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Ishii H, Hattori Y, Ozawa H. Estrogen Receptor α Isoforms Generated by Alternative Use of Cryptic Exons. J NIPPON MED SCH 2023; 90:364-371. [PMID: 37558429 DOI: 10.1272/jnms.jnms.2023_90-507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Estrogen receptor α (ERα) regulates several physiological functions. In pathophysiological conditions, ERα is involved in the development and progression of estrogen-sensitive tumors. The ERα gene contains multiple 5'-untranslated exons and eight conventional coding exons and presents multiple isoforms generated by alternative promoter usage and alternative splicing. This gene also possesses non-conventional exons in the 3'- and intronic regions, and alternative use of cryptic exons contributes to further diversity of ERα mRNAs and proteins. Recently, the genomic organization of ERα genes and the splicing profiles of their transcripts were comparatively analyzed in humans, mice, and rats, and multiple ERα isoforms with distinct structures and functions were identified. These transcripts contain cryptic sequences that encode insertion-containing or truncated ERα proteins. In particular, alternative cryptic exons with in-frame stop codons yield transcripts encoding C-terminally-truncated ERα proteins. The C-terminally-truncated ERα isoforms lack part or all of the ligand-binding domain but possess an isoform-specific sequence. Some of these isoforms exhibit constitutive transactivation and resistance to estrogen receptor antagonists. Although numerous studies have reported conflicting results regarding their functions, the critical determinant for their gain-of-function has been identified structurally. Here we review recent progress in ERα variant research concerning the genomic organization of ERα genes, splicing profiles of ERα transcripts, and transactivation properties of ERα isoforms.
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Affiliation(s)
- Hirotaka Ishii
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School
| | - Yujiro Hattori
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School
| | - Hitoshi Ozawa
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School
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Saito K, Dickey JE, Rodeghiero SR, Toth BA, Kelly MJ, Deng Y, Singh U, Deng G, Jiang J, Cui H. Hypomorphism of a Novel Long ERα Isoform Causes Severe Reproductive Dysfunctions in Female Mice. Endocrinology 2022; 163:6742225. [PMID: 36181426 DOI: 10.1210/endocr/bqac160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Indexed: 11/19/2022]
Abstract
Estrogen receptor alpha (ERα)-mediated estrogen signaling plays a pivotal role in both reproductive and nonreproductive functions. Transcriptional regulation of the ERα gene is highly complex, with multiple transcript variants being differentially produced across the tissues. However, tissue-specific variation and physiological specificity of the ERα variants are not yet fully understood. In an attempt to generate a Cre-dependently restorable ERα-null mouse for functional genetic studies, we unexpectedly produced ERα hypomorphic mice with biased downregulation of a previously unappreciated long ERα isoform that is enriched in the female reproductive organs (uterus and ovaries) and the pituitary but minimally expressed in the brain. Female homozygous mutant mice were capable of pregnancy but displayed irregular estrus cycle and rarely kept newborn pups alive. No significant morphological and pathological changes in reproductive system or disruption of body weight homeostasis were seen in female homozygous mutant mice. Collectively, our results define a tissue-specific enriched long ERα isoform and its preferential role in female reproductive function rather than body weight homeostasis.
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Affiliation(s)
- Kenji Saito
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Jacob E Dickey
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Samuel R Rodeghiero
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Brandon A Toth
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Matthew J Kelly
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Yue Deng
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Uday Singh
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Guorui Deng
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Jingwei Jiang
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
| | - Huxing Cui
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
- F.O.E. Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52241, USA
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Ishunina TA. Alternative splicing in aging and Alzheimer's disease: Highlighting the role of tau and estrogen receptor α isoforms in the hypothalamus. HANDBOOK OF CLINICAL NEUROLOGY 2021; 182:177-189. [PMID: 34266591 DOI: 10.1016/b978-0-12-819973-2.00012-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Human genes show the highest efficacy of alternative splicing (AS) in the brain as compared to other tissues. Within the brain, a remarkably rich diversity of AS events was identified in the hypothalamus. The AS frequency is increased in the aging brain. Such AS events, as intron retention and accumulation of circular RNAs, were acknowledged as some of the main hallmarks of the aging brain. In Alzheimer's disease (AD) pivotal (tau gene, in particular), risk, candidate and other genes show significant alterations in AS. Therefore AD has been suggested to be a disease of dysregulated AS. One of the reported risk factors for AD is estrogen deficiency that may interfere with the extension of neurobrillary tangles. Mounting evidence suggests that estrogens may decrease hyperphosphorylated tau deposition in the brain. Furthermore, AS of estrogen receptor α (ERα) mRNA is decreased in AD brain areas with the highest tau load. These potential interactions among tau, estrogens, and ERα AS may be important for the development of therapeutic and preventive strategies for AD. The intriguing point is that the amount of splice variants of ERα in the hypothalamus and the hippocampus is increased in aging and decreased in AD, while ERα is one of the regulators of AS and is subject to AS itself.
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Affiliation(s)
- Tatjana A Ishunina
- Department of Histology, Embryology and Cytology, Kursk State Medical University, Kursk, Russia.
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Ramírez-de-Arellano A, Pereira-Suárez AL, Rico-Fuentes C, López-Pulido EI, Villegas-Pineda JC, Sierra-Diaz E. Distribution and Effects of Estrogen Receptors in Prostate Cancer: Associated Molecular Mechanisms. Front Endocrinol (Lausanne) 2021; 12:811578. [PMID: 35087479 PMCID: PMC8786725 DOI: 10.3389/fendo.2021.811578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 12/15/2021] [Indexed: 12/19/2022] Open
Abstract
Estrogens are hormones that have been extensively presented in many types of cancer such as breast, uterus, colorectal, prostate, and others, due to dynamically integrated signaling cascades that coordinate cellular growth, differentiation, and death which can be potentially new therapeutic targets. Despite the historical use of estrogens in the pathogenesis of prostate cancer (PCa), their biological effect is not well known, nor their role in carcinogenesis or the mechanisms used to carry their therapeutic effects of neoplastic in prostate transformation. The expression and regulation of the estrogen receptors (ERs) ERα, ERβ, and GPER stimulated by agonists and antagonists, and related to prostate cancer cells are herein reviewed. Subsequently, the structures of the ERs and their splice variants, the binding of ligands to ERs, and the effect on PCa are provided. Finally, we also assessed the contribution of molecular simulation which can help us to search and predict potential estrogenic activities.
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Affiliation(s)
- Adrián Ramírez-de-Arellano
- Instituto de Investigación en Ciencias Biomédicas, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
| | - Ana Laura Pereira-Suárez
- Instituto de Investigación en Ciencias Biomédicas, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
- Departamento de Microbiología y Patología, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
| | - Cecilia Rico-Fuentes
- Centro Universitario de los Altos, Universidad de Guadalajara, Tepatitlán de Morelos, Mexico
| | - Edgar Iván López-Pulido
- Centro Universitario de los Altos, Universidad de Guadalajara, Tepatitlán de Morelos, Mexico
| | - Julio César Villegas-Pineda
- Departamento de Microbiología y Patología, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
| | - Erick Sierra-Diaz
- Departamentos de Clínicas Quirúrgicas y Salud Pública, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
- Departamento de Urología, Hospital de Especialidades Centro Médico Nacional de Occidente, Guadalajara, Mexico
- *Correspondence: Erick Sierra-Diaz,
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Frankl-Vilches C, Gahr M. Androgen and estrogen sensitivity of bird song: a comparative view on gene regulatory levels. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:113-126. [PMID: 29209770 PMCID: PMC5790841 DOI: 10.1007/s00359-017-1236-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 11/02/2017] [Accepted: 11/09/2017] [Indexed: 12/16/2022]
Abstract
Singing of songbirds is sensitive to testosterone and its androgenic and estrogenic metabolites in a species-specific way. The hormonal effects on song pattern are likely mediated by androgen receptors (AR) and estrogen receptor alpha (ERα), ligand activated transcription factors that are expressed in neurons of various areas of the songbirds' vocal control circuit. The distribution of AR in this circuit is rather similar between species while that of ERα is species variant and concerns a key vocal control area, the HVC (proper name). We discuss the regulation of the expression of the cognate AR and ERα and putative splice variants. In particular, we suggest that transcription factor binding sites in the promoter of these receptors differ between bird species. Further, we suggest that AR- and ERα-dependent gene regulation in vocal areas differs between species due to species-specific DNA binding sites of putative target genes that are required for the transcriptional activity of the receptors. We suggest that species differences in the distribution of AR and ERα in vocal areas and in the genomic sensitivity to these receptors contribute to species-specific hormonal regulation of the song.
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Affiliation(s)
- Carolina Frankl-Vilches
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany
| | - Manfred Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
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Ishii H, Hattori Y, Munetomo A, Watanabe H, Sakuma Y, Ozawa H. Characterization of rodent constitutively active estrogen receptor α variants and their constitutive transactivation mechanisms. Gen Comp Endocrinol 2017; 248:16-26. [PMID: 28412386 DOI: 10.1016/j.ygcen.2017.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/24/2017] [Accepted: 04/12/2017] [Indexed: 12/17/2022]
Abstract
Estrogen receptor α (ERα) mRNAs exhibit remarkable heterogeneity owing to complicated alternative splicing. Some encode C-terminally-truncated ERα proteins, which display ligand-independent transactivation or dominant-negative activity. We previously characterized C-terminally-truncated ERα mRNA variants with cryptic sequences in humans and mice, and demonstrated that helices in the ligand-binding domains (LBDs) of ERα variants contribute to ligand-independent transcriptional activity. However, existence of non-conventional coding exons and generation of constitutively active ERα variants have remained to be examined in rats. To comparatively analyze modular organization and splicing profiles of the ERα genes, the range of C-terminally-truncated ERα variants was explored in rats and mice using rapid amplification of cDNA ends and RT-PCR cloning. Furthermore, their functions were determined in transiently transfected cells using expression constructs and luciferase reporter assays. Multiple cryptic exons and C-terminally-truncated ERα variant mRNAs were identified in rats and mice. Naturally occurring and artificially truncated variants/constructs lacking helix 5 potentially exhibited gain-of-function in transfected cells. Although cryptic exons and splicing profiles were poorly conserved among humans, mice, and rats, constitutively active variants were generated from the ERα genes. Moreover, the primary mechanism of ligand-independent activation by C-terminally-truncated ERα variants is C-terminus to helix 5 deletion in the LBD. This comparative study documented the complexity of ERα genes, mRNAs, and proteins, and further determined the underlying structural basis of ligand-independent activation by C-terminally-truncated ERα variants.
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Affiliation(s)
- Hirotaka Ishii
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
| | - Yujiro Hattori
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Neurosurgery, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.
| | - Arisa Munetomo
- Laboratory of Behavior Neuroscience, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681, Japan.
| | - Hiroshi Watanabe
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Orthopaedic Surgery, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.
| | - Yasuo Sakuma
- University of Tokyo Health Sciences, 4-11 Ochiai, Tama, Tokyo 206-0033, Japan.
| | - Hitoshi Ozawa
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
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Bhattacharjee P, Das R, Mandal A, Kundu P. Functional characterization of tomato membrane-bound NAC transcription factors. PLANT MOLECULAR BIOLOGY 2017; 93:511-532. [PMID: 28039561 DOI: 10.1007/s11103-016-0579-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 12/10/2016] [Indexed: 05/18/2023]
Abstract
Genome-wide analysis was carried out to identify and analyze differential expression pattern of tomato membrane bound NAC transcription factors (SlNACMTFs) during stresses. Two biotic-stress-related SlNACMTFs have been characterized to elucidate their regulatory function. NAC transcription factors are known regulators of stress-related gene expression. As Stresses are perceived and transmitted by membrane-bound proteins, functional characterization of membrane-associated NAC transcription factors in tomato can reveal valuable insight about membrane-mediated stress-signalling. Tomato genome encodes 13 NAC genes which have predicted transmembrane domain(s) (SlNACMTFs). mRNA of 12 SlNACMTFs were readily detected in multiple tissues, and also in polysome isolated from leaf, confirming active transcription and translation from these genes occur under normal physiological condition. Additionally, most of the SlNACMTFs were differentially regulated during stresses and stress-related transcription factor binding sites are prevalent in their promoters. SlNACMTF3 and 8 were majorly regulated in biotic and abiotic stresses. Like other MTFs, SlNACMTF3 was translocated to the plasma membrane, whereas the C-terminus truncated (ΔC) form localized in the cytoplasm and the nucleus. Accordingly, the ΔC forms significantly influenced the activity of promoters harbouring NAC binding sites (NACbs). Furthermore, the NAC domain of these transcription factors could directly interact with an NACbs, and the proteins failed to regulate a promoter lacking a crucial NACbs. Interestingly, the type of influence to an NACbs containing promoter was dependent on the context of the NACbs, as the same SlNACMTF showed an alternative mode of regulation on different promoters, as well as the same promoter activity was oppositely regulated by two different SlNACMTF. Finally, both SlNACMTFs demonstrated the differential regulatory effect on the expression of several stress-related genes by interacting with the putative NACbs in their promoter region, suggesting their direct role in plant stress response.
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Affiliation(s)
- Payel Bhattacharjee
- Division of Plant Biology, Bose Institute, P1/12 CIT Scheme VII (M), Kolkata, 700054, India
| | - Rohit Das
- Division of Plant Biology, Bose Institute, P1/12 CIT Scheme VII (M), Kolkata, 700054, India
| | - Arunava Mandal
- Division of Plant Biology, Bose Institute, P1/12 CIT Scheme VII (M), Kolkata, 700054, India
| | - Pallob Kundu
- Division of Plant Biology, Bose Institute, P1/12 CIT Scheme VII (M), Kolkata, 700054, India.
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Hattori Y, Ishii H, Munetomo A, Watanabe H, Morita A, Sakuma Y, Ozawa H. Human C-terminally truncated ERα variants resulting from the use of alternative exons in the ligand-binding domain. Mol Cell Endocrinol 2016; 425:111-22. [PMID: 26835991 DOI: 10.1016/j.mce.2016.01.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Revised: 01/28/2016] [Accepted: 01/28/2016] [Indexed: 11/29/2022]
Abstract
The nuclear receptor genes contain alternative internal and terminal exons, with alternative exon incorporation yielding mRNA variants that encode various receptor types, including some with C-terminal truncation that exhibit constitutive activation or dominant-negative transcriptional transactivation. However, C-terminally truncated estrogen receptor α (ERα) variants with alternative sequences have rarely been reported in humans. Therefore, we assessed human ERα genomic organization and alternative splicing profiles, and identified both alternative exons and C-terminally truncated ERα variants. These naturally occurring C-terminally truncated ERα proteins were localized in the nuclei of transfected cells. In addition, ERαi45c and ERαΔ5 variants exhibited constitutive transactivation of an estrogen responsive element-driven promoter in transfected cells. We manufactured expression vectors encoding artificially truncated ERα constructs and evaluated their transactivation abilities to establish mechanisms determining the constitutive activity and dominant-negative properties of truncated variants. Lack of the region encoded in exon 8 eliminated basal and ligand-induced transcriptional transactivation. The C-terminally truncated ERα variants/constructs containing the helices 5 in their ligand-binding domains did not exhibit constitutive transactivation. Furthermore, we demonstrated that truncation from C-termini to helices 5 in the variant ligand-binding domains was required for constitutive activation and found that the remnant regions of the ligand-binding domains and variant-specific sequences influenced transcriptional transactivation efficiency. In conclusion, we elucidated the structural and functional features of novel C-terminally truncated ERα variants and revealed the mechanisms underlying constitutive transactivation by C-terminally truncated nuclear receptor variants.
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Affiliation(s)
- Yujiro Hattori
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Neurosurgery, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
| | - Hirotaka Ishii
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
| | - Arisa Munetomo
- Laboratory of Behavior Neuroscience, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681, Japan
| | - Hiroshi Watanabe
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan; Department of Orthopaedic Surgery, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
| | - Akio Morita
- Department of Neurosurgery, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
| | - Yasuo Sakuma
- University of Tokyo Health Sciences, 4-11 Ochiai, Tama, Tokyo 206-0033, Japan
| | - Hitoshi Ozawa
- Department of Anatomy and Neurobiology, Graduate School of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
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