VGF: A prospective biomarker and therapeutic target for neuroendocrine and nervous system disorders

Lower Plasma Levels of Selective VGF (Non-Acronymic) Peptides in Bipolar Disorder: Comparative Analysis Reveals Distinct Patterns across Mood Disorders and Healthy Controls

INTRODUCTION

Discriminating bipolar disorder (BD) from major depressive disorder (MDD) remains a challenging clinical task. Identifying specific peripheral biosignatures that can differentiate between BD and MDD would significantly increase diagnostic accuracy. Dysregulated neuroplasticity is implicated in BD and MDD, and psychotropic medications restore specific disrupted processes by increasing neurotrophic signalling. The nerve growth factor inducible vgf gene (non-acronymic) encodes a precursor protein named proVGF, which undergoes proteolytic processing to produce several VGF peptides, some of which were suggested to be implicated in mood disorders and have antidepressant effects. Since the presence of VGF peptides in humans has been exclusively investigated in brain and cerebrospinal fluid, we aimed to identify which VGF peptides are present in the plasma and to investigate whether their levels could differentiate BD from MDD as well as responders from non-responders to pharmacological interventions.

METHODS

VGF peptides were investigated in plasma from patients diagnosed with MDD (n = 37) or BD (n = 40 under lithium plus n = 29 never exposed to lithium), as well as healthy controls (HC; n = 36).

RESULTS

Three VGF peptides (TLQP-11, AQEE-14, and NAPP-19) were identified using spectrometry analysis of plasma from HC. These peptides were then measured in the entire sample using ELISA, which showed significantly lower levels of AQEE and NAPP in BD than in HC and MDD (p = 5.0 × 10-5, p = 0.001, respectively).

CONCLUSION

Our findings suggest that lower plasma levels of NAPP and AQEE are specifically associated with BD, thus possibly representing a diagnostic biomarker in mood disorders.

BDNF-VGF Pathway Aggravates Incision Induced Acute Postoperative Pain via Upregulating the Neuroinflammation in Dorsal Root Ganglia

Approximately one-third of postoperative patients are troubled by postoperative pain. Effective treatments are still lacking. The aim of this study is to investigate the role of brain-derived neurotrophic factor (BDNF)-VGF (non-acronymic) in dorsal root ganglia (DRG) in postoperative pain. Pain behaviors were assessed through measurements of paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). Transcriptome analysis was conducted to identify potential targets associated with postoperative pain. Western blotting, immunofluorescence, and ELISA were employed to further detect macrophage activation as well as the expression of BDNF, VGF, TNF-α, IL-1β, and IL-6. Results showed that plantar incision induced both mechanical and thermal hyperalgesia. Transcriptome analysis suggested that plantar incision caused upregulation of BDNF and VGF. The expressions of BDNF and VGF were upregulated in isolectin B4-positive (IB4+) and calcitonin gene-related peptide-positive (CGRP+) neurons, rather than neurofilament 200-positive (NF200+) neurons. The activation of BDNF-VGF pathway upregulated expression of IL-6, TNF-α, and IL-1β and promoted the activation of macrophages. In conclusion, BDNF-VGF pathway aggravates acute postoperative pain by promoting macrophage activation and pro-inflammatory cytokine production, which may provide a new target for the treatment of postoperative pain.

A targeted CRISPR-Cas9 mediated F0 screen identifies genes involved in establishment of the enteric nervous system

The vertebrate enteric nervous system (ENS) is a crucial network of enteric neurons and glia resident within the entire gastrointestinal tract (GI). Overseeing essential GI functions such as gut motility and water balance, the ENS serves as a pivotal bidirectional link in the gut-brain axis. During early development, the ENS is primarily derived from enteric neural crest cells (ENCCs). Disruptions to ENCC development, as seen in conditions like Hirschsprung disease (HSCR), lead to the absence of ENS in the GI, particularly in the colon. In this study, using zebrafish, we devised an in vivo F0 CRISPR-based screen employing a robust, rapid pipeline integrating single-cell RNA sequencing, CRISPR reverse genetics, and high-content imaging. Our findings unveil various genes, including those encoding opioid receptors, as possible regulators of ENS establishment. In addition, we present evidence that suggests opioid receptor involvement in the neurochemical coding of the larval ENS. In summary, our work presents a novel, efficient CRISPR screen targeting ENS development, facilitating the discovery of previously unknown genes, and increasing knowledge of nervous system construction.

NeuroPep 2.0: An Updated Database Dedicated to Neuropeptide and Its Receptor Annotations

Neuropeptides not only work through nervous system but some of them also work peripherally to regulate numerous physiological processes. They are important in regulation of numerous physiological processes including growth, reproduction, social behavior, inflammation, fluid homeostasis, cardiovascular function, and energy homeostasis. The various roles of neuropeptides make them promising candidates for prospective therapeutics of different diseases. Currently, NeuroPep has been updated to version 2.0, it now holds 11,417 unique neuropeptide entries, which is nearly double of the first version of NeuroPep. When available, we collected information about the receptor for each neuropeptide entry and predicted the 3D structures of those neuropeptides without known experimental structure using AlphaFold2 or APPTEST according to the peptide sequence length. In addition, DeepNeuropePred and NeuroPred-PLM, two neuropeptide prediction tools developed by us recently, were also integrated into NeuroPep 2.0 to help to facilitate the identification of new neuropeptides. NeuroPep 2.0 is freely accessible at https://isyslab.info/NeuroPepV2/.

A targeted CRISPR-Cas9 mediated F0 screen identifies genes involved in establishment of the enteric nervous system

The vertebrate enteric nervous system (ENS) is a crucial network of enteric neurons and glia resident within the entire gastrointestinal tract (GI). Overseeing essential GI functions such as gut motility and water balance, the ENS serves as a pivotal bidirectional link in the gut-brain axis. During early development, the ENS is primarily derived from enteric neural crest cells (ENCCs). Disruptions to ENCC development, as seen in conditions like Hirschsprung disease (HSCR), lead to absence of ENS in the GI, particularly in the colon. In this study, using zebrafish, we devised an in vivo F0 CRISPR-based screen employing a robust, rapid pipeline integrating single-cell RNA sequencing, CRISPR reverse genetics, and high-content imaging. Our findings unveil various genes, including those encoding for opioid receptors, as possible regulators of ENS establishment. In addition, we present evidence that suggests opioid receptor involvement in neurochemical coding of the larval ENS. In summary, our work presents a novel, efficient CRISPR screen targeting ENS development, facilitating the discovery of previously unknown genes, and increasing knowledge of nervous system construction.

METTL3 exerts synergistic effects on m6A methylation and histone modification to regulate the function of VGF in lung adenocarcinoma

BACKGROUND

Multiple genetic and epigenetic regulatory mechanisms play a vital role in tumorigenesis and development. Understanding the interplay between different epigenetic modifications and its contribution to transcriptional regulation in cancer is essential for precision medicine. Here, we aimed to investigate the interplay between N6-methyladenosine (m6A) modifications and histone modifications in lung adenocarcinoma (LUAD).

RESULTS

Based on the data from public databases, including chromatin property data (ATAC-seq, DNase-seq), methylated RNA immunoprecipitation sequencing (MeRIP-seq), and gene expression data (RNA-seq), a m6A-related differentially expressed gene nerve growth factor inducible (VGF) was identified between LUAD tissues and normal lung tissues. VGF was significantly highly expressed in LUAD tissues and cells, and was associated with a worse prognosis for LUAD, silencing of VGF inhibited the malignant phenotype of LUAD cells by inactivating the PI3K/AKT/mTOR pathway. Through the weighted correlation network analysis (WGCNA) and integration of TCGA-LUAD RNA-seq and m6A methyltransferase METTL3-knockdown RNA-seq data, a significant positive correlation between METTL3 and VGF was observed. By using the MeRIP-qPCR and dual-luciferase reporter assays, we demonstrated that METTL3 knockdown decreased m6A modification level of VGF coding sequences in LUAD cells, the colorimetric m6A quantification assay also showed that METTL3 knockdown significantly decreased global m6A modification level in LUAD cells. Interestingly, we found that METTL3 knockdown also reduced VGF expression by increasing H3K36me3 modification at the VGF promoter. Further research revealed that METTL3 knockdown upregulated the expression of histone methylase SETD2, the major H3K36me3 methyltransferase, by methylating the m6A site in the 3'UTR of SETD2 mRNA in LUAD cells.

CONCLUSIONS

Overall, our results reveal that the expression of VGF in LUAD cells is regulated spatio-temporally by METTL3 through both transcriptional (via histone modifications) and post-transcriptional (via m6A modifications) mechanisms. The synergistic effect of these multiple epigenetic mechanisms provides new opportunities for the diagnosis and precision treatment of tumors.

Superhydrophilic nanocomposite adsorbents modified via nitrogen-rich phosphonate-functionalized ionic liquid linkers: enhanced phosphopeptide enrichment and phosphoproteome analysis of tau phosphorylation in the hippocampal lysate of Alzheimer's transgenic mice

In this study, new graphene-based IMAC nanocomposites for phosphopeptide enrichment were prepared according to the guideline of our new design strategy. Superhydrophilic polyethyleneimine (PEI) was introduced, to which a phosphonate-functionalized ionic liquid (PFIL) was covalently bound, to form superhydrophilic and cationic surface layers with high densities of nitrogen atoms, phosphonate functional groups, and high-loading metal ions. Due to the combined features of superhydrophilicity, flexibility, highly dense metal binding sites, large surface area and excellent size-exclusion effect, the fabricated nanocomposite G@mSiO₂@PEI-PFIL-Ti⁴⁺ exhibits superior detection sensitivity to enrich phosphopeptides (tryptic β-casein digest, 0.1 fmol), and extraordinary enrichment specificity to enrich phosphopeptides from a digest mixture of β-casein and bovine serum albumin (BSA) (molar ratio, 1 : 12 000). The excellent size-exclusion effect was also observed, and 27 endogenous phosphopeptides were identified in human saliva. All these results could be attributed to the unique superhydrophilic nanocomposite structure with a high density of a cationic linker modified with phosphonate functionality. Moreover, G@mSiO₂@PEI-PFIL-Ti⁴⁺ adsorbents were used to extract phosphopeptides from the tryptic digests of hippocampal lysates for quantitative phosphoproteome analysis. The preliminary results indicate that 1649 phosphoproteins, 3286 phosphopeptides and 4075 phosphorylation sites were identified. A total of 13 Alzheimer's disease (AD)-related phosphopeptides within tau proteins were detected with a wide coverage from p-Thr111 to p-Ser404, in which the amounts of some phoshopeptides at certain sites in AD transgenic mice were found statistically higher than those in wild type littermates. Besides, phosphorylated neurofilament heavy chains, a potential biomarker for amyotrophic lateral sclerosis and traumatic brain injury, were also identified. Finally, the adsorbent was applied to human cerebrospinal fluid (CSF) and blood samples. 5 unique phosphopeptides of neuroendocrine specific VGF were identified in the CSF, while many phosphopeptides originated from the nervous system were found in the blood sample. All these results suggest that our new IMAC materials exhibit unbiased enrichment ability with superior detection sensitivity and specificity, allowing the global phosphoproteome analysis of complicated biological samples more convincible and indicating the potential use in disease diagnosis.