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Sachan N, Sharma V, Mutsuddi M, Mukherjee A. Notch signalling: multifaceted role in development and disease. FEBS J 2024; 291:3030-3059. [PMID: 37166442 DOI: 10.1111/febs.16815] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 02/08/2023] [Accepted: 05/10/2023] [Indexed: 05/12/2023]
Abstract
Notch pathway is an evolutionarily conserved signalling system that operates to influence an astonishing array of cell fate decisions in different developmental contexts. Notch signalling plays important roles in many developmental processes, making it difficult to name a tissue or a developing organ that does not depend on Notch function at one stage or another. Thus, dysregulation of Notch signalling is associated with many developmental defects and various pathological conditions, including cancer. Although many recent advances have been made to reveal different aspects of the Notch signalling mechanism and its intricate regulation, there are still many unanswered questions related to how the Notch signalling pathway functions in so many developmental events. The same pathway can be deployed in numerous cellular contexts to play varied and critical roles in an organism's development and this is only possible because of the complex regulatory mechanisms of the pathway. In this review, we provide an overview of the mechanism and regulation of the Notch signalling pathway along with its multifaceted functions in different aspects of development and disease.
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Affiliation(s)
- Nalani Sachan
- Department of Molecular and Human Genetics, Institute of Science, Banaras Hindu University, Varanasi, India
- Department of Cell Biology, NYU Grossman School of Medicine, New York, NY, USA
| | - Vartika Sharma
- Department of Molecular and Human Genetics, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Mousumi Mutsuddi
- Department of Molecular and Human Genetics, Institute of Science, Banaras Hindu University, Varanasi, India
| | - Ashim Mukherjee
- Department of Molecular and Human Genetics, Institute of Science, Banaras Hindu University, Varanasi, India
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2
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Ikeda T, Inamori K, Kawanishi T, Takeda H. Reemployment of Kupffer's vesicle cells into axial and paraxial mesoderm via transdifferentiation. Dev Growth Differ 2022; 64:163-177. [PMID: 35129208 DOI: 10.1111/dgd.12774] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/17/2022] [Accepted: 01/25/2022] [Indexed: 01/25/2023]
Abstract
Kupffer's vesicle (KV) in the teleost embryo is a fluid-filled vesicle surrounded by a layer of epithelial cells with rotating primary cilia. KV transiently acts as the left-right organizer and degenerates after the establishment of left-right asymmetric gene expression. Previous labelling experiments in zebrafish embryos indicated that descendants of KV-epithelial cells are incorporated into mesodermal tissues after the collapse of KV. However, the overall picture of their differentiation potency had been unclear due to the lack of suitable genetic tools and molecular analyses. In the present study, we established a novel zebrafish transgenic line with a promoter of dand5, in which all KV-epithelial cells and their descendants are specifically labelled until the larval stage. We found that KV-epithelial cells undergo epithelial-mesenchymal transition upon KV collapse and infiltrate into adjacent mesodermal progenitors, the presomitic mesoderm and chordoneural hinge. Once incorporated, the descendants of KV-epithelial cells expressed distinct mesodermal differentiation markers and contributed to the mature populations such as the axial muscles and notochordal sheath through normal developmental process. These results indicate that differentiated KV-epithelial cells possess unique plasticity in that they are reemployed into mesodermal lineages through transdifferentiation after they complete their initial role in KV.
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Affiliation(s)
- Takafumi Ikeda
- Laboratory of Embryology, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Kiichi Inamori
- Laboratory of Embryology, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Toru Kawanishi
- Laboratory of Embryology, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Hiroyuki Takeda
- Laboratory of Embryology, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
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3
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Jacinto R, Sampaio P, Roxo-Rosa M, Pestana S, Lopes SS. Pkd2 Affects Cilia Length and Impacts LR Flow Dynamics and Dand5. Front Cell Dev Biol 2021; 9:624531. [PMID: 33869175 PMCID: PMC8047213 DOI: 10.3389/fcell.2021.624531] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 03/12/2021] [Indexed: 11/29/2022] Open
Abstract
The left-right (LR) field recognizes the importance of the mechanism involving the calcium permeable channel Polycystin-2. However, whether the early LR symmetry breaking mechanism is exclusively via Polycystin-2 has not been tested. For that purpose, we need to be able to isolate the effects of decreasing the levels of Pkd2 protein from any eventual effects on flow dynamics. Here we demonstrate that curly-up (cup) homozygous mutants have abnormal flow dynamics. In addition, we performed one cell stage Pkd2 knockdowns and LR organizer specific Pkd2 knockdowns and observed that both techniques resulted in shorter cilia length and abnormal flow dynamics. We conclude that Pkd2 reduction leads to LR defects that cannot be assigned exclusively to its putative role in mediating mechanosensation because indirectly, by modifying cell shape or decreasing cilia length, Pkd2 deficit affects LR flow dynamics.
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Affiliation(s)
- Raquel Jacinto
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Pedro Sampaio
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Mónica Roxo-Rosa
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Sara Pestana
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Susana S Lopes
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
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Miletto Petrazzini ME, Sovrano VA, Vallortigara G, Messina A. Brain and Behavioral Asymmetry: A Lesson From Fish. Front Neuroanat 2020; 14:11. [PMID: 32273841 PMCID: PMC7113390 DOI: 10.3389/fnana.2020.00011] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 03/05/2020] [Indexed: 11/27/2022] Open
Abstract
It is widely acknowledged that the left and right hemispheres of human brains display both anatomical and functional asymmetries. For more than a century, brain and behavioral lateralization have been considered a uniquely human feature linked to language and handedness. However, over the past decades this idea has been challenged by an increasing number of studies describing structural asymmetries and lateralized behaviors in non-human species extending from primates to fish. Evidence suggesting that a similar pattern of brain lateralization occurs in all vertebrates, humans included, has allowed the emergence of different model systems to investigate the development of brain asymmetries and their impact on behavior. Among animal models, fish have contributed much to the research on lateralization as several fish species exhibit lateralized behaviors. For instance, behavioral studies have shown that the advantages of having an asymmetric brain, such as the ability of simultaneously processing different information and perform parallel tasks compensate the potential costs associated with poor integration of information between the two hemispheres thus helping to better understand the possible evolutionary significance of lateralization. However, these studies inferred how the two sides of the brains are differentially specialized by measuring the differences in the behavioral responses but did not allow to directly investigate the relation between anatomical and functional asymmetries. With respect to this issue, in recent years zebrafish has become a powerful model to address lateralization at different level of complexity, from genes to neural circuitry and behavior. The possibility of combining genetic manipulation of brain asymmetries with cutting-edge in vivo imaging technique and behavioral tests makes the zebrafish a valuable model to investigate the phylogeny and ontogeny of brain lateralization and its relevance for normal brain function and behavior.
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Affiliation(s)
| | - Valeria Anna Sovrano
- Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy.,Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy
| | | | - Andrea Messina
- Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy
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5
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Left-right asymmetric heart jogging increases the robustness of dextral heart looping in zebrafish. Dev Biol 2019; 459:79-86. [PMID: 31758943 DOI: 10.1016/j.ydbio.2019.11.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 12/31/2022]
Abstract
Building a left-right (L-R) asymmetric organ requires asymmetric information. This comes from various sources, including asymmetries in embryo-scale genetic cascades (including the left-sided Nodal cascade), organ-intrinsic mechanical forces, and cell-level chirality, but the relative influence of these sources and how they collaborate to drive asymmetric morphogenesis is not understood. During zebrafish heart development, the linear heart tube extends to the left of the midline in a process known as jogging. The jogged heart then undergoes dextral (i.e. rightward) looping to correctly position the heart chambers relative to one another. Left lateralized jogging is governed by the left-sided expression of Nodal in mesoderm tissue, while looping laterality is mainly controlled by heart-intrinsic cell-level asymmetries in the actomyosin cytoskeleton. The purpose of lateralized jogging is not known. Moreover, after jogging, the heart tube returns to an almost midline position and so it is not clear whether or how jogging may impact the dextral loop. Here, we characterize a novel loss-of-function mutant in the zebrafish Nodal homolog southpaw (spaw) that appears to be a true null. We then assess the relationship between jogging and looping laterality in embryos lacking asymmetric Spaw signals. We found that the probability of a dextral loop occurring, does not depend on asymmetric Spaw signals per se, but does depend on the laterality of jogging. Thus, we conclude that the role of leftward jogging is to spatially position the heart tube in a manner that promotes robust dextral looping. When jogging laterality is abnormal, the robustness of dextral looping decreases. This establishes a cooperation between embryo-scale Nodal-dependent L-R asymmetries and organ-intrinsic cellular chirality in the control of asymmetric heart morphogenesis and shows that the transient laterality of the early heart tube has consequences for later heart morphogenetic events.
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Abstract
TGF-β family ligands function in inducing and patterning many tissues of the early vertebrate embryonic body plan. Nodal signaling is essential for the specification of mesendodermal tissues and the concurrent cellular movements of gastrulation. Bone morphogenetic protein (BMP) signaling patterns tissues along the dorsal-ventral axis and simultaneously directs the cell movements of convergence and extension. After gastrulation, a second wave of Nodal signaling breaks the symmetry between the left and right sides of the embryo. During these processes, elaborate regulatory feedback between TGF-β ligands and their antagonists direct the proper specification and patterning of embryonic tissues. In this review, we summarize the current knowledge of the function and regulation of TGF-β family signaling in these processes. Although we cover principles that are involved in the development of all vertebrate embryos, we focus specifically on three popular model organisms: the mouse Mus musculus, the African clawed frog of the genus Xenopus, and the zebrafish Danio rerio, highlighting the similarities and differences between these species.
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Affiliation(s)
- Joseph Zinski
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
| | - Benjamin Tajer
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
| | - Mary C Mullins
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
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Zhu P, Xu X, Lin X. Both ciliary and non-ciliary functions of Foxj1a confer Wnt/β-catenin signaling in zebrafish left-right patterning. Biol Open 2015; 4:1376-86. [PMID: 26432885 PMCID: PMC4728341 DOI: 10.1242/bio.012088] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Wnt/β-catenin pathway is implicated in left-right (LR) axis determination; however, the underlying mechanism remains elusive. Prompted by our recent discovery that Wnt signaling regulates ciliogenesis in the zebrafish Kupffer's vesicle (KV) via Foxj1a, a ciliogenic transcription factor, we decided to elucidate functions of Foxj1a in Wnt-regulated LR pattern formation. We showed that targeted injection of wnt8a mRNA into a single cell at the 128-cell stage is sufficient to induce ectopic foxj1a expression and ectopic cilia. By interrogating the transcription circuit of foxj1a regulation, we found that both Lef1 and Tcf7 bind to a consensus element in the foxj1a promoter region. Depletion of Lef1 and Tcf7 inhibits foxj1a transcription in the dorsal forerunner cells, downregulates cilia length and number in KV, and randomizes LR asymmetry. Targeted overexpression of a constitutively active form of Lef1 also induced an ectopic protrusion that contains ectopic transcripts for sox17, foxj1a, and charon, and ectopic monocilia. Further genetic studies using this ectopic expression platform revealed two distinct functions of Foxj1a; mediating Wnt-governed monocilia length elongation as well as charon transcription. The novel Foxj1a-charon regulation is conserved in KV, and importantly, it is independent of the canonical role of Foxj1a in the biosynthesis of motile cilia. Together with the known function of motile cilia movement in generating asymmetric expression of charon, our data put forward a hypothesis that Foxj1a confers both ciliary and non-ciliary functions of Wnt signaling, which converge on charon to regulate LR pattern formation. Summary: Using a targeted overexpression platform, we showed that Wnt activation induces ectopic foxj1a expression and ectopic cilia formation, and revealed two distinct roles of Foxj1a in conferring Wnt-governed left-right patterning.
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Affiliation(s)
- Ping Zhu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Xiaolei Xu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Xueying Lin
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
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Bessodes N, Haillot E, Duboc V, Röttinger E, Lahaye F, Lepage T. Reciprocal signaling between the ectoderm and a mesendodermal left-right organizer directs left-right determination in the sea urchin embryo. PLoS Genet 2012; 8:e1003121. [PMID: 23271979 PMCID: PMC3521660 DOI: 10.1371/journal.pgen.1003121] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 10/12/2012] [Indexed: 02/01/2023] Open
Abstract
During echinoderm development, expression of nodal on the right side plays a crucial role in positioning of the rudiment on the left side, but the mechanisms that restrict nodal expression to the right side are not known. Here we show that establishment of left-right asymmetry in the sea urchin embryo relies on reciprocal signaling between the ectoderm and a left-right organizer located in the endomesoderm. FGF/ERK and BMP2/4 signaling are required to initiate nodal expression in this organizer, while Delta/Notch signaling is required to suppress formation of this organizer on the left side of the archenteron. Furthermore, we report that the H(+)/K(+)-ATPase is critically required in the Notch signaling pathway upstream of the S3 cleavage of Notch. Our results identify several novel players and key early steps responsible for initiation, restriction, and propagation of left-right asymmetry during embryogenesis of a non-chordate deuterostome and uncover a functional link between the H(+)/K(+)-ATPase and the Notch signaling pathway.
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Affiliation(s)
- Nathalie Bessodes
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Emmanuel Haillot
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Véronique Duboc
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Eric Röttinger
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - François Lahaye
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Thierry Lepage
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
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Windner SE, Bird NC, Patterson SE, Doris RA, Devoto SH. Fss/Tbx6 is required for central dermomyotome cell fate in zebrafish. Biol Open 2012; 1:806-14. [PMID: 23213474 PMCID: PMC3507223 DOI: 10.1242/bio.20121958] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 05/29/2012] [Indexed: 12/18/2022] Open
Abstract
The dermomyotome is a pool of progenitor cells on the surface of the myotome. In zebrafish, dermomyotome precursors (anterior border cells, ABCs) can be first identified in the anterior portion of recently formed somites. They must be prevented from undergoing terminal differentiation during segmentation, even while mesodermal cells around them respond to signaling cues and differentiate. T-box containing transcription factors regulate many aspects of mesoderm fate including segmentation and somite patterning. The fused somites (fss) gene is the zebrafish ortholog of tbx6. We demonstrate that in addition to its requirement for segmentation, fss/tbx6 is also required for the specification of ABCs and subsequently the central dermomyotome. The absence of Tbx6-dependent central dermomyotome cells in fss/tbx6 mutants is spatially coincident with a patterning defect in the myotome. Using transgenic fish with a heat-shock inducible tbx6 gene in the fss/tbx6 mutant background, we further demonstrate that ubiquitous fss/tbx6 expression has spatially distinct effects on recovery of the dermomyotome and segment boundaries, suggesting that the mechanism of Fss/Tbx6 action is distinct with respect to dermomyotome development and segmentation. We propose that Fss/Tbx6 is required for preventing myogenic differentiation of central dermomyotome precursors before and after segmentation and that central dermomyotome cells represent a genetically and functionally distinct subpopulation within the zebrafish dermomyotome.
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Affiliation(s)
- Stefanie Elisabeth Windner
- Department of Biology, Wesleyan University , Middletown, CT 06459 , USA ; Division of Zoology and Functional Anatomy, Department of Organismic Biology, University of Salzburg , A-5020 Salzburg, Austria
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Zhang M, Zhang J, Lin SC, Meng A. β-Catenin 1 and β-catenin 2 play similar and distinct roles in left-right asymmetric development of zebrafish embryos. Development 2012; 139:2009-19. [PMID: 22535411 DOI: 10.1242/dev.074435] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
β-Catenin-mediated canonical Wnt signaling has been found to be required for left-right (LR) asymmetric development. However, the implication of endogenous β-catenin in LR development has not been demonstrated by loss-of-function studies. In zebrafish embryos, two β-catenin genes, β-catenin 1 (ctnnb1) and β-catenin 2 (ctnnb2) are maternally expressed and their zygotic expression occurs in almost all types of tissues, including Kupffer's vesicle (KV), an essential organ that initiates LR development in teleost fish. We demonstrate here that morpholino-mediated knockdown of ctnnb1, ctnnb2, or both, in the whole embryo or specifically in dorsal forerunner cells (DFCs) interrupts normal asymmetry of the heart, liver and pancreas. Global knockdown of ctnnb2 destroys the midline physical and molecular barrier, while global knockdown of ctnnb1 impairs the formation of the midline molecular barrier. Depletion of either gene or both in DFCs/KV leads to poor KV cell proliferation, abnormal cilia formation and disordered KV fluid flow with downregulation of ntl and tbx16 expression. ctnnb1 and ctnnb2 in DFCs/KV differentially regulate the expression of charon, a Nodal antagonist, and spaw, a key Nodal gene for laterality development in zebrafish. Loss of ctnnb1 in DFCs/KV inhibits the expression of charon around KV and of spaw in the posterior lateral plate mesoderm, while ctnnb2 knockdown results in loss of spaw expression in the anterior lateral plate mesoderm with little alteration of charon expression. Taken together, our findings suggest that ctnnb1 and ctnnb2 regulate multiple processes of laterality development in zebrafish embryos through similar and distinct mechanisms.
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Affiliation(s)
- Min Zhang
- State Key Laboratory of Biomembrane and Membrane Engineering, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
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Lenhart KF, Lin SY, Titus TA, Postlethwait JH, Burdine RD. Two additional midline barriers function with midline lefty1 expression to maintain asymmetric Nodal signaling during left-right axis specification in zebrafish. Development 2011; 138:4405-10. [PMID: 21937597 DOI: 10.1242/dev.071092] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Left-right (L/R) patterning is crucial for the proper development of all vertebrates and requires asymmetric expression of nodal in the lateral plate mesoderm (LPM). The mechanisms governing asymmetric initiation of nodal have been studied extensively, but because Nodal is a potent activator of its own transcription, it is also crucial to understand the regulation required to maintain this asymmetry once it is established. The 'midline barrier', consisting of lefty1 expression, is a conserved mechanism for restricting Nodal activity to the left. However, the anterior and posterior extremes of the LPM are competent to respond to Nodal signals yet are not adjacent to this barrier, suggesting that lefty1 is not the only mechanism preventing ectopic Nodal activation. Here, we demonstrate the existence of two additional midline barriers. The first is a 'posterior barrier' mediated by Bmp signaling that prevents nodal propagation through the posterior LPM. In contrast to previous reports, we find that Bmp represses Nodal signaling independently of lefty1 expression and through the activity of a ligand other than Bmp4. The 'anterior barrier' is mediated by lefty2 expression in the left cardiac field and prevents Nodal activation from traveling across the anterior limit of the notochord and propagating down the right LPM. Both barriers appear to be conserved across model systems and are thus likely to be present in all vertebrates.
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Affiliation(s)
- Kari F Lenhart
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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12
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Kato Y. The multiple roles of Notch signaling during left-right patterning. Cell Mol Life Sci 2011; 68:2555-67. [PMID: 21544546 PMCID: PMC11114802 DOI: 10.1007/s00018-011-0695-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Revised: 03/28/2011] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
Abstract
The establishment of left-right (LR) asymmetry is regulated by intricate signaling mechanisms during embryogenesis and this asymmetry is critical for morphogenesis as well as the positioning of internal organs within the organism. Recent progress including elucidation of ion transporters, leftward nodal flow, and regulation of asymmetric gene expression contributes to our understanding of how the breaking of the symmetry is initiated and how this laterality information is subsequently transmitted to the organ primordium. A number of developmental signaling pathways have been implicated in this complex process. In this review, we will focus on the roles of the Notch signaling pathway during development of LR asymmetry. The Notch signaling pathway is a short-range communication system between neighboring cells. While Notch signaling plays essential roles in regulating the morphogenesis of the node and left-specific expression of Nodal in the lateral plate mesoderm, a hallmark gene in LR patterning, Notch signaling also suppresses the expression of Pitx2 that is a direct downstream target of Nodal during later stages of development. This negative activity of Notch signaling towards left-specific activity was recently shown to be inhibited by the B cell lymphoma 6 (BCL6)/BCL6 co-repressor (BcoR) transcriptional repressor complex in a target-specific manner. The complex regulation of Notch-dependent gene expression for LR asymmetry will be highlighted in this review.
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Affiliation(s)
- Yoichi Kato
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306, USA.
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13
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Lourenço R, Lopes SS, Saúde L. Left-right function of dmrt2 genes is not conserved between zebrafish and mouse. PLoS One 2010; 5:e14438. [PMID: 21203428 PMCID: PMC3010978 DOI: 10.1371/journal.pone.0014438] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Accepted: 12/07/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Members of the Dmrt family, generally associated with sex determination, were shown to be involved in several other functions during embryonic development. Dmrt2 has been studied in the context of zebrafish development where, due to a duplication event, two paralog genes dmrt2a and dmrt2b are present. Both zebrafish dmrt2a/terra and dmrt2b are important to regulate left-right patterning in the lateral plate mesoderm. In addition, dmrt2a/terra is necessary for symmetric somite formation while dmrt2b regulates somite differentiation impacting on slow muscle development. One dmrt2 gene is also expressed in the mouse embryo, where it is necessary for somite differentiation but with an impact on axial skeleton development. However, nothing was known about its role during left-right patterning in the lateral plate mesoderm or in the symmetric synchronization of somite formation. METHODOLOGY/PRINCIPAL FINDINGS Using a dmrt2 mutant mouse line, we show that this gene is not involved in symmetric somite formation and does not regulate the laterality pathway that controls left-right asymmetric organ positioning. We reveal that dmrt2a/terra is present in the zebrafish laterality organ, the Kupffer's vesicle, while its homologue is excluded from the mouse equivalent structure, the node. On the basis of evolutionary sub-functionalization and neo-functionalization theories we discuss this absence of functional conservation. CONCLUSIONS/SIGNIFICANCE Our results show that the role of dmrt2 gene is not conserved during zebrafish and mouse embryonic development.
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Affiliation(s)
- Raquel Lourenço
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
| | - Susana S. Lopes
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
| | - Leonor Saúde
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- * E-mail:
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14
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Lopes SS, Lourenço R, Pacheco L, Moreno N, Kreiling J, Saúde L. Notch signalling regulates left-right asymmetry through ciliary length control. Development 2010; 137:3625-32. [DOI: 10.1242/dev.054452] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The importance of cilia in embryonic development and adult physiology is emphasized by human ciliopathies. Despite its relevance, molecular signalling pathways behind cilia formation are poorly understood. We show that Notch signalling is a key pathway for cilia length control. In deltaD zebrafish mutants, cilia length is reduced in Kupffer's vesicle and can be rescued by the ciliogenic factor foxj1a. Conversely, cilia length increases when Notch signalling is hyperactivated. Short cilia found in deltaD mutants reduce the fluid flow velocity inside Kupffer's vesicle, thus compromising the asymmetric expression of the flow sensor charon. Notch signalling brings together ciliary length control and fluid flow hydrodynamics with transcriptional activation of laterality genes. In addition, our deltaD mutant analysis discloses an uncoupling between gut and heart laterality.
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Affiliation(s)
- Susana S. Lopes
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
- Instituto Gulbenkian de Ciência, P-2780-156 Oeiras, Portugal
| | - Raquel Lourenço
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
- Instituto Gulbenkian de Ciência, P-2780-156 Oeiras, Portugal
| | - Luís Pacheco
- Instituto Gulbenkian de Ciência, P-2780-156 Oeiras, Portugal
| | - Nuno Moreno
- Instituto Gulbenkian de Ciência, P-2780-156 Oeiras, Portugal
| | - Jill Kreiling
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Leonor Saúde
- Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
- Instituto Gulbenkian de Ciência, P-2780-156 Oeiras, Portugal
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15
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Zebrafish Nkd1 promotes Dvl degradation and is required for left-right patterning. Dev Biol 2010; 348:22-33. [PMID: 20858476 DOI: 10.1016/j.ydbio.2010.08.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 08/22/2010] [Accepted: 08/27/2010] [Indexed: 12/20/2022]
Abstract
The establishment of the left-right (LR) axis in zebrafish embryos relies on signals from the dorsal forerunner cells (DFC) and the Kupffer's vesicle (KV). While the Wnt signaling network influences many aspects of embryonic development, its precise role in LR patterning is still unclear. One branch of the Wnt network leads to stabilization of β-catenin and activation of downstream target genes. Other Wnt ligands appear to act independently of β-catenin to modulate calcium release and influence cell polarity. Central to regulation of β-catenin and coordination of convergent extension (CE) movements is Dishevelled (Dvl). Naked Cuticle (Nkd) binds Dvl and modulates β-catenin-dependent and independent Wnt signaling. Here, we analyze the expression patterns of three zebrafish Nkd homologs and find enriched expression of nkd1 in DFCs and KV. Dvl is degraded upon Nkd1 overexpression in zebrafish. Knockdown of Nkd1 specifically in the DFC results in β-catenin nuclear localization and transcriptional activation as well as alterations to DFC migration, KV formation, ciliogenesis and LR patterning. Furthermore, we identify asymmetric expression of the Nodal antagonist charon around the KV and show that Nkd1 knockdown impacts asymmetric charon expression. Our findings show that Nkd1 acts as a β-catenin antagonist in the DFCs necessary for LR patterning.
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16
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Francescatto L, Rothschild SC, Myers AL, Tombes RM. The activation of membrane targeted CaMK-II in the zebrafish Kupffer's vesicle is required for left-right asymmetry. Development 2010; 137:2753-62. [DOI: 10.1242/dev.049627] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Intracellular calcium ion (Ca2+) elevation on the left side of the mouse embryonic node or zebrafish Kupffer's vesicle (KV) is the earliest asymmetric molecular event that is functionally linked to lateral organ placement in these species. In this study, Ca2+/CaM-dependent protein kinase (CaMK-II) is identified as a necessary target of this Ca2+ elevation in zebrafish embryos. CaMK-II is transiently activated in approximately four interconnected cells along the anterior left wall of the KV between the six- and 12-somite stages, which is coincident with known left-sided Ca2+ elevations. Within these cells, activated CaMK-II is observed at the surface and in clusters, which appear at the base of some KV cilia. Although seven genes encode catalytically active CaMK-II in early zebrafish embryos, one of these genes also encodes a truncated inactive variant (αKAP) that can hetero-oligomerize with and target active enzyme to membranes. αKAP, β2 CaMK-II and γ1 CaMK-II antisense morpholino oligonucleotides, as well as KV-targeted dominant negative CaMK-II, randomize organ laterality and southpaw (spaw) expression in lateral plate mesoderm (LPM). Left-sided CaMK-II activation was most dependent on an intact KV, the PKD2 Ca2+ channel and γ1 CaMK-II; however, αKAP, β2 CaMK-II and the RyR3 ryanodine receptor were also necessary for full CaMK-II activation. This is the first report to identify a direct Ca2+-sensitive target in left-right asymmetry and supports a model in which membrane targeted CaMK-II hetero-oligomers in nodal cells transduce the left-sided PKD2-dependent Ca2+ signals to the LPM.
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Affiliation(s)
- Ludmila Francescatto
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012, USA
| | - Sarah C. Rothschild
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012, USA
| | - Alexandra L. Myers
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012, USA
| | - Robert M. Tombes
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284-2012, USA
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17
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18
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Nornes S, Newman M, Wells S, Verdile G, Martins RN, Lardelli M. Independent and cooperative action of Psen2 with Psen1 in zebrafish embryos. Exp Cell Res 2009; 315:2791-801. [PMID: 19563801 DOI: 10.1016/j.yexcr.2009.06.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 06/22/2009] [Accepted: 06/22/2009] [Indexed: 02/05/2023]
Abstract
Presenilin1 (PSEN1) and presenilin2 (PSEN2) are involved in the processing of type-1 transmembrane proteins including the amyloid precursor protein (APP), Notch and several others. PSEN1 has been shown to be crucial for proteolytic cleavage of Notch in developing animal embryos. Mouse embryos lacking Psen1 function show disturbed neurogenesis and somite formation, resembling Notch pathway mutants. However, loss of Psen2 activity reveals only a minor phenotype. Zebrafish embryos are a valuable tool for analysis of the molecular genetic control of cell differentiation since endogenous gene expression can be modulated in subtle and complex ways to give a phenotypic readout. Using injection of morpholino antisense oligonucleotides to inhibit protein translation in zebrafish embryos, we show that reduced Psen2 activity decreases the number of melanocytes in the trunk but not in the cranial area at 2 days post fertilisation (dpf). Reduced Psen2 activity apparently reduces Notch signalling resulting in perturbed spinal neurogenin1 (neurog1) expression, neurogenesis and trunk and tail neural crest development. Similar effects are seen for reduced Psen1 activity. These results suggest that Psen2 plays a more prominent role in Notch signalling and embryo development in zebrafish than in mammals. Intriguingly, decreased Psen2 activity increases the number of Dorsal Longitudinal Ascending (DoLA) interneurons in the spinal cord while decreased Psen1 activity has no effect. However, the effect on DoLAs of reduced Psen2 can be ameliorated by Psen1 loss. The effects of changes in Psen2 activity on DoLA interneurons and other cells in zebrafish embryos provide bioassays for more detailed dissection of Psen2 function.
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Affiliation(s)
- Svanhild Nornes
- Discipline of Genetics, School of Molecular and Biomedical Science, The University of Adelaide, SA 5005, Australia
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19
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Bakkers J, Verhoeven MC, Abdelilah-Seyfried S. Shaping the zebrafish heart: from left-right axis specification to epithelial tissue morphogenesis. Dev Biol 2009; 330:213-20. [PMID: 19371733 DOI: 10.1016/j.ydbio.2009.04.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 04/07/2009] [Accepted: 04/07/2009] [Indexed: 11/18/2022]
Abstract
Although vertebrates appear bilaterally symmetric on the outside, various internal organs, including the heart, are asymmetric with respect to their position and/or their orientation based on the left/right (L/R) axis. The L/R axis is determined during embryo development. Determination of the L/R axis is fundamentally different from the determination of the anterior-posterior or the dorsal-ventral axis. In all vertebrates a ciliated organ has been described that induces a left-sided gene expression program, which includes Nodal expression in the left lateral plate mesoderm. To have a better understanding of organ laterality it is important to understand how L/R patterning induces cellular responses during organogenesis. In this review, we discuss the current understanding of the mechanisms of L/R patterning during zebrafish development and focus on how this affects cardiac morphogenesis. Several recent studies have provided unprecedented insights into the intimate link between L/R signaling and the cellular responses that drive morphogenesis of this organ.
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Affiliation(s)
- Jeroen Bakkers
- Hubrecht Institute and University Medical Centre Utrecht, 3584 CT, Utrecht, The Netherlands.
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20
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Lin X, Xu X. Distinct functions of Wnt/beta-catenin signaling in KV development and cardiac asymmetry. Development 2009; 136:207-17. [PMID: 19103803 DOI: 10.1242/dev.029561] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Wnt/beta-catenin pathway exhibits distinct and developmental stage-specific roles during cardiogenesis. However, little is known about the molecular mechanisms of Wnt/beta-catenin signaling in the establishment of cardiac left-right (LR) asymmetry. Using zebrafish as an animal model, we show here that Wnt/beta-catenin signaling is differentially required in cardiac LR patterning. At an early stage, during asymmetric signal generation, Wnt/beta-catenin signaling is necessary for Kupffer's vesicle development and for the regulation of both heart and visceral laterality. At a later stage, during asymmetric signal propagation, excessive Wnt/beta-catenin signaling inhibits the transmission of asymmetric cues from the lateral plate mesoderm (LPM) to the cardiac field but not to the developing gut; as such, it only regulates heart laterality. Molecular analysis identifies Gata4 as the downstream target of Wnt/beta-catenin signaling in the cardiac field that responds to the Wnt/beta-catenin signaling and regulates the competence of the heart field to express left-sided genes. In summary, our results reveal a previously unexpected role of Wnt-Gata4 signaling in the control of asymmetric signal propagation from the LPM to the cardiac field.
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Affiliation(s)
- Xueying Lin
- Department of Biochemistry and Molecular Biology, Division of Cardiovascular Diseases, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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21
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Garnett AT, Han TM, Gilchrist MJ, Smith JC, Eisen MB, Wardle FC, Amacher SL. Identification of direct T-box target genes in the developing zebrafish mesoderm. Development 2009; 136:749-60. [PMID: 19158186 PMCID: PMC2685943 DOI: 10.1242/dev.024703] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2008] [Indexed: 11/20/2022]
Abstract
The zebrafish genes spadetail (spt) and no tail (ntl) encode T-box transcription factors that are important for early mesoderm development. Although much has been done to characterize these genes, the identity and location of target regulatory elements remain largely unknown. Here, we survey the genome for downstream target genes of the Spt and Ntl T-box transcription factors. We find evidence for extensive additive interactions towards gene activation and limited evidence for combinatorial and antagonistic interactions between the two factors. Using in vitro binding selection assays to define Spt- and Ntl-binding motifs, we searched for target regulatory sequence via a combination of binding motif searches and comparative genomics. We identified regulatory elements for tbx6 and deltaD, and, using chromatin immunoprecipitation, in vitro DNA binding assays and transgenic methods, we provide evidence that both are directly regulated by T-box transcription factors. We also find that deltaD is directly activated by T-box factors in the tail bud, where it has been implicated in starting the segmentation clock, suggesting that spt and ntl act upstream of this process.
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Affiliation(s)
- Aaron T Garnett
- Department of Molecular and Cell Biology and Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA
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22
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A gene regulatory network directed by zebrafish No tail accounts for its roles in mesoderm formation. Proc Natl Acad Sci U S A 2009; 106:3829-34. [PMID: 19225104 DOI: 10.1073/pnas.0808382106] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using chromatin immunoprecipitation combined with genomic microarrays we have identified targets of No tail (Ntl), a zebrafish Brachyury ortholog that plays a central role in mesoderm formation. We show that Ntl regulates a downstream network of other transcription factors and identify an in vivo Ntl binding site that resembles the consensus T-box binding site (TBS) previously identified by in vitro studies. We show that the notochord-expressed gene floating head (flh) is a direct transcriptional target of Ntl and that a combination of TBSs in the flh upstream region are required for Ntl-directed expression. Using our genome-scale data we have assembled a preliminary gene regulatory network that begins to describe mesoderm formation and patterning in the early zebrafish embryo.
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23
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Langenbacher A, Chen JN. Calcium signaling: a common thread in vertebrate left-right axis development. Dev Dyn 2009; 237:3491-6. [PMID: 18792114 DOI: 10.1002/dvdy.21704] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The establishment of a left-right axis during vertebrate development is essential for coordinating the relative positions of the internal organs to ensure that they function appropriately. Studies in numerous model organisms have revealed differences in regulative mechanisms upstream of nodal signaling, a conserved pathway in left-right axis specification. This review will summarize the diverse pathways involved in the break of left-right symmetry and explore in depth the multiple roles of calcium in vertebrate left-right axis specification.
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Affiliation(s)
- Adam Langenbacher
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
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24
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Aamar E, Dawid IB. Isolation and expression analysis of foxj1 and foxj1.2 in zebrafish embryos. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2009; 52:985-91. [PMID: 18956329 DOI: 10.1387/ijdb.072477ea] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In this report, we present the isolation and identification of a zebrafish homolog of the winged helix\forkhead transcription factor Foxj1. Foxj1 was identified in other species but not in zebrafish. Foxj1 was shown in mice to be required in ciliogenesis and left-right asymmetry establishment. Here we present a spatio-temporal expression pattern of zebrafish foxj1, showing that this gene is expressed in dorsal forerunner cells, Kupffers vesicle, the floor plate, pronephric ducts and kidney. This expression pattern is overlapping but different from that of the foxj1.2, the closest related gene in zebrafish. Foxj1 in zebrafish appears to have similar functions as those reported in other species connected to ciliogenesis and left-right asymmetry.
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Affiliation(s)
- Emil Aamar
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Wardle FC, Papaioannou VE. Teasing out T-box targets in early mesoderm. Curr Opin Genet Dev 2008; 18:418-25. [PMID: 18778771 PMCID: PMC2700021 DOI: 10.1016/j.gde.2008.07.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Accepted: 07/31/2008] [Indexed: 11/21/2022]
Abstract
T-box transcription factor genes are widely conserved in metazoan development and widely involved in developmental processes. With the phase of T-box gene discovery winding down, the phase of transcriptional target discovery for T-box transcription factors is finally taking off and yielding rich rewards. Mutant phenotypes in mouse and zebrafish as well as morpholino studies in zebrafish have helped to link the T-box genes to a variety of signaling pathways through diverse target genes and feedback loops. Particularly in early mesoderm development, it is emerging that a network of T-box genes interacts with Wnt/beta-catenin and Notch/Delta signaling pathways, among others, to control the important processes of mesoderm specification, somite segmentation, and left/right body axis determination.
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Affiliation(s)
- Fiona C. Wardle
- Department of Physiology, Development and Neuroscience, Downing Street, Cambridge, CB2 3DY, UK,
| | - Virginia E. Papaioannou
- Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, 701 W 168 St., New York, NY 10032, USA,
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26
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Hadjantonakis AK, Pisano E, Papaioannou VE. Tbx6 regulates left/right patterning in mouse embryos through effects on nodal cilia and perinodal signaling. PLoS One 2008; 3:e2511. [PMID: 18575602 PMCID: PMC2427182 DOI: 10.1371/journal.pone.0002511] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 05/24/2008] [Indexed: 01/14/2023] Open
Abstract
Background The determination of left/right body axis during early embryogenesis sets up a developmental cascade that coordinates the development of the viscera and is essential to the correct placement and alignment of organ systems and vasculature. Defective left-right patterning can lead to congenital cardiac malformations, vascular anomalies and other serious health problems. Here we describe a novel role for the T-box transcription factor gene Tbx6 in left/right body axis determination in the mouse. Results Embryos lacking Tbx6 show randomized embryo turning and heart looping. Our results point to multiple mechanisms for this effect. First, Dll1, a direct target of Tbx6, is down regulated around the node in Tbx6 mutants and there is a subsequent decrease in nodal signaling, which is required for laterality determination. Secondly, in spite of a lack of expression of Tbx6 in the node, we document a profound effect of the Tbx6 mutation on the morphology and motility of nodal cilia. This results in the loss of asymmetric calcium signaling at the periphery of the node, suggesting that unidirectional nodal flow is disrupted. To carry out these studies, we devised a novel method for direct labeling and live imaging cilia in vivo using a genetically-encoded fluorescent protein fusion that labels tubulin, combined with laser point scanning confocal microscopy for direct visualization of cilia movement. Conclusions We conclude that the transcription factor gene Tbx6 is essential for correct left/right axis determination in the mouse and acts through effects on notch signaling around the node as well as through an effect on the morphology and motility of the nodal cilia.
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Affiliation(s)
| | - Elinor Pisano
- Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, New York, New York, United States of America
| | - Virginia E. Papaioannou
- Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, New York, New York, United States of America
- * E-mail:
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27
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Snelson CD, Santhakumar K, Halpern ME, Gamse JT. Tbx2b is required for the development of the parapineal organ. Development 2008; 135:1693-702. [PMID: 18385257 DOI: 10.1242/dev.016576] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Structural differences between the left and right sides of the brain exist throughout the vertebrate lineage. By studying the zebrafish pineal complex, which exhibits notable asymmetries, both the genes and the cell movements that result in left-right differences can be characterized. The pineal complex consists of the midline pineal organ and the left-sided parapineal organ. The parapineal is responsible for instructing the asymmetric architecture of the bilateral habenulae, the brain nuclei that flank the pineal complex. Using in vivo time-lapse confocal microscopy, we find that the cells that form the parapineal organ migrate as a cluster of cells from the pineal complex anlage to the left side of the brain. In a screen for mutations that disrupted brain laterality, we identified a nonsense mutation in the T-box2b (tbx2b) gene, which encodes a transcription factor expressed in the pineal complex anlage. The tbx2b mutant makes fewer parapineal cells, and they remain as individuals near the midline rather than migrating leftward as a group. The reduced number and incorrect placement of parapineal cells result in symmetric development of the adjacent habenular nuclei. We conclude that tbx2b functions to specify the correct number of parapineal cells and to regulate their asymmetric migration.
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Affiliation(s)
- Corey D Snelson
- Department of Biological Sciences, Vanderbilt University, VU Station B, Box 35-1634, Nashville, TN 37235, USA
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28
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Recent Papers on Zebrafish and Other Aquarium Fish Models. Zebrafish 2007. [DOI: 10.1089/zeb.2007.9983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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