Altered expression pattern of testican-1 mRNA after brain injury

Human dermal fibroblast-derived secretory proteins for regulating nerve restoration: A bioinformatic approach

BACKGROUND

Human dermal fibroblasts secrete diverse proteins that regulate wound repair and tissue regeneration.

METHODS

In this study, dermal fibroblast-conditioned medium (DFCM) proteins potentially regulating nerve restoration were bioinformatically selected among the 337 protein lists identified by quantitative liquid chromatography-tandem mass spectrometry. Using these proteins, protein-protein interaction network analysis was conducted. In addition, the roles of DFCM proteins were reviewed according to their protein classifications.

RESULTS

Gene Ontology protein classification categorized these 57 DFCM proteins into various classes, including protein-binding activity modulator (N = 11), cytoskeletal protein (N = 8), extracellular matrix protein (N = 6), metabolite interconversion enzyme (N = 5), chaperone (N = 4), scaffold/adapter protein (N = 4), calcium-binding protein (N = 3), cell adhesion molecule (N = 2), intercellular signal molecule (N = 2), protein modifying enzyme (N = 2), transfer/carrier protein (N = 2), membrane traffic protein (N = 1), translational protein (N = 1), and unclassified proteins (N = 6). Further protein-protein interaction network analysis of 57 proteins revealed significant interactions among the proteins that varied according to the settings of confidence score.

CONCLUSIONS

Our bioinformatic analysis demonstrated that DFCM contains many secretory proteins that form significant protein-protein interaction networks crucial for regulating nerve restoration. These findings underscore DFCM proteins' critical roles in various nerve restoration stages during the wound repair process.

Transcriptomic evidence for Brachyury expression in the caudal tip region of adult Ptychodera flava (Hemichordata)

Most metazoans have a single copy of the T-box transcription factor gene Brachyury. This gene is expressed in cells of the blastopore of late blastulae and the archenteron invagination region of gastrulae. It appears to be crucial for gastrulation and mesoderm differentiation of embryos. Although this expression pattern is shared by most deuterostomes, Brachyury expression has not been reported in adult stages. Here we show that Brachyury of an indirect developer, the hemichordate acorn worm Ptychodera flava, is expressed not only in embryonic cells, but also in cells of the caudal tip (anus) region of adults. This spatially restricted expression, shown by whole-mount in situ hybridization, was confirmed by Iso-Seq RNA sequencing and single-cell RNA-seq (scRNA-seq) analysis. Iso-Seq analysis showed that gene expression occurs only in the caudal region of adults, but not in anterior regions, including the stomochord. scRNA-seq analysis showed a cluster that contained Brachyury-expressing cells comprising epidermis- and mesoderm-related cells, but which is unlikely to be associated with the nervous system or muscle. Although further investigation is required to examine the roles of Brachyury in adults, this study provides important clues for extending studies on Brachyury expression involved in development of the most posterior region of deuterostomes.

SPOCK1 with unexpected function. The start of a new career

SPOCK1, 2 and 3 are considered as matricellular proteoglycans without structural role. Their functions are only partly elucidated. SPOCK1 was detected in the brain as a member of the neural synapses, then in the neuromuscular junctions. It plays a role in the regulation of blood-brain barrier. Its best characterized activity was its oncogenic potential discovered in 2012. Its deleterious effect on tumor progression was detected on 36 different types of tumors by the end of 2020. However, its mode of actions is still not completely understood. Furthermore, even less was discovered about its physiological function. The fact that it was found to localize in the mitochondria and interfered with the lipid metabolism indicated, that the full discovery of SPOCK1 still waiting for us.

Cerebrospinal fluid proteomics targeted for central nervous system processes in bipolar disorder

The etiopathology of bipolar disorder is largely unknown. We collected cerebrospinal fluid (CSF) samples from two independent case-control cohorts (total n = 351) to identify proteins associated with bipolar disorder. A panel of 92 proteins targeted towards central nervous system processes identified two proteins that replicated across the cohorts: the CSF concentrations of testican-1 were lower, and the CSF concentrations of C-type lectin domain family 1 member B (CLEC1B) were higher, in cases than controls. In a restricted subgroup analysis, we compared only bipolar type 1 with controls and identified two additional proteins that replicated in both cohorts: draxin and tumor necrosis factor receptor superfamily member 21 (TNFRSF21), both lower in cases than controls. This analysis additionally revealed several proteins significantly associated with bipolar type 1 in one cohort, falling just short of replicated statistical significance in the other (tenascin-R, disintegrin and metalloproteinase domain-containing protein 23, cell adhesion molecule 3, RGM domain family member B, plexin-B1, and brorin). Next, we conducted genome-wide association analyses of the case-control-associated proteins. In these analyses, we found associations with the voltage-gated calcium channel subunit CACNG4, and the lipid-droplet-associated gene PLIN5 with CSF concentrations of TNFRSF21 and CLEC1B, respectively. The reported proteins are involved in neuronal cell-cell and cell-matrix interactions, particularly in the developing brain, and in pathways of importance for lithium's mechanism of action. In summary, we report four novel CSF protein associations with bipolar disorder that replicated in two independent case-control cohorts, shedding new light on the central nervous system processes implicated in bipolar disorder.

Neural Tissue Homeostasis and Repair Is Regulated via CS and DS Proteoglycan Motifs

Chondroitin sulfate (CS) is the most abundant and widely distributed glycosaminoglycan (GAG) in the human body. As a component of proteoglycans (PGs) it has numerous roles in matrix stabilization and cellular regulation. This chapter highlights the roles of CS and CS-PGs in the central and peripheral nervous systems (CNS/PNS). CS has specific cell regulatory roles that control tissue function and homeostasis. The CNS/PNS contains a diverse range of CS-PGs which direct the development of embryonic neural axonal networks, and the responses of neural cell populations in mature tissues to traumatic injury. Following brain trauma and spinal cord injury, a stabilizing CS-PG-rich scar tissue is laid down at the defect site to protect neural tissues, which are amongst the softest tissues of the human body. Unfortunately, the CS concentrated in gliotic scars also inhibits neural outgrowth and functional recovery. CS has well known inhibitory properties over neural behavior, and animal models of CNS/PNS injury have demonstrated that selective degradation of CS using chondroitinase improves neuronal functional recovery. CS-PGs are present diffusely in the CNS but also form denser regions of extracellular matrix termed perineuronal nets which surround neurons. Hyaluronan is immobilized in hyalectan CS-PG aggregates in these perineural structures, which provide neural protection, synapse, and neural plasticity, and have roles in memory and cognitive learning. Despite the generally inhibitory cues delivered by CS-A and CS-C, some CS-PGs containing highly charged CS disaccharides (CS-D, CS-E) or dermatan sulfate (DS) disaccharides that promote neural outgrowth and functional recovery. CS/DS thus has varied cell regulatory properties and structural ECM supportive roles in the CNS/PNS depending on the glycoform present and its location in tissue niches and specific cellular contexts. Studies on the fruit fly, Drosophila melanogaster and the nematode Caenorhabditis elegans have provided insightful information on neural interconnectivity and the role of the ECM and its PGs in neural development and in tissue morphogenesis in a whole organism environment.

Hippocampal CA3 transcriptional modules associated with granule cell alterations and cognitive impairment in refractory mesial temporal lobe epilepsy patients

In about a third of the patients with epilepsy the seizures are not drug-controlled. The current limitation of the antiepileptic drug therapy derives from an insufficient understanding of epilepsy pathophysiology. In order to overcome this situation, it is necessary to consider epilepsy as a disturbed network of interactions, instead of just looking for changes in single molecular components. Here, we studied CA3 transcriptional signatures and dentate gyrus histopathologic alterations in hippocampal explants surgically obtained from 57 RMTLE patients submitted to corticoamygdalohippocampectomy. By adopting a systems biology approach, integrating clinical, histopathological, and transcriptomic data (weighted gene co-expression network analysis), we were able to identify transcriptional modules highly correlated with age of disease onset, cognitive dysfunctions, and granule cell alterations. The enrichment analysis of transcriptional modules and the functional characterization of the highly connected genes in each trait-correlated module allowed us to unveil the modules’ main biological functions, paving the way for further investigations on their roles in RMTLE pathophysiology. Moreover, we found 15 genes with high gene significance values which have the potential to become novel biomarkers and/or therapeutic targets in RMTLE.

SPOCK1 Involvement in Epithelial-to-Mesenchymal Transition: A New Target in Cancer Therapy?

Background

Cancer metastasis is the main obstacle to increasing the lifespan of cancer patients. Epithelial-to-mesenchymal transition (EMT) plays a significant role in oncogenic processes, including tumor invasion, intravasation, and micrometastasis formation, and is especially critical for cancer invasion and metastasis. The extracellular matrix (ECM) plays a crucial role in the occurrence of EMT corresponding to the change in adhesion between cells and matrices.

Conclusion

SPOCK1 is a critical regulator of the ECM and mediates EMT in cancer cells. This suggests an important role for SPOCK1 in tumorigenesis, migration and invasion. SPOCK1 is a critical regulator of some processes involved in cancer progression, including cancer cell proliferation, apoptosis and migration. Herein, the functions of SPOCK1 in cancer progression are expounded, revealing the association between SPOCK1 and EMT in cancer metastasis. SPOCK1 is a positive downstream regulator of transforming growth factor-β, and SPOCK1-mediated EMT regulates invasion and metastasis through the Wnt/β-catenin pathway and PI3K/Akt signaling pathway. It is of significance that SPOCK1 may be an attractive prognostic biomarker and therapeutic target in cancer treatment.

A Genome-Wide Association Study Identifies Genetic Variants Associated with Mathematics Ability

Mathematics ability is a complex cognitive trait with polygenic heritability. Genome-wide association study (GWAS) has been an effective approach to investigate genetic components underlying mathematic ability. Although previous studies reported several candidate genetic variants, none of them exceeded genome-wide significant threshold in general populations. Herein, we performed GWAS in Chinese elementary school students to identify potential genetic variants associated with mathematics ability. The discovery stage included 494 and 504 individuals from two independent cohorts respectively. The replication stage included another cohort of 599 individuals. In total, 28 of 81 candidate SNPs that met validation criteria were further replicated. Combined meta-analysis of three cohorts identified four SNPs (rs1012694, rs11743006, rs17778739 and rs17777541) of SPOCK1 gene showing association with mathematics ability (minimum p value 5.67 × 10⁻¹⁰, maximum β −2.43). The SPOCK1 gene is located on chromosome 5q31.2 and encodes a highly conserved glycoprotein testican-1 which was associated with tumor progression and prognosis as well as neurogenesis. This is the first study to report genome-wide significant association of individual SNPs with mathematics ability in general populations. Our preliminary results further supported the role of SPOCK1 during neurodevelopment. The genetic complexities underlying mathematics ability might contribute to explain the basis of human cognition and intelligence at genetic level.

Amyloid-β Precursor Protein Modulates the Sorting of Testican-1 and Contributes to Its Accumulation in Brain Tissue and Cerebrospinal Fluid from Patients with Alzheimer Disease

The mechanisms leading to amyloid-β (Aβ) accumulation in sporadic Alzheimer disease (AD) are unknown but both increased production or impaired clearance likely contribute to aggregation. To understand the potential roles of the extracellular matrix proteoglycan Testican-1 in the pathophysiology of AD, we used samples from AD patients and controls and an in vitro approach. Protein expression analysis showed increased levels of Testican-1 in frontal and temporal cortex of AD patients; histological analysis showed that Testican-1 accumulates and co-aggregates with Aβ plaques in the frontal, temporal and entorhinal cortices of AD patients. Proteomic analysis identified 10 fragments of Testican-1 in cerebrospinal fluid (CSF) from AD patients. HEK293T cells expressing human wild type or mutant Aβ precursor protein (APP) were transfected with Testican-1. The co-expression of both proteins modified the sorting of Testican-1 into the endocytic pathway leading to its transient accumulation in Golgi, which seemed to affect APP processing, as indicated by reduced Aβ40 and Aβ42 levels in APP mutant cells. In conclusion, patient data reflect a clearance impairment that may favor Aβ accumulation in AD brains and our in vitro model supports the notion that the interaction between APP and Testican-1 may be a key step in the production and aggregation of Aβ species.

Proteoglycans of reactive rat cortical astrocyte cultures: abundance of N-unsubstituted glucosamine-enriched heparan sulfate

"Reactive" astrocytes and other glial cells in the injured CNS produce an altered extracellular matrix (ECM) that influences neuronal regeneration. We have profiled the glycosaminoglycan (GAG) component of proteoglycans (PGs) produced by reactive neonatal rat cortical astrocytes, and have quantified their neurite-outgrowth inhibitory activity. PGs extracted from cell layers and medium were fractionated on DEAE-Sephacel with a gradient of NaCl from 0.15 to 1.0 M. Monosaccharide analysis of the major peaks eluting at 0.6 M NaCl indicated an excess of GlcNH₂ to GalNH₂, suggesting an approximate HS/CS ratio of 6.2 in the cell layer and 4.2 in the medium. Chondroitinase ABC-generated disaccharide analysis of cell and medium PGs showed a >5-fold excess of chondroitin 4-sulfate over chondroitin 6-sulfate. Heparin lyase-generated disaccharides characteristic of the highly sulfated S-domain regions within HS were more abundant in cell layer than medium-derived PGs. Cell layer and medium HS disaccharides contained ~20% and ~40% N-unsubstituted glucosamine respectively, which is normally rare in HS isolated from most tissues. NGF-stimulated neurite outgrowth assays using NS-1 (PC12) neuronal cells on adsorbed substrata of PGs isolated from reactive astrocyte medium showed pronounced inhibition of neurite outgrowth, and aggregation of NS-1 cells. Cell layer PGs from DEAE-Sephacel pooled fractions having high charge density permitted greater NGF-stimulated outgrowth than PGs with lower charge density. Our results indicate the synthesis of both inhibitory and permissive PGs by activated astrocytes that may correlate with sulfation patterns and HS/CS ratios.

SPOCK3, a risk gene for adult ADHD and personality disorders

Attention-deficit/hyperactivity disorder (ADHD) is the most frequent psychiatric disorder in children, where it displays a global prevalence of 5 %. In up to 50 % of the cases, ADHD may persist into adulthood (aADHD), where it is often comorbid with personality disorders. Due to a potentially heritable nature of this comorbidity, we hypothesized that their genetic framework may contain common risk-modifying genes. SPOCK3, a poorly characterized, putatively Ca(2+)-binding extracellular heparan/chondroitin sulfate proteoglycan gene encoded by the human chromosomal region 4q32.3, was found to be associated with polymorphisms among the top ranks in a genome-wide association study (GWAS) on ADHD and a pooled GWAS on personality disorder (PD). We therefore genotyped 48 single nucleotide polymorphisms (SNPs) representative of the SPOCK3 gene region in 1,790 individuals (n aADHD = 624, n PD = 630, n controls = 536). In this analysis, we found two SNPs to be nominally associated with aADHD (rs7689440, rs897511) and four PD-associated SNPs (rs7689440, rs897511, rs17052671 and rs1485318); the latter even reached marginal significance after rigorous Bonferroni correction. Bioinformatics tools predicted a possible influence of rs1485318 on transcription factor binding, whereas the other candidate SNPs may have effects on alternative splicing. Our results suggest that SPOCK3 may modify the genetic risk for ADHD and PD; further studies are, however, needed to identify the underlying mechanisms.

Strategies for repair of white matter: influence of osmolarity and microglia on proliferation and apoptosis of oligodendrocyte precursor cells in different basal culture media

The aim of the present study has been to obtain high yields of oligodendrocyte precursor cells (OPCs) in culture. This is a first step in facilitation of myelin repair. We show that, in addition to factors, known to promote proliferation, such as basic fibroblast growth factor (FGF-2) and platelet derived growth factor (PDGF) the choice of the basal medium exerts a significant influence on the yield of OPCs in cultures from newborn rats. During a culture period of up to 9 days we observed larger numbers of surviving cells in Dulbecco's Modified Eagle Medium (DMEM), and Roswell Park Memorial Institute Medium (RPMI) compared with Neurobasal Medium (NB). A larger number of A2B5-positive OPCs was found after 6 days in RPMI based media compared with NB. The percentage of bromodeoxyuridine (BrdU)-positive cells was largest in cultures maintained in DMEM and RPMI. The percentage of caspase-3 positive cells was largest in NB, suggesting that this medium inhibits OPC proliferation and favors apoptosis. A difference between NB and DMEM as well as RPMI is the reduced Na⁺-content. The addition of equiosmolar supplements of mannitol or NaCl to NB medium rescued the BrdU-incorporation rate. This suggested that the osmolarity influences the proliferation of OPCs. Plating density as well as residual microglia influence OPC survival, BrdU incorporation, and caspase-3 expression. We found, that high density cultures secrete factors that inhibit BrdU incorporation whereas the presence of additional microglia induces an increase in caspase-3 positive cells, indicative of enhanced apoptosis. An enhanced number of microglia could thus also explain the stronger inhibition of OPC differentiation observed in high density cultures in response to treatment with the cytokines TNF-α and IFN-γ. We conclude that a maximal yield of OPCs is obtained in a medium of an osmolarity higher than 280 mOsm plated at a relatively low density in the presence of as little microglia as technically achievable.