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Kitamura D, Taniguchi K, Nakamura M, Igaki T. In vivo evidence for homeostatic regulation of ribosomal protein levels in Drosophila. Cell Struct Funct 2024; 49:11-20. [PMID: 38199250 DOI: 10.1247/csf.23088] [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: 01/12/2024] Open
Abstract
The ribosome is a molecular machine essential for protein synthesis, which is composed of approximately 80 different ribosomal proteins (Rps). Studies in yeast and cell culture systems have revealed that the intracellular level of Rps is finely regulated by negative feedback mechanisms or ubiquitin-proteasome system, which prevents over- or under-abundance of Rps in the cell. However, in vivo evidence for the homeostatic regulation of intracellular Rp levels has been poor. Here, using Drosophila genetics, we show that intracellular Rp levels are regulated by proteasomal degradation of excess Rps that are not incorporated into the ribosome. By establishing an EGFP-fused Rp gene system that can monitor endogenously expressed Rp levels, we found that endogenously expressed EGFP-RpS20 or -RpL5 is eliminated from the cell when RpS20 or RpL5 is exogenously expressed. Notably, the level of endogenously expressed Hsp83, a housekeeping gene, was not affected by exogenous expression of Hsp83, suggesting that the strict negative regulation of excess protein is specific for intracellular Rps. Further analyses revealed that the maintenance of cellular Rp levels is not regulated at the transcriptional level but by proteasomal degradation of excess free Rps as a protein quality control mechanism. Our observations provide not only the in vivo evidence for the homeostatic regulation of Rp levels but also a novel genetic strategy to study in vivo regulation of intracellular Rp levels and its role in tissue homeostasis via cell competition.Key words: ribosomal protein, proteasomal degradation, Drosophila.
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Affiliation(s)
- Daiki Kitamura
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University
| | | | - Mai Nakamura
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University
| | - Tatsushi Igaki
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University
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Zhou P, Zong X, Yan S, Zhang J, Wang D, Shen J. The Wnt pathway regulates wing morph determination in Acyrthosiphon pisum. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2023; 161:104003. [PMID: 37657610 DOI: 10.1016/j.ibmb.2023.104003] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/23/2023] [Accepted: 08/29/2023] [Indexed: 09/03/2023]
Abstract
Wing dimorphism occurs in insects as a survival strategy to adapt to environmental changes. In response to environmental cues, mother aphids transmit signals to their offspring, and the offspring either emerge as winged adults or develop as wingless adults with degeneration of the wing primordia in the early instar stage. However, how the wing morph is determined in the early instar stage is still unclear. Here, we established a surgical sampling method to obtain precise wing primordium tissues for transcriptome analysis. We identified Wnt as a regulator of wing determination in the early second instar stage in the pea aphid. Inhibiting Wnt signaling via knockdown of Wnt2, Wnt11b, the Wnt receptor-encoding gene fz2 or the downstream targets vg and omb resulted in a decreased proportion of winged aphids. Activation of Wnt signaling via knockdown of miR-8, an inhibitor of the Wnt/Wg pathway, led to an increased proportion of winged aphids. Furthermore, the wing primordia of wingless nymphs underwent apoptosis in the early second instar, and cell death was activated by knockdown of fz2 under the wing-inducing condition. These results indicate that the developmental plasticity of aphid wings is modulated by the intrinsic Wnt pathway in response to environmental challenges.
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Affiliation(s)
- Ping Zhou
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China
| | - Xin Zong
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China
| | - Shuo Yan
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China
| | - Junzheng Zhang
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China
| | - Dan Wang
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China.
| | - Jie Shen
- Department of Plant Biosecurity and MARA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing, 100193, China.
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Merino MM, Garcia-Sanz JA. Stemming Tumoral Growth: A Matter of Grotesque Organogenesis. Cells 2023; 12:cells12060872. [PMID: 36980213 PMCID: PMC10047265 DOI: 10.3390/cells12060872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/16/2023] Open
Abstract
The earliest metazoans probably evolved from single-celled organisms which found the colonial system to be a beneficial organization. Over the course of their evolution, these primary colonial organisms increased in size, and division of labour among the cells became a remarkable feature, leading to a higher level of organization: the biological organs. Primitive metazoans were the first organisms in evolution to show organ-type structures, which set the grounds for complex organs to evolve. Throughout evolution, and concomitant with organogenesis, is the appearance of tissue-specific stem cells. Tissue-specific stem cells gave rise to multicellular living systems with distinct organs which perform specific physiological functions. This setting is a constructive role of evolution; however, rebel cells can take over the molecular mechanisms for other purposes: nowadays we know that cancer stem cells, which generate aberrant organ-like structures, are at the top of a hierarchy. Furthermore, cancer stem cells are the root of metastasis, therapy resistance, and relapse. At present, most therapeutic drugs are unable to target cancer stem cells and therefore, treatment becomes a challenging issue. We expect that future research will uncover the mechanistic “forces” driving organ growth, paving the way to the implementation of new strategies to impair human tumorigenesis.
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Affiliation(s)
- Marisa M. Merino
- Department of Biochemistry, Faculty of Sciences, University of Geneva, 1205 Geneva, Switzerland
- Correspondence: (M.M.M.); (J.A.G.-S.)
| | - Jose A. Garcia-Sanz
- Department of Molecular Biomedicine, Centro de Investigaciones Biologicas Margarita Salas, Spanish National Research Council (CIB-CSIC), 28040 Madrid, Spain
- Correspondence: (M.M.M.); (J.A.G.-S.)
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Breznak SM, Kotb NM, Rangan P. Dynamic regulation of ribosome levels and translation during development. Semin Cell Dev Biol 2023; 136:27-37. [PMID: 35725716 DOI: 10.1016/j.semcdb.2022.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/20/2022] [Accepted: 06/12/2022] [Indexed: 01/11/2023]
Abstract
The ability of ribosomes to translate mRNAs into proteins is the basis of all life. While ribosomes are essential for cell viability, reduction in levels of ribosomes can affect cell fate and developmental transitions in a tissue specific manner and can cause a plethora of related diseases called ribosomopathies. How dysregulated ribosomes homeostasis influences cell fate and developmental transitions is not fully understood. Model systems such as Drosophila and C. elegans oogenesis have been used to address these questions since defects in conserved steps in ribosome biogenesis result in stem cell differentiation and developmental defects. In this review, we first explore how ribosome levels affect stem cell differentiation. Second, we describe how ribosomal modifications and incorporation of ribosomal protein paralogs contribute to development. Third, we summarize how cells with perturbed ribosome biogenesis are sensed and eliminated during organismal growth.
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Affiliation(s)
- Shane M Breznak
- Department of Biological Sciences/RNA Institute, University at Albany SUNY, Albany, NY, 12222, USA
| | - Noor M Kotb
- Department of Biomedical Sciences, The School of Public Health, University at Albany SUNY, 11 Albany, NY 12222, USA
| | - Prashanth Rangan
- Department of Cell, Developmental, and Regenerative Biology, Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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Singh A, Yeates C, Deshpande P, Kango-Singh M. Signaling interactions among neurons impact cell fitness and death in Alzheimer’s disease. Neural Regen Res 2023; 18:784-789. [DOI: 10.4103/1673-5374.354516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Wada Y, Ohsawa S, Igaki T. Yorkie ensures robust tissue growth in Drosophila ribosomal protein mutants. Development 2021; 148:dev198705. [PMID: 34313318 DOI: 10.1242/dev.198705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 06/25/2021] [Indexed: 11/20/2022]
Abstract
Heterozygosity of ribosomal protein genes causes a variety of developmental abnormalities in humans, which are collectively known as ribosomopathies, yet the underlying mechanisms remain elusive. Here, we analyzed Drosophila Minute (M)/+ mutants, a group of mutants heterozygous for ribosomal protein genes that exhibit a characteristic thin-bristle phenotype. We found that, although M/+ flies develop essentially normal wings, simultaneous deletion of one copy of the Hippo pathway effector yki resulted in severe wing growth defects. These defects were caused by JNK-mediated cell death in the wing pouch via Eiger/TNF signaling. The JNK activation in M/+, yki/+ wing discs required the caspase Dronc, which is normally blocked by DIAP1. Notably, heterozygosity of yki reduced DIAP1 expression in the wing pouch, leading to elevation of Dronc activity. Dronc and JNK formed a positive-feedback loop that amplifies Dronc activation, leading to apoptosis. Our observations suggest a mechanism of robust tissue growth whereby tissues with reduced ribosomal protein prevent ectopic apoptosis via Yki activity.
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Affiliation(s)
- Yayoi Wada
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyoku, Kyoto 607-8501, Japan
| | - Shizue Ohsawa
- Group of Genetics, Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan
| | - Tatsushi Igaki
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyoku, Kyoto 607-8501, Japan
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Paraskevopoulos M, McGuigan AP. Application of CRISPR screens to investigate mammalian cell competition. Brief Funct Genomics 2021; 20:135-147. [PMID: 33782689 DOI: 10.1093/bfgp/elab020] [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] [Received: 09/17/2020] [Revised: 02/26/2021] [Accepted: 03/08/2021] [Indexed: 11/14/2022] Open
Abstract
Cell competition is defined as the context-dependent elimination of cells that is mediated by intercellular communication, such as paracrine or contact-dependent cell signaling, and/or mechanical stresses. It is considered to be a quality control mechanism that facilitates the removal of suboptimal cells from both adult and embryonic tissues. Cell competition, however, can also be hijacked by transformed cells to acquire a 'super-competitor' status and outcompete the normal epithelium to establish a precancerous field. To date, many genetic drivers of cell competition have been identified predominately through studies in Drosophila. Especially during the last couple of years, ethylmethanesulfonate-based genetic screens have been instrumental to our understanding of the molecular regulators behind some of the most common competition mechanisms in Drosophila, namely competition due to impaired ribosomal function (or anabolism) and mechanical sensitivity. Despite recent findings in Drosophila and in mammalian models of cell competition, the drivers of mammalian cell competition remain largely elusive. Since the discovery of CRISPR/Cas9, its use in functional genomics has been indispensable to uncover novel cancer vulnerabilities. We envision that CRISPR/Cas9 screens will enable systematic, genome-scale probing of mammalian cell competition to discover novel mutations that not only trigger cell competition but also identify novel molecular components that are essential for the recognition and elimination of less fit cells. In this review, we summarize recent contributions that further our understanding of the molecular mechanisms of cell competition by genetic screening in Drosophila, and provide our perspective on how similar and novel screening strategies made possible by whole-genome CRISPR/Cas9 screening can advance our understanding of mammalian cell competition in the future.
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Akai N, Ohsawa S, Sando Y, Igaki T. Epithelial cell-turnover ensures robust coordination of tissue growth in Drosophila ribosomal protein mutants. PLoS Genet 2021; 17:e1009300. [PMID: 33507966 PMCID: PMC7842893 DOI: 10.1371/journal.pgen.1009300] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 12/07/2020] [Indexed: 12/30/2022] Open
Abstract
Highly reproducible tissue development is achieved by robust, time-dependent coordination of cell proliferation and cell death. To study the mechanisms underlying robust tissue growth, we analyzed the developmental process of wing imaginal discs in Drosophila Minute mutants, a series of heterozygous mutants for a ribosomal protein gene. Minute animals show significant developmental delay during the larval period but develop into essentially normal flies, suggesting there exists a mechanism ensuring robust tissue growth during abnormally prolonged developmental time. Surprisingly, we found that both cell death and compensatory cell proliferation were dramatically increased in developing wing pouches of Minute animals. Blocking the cell-turnover by inhibiting cell death resulted in morphological defects, indicating the essential role of cell-turnover in Minute wing morphogenesis. Our analyses showed that Minute wing discs elevate Wg expression and JNK-mediated Dilp8 expression that causes developmental delay, both of which are necessary for the induction of cell-turnover. Furthermore, forced increase in Wg expression together with developmental delay caused by ecdysone depletion induced cell-turnover in the wing pouches of non-Minute animals. Our findings suggest a novel paradigm for robust coordination of tissue growth by cell-turnover, which is induced when developmental time axis is distorted. Animal development can be disturbed by various stimuli such as genetic mutations, environmental fluctuations, and physical injuries. However, animals often accomplish normal tissue growth and morphogenesis even in the presence of developmental perturbations. Drosophila Minute mutants, a series of fly mutants for a ribosomal protein gene, show significantly prolonged larval period but develop into essentially normal flies. We found an unexpected massive cell death and subsequent compensatory cell proliferation in developing wing discs of Minute animals. This ‘cell-turnover’ was essential for normal wing morphogenesis in Minute flies. We found that the cell-turnover was induced by elevated Wg expression in the wing pouch and JNK-mediated Dilp8 expression that causes developmental delay. Indeed, cell-turnover was reproduced in non-Minute animals’ wing discs by overexpressing Wg using the wg promoter together with developmental delay caused by ecdysone depletion. Our findings propose a novel paradigm for morphogenetic robustness by cell-turnover, which ensures normal wing growth during the abnormally prolonged larval period, possibly by creating a flexible cell death and proliferation platform to adjust cell numbers in the prospective wing blade.
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Affiliation(s)
- Nanami Akai
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Group of Genetics, Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Shizue Ohsawa
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Group of Genetics, Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Yukari Sando
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Tatsushi Igaki
- Laboratory of Genetics, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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Drosophila RpS12 controls translation, growth, and cell competition through Xrp1. PLoS Genet 2019; 15:e1008513. [PMID: 31841522 PMCID: PMC6936874 DOI: 10.1371/journal.pgen.1008513] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 12/30/2019] [Accepted: 11/08/2019] [Indexed: 01/01/2023] Open
Abstract
Whereas complete loss of Rp function is generally lethal, most heterozygous Rp mutants grow more slowly and are subject to competitive loss from mosaics tissues that also contain wild type cells. The rpS12 gene has a special role in the cell competition of other Ribosomal Protein (Rp) mutant cells in Drosophila. Elimination by cell competition is promoted by higher RpS12 levels and prevented by a specific rpS12 mis-sense mutation, identifying RpS12 as a key effector of cell competition due to mutations in other Rp genes. Here we show that RpS12 is also required for other aspects of Rp mutant phenotypes, including hundreds of gene expression changes that occur in 'Minute' Rp heterozygous wing imaginal discs, overall translation rate, and the overall rate of organismal development, all through the bZip protein Xrp1 that is one of the RpS12-regulated genes. Our findings outline the regulatory response to mutations affecting essential Rp genes that controls overall translation, growth, and cell competition, and which may contribute to cancer and other diseases.
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Nagata R, Igaki T. Cell competition: Emerging mechanisms to eliminate neighbors. Dev Growth Differ 2018; 60:522-530. [DOI: 10.1111/dgd.12575] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 09/23/2018] [Accepted: 09/23/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Rina Nagata
- Laboratory of GeneticsGraduate School of BiostudiesKyoto University Kyoto Japan
| | - Tatsushi Igaki
- Laboratory of GeneticsGraduate School of BiostudiesKyoto University Kyoto Japan
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Sollazzo M, Genchi C, Paglia S, Di Giacomo S, Pession A, de Biase D, Grifoni D. High MYC Levels Favour Multifocal Carcinogenesis. Front Genet 2018; 9:612. [PMID: 30619451 PMCID: PMC6297171 DOI: 10.3389/fgene.2018.00612] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Accepted: 11/20/2018] [Indexed: 02/05/2023] Open
Abstract
The term "field cancerisation" describes the formation of tissue sub-areas highly susceptible to multifocal tumourigenesis. In the earlier stages of cancer, cells may indeed display a series of molecular alterations that allow them to proliferate faster, eventually occupying discrete tissue regions with irrelevant morphological anomalies. This behaviour recalls cell competition, a process based on a reciprocal fitness comparison: when cells with a growth advantage arise in a tissue, they are able to commit wild-type neighbours to death and to proliferate at their expense. It is known that cells expressing high MYC levels behave as super-competitors, able to kill and replace less performant adjacent cells; given MYC upregulation in most human cancers, MYC-mediated cell competition is likely to pioneer field cancerisation. Here we show that MYC overexpression in a sub-territory of the larval wing epithelium of Drosophila is sufficient to trigger a number of cellular responses specific to mammalian pre-malignant tissues. Moreover, following induction of different second mutations, high MYC-expressing epithelia were found to be susceptible to multifocal growth, a hallmark of mammalian pre-cancerous fields. In summary, our study identified an early molecular alteration implicated in field cancerisation and established a genetically amenable model which may help study the molecular basis of early carcinogenesis.
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