMRI. We first functionally localized 24 cortical and subcortical regions that responded to heat nociceptive stimuli (somatosensory area 1/2, area 3a/3b, S2, posterior insula (pIns), anterior insula, area 7b, posterior parietal cortex, anterior cingulate cortex (ACC), prefrontal cortex, caudate, and mediodorsal (MD) and ventral posterior lateral (VPL) thalamic nuclei) and used them as seeds in resting state fMRI (rsfMRI) data analysis. We applied both hierarchical clustering and graph-theory analyses of the pairwise rsfMRI correlation metrics and identified five cortical and one subcortical sub-networks: strong resting state functional connectivity (rsFC) between ACC and prefrontal regions, parietal cortex and area 7b, S2 and posterior insula, areas 3a/3b and 1/2 within the S1 cortex, and thalamic MD and caudate nuclei. The rsFC strengths between cortical areas within each subnetwork were significantly stronger than those between subcortical regions. Regions within each sub-network also exhibited highly correlated temporal dynamics at rest, but the overall dynamic patterns varied drastically across sub-networks. Graph-theory analysis identified the MD nucleus as a hub that connects subcortical and cortical nociceptive sub-networks. The S2-pIns connection joins the sensory and affective/cognitive sub-networks.

Graph theory analysis identified two hubs that connect sensorimotor and cognitive and cortical and subcortical nociceptive networks in the non-human primate.

Cortical reactivation and regain of interareal functional connections have been linked to the recovery of hand grasping behavior after loss of sensory inputs in primates. We investigated contributions of neurons in two hierarchically organized somatosensory areas, 3b and S2, by characterizing local field potential (LFP) and multiunit spiking activity in five states (rest, stimulus-on, sustained, stimulus-off, and induced) and interareal communication after grasping behavior of dorsal column lesioned male squirrel monkeys had mostly recovered. Compared with normal cortex, fMRI, LFP, and spiking response magnitudes to step indentations were significantly weaker. The sustained component of the spiking recovered much better than the stimulus-off response. Correlation between overall spiking and γ LFP remained strong within each recovered areas 3b and S2. The interareal correlations of γ LFP were severely disrupted, except in the resting and stimulus-on periods. Interareal correlation of spiking was disrupted in the stimulus-off period only. In summary, submodality of low threshold mechanoreceptive neurons recovered differentially in input-deprived area 3b and S2 when impaired global hand grasping behavior returned. Slow-adapting-like neurons recovered, whereas rapid-adapting-like neurons did not. Interareal communications were also severely compromised. We propose that slow-adapting-like neurons and afferents in recovered area 3b and S2 mediate recovery of impaired grasping behavior after dorsal column tract lesion. Sensory feedback is essential for execution of hand grasping behavior in primates. Reactivations of somatosensory cortices have been attributed to recovery of such behavior after loss of sensory inputs via largely unknown mechanisms. In input-deprived area 3b and S2 cortex, after hand grasping behavior mostly recovered, we found slow-adapting-like neurons were greatly recovered, whereas rapid-adapting-like neurons did not. Communications between area 3b and S2 neurons were severely compromised. We suggest that recovery of slow-adapting-like neurons in input-deprived area 3b and S2 may mediate the recovery of hand grasping behavior.

Differential Recovery of Submodality Touch Neurons and Interareal Communication in Sensory Input-Deprived Area 3b and S2 Cortices.

The reinvigoration of anti-tumor T cells in response to immune checkpoint blockade (ICB) therapy is well established. Whether and how ICB therapy manipulates antibody-mediated immune response in cancer environments, however, remains elusive. Using tandem mass spectrometric analysis of modification of immunoglobulin G (IgG) from hepatoma tissues, we identified a role of ICB therapy in catalyzing IgG sialylation in the Fc region. Effector T cells triggered sialylation of IgG via an interferon (IFN)-γ-ST6Gal-I-dependent pathway. DC-SIGN macrophages represented the main target cells of sialylated IgG. Upon interacting with sialylated IgG, DC-SIGN stimulated Raf-1-elicited elevation of ATF3, which inactivated cGAS-STING pathway and eliminated subsequent type-I-IFN-triggered antitumorigenic immunity. Although enhanced IgG sialylation in tumors predicted improved therapeutic outcomes for patients receiving ICB therapy, impeding IgG sialylation augmented antitumorigenic T cell immunity after ICB therapy. Thus, targeting antibody-based negative feedback action of ICB therapy has potential for improving efficacy of cancer immunotherapies.

Immune checkpoint therapy-elicited sialylation of IgG antibodies impairs antitumorigenic type I interferon responses in hepatocellular carcinoma.

To establish a deep learning (DL) model for predicting tumor grades and expression of pathologic markers of meningioma.

Predicting meningioma grades and pathologic marker expression via deep learning.

The directional organization of multiple nociceptive regions, particularly within obscure operculoinsular areas, underlying multidimensional pain processing remains elusive. This study aims to establish the fundamental organization between somatosensory and insular cortices in routing nociceptive information. By employing an integrated multimodal approach of high-field fMRI, intracranial electrophysiology, and transsynaptic viral tracing in rats, we observed a hierarchically organized connection of S1/S2 → posterior insula → anterior insula in routing nociceptive information. The directional nociceptive pathway determined by early fMRI responses was consistent with that examined by early evoked LFP, intrinsic effective connectivity, and anatomical projection, suggesting fMRI could provide a valuable facility to discern directional neural circuits in animals and humans non-invasively. Moreover, our knowledge of the nociceptive hierarchical organization of somatosensory and insular cortices and the interface role of the posterior insula may have implications for the development of targeted pain therapies.

fMRI, LFP, and anatomical evidence for hierarchical nociceptive routing pathway between somatosensory and insular cortices.

Facial palsy can result in a serious complication known as facial synkinesis, causing both physical and psychological harm to the patients. There is growing evidence that patients with facial synkinesis have brain abnormalities, but the brain mechanisms and underlying imaging biomarkers remain unclear. Here, we employed functional magnetic resonance imaging (fMRI) to investigate brain function in 31 unilateral post facial palsy synkinesis patients and 25 healthy controls during different facial expression movements and at rest. Combining surface-based mass-univariate analysis and multivariate pattern analysis, we identified diffused activation and intrinsic connection patterns in the primary motor cortex and the somatosensory cortex on the patient's affected side. Further, we classified post facial palsy synkinesis patients from healthy subjects with favorable accuracy using the support vector machine based on both task-related and resting-state functional magnetic resonance imaging data. Together, these findings indicate the potential of the identified functional reorganizations to serve as neuroimaging biomarkers for facial synkinesis diagnosis.

Spatial functional reorganizations can serve as potential biomarkers of post facial palsy synkinesis.

Thermosensation is vital for the survival, propagation, and adaption of all organisms, but its mechanism is not fully understood yet. Here, we find that TMC6, a membrane protein of unknown function, is highly expressed in dorsal root ganglion (DRG) neurons and functions as a Gαq-coupled G protein-coupled receptor (GPCR)-like receptor to sense noxious heat. TMC6-deficient mice display a substantial impairment in noxious heat sensation while maintaining normal perception of cold, warmth, touch, and mechanical pain. Further studies show that TMC6 interacts with Gαq via its intracellular C-terminal region spanning Ser to Pro. Specifically disrupting such interaction using polypeptide in DRG neurons, genetically ablating Gαq, or pharmacologically blocking Gαq-coupled GPCR signaling can replicate the phenotype of TMC6 deficient mice regarding noxious heat sensation. Noxious heat stimulation triggers intracellular calcium release from the endoplasmic reticulum (ER) of TMC6- but not control vector-transfected HEK293T cell, which can be significantly inhibited by blocking PLC or IP3R. Consistently, noxious heat-induced intracellular Ca release from ER and action potentials of DRG neurons largely reduced when ablating TMC6 or blocking Gαq/PLC/IP3R signaling pathway as well. In summary, our findings indicate that TMC6 can directly function as a Gαq-coupled GPCR-like receptor sensing noxious heat.

Ruiqi Wu

State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science,
Institutes of Brain Science,
State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science

Fudan University

An Integrated Method for Crafting Flexible and Convenient Electrophysiological Optrodes for Multi-Region In Vivo Recording