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14 pages, 2018 KiB

Open AccessArticle

Characterization of TTN Novex Splicing Variants across Species and the Role of RBM20 in Novex-Specific Exon Splicing

by Zhilong Chen, Jiangping Song, Liang Chen, Chaoqun Zhu, Hanfang Cai, Mingming Sun, Allysa Stern, Paul Mozdziak, Ying Ge, Warrie J. Means and Wei Guo

Genes 2018, 9(2), 86; https://doi.org/10.3390/genes9020086 - 13 Feb 2018

Cited by 8 | Viewed by 5801

Abstract

Titin (TTN) is a major disease-causing gene in cardiac muscle. Titin (TTN) contains 363 exons in human encoding various sizes of TTN protein due to alternative splicing regulated mainly by RNA binding motif 20 (RBM20). Three isoforms of TTN [...] Read more.

Titin (TTN) is a major disease-causing gene in cardiac muscle. Titin (TTN) contains 363 exons in human encoding various sizes of TTN protein due to alternative splicing regulated mainly by RNA binding motif 20 (RBM20). Three isoforms of TTN protein are produced by mutually exclusive exons 45 (Novex 1), 46 (Novex 2), and 48 (Novex 3). Alternatively splicing in Novex isoforms across species and whether Novex isoforms are associated with heart disease remains completely unknown. Cross-species exon comparison with the mVISTA online tool revealed that exon 45 is more highly conserved across all species than exons 46 and 48. Importantly, a conserved region between exons 47 and 48 across species was revealed for the first time. Reverse transcript polymerase chain reaction (RT-PCR) and DNA sequencing confirmed a new exon named as 48′ in Novex 3. In addition, with primer pairs for Novex 1, a new truncated form preserving introns 44 and 45 was discovered. We discovered that Novex 2 is not expressed in the pig, mouse, and rat with Novex 2 primer pairs. Unexpectedly, three truncated forms were identified. One TTN variant with intron 46 retention is mainly expressed in the human and frog heart, another variant with co-expression of exons 45 and 46 exists predominantly in chicken and frog heart, and a third with retention of introns 45 and 46 is mainly expressed in pig, mouse, rat, and chicken. Using Rbm20 knockout rat heart, we revealed that RBM20 is not a splicing regulator of Novex variants. Furthermore, the expression levels of Novex variants in human hearts with cardiomyopathies suggested that Novexes 2 and 3 could be associated with dilated cardiomyopathy (DCM) and/or arrhythmogenic right ventricular cardiomyopathy (ARVC). Taken together, our study reveals that splicing diversity of Novex exons across species and Novex variants might play a role in cardiomyopathy. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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14 pages, 1879 KiB

Open AccessArticle

Splicing Analysis of Exonic OCRL Mutations Causing Lowe Syndrome or Dent-2 Disease

by Lorena Suarez-Artiles, Ana Perdomo-Ramirez, Elena Ramos-Trujillo and Felix Claverie-Martin

Genes 2018, 9(1), 15; https://doi.org/10.3390/genes9010015 - 4 Jan 2018

Cited by 19 | Viewed by 6571

Abstract

Mutations in the OCRL gene are associated with both Lowe syndrome and Dent-2 disease. Patients with Lowe syndrome present congenital cataracts, mental disabilities and a renal proximal tubulopathy, whereas patients with Dent-2 disease exhibit similar proximal tubule dysfunction but only mild, or no [...] Read more.

Mutations in the OCRL gene are associated with both Lowe syndrome and Dent-2 disease. Patients with Lowe syndrome present congenital cataracts, mental disabilities and a renal proximal tubulopathy, whereas patients with Dent-2 disease exhibit similar proximal tubule dysfunction but only mild, or no additional clinical defects. It is not yet understood why some OCRL mutations cause the phenotype of Lowe syndrome, while others develop the milder phenotype of Dent-2 disease. Our goal was to gain new insights into the consequences of OCRL exonic mutations on pre-mRNA splicing. Using predictive bioinformatics tools, we selected thirteen missense mutations and one synonymous mutation based on their potential effects on splicing regulatory elements or splice sites. These mutations were analyzed in a minigene splicing assay. Results of the RNA analysis showed that three presumed missense mutations caused alterations in pre-mRNA splicing. Mutation c.741G>T; p.(Trp247Cys) generated splicing silencer sequences and disrupted splicing enhancer motifs that resulted in skipping of exon 9, while mutations c.2581G>A; p.(Ala861Thr) and c.2581G>C; p.(Ala861Pro) abolished a 5′ splice site leading to skipping of exon 23. Mutation c.741G>T represents the first OCRL exonic variant outside the conserved splice site dinucleotides that results in alteration of pre-mRNA splicing. Our results highlight the importance of evaluating the effects of OCRL exonic mutations at the mRNA level. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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Review

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19 pages, 1330 KiB

Open AccessReview

Alternative Splicing in the Hippo Pathway—Implications for Disease and Potential Therapeutic Targets

by Sean Porazinski and Michael Ladomery

Genes 2018, 9(3), 161; https://doi.org/10.3390/genes9030161 - 13 Mar 2018

Cited by 12 | Viewed by 7209

Abstract

Alternative splicing is a well-studied gene regulatory mechanism that produces biological diversity by allowing the production of multiple protein isoforms from a single gene. An involvement of alternative splicing in the key biological signalling Hippo pathway is emerging and offers new therapeutic avenues. [...] Read more.

Alternative splicing is a well-studied gene regulatory mechanism that produces biological diversity by allowing the production of multiple protein isoforms from a single gene. An involvement of alternative splicing in the key biological signalling Hippo pathway is emerging and offers new therapeutic avenues. This review discusses examples of alternative splicing in the Hippo pathway, how deregulation of these processes may contribute to disease and whether these processes offer new potential therapeutic targets. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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31 pages, 1314 KiB

Open AccessReview

Alternative Splicing of Transcription Factors Genes in Muscle Physiology and Pathology

by Carol Imbriano and Susanna Molinari

Genes 2018, 9(2), 107; https://doi.org/10.3390/genes9020107 - 19 Feb 2018

Cited by 22 | Viewed by 9057

Abstract

Skeletal muscle formation is a multi-step process that is governed by complex networks of transcription factors. The regulation of their functions is in turn multifaceted, including several mechanisms, among them alternative splicing (AS) plays a primary role. On the other hand, altered AS [...] Read more.

Skeletal muscle formation is a multi-step process that is governed by complex networks of transcription factors. The regulation of their functions is in turn multifaceted, including several mechanisms, among them alternative splicing (AS) plays a primary role. On the other hand, altered AS has a role in the pathogenesis of numerous muscular pathologies. Despite these premises, the causal role played by the altered splicing pattern of transcripts encoding myogenic transcription factors in neuromuscular diseases has been neglected so far. In this review, we systematically investigate what has been described about the AS patterns of transcription factors both in the physiology of the skeletal muscle formation process and in neuromuscular diseases, in the hope that this may be useful in re-evaluating the potential role of altered splicing of transcription factors in such diseases. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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10 pages, 1010 KiB

Open AccessReview

Modulation of VEGF-A Alternative Splicing as a Novel Treatment in Chronic Kidney Disease

by Megan Stevens and Sebastian Oltean

Genes 2018, 9(2), 98; https://doi.org/10.3390/genes9020098 - 15 Feb 2018

Cited by 16 | Viewed by 7050

Abstract

Vascular endothelial growth factor A (VEGF-A) is a prominent pro-angiogenic and pro-permeability factor in the kidney. Alternative splicing of the terminal exon of VEGF-A through the use of an alternative 3′ splice site gives rise to a functionally different family of isoforms, termed [...] Read more.

Vascular endothelial growth factor A (VEGF-A) is a prominent pro-angiogenic and pro-permeability factor in the kidney. Alternative splicing of the terminal exon of VEGF-A through the use of an alternative 3′ splice site gives rise to a functionally different family of isoforms, termed VEGF-A_xxxb, known to have anti-angiogenic and anti-permeability properties. Dysregulation of the VEGF-A_xxx/VEGF-A_xxxb isoform balance has recently been reported in several kidney pathologies, including diabetic nephropathy (DN) and Denys–Drash syndrome. Using mouse models of kidney disease where the VEGF-A isoform balance is disrupted, several reports have shown that VEGF-A₁₆₅b treatment/over-expression in the kidney is therapeutically beneficial. Furthermore, inhibition of certain splice factor kinases involved in the regulation of VEGF-A terminal exon splicing has provided some mechanistic insight into how VEGF-A splicing could be regulated in the kidney. This review highlights the importance of further investigation into the novel area of VEGF-A splicing in chronic kidney disease pathogenesis and how future studies may allow for the development of splicing-modifying therapeutic drugs. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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16 pages, 1794 KiB

Open AccessReview

Impact, Characterization, and Rescue of Pre-mRNA Splicing Mutations in Lysosomal Storage Disorders

by Andrea Dardis and Emanuele Buratti

Genes 2018, 9(2), 73; https://doi.org/10.3390/genes9020073 - 6 Feb 2018

Cited by 11 | Viewed by 6720

Abstract

Lysosomal storage disorders (LSDs) represent a group of more than 50 severe metabolic diseases caused by the deficiency of specific lysosomal hydrolases, activators, carriers, or lysosomal integral membrane proteins, leading to the abnormal accumulation of substrates within the lysosomes. Numerous mutations have been [...] Read more.

Lysosomal storage disorders (LSDs) represent a group of more than 50 severe metabolic diseases caused by the deficiency of specific lysosomal hydrolases, activators, carriers, or lysosomal integral membrane proteins, leading to the abnormal accumulation of substrates within the lysosomes. Numerous mutations have been described in each disease-causing gene; among them, about 5–19% affect the pre-mRNA splicing process. In the last decade, several strategies to rescue/increase normal splicing of mutated transcripts have been developed and LSDs represent excellent candidates for this type of approach: (i) most of them are inherited in an autosomic recessive manner and patients affected by late-onset (LO) phenotypes often retain a fair amount of residual enzymatic activity; thus, even a small recovery of normal splicing may be beneficial in clinical settings; (ii) most LSDs still lack effective treatments or are currently treated with extremely expensive approaches; (iii) in few LSDs, a single splicing mutation accounts for up to 40–70% of pathogenic alleles. At present, numerous preclinical studies support the feasibility of reverting the pathological phenotype by partially rescuing splicing defects in LSDs. This review provides an overview of the impact of splicing mutations in LSDs and the related therapeutic approaches currently under investigation in these disorders. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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22 pages, 1329 KiB

Open AccessReview

Alternative Splicing of Alpha- and Beta-Synuclein Genes Plays Differential Roles in Synucleinopathies

by Ana Gámez-Valero and Katrin Beyer

Genes 2018, 9(2), 63; https://doi.org/10.3390/genes9020063 - 25 Jan 2018

Cited by 28 | Viewed by 8492

Abstract

The synuclein family is composed of three members, two of which, α- and β-synuclein, play a major role in the development of synucleinopathies, including Parkinson’s disease (PD) as most important movement disorder, dementia with Lewy bodies (DLB) as the second most frequent cause [...] Read more.

The synuclein family is composed of three members, two of which, α- and β-synuclein, play a major role in the development of synucleinopathies, including Parkinson’s disease (PD) as most important movement disorder, dementia with Lewy bodies (DLB) as the second most frequent cause of dementia after Alzheimer’s disease and multiple system atrophy. Whereas abnormal oligomerization and fibrillation of α-synuclein are now well recognized as initial steps in the development of synucleinopathies, β-synuclein is thought to be a natural α-synuclein anti-aggregant. α-synuclein is encoded by the SNCA gene, and β-synuclein by SNCB. Both genes are homologous and undergo complex splicing events. On one hand, in-frame splicing of coding exons gives rise to at least three shorter transcripts, and the functional properties of the corresponding protein isoforms are different. Another type of alternative splicing is the alternative inclusion of at least four initial exons in the case of SNCA, and two in the case of SNCB. Finally, different lengths of 3’ untranslated regions have been also reported for both genes. SNCB only expresses in the brain, but some of the numerous SNCA transcripts are also brain-specific. With the present article, we aim to provide a systematic review of disease related changes in the differential expression of the various SNCA and SNCB transcript variants in brain, blood, and non-neuronal tissue of synucleinopathies, but especially PD and DLB as major neurodegenerative disorders. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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13 pages, 6526 KiB

Open AccessReview

Muscle-Specific Mis-Splicing and Heart Disease Exemplified by RBM20

by Maimaiti Rexiati, Mingming Sun and Wei Guo

Genes 2018, 9(1), 18; https://doi.org/10.3390/genes9010018 - 5 Jan 2018

Cited by 26 | Viewed by 7207

Abstract

Alternative splicing is an essential post-transcriptional process to generate multiple functional RNAs or proteins from a single transcript. Progress in RNA biology has led to a better understanding of muscle-specific RNA splicing in heart disease. The recent discovery of the muscle-specific splicing factor [...] Read more.

Alternative splicing is an essential post-transcriptional process to generate multiple functional RNAs or proteins from a single transcript. Progress in RNA biology has led to a better understanding of muscle-specific RNA splicing in heart disease. The recent discovery of the muscle-specific splicing factor RNA-binding motif 20 (RBM20) not only provided great insights into the general alternative splicing mechanism but also demonstrated molecular mechanism of how this splicing factor is associated with dilated cardiomyopathy. Here, we review our current knowledge of muscle-specific splicing factors and heart disease, with an emphasis on RBM20 and its targets, RBM20-dependent alternative splicing mechanism, RBM20 disease origin in induced Pluripotent Stem Cells (iPSCs), and RBM20 mutations in dilated cardiomyopathy. In the end, we will discuss the multifunctional role of RBM20 and manipulation of RBM20 as a potential therapeutic target for heart disease. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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621 KiB

Open AccessReview

Signaling Pathways Driving Aberrant Splicing in Cancer Cells

by Vânia Gonçalves, Joana F. S. Pereira and Peter Jordan

Genes 2018, 9(1), 9; https://doi.org/10.3390/genes9010009 - 29 Dec 2017

Cited by 50 | Viewed by 8672

Abstract

Aberrant profiles of pre-mRNA splicing are frequently observed in cancer. At the molecular level, an altered profile results from a complex interplay between chromatin modifications, the transcriptional elongation rate of RNA polymerase, and effective binding of the spliceosome to the generated transcripts. Key [...] Read more.

Aberrant profiles of pre-mRNA splicing are frequently observed in cancer. At the molecular level, an altered profile results from a complex interplay between chromatin modifications, the transcriptional elongation rate of RNA polymerase, and effective binding of the spliceosome to the generated transcripts. Key players in this interplay are regulatory splicing factors (SFs) that bind to gene-specific splice-regulatory sequence elements. Although mutations in genes of some SFs were described, a major driver of aberrant splicing profiles is oncogenic signal transduction pathways. Signaling can affect either the transcriptional expression levels of SFs or the post-translational modification of SF proteins, and both modulate the ratio of nuclear versus cytoplasmic SFs in a given cell. Here, we will review currently known mechanisms by which cancer cell signaling, including the mitogen-activated protein kinases (MAPK), phosphatidylinositol 3 (PI3)-kinase pathway (PI3K) and wingless (Wnt) pathways but also signals from the tumor microenvironment, modulate the activity or subcellular localization of the Ser/Arg rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs) families of SFs. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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724 KiB

Open AccessReview

Circular RNAs (circRNAs) in Health and Disease

by Shahnaz Haque and Lorna W. Harries

Genes 2017, 8(12), 353; https://doi.org/10.3390/genes8120353 - 28 Nov 2017

Cited by 228 | Viewed by 10707

Abstract

Splicing events do not always produce a linear transcript. Circular RNAs (circRNAs) are a class of RNA that are emerging as key new members of the gene regulatory milieu, which are produced by back-splicing events within genes. In circRNA formation, rather than being [...] Read more.

Splicing events do not always produce a linear transcript. Circular RNAs (circRNAs) are a class of RNA that are emerging as key new members of the gene regulatory milieu, which are produced by back-splicing events within genes. In circRNA formation, rather than being spliced in a linear fashion, exons can be circularised by use of the 3′ acceptor splice site of an upstream exon, leading to the formation of a circular RNA species. circRNAs have been demonstrated across species and have the potential to present genetic information in new orientations distinct from their parent transcript. The importance of these RNA players in gene regulation and normal cellular homeostasis is now beginning to be recognised. They have several potential modes of action, from serving as sponges for micro RNAs and RNA binding proteins, to acting as transcriptional regulators. In accordance with an important role in the normal biology of the cell, perturbations of circRNA expression are now being reported in association with disease. Furthermore, the inherent stability of circRNAs conferred by their circular structure and exonuclease resistance, and their expression in blood and other peripheral tissues in association with endosomes and microvesicles, renders them excellent candidates as disease biomarkers. In this review, we explore the state of knowledge on this exciting class of transcripts in regulating gene expression and discuss their emerging role in health and disease. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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2019 KiB

Open AccessReview

Alternative Splicing of L-type Ca_V1.2 Calcium Channels: Implications in Cardiovascular Diseases

by Zhenyu Hu, Mui Cheng Liang and Tuck Wah Soong

Genes 2017, 8(12), 344; https://doi.org/10.3390/genes8120344 - 24 Nov 2017

Cited by 44 | Viewed by 9580

Abstract

L-type Ca_V1.2 calcium channels are the major pathway for Ca²⁺ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Ca_V1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. [...] Read more.

L-type Ca_V1.2 calcium channels are the major pathway for Ca²⁺ influx to initiate the contraction of smooth and cardiac muscles. Alteration of Ca_V1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands Ca_V1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI), or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse Ca_V1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of Ca_V1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2), polypyrimidine tract-binding protein (PTBP1) and RNA-binding motif protein 20 (RBM20). Understanding how Ca_V1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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1831 KiB

Open AccessReview

Alternative Splicing in Breast Cancer and the Potential Development of Therapeutic Tools

by Nancy Martínez-Montiel, Maricruz Anaya-Ruiz, Martín Pérez-Santos and Rebeca D. Martínez-Contreras

Genes 2017, 8(10), 217; https://doi.org/10.3390/genes8100217 - 5 Oct 2017

Cited by 28 | Viewed by 7357

Abstract

Alternative splicing is a key molecular mechanism now considered as a hallmark of cancer that has been associated with the expression of distinct isoforms during the onset and progression of the disease. The leading cause of cancer-related deaths in women worldwide is breast [...] Read more.

Alternative splicing is a key molecular mechanism now considered as a hallmark of cancer that has been associated with the expression of distinct isoforms during the onset and progression of the disease. The leading cause of cancer-related deaths in women worldwide is breast cancer, and even when the role of alternative splicing in this type of cancer has been established, the function of this mechanism in breast cancer biology is not completely decoded. In order to gain a comprehensive view of the role of alternative splicing in breast cancer biology and development, we summarize here recent findings regarding alternative splicing events that have been well documented for breast cancer evolution, considering its prognostic and therapeutic value. Moreover, we analyze how the response to endocrine and chemical therapies could be affected due to alternative splicing and differential expression of variant isoforms. With all this knowledge, it becomes clear that targeting alternative splicing represents an innovative approach for breast cancer therapeutics and the information derived from current studies could guide clinical decisions with a direct impact in the clinical advances for breast cancer patients nowadays. Full article

(This article belongs to the Special Issue Aberrant Pre-mRNA Splicing in Disease)

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