Unveiling alterative splice diversity from human oligodendrocyte proteome data

RNA splicing regulator EIF3D regulates the tumor microenvironment through immunogene-related alternative splicing in head and neck squamous cell carcinoma

Study finds that eukaryotic translation initiation factor 3 subunit D (EIF3D) may play an important role in aberrant alternative splicing (AS) events in tumors. AS possesses a pivotal role in both tumour progression and the constitution of the tumour microenvironment (TME). Regrettably, our current understanding of AS remains circumscribed especially in the context of immunogene-related alternative splicing (IGAS) profiles within Head and Neck Squamous Cell Carcinoma (HNSC). In this study, we comprehensively analyzed the function and mechanism of action of EIF3D by bioinformatics analysis combined with in vitro cellular experiments, and found that high expression of EIF3D in HNSC was associated with poor prognosis of overall survival (OS) and progression-free survival (PFS). The EIF3D low expression group had a higher degree of immune infiltration and better efficacy against PD1 and CTLA4 immunotherapy compared to the EIF3D high expression group. TCGA SpliceSeq analysis illustrated that EIF3D influenced differentially spliced alternative splicing (DSAS) events involving 105 differentially expressed immunogenes (DEIGs). We observed an induction of apoptosis and a suppression of cell proliferation, migration, and invasion in EIF3D knock-down FaDu cells. RNA-seq analysis unveiled that 531 genes exhibited differential expression following EIF3D knockdown in FaDu cells. These include 52 DEIGs. Furthermore, EIF3D knockdown influenced the patterns of 1923 alternative splicing events (ASEs), encompassing 129 IGASs. This study identified an RNA splicing regulator and revealed its regulatory role in IGAS and the TME of HNSC, suggesting that EIF3D may be a potential target for predicting HNSC prognosis and immunotherapeutic response.

SpliceProt 2.0: A Sequence Repository of Human, Mouse, and Rat Proteoforms

SpliceProt 2.0 is a public proteogenomics database that aims to list the sequence of known proteins and potential new proteoforms in human, mouse, and rat proteomes. This updated repository provides an even broader range of computationally translated proteins and serves, for example, to aid with proteomic validation of splice variants absent from the reference UniProtKB/SwissProt database. We demonstrate the value of SpliceProt 2.0 to predict orthologous proteins between humans and murines based on transcript reconstruction, sequence annotation and detection at the transcriptome and proteome levels. In this release, the annotation data used in the reconstruction of transcripts based on the methodology of ternary matrices were acquired from new databases such as Ensembl, UniProt, and APPRIS. Another innovation implemented in the pipeline is the exclusion of transcripts predicted to be susceptible to degradation through the NMD pathway. Taken together, our repository and its applications represent a valuable resource for the proteogenomics community.

Exploring the mediation of DNA methylation across the epigenome between childhood adversity and First Episode of Psychosis-findings from the EU-GEI study

ABTRACT

Studies conducted in psychotic disorders have shown that DNA-methylation (DNAm) is sensitive to the impact of Childhood Adversity (CA). However, whether it mediates the association between CA and psychosis is yet to be explored. Epigenome wide association studies (EWAS) using the Illumina Infinium-Methylation EPIC array in peripheral blood tissue from 366 First-episode of psychosis and 517 healthy controls was performed. Adversity scores were created for abuse, neglect and composite adversity with the Childhood Trauma Questionnaire (CTQ). Regressions examining (I) CTQ scores with psychosis; (II) with DNAm EWAS level and (III) between DNAm and caseness, adjusted for a variety of confounders were conducted. Divide-Aggregate Composite-null Test for the composite null-hypothesis of no mediation effect was conducted. Enrichment analyses were conducted with missMethyl package and the KEGG database. Our results show that CA was associated with psychosis (Composite: OR = 1.68; p = <0.001; abuse: OR = 2.16; p < 0.001; neglect: OR = 2.27; p = <0.001). None of the CpG sites significantly mediated the adversity-psychosis association after Bonferroni correction (p < 8.1 × 10-8). However, 28, 34 and 29 differentially methylated probes associated with 21, 27, 20 genes passed a less stringent discovery threshold (p < 5 × 10-5) for composite, abuse and neglect respectively, with a lack of overlap between abuse and neglect. These included genes previously associated to psychosis in EWAS studies, such as PANK1, SPEG TBKBP1, TSNARE1 or H2R. Downstream gene ontology analyses did not reveal any biological pathways that survived false discovery rate correction. Although at a non-significant level, DNAm changes in genes previously associated with schizophrenia in EWAS studies may mediate the CA-psychosis association. These results and associated involved processes such as mitochondrial or histaminergic disfunction, immunity or neural signalling requires replication in well powered samples. The lack of overlap between mediating genes associated with abuse and neglect suggests differential biological trajectories linking CA subtypes and psychosis.

The role of EEF1D in disease pathogenesis: a narrative review

Objective

The purpose of this paper was to investigate the role and mechanism of EEF1D in various diseases, especially in tumorigenesis and development, and explore the possibility of EEF1D as a biological target.

Background

EEF1D is a part of the EEF1 protein complex, which can produce four protein isoforms, of which three short isoforms are used as translation elongation factors. The three short isoforms play a role in anti-aging, regulating the cell cycle, and promoting the occurrence and development of malignant tumors, and the only long-form isoform plays a role in the development of the nervous system.

Methods

We searched the PubMed and Web of Science databases for literature up to January 2021 using relevant keywords, including “EEF1D”, “eukaryotic translation elongation factor 1 delta”, “translation elongation factor”, “translation elongation factor and cancer”, and “translation elongation factor and nervous system disease”. We then created an overview of the literature and summarized the results of the paper.

Conclusions

Through the review of relevant articles, we found that EEF1D is obviously overexpressed in a variety of tumors, and can regulate the proliferation of tumor cells and tumor growth, as well as play a role in tumor invasion. EEF1D is likely to become a new biological target for tumor therapy and diagnosis.

Proteogenomics Reveals Orthologous Alternatively Spliced Proteoforms in the Same Human and Mouse Brain Regions with Differential Abundance in an Alzheimer's Disease Mouse Model

Alternative splicing (AS) may increase the number of proteoforms produced by a gene. Alzheimer's disease (AD) is a neurodegenerative disease with well-characterized AS proteoforms. In this study, we used a proteogenomics strategy to build a customized protein sequence database and identify orthologous AS proteoforms between humans and mice on publicly available shotgun proteomics (MS/MS) data of the corpus callosum (CC) and olfactory bulb (OB). Identical proteotypic peptides of six orthologous AS proteoforms were found in both species: PKM1 (gene PKM/Pkm), STXBP1a (gene STXBP1/Stxbp1), Isoform 3 (gene HNRNPK/Hnrnpk), LCRMP-1 (gene CRMP1/Crmp1), SP3 (gene CADM1/Cadm1), and PKCβII (gene PRKCB/Prkcb). These AS variants were also detected at the transcript level by publicly available RNA-Seq data and experimentally validated by RT-qPCR. Additionally, PKM1 and STXBP1a were detected at higher abundances in a publicly available MS/MS dataset of the AD mouse model APP/PS1 than its wild type. These data corroborate other reports, which suggest that PKM1 and STXBP1a AS proteoforms might play a role in amyloid-like aggregate formation. To the best of our knowledge, this report is the first to describe PKM1 and STXBP1a overexpression in the OB of an AD mouse model. We hope that our strategy may be of use in future human neurodegenerative studies using mouse models.

Functional and structural features of proteins associated with alternative splicing

The alternative splicing is a mechanism increasing the number of expressed proteins and a variety of these functions. We uncovered the protein domains most frequently lacked or occurred in the splice variants. Proteins presented by several isoforms participate in such processes as transcription regulation, immune response, etc. Our results displayed the association of alternative splicing with branched regulatory pathways. By considering the published data on the protein proteins encoded by the 18th human chromosome, we noted that alternative products display the differences in several functional features, such as phosphorylation, subcellular location, ligand specificity, protein-protein interactions, etc. The investigation of alternative variants referred to the protein kinase domain was performed by comparing the alternative sequences with 3D structures. It was shown that large enough insertions/deletions could be compatible with the kinase fold if they match between the conserved secondary structures. Using the 3D data on human proteins, we showed that conformational flexibility could accommodate fold alterations in splice variants. The investigations of structural and functional differences in splice isoforms are required to understand how to distinguish the isoforms expressed as functioning proteins from the non-realized transcripts. These studies allow filling the gap between genomic and proteomic data.

The Challenge to Search for New Nervous System Disease Biomarker Candidates: the Opportunity to Use the Proteogenomics Approach

Alzheimer's disease, Parkinson's disease, prion diseases, schizophrenia, and multiple sclerosis are the most common nervous system diseases, affecting millions of people worldwide. The current scientific literature associates these pathological conditions to abnormal expression levels of certain proteins, which in turn improved the knowledge concerning normal and affected brains. However, there is no available cure or preventive therapy for any of these disorders. Proteogenomics is a recent approach defined as the data integration of both nucleotide high-throughput sequencing and protein mass spectrometry technologies. In the last years, proteogenomics studies in distinct diseases have emerged as a strategy for the identification of uncharacterized proteoforms, which are all the different protein forms derived from a single gene. For many of these diseases, at least one protein used as biomarker presents more than one proteoform, which fosters the analysis of publicly available data focusing proteoforms. Given this context, we describe the most important biomarkers for each neurodegenerative disease and how genomics, transcriptomics, and proteomics separately contributed to unveil them. Finally, we present a selection of proteogenomics studies in which the combination of nucleotide and proteome high-throughput data, from cell lines or brain tissue samples, is used to uncover proteoforms not previously described. We believe that this new approach may improve our knowledge about nervous system diseases and brain function and an opportunity to identify new biomarker candidates.

Insights into nuclear dynamics using live-cell imaging approaches

The nucleus contains the genetic blueprint of the cell and myriad interactions within this subcellular structure are required for gene regulation. In the current scientific era, characterization of these gene regulatory networks through biochemical techniques coupled with systems-wide 'omic' approaches has become commonplace. However, these strategies are limited because they represent a mere snapshot of the cellular state. To obtain a holistic understanding of nuclear dynamics, relevant molecules must be studied in their native contexts in living systems. Live-cell imaging approaches are capable of providing quantitative assessment of the dynamics of gene regulatory interactions within the nucleus. We survey recent insights into what live-cell imaging approaches have provided the field of nuclear dynamics. In this review, we focus on interactions of DNA with other DNA loci, proteins, RNA, and the nuclear envelope. WIREs Syst Biol Med 2017, 9:e1372. doi: 10.1002/wsbm.1372 For further resources related to this article, please visit the WIREs website.