Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Newborn apical resection preserves the proliferative capacity of cardiomyocytes located throughout the left ventricle

BACKGROUND

When pigs underwent apical resection (AR) on postnatal day (P) 1 (ARP1) followed by myocardial infarction (MI) on P28, the hearts had little evidence of scarring; meanwhile, hearts underwent MI on P28 without ARP1 showed large infarcts on P56; and the improvement of ARP1 hearts was driven primarily by cardiomyocyte proliferation. AR and MI were performed ~5 mm (AR) and ~20 mm (MI) above the heart apex; thus, we hypothesize that ARP1 preserved the cardiomyocytes cell-cycle throughout the left ventricle, rather than only near the resection site.

METHODS

Sections of cardiac tissue were collected from the left ventricle of uninjured pigs and from both the border zone (BZ) of AR and uninjured regions (remote zone, [RZ]) in ARP1 hearts. Cardiomyocyte proliferation was evaluated via immunofluorescence analysis of phosphorylated histone 3 [PH3] and symmetric Aurora B (sAuB). Single nucleus RNA sequencing (snRNAseq) data collected from the hearts of fetal pigs, uninjured pigs, and the BZ and RZ of ARP1 pigs was evaluated via our cell-cycle-specific autoencoder to identify proliferating cardiomyocytes.

RESULTS

Cardiomyocyte PH3 and sAuB expression, and percentage of proliferating cardiomyocytes in snRNA data was significantly more common in both BZ and RZ of ARP1 than uninjured hearts but did not differ significantly between the ARP1-BZ and ARP1-RZ at any time point. Heat shock proteins HSPA5 and HSP90B1 were overexpressed at both ARP1-BZ and ARP1-RZ. In AC16 cell, overexpression (and knockdown) of HSPA5-HSP90B1 increased (and decrease) cell-cycle activity.

CONCLUSION

ARP1 preserved proliferative capacity of cardiomyocytes located throughout the left ventricle.

Value of Bioinformatics Models for Predicting Translational Control of Angiogenesis

Angiogenesis, the formation of new blood vessels, is a fundamental biological process with implications for both physiological functions and pathological conditions. While the transcriptional regulation of angiogenesis, mediated by factors such as HIF-1α (hypoxia-inducible factor 1-alpha) and VEGF (vascular endothelial growth factor), is well-characterized, the translational regulation of this process remains underexplored. Bioinformatics has emerged as an indispensable tool for advancing our understanding of translational regulation, offering predictive models that leverage large data sets to guide research and optimize experimental approaches. However, a significant gap persists between bioinformatics experts and other researchers, limiting the accessibility and utility of these tools in the broader scientific community. To address this divide, user-friendly bioinformatics platforms are being developed to democratize access to predictive analytics and empower researchers across disciplines. Translational control, compared with transcriptional control, offers a more energy-efficient mechanism that facilitates rapid cellular responses to environmental changes. Furthermore, transcriptional regulators themselves are often subject to translational control, emphasizing the interconnected nature of these regulatory layers. Investigating translational regulation requires advanced, accessible bioinformatics tools to analyze RNA structures, interacting micro-RNAs, long noncoding RNAs, and RBPs (RNA-binding proteins). Predictive platforms such as RNA structure, human internal ribosome entry site Atlas, and RBPSuite enable the study of RNA motifs and RNA-protein interactions, shedding light on these critical regulatory mechanisms. This review highlights the transformative role of bioinformatics using widely accessible user-friendly tools with a Web-browser interface to elucidate translational regulation in angiogenesis. The bioinformatics tools discussed extend beyond angiogenesis, with applications in diverse fields, including clinical care. By integrating predictive models and experimental insights, researchers can streamline hypothesis generation, reduce experimental costs, and find novel translational regulators. By bridging the bioinformatics knowledge gap, this review aims to empower researchers worldwide to adopt bioinformatics tools in their work, fostering innovation and accelerating scientific discovery.

Regulation of Protein Synthesis at the Translational Level: Novel Findings in Cardiovascular Biology

Translational regulation plays a pivotal role in cardiac gene expression, influencing protein synthesis in response to physiological and pathological stimuli. Although transcription regulates gene expression, translation ultimately determines protein levels, making it a crucial research focus. In cardiomyocytes, disruptions in this process contribute to various cardiac diseases, including hypertrophy, fibrosis, dilated cardiomyopathy, ischemic heart disease, and diabetic cardiomyopathy. Emerging evidence highlights the significance of translational regulation across multiple cardiac cell types, such as cardiomyocytes and fibroblasts, and its role in disease progression. During cardiac remodeling, transcriptomic changes are often modest, suggesting that post-transcriptional mechanisms, particularly translation, play a dominant role in cellular adaptation. This review discusses key methodologies for studying translational regulation and novel mechanisms of translational regulation related to different cardiac pathologies and highlights relevant therapeutic avenues for targeting these pathways.

RNA-based therapies for neurodegenerative disease: Targeting molecular mechanisms for disease modification

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are characterized by progressive neuronal damage, protein aggregation, and chronic inflammation, leading to cognitive and motor impairments. Despite symptomatic relief from current therapies, disease-modifying treatments targeting the core molecular mechanism are still lacking. RNA-based therapies offer a promising approach to treating neurodegenerative disease by targeting molecular mechanisms such as gene expression, protein synthesis, and neuroinflammation. Therapeutic strategies include Long non-coding RNA (lncRNA), Antisense oligonucleotides (ASOs), RNA interference (RNAi), small interfering RNA (siRNA) and short hairpin RNA (shRNA), messenger RNA (mRNA) therapies, and microRNA (miRNA)-based interventions. These therapies aim to decrease toxic protein accumulation, restore deficient proteins, and modulate inflammatory responses in conditions like AD, PD, and HD. Unlike conventional treatments that primarily manage symptoms, RNA-based therapies have the potential to modify disease progression by addressing its root causes. This review aims to provide a comprehensive overview of current RNA-based therapeutic strategies for neurodegenerative diseases, discussing their mechanism of action, preclinical and clinical advancement. It further explores innovative solutions, including nanocarrier-mediated delivery, chemical modifications to enhance RNA stability, and personalized medicine approaches guided by genetic profiling that are being developed to overcome these barriers. This review also underscores the therapeutic opportunities and current limitations of RNA-based interventions, highlighting their potential to transform the future of neurodegenerative disease management.

Nucleic Acid Drugs in Radiotherapy

Radiotherapy remains a cornerstone of cancer treatment, using high-energy radiation to induce DNA damage in tumor cells, leading to cell death. However, its efficacy is often hindered by challenges such as radiation resistance and side effects. As a powerful class of functional molecules, nucleic acid drugs (NADs) present a promising solution to these limitations. Engineered to target key pathways like DNA repair and tumor hypoxia, NADs can enhance radiotherapy sensitivity. NADs can also serve as delivery vehicles for radiotherapy agents such as radionuclides, improving targeting accuracy and minimizing side effects. This review explores the role of NADs in optimizing radiotherapy, highlighting their mechanisms, clinical applications, and synergies with radiotherapy, ultimately offering a promising strategy for improving patient outcomes in cancer therapy.

uORF-targeting steric block antisense oligonucleotides do not reproducibly increase RNASEH1 expression

Upstream open reading frames (uORFs) are cis-regulatory motifs that are predicted to occur in the 5' UTRs of the majority of human protein-coding transcripts and are typically associated with translational repression of the downstream primary open reading frame (pORF). Interference with uORF activity provides a potential mechanism for targeted upregulation of the expression of specific transcripts. It was previously reported that steric block antisense oligonucleotides (ASOs) can bind to and mask uORF start codons to inhibit translation initiation, and thereby disrupt uORF-mediated gene regulation. Given the relative maturity of the oligonucleotide field, such a uORF blocking mechanism might have widespread therapeutic utility. Here, we re-synthesized three of the most potent ASOs targeting the RNASEH1 uORF described in a study by Liang et al. and investigated their potential for RNASEH1 protein upregulation, with care taken to replicate the conditions of the original study. No upregulation (of endogenous or reporter protein expression) was observed with any of the oligonucleotides tested at doses ranging from 25 to 300 nM. Conversely, we observed downregulation of expression in some instances. We conclude that previously described RNASEH1 uORF-targeting steric block ASOs are incapable of upregulating pORF protein expression in our hands.

Engineering crop performance with upstream open reading frames

Plants intricately regulate the expression of protein-coding genes at multiple stages - including mRNA transcription, translation, decay, and protein degradation - to control growth, development, and responses to environmental challenges. Recent research highlights the importance of translational reprogramming as a pivotal mechanism in regulating gene expression across diverse physiological scenarios. This regulatory mechanism bears practical implications, particularly in bolstering crop productivity by manipulating RNA regulatory elements (RREs) to modulate heterologous gene expression through transgene and endogenous gene expression through gene editing. Here, we elucidate the potential of upstream open reading frames (uORFs), a prominent and stringent class of RREs, in optimizing crop performance, exemplifying the efficacy of translational control in enhancing agricultural yields.

RNA dysregulation in neurodegenerative diseases

Dysregulation of RNA processing has in recent years emerged as a significant contributor to neurodegeneration. The diverse mechanisms and molecular functions underlying RNA processing underscore the essential role of RNA regulation in maintaining neuronal health and function. RNA molecules are bound by RNA-binding proteins (RBPs), and interactions between RNAs and RBPs are commonly affected in neurodegeneration. In this review, we highlight recent progress in understanding dysregulated RNA-processing pathways and the causes of RBP dysfunction across various neurodegenerative diseases. We discuss both established and emerging mechanisms of RNA-mediated neuropathogenesis in this rapidly evolving field. Furthermore, we explore the development of potential RNA-targeting therapeutic approaches for the treatment of neurodegenerative diseases.

Pathogenetic mechanisms of muscle-specific ribosomes in dilated cardiomyopathy

The heart employs a specialized ribosome in its muscle cells to translate genetic information into proteins, a fundamental adaptation with an elusive physiological role1-3. Its significance is underscored by the discovery of neonatal patients suffering from often fatal heart failure caused by severe dilated cardiomyopathy when both copies of the gene RPL3L are mutated4-9. RPL3L is a muscle-specific paralog1-3 of the ubiquitous ribosomal protein L3 (RPL3), which makes the closest contact of any protein to the ribosome's RNA-based catalytic center10. RPL3L-linked heart failure represents the only known human disease associated with tissue-specific ribosomes, yet the underlying pathogenetic mechanisms remain poorly understood. Intriguingly, disease is linked to a large number of mostly missense variants in RPL3L, and RPL3L-knockout resulted in no severe heart defect in either human or mice3, 11-13, challenging the prevailing view that autosomal recessive diseases are caused by loss-of-function mutations. Here, we report three new cases of RPL3L-linked severe neonatal heart failure and present a unifying pathogenetic mechanism by which a large number of variants in the muscle-specific ribosome led to disease. Specifically, affected families often carry one of two recurrent toxic gain-of-function variants alongside a family-specific putative loss-of-function variant. While the non-recurrent variants often trigger partial compensation of RPL3 similar to Rpl3l-knockout mice, both recurrent variants exhibit increased affinity for the RPL3/RPL3L chaperone GRWD114-16 and 60S biogenesis factors, sequester 28S rRNA in the nucleus, disrupt ribosome biogenesis, and trigger severe cellular toxicity that extends beyond the loss of ribosomes. These findings provide critical insights for genetic screening and therapeutic development of neonatal heart failure. Our results suggest that gain-of-toxicity mechanisms may be more prevalent in autosomal recessive diseases, and a combination of gain-of-toxicity and loss-of-function mechanisms could underlie many diseases involving genes with paralogs.

Protein binding in an mRNA 5'-UTR sterically hinders translation

Structures in the 5' untranslated regions (UTRs) of mRNAs can physically modulate translation efficiency by impeding the scanning ribosome or by sequestering the translational start site. We assessed the impact of stable protein binding in 5'- and 3'-UTRs on translation efficiency by targeting the MS2 coat protein to a reporter RNA via its hairpin recognition site. Translation was assessed from the reporter RNA when coexpressed with MS2 coat proteins of varying affinities for the RNA, and at different expression levels. Binding of high-affinity proteins in the 5'-UTR hindered translation, whereas no effect was observed when the coat protein was targeted to the 3'-UTR. Inhibition of translation increased with coat protein concentration and affinity, reaching a maximum of 50%-70%. MS2 proteins engineered to bind two reporter mRNA sites had a stronger effect than those binding a single site. Our findings demonstrate that protein binding in an mRNA 5'-UTR physically impedes translation, with the effect governed by affinity, concentration, and sterics.

Tiny but mighty: Diverse functions of uORFs that regulate gene expression

Upstream open reading frames (uORFs) are critical cis-acting regulators of downstream gene expression. Specifically, uORFs regulate translation by disrupting translation initiation or mediating mRNA decay. We herein summarize the effects of several uORFs that regulate gene expression in microbes to illustrate the detailed mechanisms mediating uORF functions. Microbes are ideal for uORF studies because of their prompt responses to stimuli. Recent studies revealed uORFs are ubiquitous in higher eukaryotes. Moreover, they influence various physiological processes in mammalian cells by regulating gene expression, mostly at the translational level. Research conducted using rapidly evolving methods for ribosome profiling combined with protein analyses and computational annotations showed that uORFs in mammalian cells control gene expression similar to microbial uORFs, but they also have unique tumorigenesis-related roles because of their protein-encoding capacities. We briefly introduce cutting-edge research findings regarding uORFs in mammalian cells.

A novel RUNX2 splice site mutation in Chinese associated with cleidocranial dysplasia

Pathogenic genes in most patients with cleidocranial dysplasia have been confirmed to be runt-related transcription factor 2 (RUNX2), which controls mutations in specific osteoblast transcription factors and affects skull ossification and suture adhesion. This study aimed to explore the role of RUNX2 mutations. Here, we report a rare case of a splice site mutation in a Chinese population with typical cleidocranial dysplasia symptoms, cranial suture insufficiency, clavicle dysplasia, and dental anomalies. Peripheral blood samples from the proband and her mother were subjected to Sanger sequencing. The expression levels of RUNX2 before and after mutation were verified using digital PCR (dPCR). The results revealed a classic mutation at the fifth base of the intron 5 initiation splicing sequence (NM001024630.4: C.685+5G > A). The mutation rate in the proband was 53 %, while the mother did not have any mutations. The secondary RNA structure of the RUNX2 gene in the progenitor was predicted to change, and the structural free energy was low in the wild-type, with the stem folded first and the structure being relatively stable. After the mutation, the free energy increased. This finding enriches the RUNX2 mutation library of CD-related genes in Chinese individuals.

Homozygous EPRS1 missense variant causing hypomyelinating leukodystrophy-15 alters variant-distal mRNA m6A site accessibility

Hypomyelinating leukodystrophy (HLD) is an autosomal recessive disorder characterized by defective central nervous system myelination. Exome sequencing of two siblings with severe cognitive and motor impairment and progressive hypomyelination characteristic of HLD revealed homozygosity for a missense single-nucleotide variant (SNV) in EPRS1 (c.4444 C > A; p.Pro1482Thr), encoding glutamyl-prolyl-tRNA synthetase, consistent with HLD15. Patient lymphoblastoid cell lines express markedly reduced EPRS1 protein due to dual defects in nuclear export and cytoplasmic translation of variant EPRS1 mRNA. Variant mRNA exhibits reduced METTL3 methyltransferase-mediated writing of N6-methyladenosine (m6A) and reduced reading by YTHDC1 and YTHDF1/3 required for efficient mRNA nuclear export and translation, respectively. In contrast to current models, the variant does not alter the sequence of m6A target sites, but instead reduces their accessibility for modification. The defect was rescued by antisense morpholinos predicted to expose m6A sites on target EPRS1 mRNA, or by m6A modification of the mRNA by METTL3-dCas13b, a targeted RNA methylation editor. Our bioinformatic analysis predicts widespread occurrence of SNVs associated with human health and disease that similarly alter accessibility of distal mRNA m6A sites. These results reveal a new RNA-dependent etiologic mechanism by which SNVs can influence gene expression and disease, consequently generating opportunities for personalized, RNA-based therapeutics targeting these disorders.