The Susd2 protein regulates neurite growth and excitatory synaptic density in hippocampal cultures

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential environmental dangers. However, this function can be detrimental during allergic reactions, as vagal nociceptors contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we investigate the changes in the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identify a specific class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of allergic airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the neuropeptide Y (NPY) receptor Npy1r. A screening of cytokines and neurotrophins reveals that interleukin 1β (IL-1β), IL-13, and brain-derived neurotrophic factor (BDNF) drive part of this reprogramming. IL-13 triggers Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, NPY is released into the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells reveals that a cell-specific knockout of NPY1R in nociceptor neurons in asthmatic mice altered T cell infiltration. Opposite findings are observed in asthmatic mice in which nociceptor neurons are chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits the activity of nociceptor neurons.

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential dangers in the environment. However, this function can be detrimental during allergic reactions, since vagal nociceptors can contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance, in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we aimed to investigate the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identified a unique class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the NPY receptor Npy1r. A screening of cytokines and neurotrophins revealed that IL-1β, IL-13 and BDNF drive part of this reprogramming. IL-13 triggered Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, sympathetic neurons and macrophages release NPY in the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells has revealed that a cell-specific knockout of Npy1r in nociceptor neurons in asthmatic mice leads to an increase in airway inflammation mediated by T cells. Opposite findings were observed in asthmatic mice in which nociceptor neurons were chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits nociceptor neurons' activity.

The dual role of SUSD2 in cancer development

Sushi domain-containing protein 2 (SUSD2, also known as the complement control protein domain) is a representative and vital protein in the SUSD protein family involved in many physiological and pathological processes beyond complement regulation. Cancer is one of the leading causes of death worldwide. The complex role of SUSD2 in tumorigenesis and cancer progression has raised increasing concerns. Studies suggest that SUSD2 has different regulatory tendencies among different tumors and exerts its biological effects in a cancer type-specific manner; for instance, it has oncogenic effects on breast cancer, gastric cancer, and glioma and has tumor-suppression effects on lung cancer, bladder cancer, and colon cancer. Moreover, SUSD2 can be regulated by noncoding RNAs, its promoter methylation and other molecules, such as Galectin-1 (Gal-1), tropomyosin alpha-4 chain (TPM4), and p63. The therapeutic implications of targeting SUSD2 have already been preliminarily revealed in some malignancies, including melanoma, colon cancer, and breast cancer. This article reviews the role and regulatory mechanisms of SUSD2 in cancer development, as well as its structure and distribution. We hope that this review will advance the understanding of SUSD2 as a diagnostic and/or prognostic biomarker and provide new avenues for the development of novel cancer therapies.

CSMD1 regulates brain complement activity and circuit development

Complement proteins facilitate synaptic elimination during neurodevelopmental pruning, but neural complement regulation is not well understood. CUB and Sushi Multiple Domains 1 (CSMD1) can regulate complement activity in vitro, is expressed in the brain, and is associated with increased schizophrenia risk. Beyond this, little is known about CSMD1 including whether it regulates complement activity in the brain or otherwise plays a role in neurodevelopment. We used biochemical, immunohistochemical, and proteomic techniques to examine the regional, cellular, and subcellular distribution as well as protein interactions of CSMD1 in the brain. To evaluate whether CSMD1 is involved in complement-mediated synapse elimination, we examined Csmd1-knockout mice and CSMD1-knockout human stem cell-derived neurons. We interrogated synapse and circuit development of the mouse visual thalamus, a process that involves complement pathway activity. We also quantified complement deposition on synapses in mouse visual thalamus and on cultured human neurons. Finally, we assessed uptake of synaptosomes by cultured microglia. We found that CSMD1 is present at synapses and interacts with complement proteins in the brain. Mice lacking Csmd1 displayed increased levels of complement component C3, an increased colocalization of C3 with presynaptic terminals, fewer retinogeniculate synapses, and aberrant segregation of eye-specific retinal inputs to the visual thalamus during the critical period of complement-dependent refinement of this circuit. Loss of CSMD1 in vivo enhanced synaptosome engulfment by microglia in vitro, and this effect was dependent on activity of the microglial complement receptor, CR3. Finally, human stem cell-derived neurons lacking CSMD1 were more vulnerable to complement deposition. These data suggest that CSMD1 can function as a regulator of complement-mediated synapse elimination in the brain during development.

Molecular mechanisms underlying microglial sensing and phagocytosis in synaptic pruning

Microglia are the main non-neuronal cells in the central nervous system that have important roles in brain development and functional connectivity of neural circuits. In brain physiology, highly dynamic microglial processes are facilitated to sense the surrounding environment and stimuli. Once the brain switches its functional states, microglia are recruited to specific sites to exert their immune functions, including the release of cytokines and phagocytosis of cellular debris. The crosstalk of microglia between neurons, neural stem cells, endothelial cells, oligodendrocytes, and astrocytes contributes to their functions in synapse pruning, neurogenesis, vascularization, myelination, and blood-brain barrier permeability. In this review, we highlight the neuron-derived "find-me," "eat-me," and "don't eat-me" molecular signals that drive microglia in response to changes in neuronal activity for synapse refinement during brain development. This review reveals the molecular mechanism of neuron-microglia interaction in synaptic pruning and presents novel ideas for the synaptic pruning of microglia in disease, thereby providing important clues for discovery of target drugs and development of nervous system disease treatment methods targeting synaptic dysfunction.

DEC-7/SUSD2, a sushi domain-containing protein, regulates an ultradian behavior mediated by intestinal epithelial Ca2+ oscillations in Caenorhabditis elegans

In Caenorhabditis elegans, rhythmic posterior body wall muscle contractions mediate the highly regular defecation cycle. These contractions are regulated by inositol-1,4,5-trisphosphate (InsP3) receptor-dependent Ca2+ oscillations in intestinal epithelial cells. Here, we find that mutations in dec-7, which encodes the nematode ortholog of the human Sushi domain-containing 2 protein (SUSD2), lead to an increase in InsP3 receptor-dependent rhythmic posterior body wall muscle contractions. DEC-7 is highly expressed in the intestinal epithelia and localizes to the cell-cell junction. The increase in rhythmic activity caused by the loss of dec-7 is dependent on the innexin gap junction protein INX-16. Moreover, DEC-7 is required for the clustering of INX-16 to the cell-cell junction of the intestinal epithelia. We hypothesize that DEC-7/SUSD2 regulates INX-16 activity to mediate the rhythmic frequency of the defecation motor program. Thus, our data indicate a critical role of a phylogenetically conserved cell-cell junction protein in mediating an ultradian rhythm in the intestinal epithelia of C. elegans.NEW & NOTEWORTHY The conserved complement group protein DEC-7/SUSD2 acts at the apical cell-cell junction of C. elegans intestinal epithelia to mediate gap junction protein organization and function to facilitate a Ca2+ wave-regulated ultradian behavior.

Genetic Screening of Targeted Region on the Chromosome 22q11.2 in Patients with Microtia and Congenital Heart Defect

Microtia is a congenital malformation characterized by a small, abnormally shaped auricle (pinna) ranging in severity. Congenital heart defect (CHD) is one of the comorbid anomalies with microtia. However, the genetic basis of the co-existence of microtia and CHD remains unclear. Copy number variations (CNVs) of 22q11.2 contribute significantly to microtia and CHD, respectively, thus suggesting a possible shared genetic cause embedded in this genomic region. In this study, 19 sporadic patients with microtia and CHD, as well as a nuclear family, were enrolled for genetic screening of single nucleotide variations (SNVs) and CNVs in 22q11.2 by target capture sequencing. We detected a total of 105 potential deleterious variations, which were enriched in ear- or heart-development-related genes, including TBX1 and DGCR8. The gene burden analysis also suggested that these genes carry more deleterious mutations in the patients, as well as several other genes associated with cardiac development, such as CLTCL1. Additionally, a microduplication harboring SUSD2 was validated in an independent cohort. This study provides new insights into the underlying mechanisms for the comorbidity of microtia and CHD focusing on chromosome 22q11.2, and suggests that a combination of genetic variations, including SNVs and CNVs, may play a crucial role instead of single gene mutation.

Synapse Formation and Function Across Species: Ancient Roles for CCP, CUB, and TSP-1 Structural Domains

The appearance of synapses was a crucial step in the creation of the variety of nervous systems that are found in the animal kingdom. With increased complexity of the organisms came a greater number of synaptic proteins. In this review we describe synaptic proteins that contain the structural domains CUB, CCP, or TSP-1. These domains are found in invertebrates and vertebrates, and CUB and CCP domains were initially described in proteins belonging to the complement system of innate immunity. Interestingly, they are found in synapses of the nematode C. elegans, which does not have a complement system, suggesting an ancient function. Comparison of the roles of CUB-, CCP-, and TSP-1 containing synaptic proteins in various species shows that in more complex nervous systems, these structural domains are combined with other domains and that there is partial conservation of their function. These three domains are thus basic building blocks of the synaptic architecture. Further studies of structural domains characteristic of synaptic proteins in invertebrates such as C. elegans and comparison of their role in mammals will help identify other conserved synaptic molecular building blocks. Furthermore, this type of functional comparison across species will also identify structural domains added during evolution in correlation with increased complexity, shedding light on mechanisms underlying cognition and brain diseases.

Protective effects on acute hypoxic-ischemic brain damage in mfat-1 transgenic mice by alleviating neuroinflammation

Acute hypoxic-ischemic brain damage (HIBD) mainly occurs in adults as a result of perioperative cardiac arrest and asphyxia. The benefits of n-3 polyunsaturated fatty acids (n-3 PUFAs) in maintaining brain growth and development are well documented. However, possible protective targets and underlying mechanisms of mfat-1 mice on HIBD require further investigation. The mfat-1 transgenic mice exhibited protective effects on HIBD, as indicated by reduced infarct range and improved neurobehavioral defects. RNA-seq analysis showed that multiple pathways and targets were involved in this process, with the anti-inflammatory pathway as the most significant. This study has shown for the first time that mfat-1 has protective effects on HIBD in mice. Activation of a G protein-coupled receptor 120 (GPR120)-related anti-inflammatory pathway may be associated with perioperative and postoperative complications, thus innovating clinical intervention strategy may potentially benefit patients with HIBD.

Estrogen Receptor α Agonist is Beneficial for Young Female Rats Against Chronic Unpredicted Mild Stress-Induced Depressive Behavior and Cognitive Deficits

BACKGROUND

Women are reported more likely to develop depression and dementia. However, the involved mechanism is poorly understood.

OBJECTIVE

Here, we clarified the role of estrogen receptor α (ERα) in depression and cognitive deficit in young female rats.

METHODS

After being exposed to 7-weeks' chronic unpredicted mild stress (CUMS), the depression resilient rats (Res rats) and depressed rats (Dep rats) were selected according to their records in sucrose preference test, forced swimming test, and open field test. Their cognition abilities were tested by Morris water maze. Proteomic assay, immunoprecipitation, western blotting, immunohistochemical, and Nissl staining were also used to understand the involved mechanism.

RESULTS

Compared with control rats and Res rats, Dep rats showed cognitive deficits and hippocampal impairments revealed by proteomic data, neuron losses, increased cleaved caspase-3, β-catenin phosphorylation, and glycogen synthase kinase3β (GSK3β) activation. As ERα, but not ERβ, was found declined in hippocampi of Dep rats, 4,4k,4a-(4-propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol (PPT, an ERα agonist, 1 mg/kg/day), was used to treat Dep rats (Dep + PPT). Twenty days later, the depressive behaviors, cognition deficits, and hippocampal neuron loss were rescued in Dep + PPT rats. Furthermore, Res and Dep + PPT rats had higher levels of β-catenin combined with ERα and lower levels of β-catenin combined with GSK3β than Dep rats in hippocampi.

CONCLUSION

These results demonstrated hippocampal ERα is an important pro-resilient factor in CUMS-induced depressive behaviors and cognitive deficits. It was also given that the neuroprotection afforded by hippocampal ERα/Wnt interactions have significant implications for cognition and emotion in young females.

Flexible Mixture Model Approaches That Accommodate Footprint Size Variability for Robust Detection of Balancing Selection

Long-term balancing selection typically leaves narrow footprints of increased genetic diversity, and therefore most detection approaches only achieve optimal performances when sufficiently small genomic regions (i.e., windows) are examined. Such methods are sensitive to window sizes and suffer substantial losses in power when windows are large. Here, we employ mixture models to construct a set of five composite likelihood ratio test statistics, which we collectively term B statistics. These statistics are agnostic to window sizes and can operate on diverse forms of input data. Through simulations, we show that they exhibit comparable power to the best-performing current methods, and retain substantially high power regardless of window sizes. They also display considerable robustness to high mutation rates and uneven recombination landscapes, as well as an array of other common confounding scenarios. Moreover, we applied a specific version of the B statistics, termed B2, to a human population-genomic data set and recovered many top candidates from prior studies, including the then-uncharacterized STPG2 and CCDC169-SOHLH2, both of which are related to gamete functions. We further applied B2 on a bonobo population-genomic data set. In addition to the MHC-DQ genes, we uncovered several novel candidate genes, such as KLRD1, involved in viral defense, and SCN9A, associated with pain perception. Finally, we show that our methods can be extended to account for multiallelic balancing selection and integrated the set of statistics into open-source software named BalLeRMix for future applications by the scientific community.

SUSD2 Proteolytic Cleavage Requires the GDPH Sequence and Inter-Fragment Disulfide Bonds for Surface Presentation of Galectin-1 on Breast Cancer Cells

Galectin-1 (Gal-1) is a 14 kDa protein that has been well characterized for promoting cancer metastasis and tumor immune evasion. By localizing to the cancer cell surface, Gal-1 induces T cell apoptosis through binding T cell surface receptors. The transmembrane protein, Sushi Domain Containing 2 (SUSD2), has been previously shown to be required for Gal-1 surface presentation in breast cancer cells. Western immunoblot analysis revealed that SUSD2 is cleaved into two fragments. However, the significance of this cleavage for Gal-1 surface localization has not been investigated. To define the location of cleavage, a mutagenesis analysis of SUSD2 was performed. Our studies demonstrated that SUSD2 is cleaved at its glycine-aspartic acid-proline-histidine (GDPH) amino acid sequence. Generation of a noncleavable SUSD2 mutant (GDPH∆-SUSD2) showed that SUSD2 cleavage was required for SUSD2 and Gal-1 plasma membrane localization. Noncleavable cysteine mutants were also unable to present Gal-1 at the cell surface, further demonstrating that SUSD2 cleavage is required for Gal-1 surface presentation. Treatment with the serine protease inhibitor, Pefabloc SC, inhibited SUSD2 cleavage in a dose dependent manner, suggesting that SUSD2 is cleaved by a serine protease. Therefore, identification and inhibition of this protease may provide a new therapeutic tool for inhibiting SUSD2 and Gal-1's combined tumorigenic function in breast cancer.

Comparative transcriptome profiling of the human and mouse dorsal root ganglia: an RNA-seq-based resource for pain and sensory neuroscience research

Molecular neurobiological insight into human nervous tissues is needed to generate next-generation therapeutics for neurological disorders such as chronic pain. We obtained human dorsal root ganglia (hDRG) samples from organ donors and performed RNA-sequencing (RNA-seq) to study the hDRG transcriptional landscape, systematically comparing it with publicly available data from a variety of human and orthologous mouse tissues, including mouse DRG (mDRG). We characterized the hDRG transcriptional profile in terms of tissue-restricted gene coexpression patterns and putative transcriptional regulators, and formulated an information-theoretic framework to quantify DRG enrichment. Relevant gene families and pathways were also analyzed, including transcription factors, G-protein-coupled receptors, and ion channels. Our analyses reveal an hDRG-enriched protein-coding gene set (∼140), some of which have not been described in the context of DRG or pain signaling. Most of these show conserved enrichment in mDRG and were mined for known drug-gene product interactions. Conserved enrichment of the vast majority of transcription factors suggests that the mDRG is a faithful model system for studying hDRG, because of evolutionarily conserved regulatory programs. Comparison of hDRG and tibial nerve transcriptomes suggests trafficking of neuronal mRNA to axons in adult hDRG, and are consistent with studies of axonal transport in rodent sensory neurons. We present our work as an online, searchable repository (https://www.utdallas.edu/bbs/painneurosciencelab/sensoryomics/drgtxome), creating a valuable resource for the community. Our analyses provide insight into DRG biology for guiding development of novel therapeutics and a blueprint for cross-species transcriptomic analyses.

A DNA Methylation Signature of Addiction in T Cells and Its Reversal With DHEA Intervention

Previous studies in animal models of cocaine craving have delineated broad changes in DNA methylation profiles in the nucleus accumbens. A crucial factor for progress in behavioral and mental health epigenetics is the discovery of epigenetic markers in peripheral tissues. Several studies in primates and humans have associated differences in behavioral phenotypes with changes in DNA methylation in T cells and brain. Herein, we present a pilot study (n = 27) showing that the T cell DNA methylation profile differentiates persons with a substance use disorder from controls. Intervention with dehydroepiandrosterone (DHEA), previously shown to have a long-term therapeutic effect on human addicts herein resulted in reversal of DNA methylation changes in genes related to pathways associated with the addictive state.

Inhibition of Transforming Growth Factor-β Receptor signaling promotes culture expansion of undifferentiated human Endometrial Mesenchymal Stem/stromal Cells

Human endometrial MSC (eMSC) are a novel source of MSC easily harvested from the highly regenerative uterine lining. We have developed protocols for eMSC isolation from single cell suspensions using magnetic bead-sorting using a perivascular marker antibody to SUSD2 and culture expansion in serum free medium (SFM). Similar to other MSC, eMSC spontaneously differentiate into fibroblasts during culture expansion decreasing their purity and efficacy. The aim of this study was to determine if A83-01, a TGF-β receptor inhibitor prevents eMSC differentiation in culture. SUSD2⁺ eMSC were cultured in SFM with bFGF/EGF in 5% O₂/5% CO₂. At passage 6, eMSC were incubated with or without A83-01 for 7 days, then analysed for MSC properties. A83-01 dose dependently promoted SUSD2⁺ eMSC proliferation and blocked apoptosis via the SMAD 2/3 pathway. Fewer A83-01 treated cells were autofluorescent or stained with β-galactosidase, indicating reduced senescence. A83-01-treated cells had higher cloning efficiency, differentiated into mesodermal lineages and expressed MSC phenotypic markers. These data suggest that A83-01 maintains SUSD2⁺ eMSC stemness, promoting proliferation by blocking senescence and apoptosis in late passage cultures through binding to TGF-β receptors. Small molecules such as A83-01 may enable the expansion of undifferentiated MSC for use in tissue engineering and cell-based therapies.