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Identification of TIA1 mRNA targets during human neuronal development

ABSTRACT: Background: Neuronal development is a tightly controlled process involving multi-layered regulatory mechanisms. While transcriptional pathways regulating neurodevelopment are well characterized, post-transcriptional programs are still poorly understood. TIA1 is an RNA-binding protein that can regulate splicing, stability, or translation of target mRNAs, and has been shown to play critical roles in neurodevelopment. However, the identity of mRNAs regulated by TIA1 during neurodevelopment is still unknown. Methods and Results: To identify the mRNAs targeted by TIA1 during the first stages of human neurodevelopment, we performed RNA immunoprecipitation-sequencing (RIP-seq) on human embryonic stem cells (hESCs) and derived neural progenitor cells (NPCs), and cortical neurons. While there was no change in TIA1 protein levels, the number of TIA1 targeted mRNAs decreased from pluripotent cells to neurons. We identified 2400, 845, and 330 TIA1 mRNA targets in hESCs, NPC, and neurons, respectively. The vast majority of mRNA targets in hESC were genes associated with neurodevelopment and included autism spectrum disorder-risk genes that were not bound in neurons. Additionally, we found that most TIA1 mRNA targets have reduced ribosomal engagement levels. Conclusion: Our results reveal TIA1 mRNA targets in hESCs and during human neurodevelopment, indicate that translation repression is a key process targeted by TIA1 binding and implicate TIA1 function in neuronal differentiation.

ORGANISM(S): Homo sapiens

PROVIDER: GSE166306 | GEO | 2021/06/01

REPOSITORIES: GEO

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Project description:T-cell intracellular antigen-1 (TIA1) is an RNA-binding protein modulating many regulatory aspects of target mRNA metabolism. Despite several reports referring to the role of TIA1 in carcinogenesis, little is known about the significance of its expression and function in human cancers including esophageal squamous cell carcinoma (ESCC). In the present study, we found that ectopic localization of overexpressed TIA1 in the cytoplasm was observed in a cohort of 143 ESCC patients using immunohistochemistry, and the cytoplasmic TIA1 was an independent prognosticator for worse overall survival. Moreover, we revealed that TIA1 was overexpression in many ESCC cell lines, and silencing of TIA1 in those cells inhibited cell growth with an accumulation of cells in G0âG1 and sub-G1 phases. The human TIA1 gene generates two major protein isoforms, TIA1a and TIA1b. Expression of TIA1a isoform tended to be higher than that of TIA1b in ESCC cells, and TIA1a was expressed both in the nucleus and cytoplasm but TIA1b was expressed mainly in the nucleus. Further studies revealed that each isoform showed opposite effects on cell proliferation through ectopically introducing each gene: TIA1a promotes anchorage-dependent and independent cell proliferation, whereas TIA1b inhibits cell proliferation and/or induces cell death. The ribonucleoprotein immunoprecipitation followed by a microarray analysis or massive-parallel sequencing identified a set of TIA1-associating mRNAs including enriched cell cycle-associated genes. Among them, SKP2 and CCNA2 mRNA were shown to be interacted with TIA1 protein through their different regions, and SKP2 and CCNA2 protein levels were positively regulated by TIA1 through suppression of mRNA decay and translational induction, respectively. These findings provide new insights into the previously unknown role of TIA1 and its isoforms as tumor-promoting molecules regulating a set of downstream oncogenic proteins, and implicate their potential application as a useful marker of malignant potential and a therapeutic target in ESCC. To investigate the target molecules regulated by TIA1 in esophageal squamous cell carcinoma cell line (KYSE180), the expression levels of mRNAs (total) and transcripts captured by RIP with TIA1 antibody (TIA1_RIP) were analyzed using microarray.

Project description:T-cell intracellular antigen-1 (TIA1) is an RNA-binding protein modulating many regulatory aspects of target mRNA metabolism. Despite several reports referring to the role of TIA1 in carcinogenesis, little is known about the significance of its expression and function in human cancers including esophageal squamous cell carcinoma (ESCC). In the present study, we found that ectopic localization of overexpressed TIA1 in the cytoplasm was observed in a cohort of 143 ESCC patients using immunohistochemistry, and the cytoplasmic TIA1 was an independent prognosticator for worse overall survival. Moreover, we revealed that TIA1 was overexpression in many ESCC cell lines, and silencing of TIA1 in those cells inhibited cell growth with an accumulation of cells in G0–G1 and sub-G1 phases. The human TIA1 gene generates two major protein isoforms, TIA1a and TIA1b. Expression of TIA1a isoform tended to be higher than that of TIA1b in ESCC cells, and TIA1a was expressed both in the nucleus and cytoplasm but TIA1b was expressed mainly in the nucleus. Further studies revealed that each isoform showed opposite effects on cell proliferation through ectopically introducing each gene: TIA1a promotes anchorage-dependent and independent cell proliferation, whereas TIA1b inhibits cell proliferation and/or induces cell death. The ribonucleoprotein immunoprecipitation followed by a microarray analysis or massive-parallel sequencing identified a set of TIA1-associating mRNAs including enriched cell cycle-associated genes. Among them, SKP2 and CCNA2 mRNA were shown to be interacted with TIA1 protein through their different regions, and SKP2 and CCNA2 protein levels were positively regulated by TIA1 through suppression of mRNA decay and translational induction, respectively. These findings provide new insights into the previously unknown role of TIA1 and its isoforms as tumor-promoting molecules regulating a set of downstream oncogenic proteins, and implicate their potential application as a useful marker of malignant potential and a therapeutic target in ESCC.

Project description:During cell stress, the transcription and translation of immediate early genes are prioritized, while most other mRNAs are stored away in stress granules or degraded in P-bodies. TIA-1 is an mRNA binding protein that needs to translocate from the nucleus to seed the formation of stress granules in the cytoplasm. Since other stress granule components such as TDP-43, FUS, ATXN2, SMN, MAPT, HNRNPA2B1 and HNRNPA1 are crucial for the motor neuron diseases ALS / SMA and for the frontotemporal dementia FTD, here we studied mouse nervous tissue to identify mRNAs with selective dependence on Tia1 deletion. Transcriptome profiling with oligonucleotide microarrays in comparison of spinal cord and cerebellum, together with independent validation in quantitative reverse transcriptase PCR and immunoblots demonstrated several strong and consistent dysregulations. In agreement with previously reported TIA1 knock-down effects, cell cycle and apoptosis regulators were affected markedly with expression changes up to 2-fold, exhibiting increased levels for Cdkn1a, Ccnf, and Tprkb versus decreased levels for Bid and Inca1 transcripts. Novel and surprisingly strong expression alterations were detected for fat storage and membrane trafficking factors, with prominent above 3-fold upregulations of Plin4, Wdfy1, Tbc1d24, and Pnpla2, versus a 0.5 -fold?? downregulation of Cntn4 transcript, encoding an axonal membrane adhesion factor with established haploinsufficiency. In comparison subtle effects on the RNA processing machinery included up to 1.2-fold upregulations of Dcp1b and Tial1. The effect on lipid dynamics factors is noteworthy, since also the gene deletion of Tardbp (encoding TDP-43) and Atxn2 led to fat metabolism phenotypes in mouse. In conclusion, genetic ablation of the stress granule nucleator TIA-1 has a novel major effect on mRNAs encoding lipid homeostasis factors in the brain. Factorial design comparing Tia1 knock-out mice with wild type littermates in four different tissues (midbrain, cerebellum, liver, spinal cord) and 2 different ages.

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Identification of TIA1 mRNA targets during human neuronal development

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