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Faria L, Canato S, Jesus TT, Gonçalves M, Guerreiro PS, Lopes CS, Meireles I, Morais-de-Sá E, Paredes J, Janody F. Activation of an actin signaling pathway in pre-malignant mammary epithelial cells by P-cadherin is essential for transformation. Dis Model Mech 2023; 16:dmm049652. [PMID: 36808468 PMCID: PMC9983776 DOI: 10.1242/dmm.049652] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 01/19/2023] [Indexed: 02/23/2023] Open
Abstract
Alterations in the expression or function of cell adhesion molecules have been implicated in all steps of tumor progression. Among those, P-cadherin is highly enriched in basal-like breast carcinomas, playing a central role in cancer cell self-renewal, collective cell migration and invasion. To establish a clinically relevant platform for functional exploration of P-cadherin effectors in vivo, we generated a humanized P-cadherin Drosophila model. We report that actin nucleators, Mrtf and Srf, are main P-cadherin effectors in fly. We validated these findings in a human mammary epithelial cell line with conditional activation of the SRC oncogene. We show that, prior to promoting malignant phenotypes, SRC induces a transient increase in P-cadherin expression, which correlates with MRTF-A accumulation, its nuclear translocation and the upregulation of SRF target genes. Moreover, knocking down P-cadherin, or preventing F-actin polymerization, impairs SRF transcriptional activity. Furthermore, blocking MRTF-A nuclear translocation hampers proliferation, self-renewal and invasion. Thus, in addition to sustaining malignant phenotypes, P-cadherin can also play a major role in the early stages of breast carcinogenesis by promoting a transient boost of MRTF-A-SRF signaling through actin regulation.
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Affiliation(s)
- Lídia Faria
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
- Master Programme in Oncology, School of Medicine and Biomedical Sciences, University of Porto (ICBAS-UP), Rua Jorge Viterbo Ferreira 228, 4050-513 Porto, Portugal
| | - Sara Canato
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
- Physiology and Cancer Program, Champalimaud Foundation, Avenida de Brasília, 1400-038 Lisboa, Portugal
| | - Tito T. Jesus
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
| | - Margarida Gonçalves
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Patrícia S. Guerreiro
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
- Vector B2B - Drug Developing - Associação Para Investigação em Biotecnologia, Av. Prof. Egas Moniz, Edifício Egas Moniz, 1649-028 Lisboa, Portugal
| | - Carla S. Lopes
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Isabel Meireles
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
| | - Eurico Morais-de-Sá
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Joana Paredes
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
- FMUP, Medical Faculty of University of Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal
| | - Florence Janody
- i3S, Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (Ipatimup), Rua Júlio Amaral de Carvalho, n 45, 4200-135 Porto, Portugal
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, P-2780-156 Oeiras, Portugal
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2
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Worley MI, Everetts NJ, Yasutomi R, Chang RJ, Saretha S, Yosef N, Hariharan IK. Ets21C sustains a pro-regenerative transcriptional program in blastema cells of Drosophila imaginal discs. Curr Biol 2022; 32:3350-3364.e6. [PMID: 35820420 PMCID: PMC9387119 DOI: 10.1016/j.cub.2022.06.040] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 04/06/2022] [Accepted: 06/14/2022] [Indexed: 12/11/2022]
Abstract
An important unanswered question in regenerative biology is to what extent regeneration is accomplished by the reactivation of gene regulatory networks used during development versus the activation of regeneration-specific transcriptional programs. Following damage, Drosophila imaginal discs, the larval precursors of adult structures, can regenerate missing portions by localized proliferation of damage-adjacent tissue. Using single-cell transcriptomics in regenerating wing discs, we have obtained a comprehensive view of the transcriptome of regenerating discs and identified two regeneration-specific cell populations within the blastema, Blastema1 and Blastema2. Collectively, these cells upregulate multiple genes encoding secreted proteins that promote regeneration including Pvf1, upd3, asperous, Mmp1, and the maturation delaying factor Ilp8. Expression of the transcription factor Ets21C is restricted to this regenerative secretory zone; it is not expressed in undamaged discs. Ets21C expression is activated by the JNK/AP-1 pathway, and it can function in a type 1 coherent feedforward loop with AP-1 to sustain expression of downstream genes. Without Ets21C function, the blastema cells fail to maintain the expression of a number of genes, which leads to premature differentiation and severely compromised regeneration. As Ets21C is dispensable for normal development, these observations indicate that Ets21C orchestrates a regeneration-specific gene regulatory network. We have also identified cells resembling both Blastema1 and Blastema2 in scribble tumorous discs. They express the Ets21C-dependent gene regulatory network, and eliminating Ets21C function reduces tumorous growth. Thus, mechanisms that function during regeneration can be co-opted by tumors to promote aberrant growth.
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Affiliation(s)
- Melanie I Worley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
| | - Nicholas J Everetts
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; Department of Electrical Engineering and Computer Science, Center for Computational Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Riku Yasutomi
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Rebecca J Chang
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Shrey Saretha
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Nir Yosef
- Department of Electrical Engineering and Computer Science, Center for Computational Biology, University of California, Berkeley, Berkeley, CA, USA; Chan Zuckerberg Biohub, San Francisco, CA, USA.
| | - Iswar K Hariharan
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
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3
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Pérez E, Venkatanarayan A, Lundell MJ. Hunchback prevents notch-induced apoptosis in the serotonergic lineage of Drosophila Melanogaster. Dev Biol 2022; 486:109-120. [PMID: 35381219 DOI: 10.1016/j.ydbio.2022.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/16/2022] [Accepted: 03/30/2022] [Indexed: 11/19/2022]
Abstract
The serotonergic lineage (NB7-3) in the Drosophila ventral nerve cord produces six cells during neurogenesis. Four of the cells differentiate into neurons: EW1, EW2, EW3 and GW. The other two cells undergo apoptosis. This simple lineage provides an opportunity to examine genes that are required to induce or repress apoptosis during cell specification. Previous studies have shown that Notch signaling induces apoptosis within the NB7-3 lineage. The three EW neurons are protected from Notch-induced apoptosis by asymmetric distribution of Numb protein, an inhibitor of Notch signaling. In a numb1 mutant EW2 and EW3 undergo apoptosis. The EW1 and GW neurons survive even in a numb1 mutant background suggesting that these cells are protected from Notch-induced apoptosis by some factor other than Numb. The EW1 and GW neurons are mitotic sister cells, and uniquely express the transcription factor Hunchback. We present evidence that Hunchback prevents apoptosis in the NB7-3 lineage during normal CNS development and can rescue the two apoptotic cells in the lineage when it is ectopically expressed. We show that hunchback overexpression produces ectopic cells that express markers similar to the EW2 neuron and changes the expression pattern of the EW3 neuron to a EW2 neuron In addition we show that hunchback overexpression can override apoptosis that is genetically induced by the pro-apoptotic genes grim and hid.
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Affiliation(s)
- Ernesto Pérez
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | | | - Martha J Lundell
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
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4
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Everetts NJ, Worley MI, Yasutomi R, Yosef N, Hariharan IK. Single-cell transcriptomics of the Drosophila wing disc reveals instructive epithelium-to-myoblast interactions. eLife 2021; 10:61276. [PMID: 33749594 PMCID: PMC8021398 DOI: 10.7554/elife.61276] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 03/21/2021] [Indexed: 12/20/2022] Open
Abstract
In both vertebrates and invertebrates, generating a functional appendage requires interactions between ectoderm-derived epithelia and mesoderm-derived cells. To investigate such interactions, we used single-cell transcriptomics to generate a temporal cell atlas of the Drosophila wing disc from two developmental time points. Using these data, we visualized gene expression using a multilayered model of the wing disc and cataloged ligand–receptor pairs that could mediate signaling between epithelial cells and adult muscle precursors (AMPs). We found that localized expression of the fibroblast growth factor ligands, Thisbe and Pyramus, in the disc epithelium regulates the number and location of the AMPs. In addition, Hedgehog ligand from the epithelium activates a specific transcriptional program within adjacent AMP cells, defined by AMP-specific targets Neurotactin and midline, that is critical for proper formation of direct flight muscles. More generally, our annotated temporal cell atlas provides an organ-wide view of potential cell–cell interactions between epithelial and myogenic cells.
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Affiliation(s)
- Nicholas J Everetts
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Department of Electrical Engineering & Computer Science, Center for Computational Biology, UC Berkeley, University of California, Berkeley, Berkeley, United States
| | - Melanie I Worley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Riku Yasutomi
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Nir Yosef
- Department of Electrical Engineering & Computer Science, Center for Computational Biology, UC Berkeley, University of California, Berkeley, Berkeley, United States
| | - Iswar K Hariharan
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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5
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Guntur AR, Venkatanarayan A, Gangula S, Lundell MJ. Zfh-2 facilitates Notch-induced apoptosis in the CNS and appendages of Drosophila melanogaster. Dev Biol 2021; 475:65-79. [PMID: 33705738 DOI: 10.1016/j.ydbio.2021.02.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 02/22/2021] [Accepted: 02/22/2021] [Indexed: 12/26/2022]
Abstract
Apoptosis is a fundamental remodeling process for most tissues during development. In this manuscript we examine a pro-apoptotic function for the Drosophila DNA binding protein Zfh-2 during development of the central nervous system (CNS) and appendages. In the CNS we find that a loss-of-function zfh-2 allele gives an overall reduction of apoptotic cells in the CNS, and an altered pattern of expression for the axonal markers 22C10 and FasII. This same loss-of-function zfh-2 allele causes specific cells in the NB7-3 lineage of the CNS that would normally undergo apoptosis to be inappropriately maintained, whereas a gain-of-function zfh-2 allele has the opposite effect, resulting in a loss of normal NB 7-3 progeny. We also demonstrate that Zfh-2 and Hunchback reciprocally repress each other's gene expression which limits apoptosis to later born progeny of the NB7-3 lineage. Apoptosis is also required for proper segmentation of the fly appendages. We find that Zfh-2 co-localizes with apoptotic cells in the folds of the imaginal discs and presumptive cuticular joints. A reduction of Zfh-2 levels with RNAi inhibits expression of the pro-apoptotic gene reaper, and produces abnormal joints in the leg, antenna and haltere. Apoptosis has previously been shown to be activated by Notch signaling in both the NB7-3 CNS lineage and the appendage joints. Our results indicate that Zfh-2 facilitates Notch-induced apoptosis in these structures.
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Affiliation(s)
- Ananya R Guntur
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | | | - Sindhura Gangula
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | - Martha J Lundell
- Department of Biology, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
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6
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Meng JL, Marshall ZD, Lobb-Rabe M, Heckscher ES. How prolonged expression of Hunchback, a temporal transcription factor, re-wires locomotor circuits. eLife 2019; 8:46089. [PMID: 31502540 PMCID: PMC6754208 DOI: 10.7554/elife.46089] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 09/09/2019] [Indexed: 12/12/2022] Open
Abstract
How circuits assemble starting from stem cells is a fundamental question in developmental neurobiology. We test the hypothesis that, in neuronal stem cells, temporal transcription factors predictably control neuronal terminal features and circuit assembly. Using the Drosophila motor system, we manipulate expression of the classic temporal transcription factor Hunchback (Hb) specifically in the NB7-1 stem cell, which produces U motor neurons (MNs), and then we monitor dendrite morphology and neuromuscular synaptic partnerships. We find that prolonged expression of Hb leads to transient specification of U MN identity, and that embryonic molecular markers do not accurately predict U MN terminal features. Nonetheless, our data show Hb acts as a potent regulator of neuromuscular wiring decisions. These data introduce important refinements to current models, show that molecular information acts early in neurogenesis as a switch to control motor circuit wiring, and provide novel insight into the relationship between stem cell and circuit.
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Affiliation(s)
- Julia L Meng
- Department of Molecular Genetics and Cell Biology, Grossman Institute for Neuroscience, Program in Cell and Molecular Biology, University of Chicago, Chicago, United States.,Program in Cell and Molecular Biology, University of Chicago, Chicago, United States
| | - Zarion D Marshall
- Department of Molecular Genetics and Cell Biology, Grossman Institute for Neuroscience, Program in Cell and Molecular Biology, University of Chicago, Chicago, United States
| | - Meike Lobb-Rabe
- Department of Molecular Genetics and Cell Biology, Grossman Institute for Neuroscience, Program in Cell and Molecular Biology, University of Chicago, Chicago, United States.,Program in Cell and Molecular Biology, University of Chicago, Chicago, United States
| | - Ellie S Heckscher
- Department of Molecular Genetics and Cell Biology, Grossman Institute for Neuroscience, Program in Cell and Molecular Biology, University of Chicago, Chicago, United States
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7
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Spirov AV, Myasnikova EM. Evolutionary Stability of Gene Regulatory Networks That Define the Temporal Identity of Neuroblasts. Mol Biol 2019. [DOI: 10.1134/s0026893319020158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Seroka AQ, Doe CQ. The Hunchback temporal transcription factor determines motor neuron axon and dendrite targeting in Drosophila. Development 2019; 146:dev175570. [PMID: 30890568 PMCID: PMC6467472 DOI: 10.1242/dev.175570] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 03/11/2019] [Indexed: 12/14/2022]
Abstract
The generation of neuronal diversity is essential for circuit formation and behavior. Morphological differences in sequentially born neurons could be due to intrinsic molecular identity specified by temporal transcription factors (henceforth called intrinsic temporal identity) or due to changing extrinsic cues. Here, we have used the Drosophila NB7-1 lineage to address this issue. NB7-1 generates the U1-U5 motor neurons sequentially; each has a distinct intrinsic temporal identity due to inheritance of different temporal transcription factors at its time of birth. We show that the U1-U5 neurons project axons sequentially, followed by sequential dendrite extension. We misexpressed the earliest temporal transcription factor, Hunchback, to create 'ectopic' U1 neurons with an early intrinsic temporal identity but later birth-order. These ectopic U1 neurons have axon muscle targeting and dendrite neuropil targeting that are consistent with U1 intrinsic temporal identity, rather than with their time of birth or differentiation. We conclude that intrinsic temporal identity plays a major role in establishing both motor axon muscle targeting and dendritic arbor targeting, which are required for proper motor circuit development.
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Affiliation(s)
- Austin Q Seroka
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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9
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Sen SQ, Chanchani S, Southall TD, Doe CQ. Neuroblast-specific open chromatin allows the temporal transcription factor, Hunchback, to bind neuroblast-specific loci. eLife 2019; 8:44036. [PMID: 30694180 PMCID: PMC6377230 DOI: 10.7554/elife.44036] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 01/24/2019] [Indexed: 12/12/2022] Open
Abstract
Spatial and temporal cues are required to specify neuronal diversity, but how these cues are integrated in neural progenitors remains unknown. Drosophila progenitors (neuroblasts) are a good model: they are individually identifiable with relevant spatial and temporal transcription factors known. Here we test whether spatial/temporal factors act independently or sequentially in neuroblasts. We used Targeted DamID to identify genomic binding sites of the Hunchback temporal factor in two neuroblasts (NB5-6 and NB7-4) that make different progeny. Hunchback targets were different in each neuroblast, ruling out the independent specification model. Moreover, each neuroblast had distinct open chromatin domains, which correlated with differential Hb-bound loci in each neuroblast. Importantly, the Gsb/Pax3 spatial factor, expressed in NB5-6 but not NB7-4, had genomic binding sites correlated with open chromatin in NB5-6, but not NB7-4. Our data support a model in which early-acting spatial factors like Gsb establish neuroblast-specific open chromatin domains, leading to neuroblast-specific temporal factor binding and the production of different neurons in each neuroblast lineage. The human brain is considered to be the most complicated object in the universe, but it only takes a handful of stem cells to make one. The process depends on two types of information: signals separated across space and time. Spatial cues tell a stem cell what type of cell it is going to be, while temporal cues work as molecular clocks to generate a sequence of different neurons over time. Together, these cues generate the large array of cell types in the nervous system. Each stem cell occupies its own space in the developing body and receives its own spatial cues, but they all follow the same timeline. For example, proteins called transcription factors act as molecular clocks and interact with specific genes, telling the cell when to turn them on or off. The same series of transcription factors operates in different stem cells, but they have different effects. So far, it has been unclear whether spatial and temporal signals work independently or sequentially to generate new cell types. To find out, Sen et al. studied two distinct, developing stem cells in fruit flies, which receive different spatial signals. Transcription factors only work if they are able to get to their target genes. Cells can open or close access to different genes by changing the structure of the chromatin wrapping that surrounds the genes. In the experiments, a marker was used to reveal the areas of open chromatin in each of the cells. Another marker was used to track the transcription factors. The results showed that the areas of open chromatin varied between stem cells. Moreover, although both cells used the same transcription factor called Hunchback, it targeted different genes in each stem cell. This was due to changes in the chromatin wrapping: Hunchback only acted in areas where the chromatin was open. This suggests that the spatial cues first sculpt the chromatin, making some genes easier to get to than others. Then, the same transcription factors go to the accessible gene, which will differ from one stem cell to another. These findings help us to understand how different types of brain cells develop, which may also aid us in finding a way how to engineer specific cell types. If we could turn stem cells into different types of brain cells, it might help us to treat brain diseases. This may involve giving the right spatial signal before starting the temporal cues.
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Affiliation(s)
- Sonia Q Sen
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Sachin Chanchani
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Tony D Southall
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
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10
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Averbukh I, Lai SL, Doe CQ, Barkai N. A repressor-decay timer for robust temporal patterning in embryonic Drosophila neuroblast lineages. eLife 2018; 7:38631. [PMID: 30526852 PMCID: PMC6303102 DOI: 10.7554/elife.38631] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 12/10/2018] [Indexed: 11/13/2022] Open
Abstract
Biological timers synchronize patterning processes during embryonic development. In the Drosophila embryo, neural progenitors (neuroblasts; NBs) produce a sequence of unique neurons whose identities depend on the sequential expression of temporal transcription factors (TTFs). The stereotypy and precision of NB lineages indicate reproducible TTF timer progression. We combine theory and experiments to define the timer mechanism. The TTF timer is commonly described as a relay of activators, but its regulatory circuit is also consistent with a repressor-decay timer, where TTF expression begins when its repressor decays. Theory shows that repressor-decay timers are more robust to parameter variations than activator-relay timers. This motivated us to experimentally compare the relative importance of the relay and decay interactions in vivo. Comparing WT and mutant NBs at high temporal resolution, we show that the TTF sequence progresses primarily by repressor-decay. We suggest that need for robust performance shapes the evolutionary-selected designs of biological circuits.
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Affiliation(s)
- Inna Averbukh
- Department of Molecular Genetics, Weizmann institute of science, Rehovot, Israel
| | - Sen-Lin Lai
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann institute of science, Rehovot, Israel
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11
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Verghese S, Su TT. Ionizing radiation induces stem cell-like properties in a caspase-dependent manner in Drosophila. PLoS Genet 2018; 14:e1007659. [PMID: 30462636 PMCID: PMC6248896 DOI: 10.1371/journal.pgen.1007659] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/27/2018] [Indexed: 11/18/2022] Open
Abstract
Cancer treatments including ionizing radiation (IR) can induce cancer stem cell-like properties in non-stem cancer cells, an outcome that can interfere with therapeutic success. Yet, we understand little about what consequences of IR induces stem cell like properties and why some cancer cells show this response but not others. In previous studies, we identified a pool of epithelial cells in Drosophila larval wing discs that display IR-induced stem cell-like properties. These cells are resistant to killing by IR and, after radiation damage, change fate and translocate to regenerate parts of the disc that suffered more cell death. Here, we report the identification of two new pools of cells with IR-induced regenerative capability. We addressed how IR exposure results in the induction of stem cell-like behavior, and found a requirement for IR-induced caspase activity and for Zfh2, a transcription factor and an effector in the JAK/STAT pathway. Unexpectedly, the requirement for caspase activity was cell-autonomous within cell populations that display regenerative behavior. We propose a model in which the requirement for caspase activity and Zfh2 can be explained by apoptotic and non-apoptotic functions of caspases in the induction of stem cell-like behavior. Ionizing Radiation (IR), alone or in combination with other therapies, is used to treat an estimated half of all cancer patients. Yet, we understand little about why some tumors cells respond to treatment while others grow back (regenerate). We identified specific pools of cells within a Drosophila organ that are capable of regeneration after damage by IR. We also identified what it is about IR damage that allows these cells to regenerate. These results help us understand how tissues regenerate after IR damage and will aid in designing better therapies that involve radiation.
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Affiliation(s)
- Shilpi Verghese
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, United States of America
| | - Tin Tin Su
- University of Colorado Comprehensive Cancer Center, Anschutz Medical Campus, Aurora, CO, United States of America
- * E-mail:
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12
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Qu W, Gurdziel K, Pique-Regi R, Ruden DM. Lead Modulates trans- and cis-Expression Quantitative Trait Loci (eQTLs) in Drosophila melanogaster Heads. Front Genet 2018; 9:395. [PMID: 30294342 PMCID: PMC6158337 DOI: 10.3389/fgene.2018.00395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/30/2018] [Indexed: 11/13/2022] Open
Abstract
Lead exposure has long been one of the most important topics in global public health because it is a potent developmental neurotoxin. Here, an eQTL analysis, which is the genome-wide association analysis of genetic variants with gene expression, was performed. In this analysis, the male heads of 79 Drosophila melanogaster inbred lines from Drosophila Synthetic Population Resource (DSPR) were treated with or without developmental exposure, from hatching to adults, to 250 μM lead acetate [Pb(C2H3O2)2]. The goal was to identify genomic intervals that influence the gene-expression response to lead. After detecting 1798 cis-eQTLs and performing an initial trans-eQTL analysis, we focused our analysis on lead-sensitive "trans-eQTL hotspots," defined as genomic regions that are associated with a cluster of genes in a lead-dependent manner. We noticed that the genes associated with one of the 14 detected trans-eQTL hotspots, Chr 2L: 6,250,000 could be roughly divided into two groups based on their differential expression profile patterns and different categories of function. This trans-eQTL hotspot validates one identified in a previous study using different recombinant inbred lines. The expression of all the associated genes in the trans-eQTL hotspot was visualized with hierarchical clustering analysis. Besides the overall expression profile patterns, the heatmap displayed the segregation of differential parental genetic contributions. This suggested that trans-regulatory regions with different genetic contributions from the parental lines have significantly different expression changes after lead exposure. We believe this study confirms our earlier study, and provides important insights to unravel the genetic variation in lead susceptibility in Drosophila model.
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Affiliation(s)
- Wen Qu
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Katherine Gurdziel
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI, United States
| | - Roger Pique-Regi
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI, United States.,Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI, United States
| | - Douglas M Ruden
- Department of Pharmacology, Wayne State University, Detroit, MI, United States.,Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI, United States.,Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
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13
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Vincent BJ, Staller MV, Lopez-Rivera F, Bragdon MDJ, Pym ECG, Biette KM, Wunderlich Z, Harden TT, Estrada J, DePace AH. Hunchback is counter-repressed to regulate even-skipped stripe 2 expression in Drosophila embryos. PLoS Genet 2018; 14:e1007644. [PMID: 30192762 PMCID: PMC6145585 DOI: 10.1371/journal.pgen.1007644] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 09/19/2018] [Accepted: 08/17/2018] [Indexed: 01/18/2023] Open
Abstract
Hunchback is a bifunctional transcription factor that can activate and repress gene expression in Drosophila development. We investigated the regulatory DNA sequence features that control Hunchback function by perturbing enhancers for one of its target genes, even-skipped (eve). While Hunchback directly represses the eve stripe 3+7 enhancer, we found that in the eve stripe 2+7 enhancer, Hunchback repression is prevented by nearby sequences-this phenomenon is called counter-repression. We also found evidence that Caudal binding sites are responsible for counter-repression, and that this interaction may be a conserved feature of eve stripe 2 enhancers. Our results alter the textbook view of eve stripe 2 regulation wherein Hb is described as a direct activator. Instead, to generate stripe 2, Hunchback repression must be counteracted. We discuss how counter-repression may influence eve stripe 2 regulation and evolution.
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Affiliation(s)
- Ben J. Vincent
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Max V. Staller
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Francheska Lopez-Rivera
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Meghan D. J. Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Edward C. G. Pym
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kelly M. Biette
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Timothy T. Harden
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Angela H. DePace
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
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14
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STAT, Wingless, and Nurf-38 determine the accuracy of regeneration after radiation damage in Drosophila. PLoS Genet 2017; 13:e1007055. [PMID: 29028797 PMCID: PMC5656321 DOI: 10.1371/journal.pgen.1007055] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/25/2017] [Accepted: 10/04/2017] [Indexed: 01/01/2023] Open
Abstract
We report here a study of regeneration in Drosophila larval wing imaginal discs after damage by ionizing radiation. We detected faithful regeneration that restored a wing disc and abnormal regeneration that produced an extra wing disc. We describe a sequence of changes in cell number, location and fate that occur to produce an ectopic disc. We identified a group of cells that not only participate in ectopic disc formation but also recruit others to do so. STAT92E (Drosophila STAT3/5) and Nurf-38, which encodes a member of the Nucleosome Remodeling Factor complex, oppose each other in these cells to modulate the frequency of ectopic disc growth. The picture that emerges is one in which activities like STAT increase after radiation damage and fulfill essential roles in rebuilding the tissue. But such activities must be kept in check so that one and only one wing disc is regenerated. Accuracy in regeneration ensures that the original structures are restored, no more and no less. Prior studies in the wing primordia of Drosophila melanogaster larvae that have been damaged by high energy radiation show that regeneration occurs to restore the original structure. We report here that, in the same experimental system, abnormal regeneration can also occur to produce extra wing structures. We describe a series of cell rearrangements and fate changes that underlie abnormal regeneration, and identify genes responsible for these events. Modulation of such genes have the potential to mitigate abnormal regeneration that occurs after radiation damage to produce such side effects as ulcers and fibrosis.
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15
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Abstract
In this review from Georgopoulos, the role of the IKAROS gene family in lymphocyte differentiation is discussed in light of recent studies on the lineage-specific transcriptional and epigenetic networks through which IKAROS proteins operate. Lymphocyte differentiation is set to produce myriad immune effector cells with the ability to respond to multitudinous foreign substances. The uniqueness of this developmental system lies in not only the great diversity of cellular functions that it can generate but also the ability of its differentiation intermediates and mature effector cells to expand upon demand, thereby providing lifelong immunity. Surprisingly, the goals of this developmental system are met by a relatively small group of DNA-binding transcription factors that work in concert to control the timing and magnitude of gene expression and fulfill the demands for cellular specialization, expansion, and maintenance. The cellular and molecular mechanisms through which these lineage-promoting transcription factors operate have been a focus of basic research in immunology. The mechanisms of development discerned in this effort are guiding clinical research on disorders with an immune cell base. Here, I focus on IKAROS, one of the earliest regulators of lymphoid lineage identity and a guardian of lymphocyte homeostasis.
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Affiliation(s)
- Katia Georgopoulos
- Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA
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16
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Hirono K, Kohwi M, Clark MQ, Heckscher ES, Doe CQ. The Hunchback temporal transcription factor establishes, but is not required to maintain, early-born neuronal identity. Neural Dev 2017; 12:1. [PMID: 28137283 PMCID: PMC5282720 DOI: 10.1186/s13064-017-0078-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 01/26/2017] [Indexed: 01/01/2023] Open
Abstract
Background Drosophila and mammalian neural progenitors typically generate a diverse family of neurons in a stereotyped order. Neuronal diversity can be generated by the sequential expression of temporal transcription factors. In Drosophila, neural progenitors (neuroblasts) sequentially express the temporal transcription factors Hunchback (Hb), Kruppel, Pdm, and Castor. Hb is necessary and sufficient to specify early-born neuronal identity in multiple lineages, and is maintained in the post-mitotic neurons produced during each neuroblast expression window. Surprisingly, nothing is currently known about whether Hb acts in neuroblasts or post-mitotic neurons (or both) to specify first-born neuronal identity. Methods Here we selectively remove Hb from post-mitotic neurons, and assay the well-characterized NB7-1 and NB1-1 lineages for defects in neuronal identity and function. Results We find that loss of Hb from embryonic and larval post-mitotic neurons does not affect neuronal identity. Furthermore, removing Hb from post-mitotic neurons throughout the entire CNS has no effect on larval locomotor velocity, a sensitive assay for motor neuron and pre-motor neuron function. Conclusions We conclude that Hb functions in progenitors (neuroblasts/GMCs) to establish heritable neuronal identity that is maintained by a Hb-independent mechanism. We suggest that Hb acts in neuroblasts to establish an epigenetic state that is permanently maintained in early-born neurons. Electronic supplementary material The online version of this article (doi:10.1186/s13064-017-0078-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Keiko Hirono
- Howard Hughes Medical Institute, Eugene, 97403, USA.,Institute of Molecular Biology, Eugene, 97403, USA.,Institute of Neuroscience, University of Oregon, Eugene, 97403, USA
| | - Minoree Kohwi
- Department of Neuroscience, Columbia University Medical Center, New York, NY, 10032, USA
| | - Matt Q Clark
- Howard Hughes Medical Institute, Eugene, 97403, USA.,Institute of Molecular Biology, Eugene, 97403, USA.,Institute of Neuroscience, University of Oregon, Eugene, 97403, USA
| | - Ellie S Heckscher
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Chris Q Doe
- Howard Hughes Medical Institute, Eugene, 97403, USA. .,Institute of Molecular Biology, Eugene, 97403, USA. .,Institute of Neuroscience, University of Oregon, Eugene, 97403, USA.
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17
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Helenius IT, Haake RJ, Kwon YJ, Hu JA, Krupinski T, Casalino-Matsuda SM, Sporn PHS, Sznajder JI, Beitel GJ. Identification of Drosophila Zfh2 as a Mediator of Hypercapnic Immune Regulation by a Genome-Wide RNA Interference Screen. THE JOURNAL OF IMMUNOLOGY 2015; 196:655-667. [PMID: 26643480 DOI: 10.4049/jimmunol.1501708] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/02/2015] [Indexed: 12/27/2022]
Abstract
Hypercapnia, elevated partial pressure of CO2 in blood and tissue, develops in many patients with chronic severe obstructive pulmonary disease and other advanced lung disorders. Patients with advanced disease frequently develop bacterial lung infections, and hypercapnia is a risk factor for mortality in such individuals. We previously demonstrated that hypercapnia suppresses induction of NF-κB-regulated innate immune response genes required for host defense in human, mouse, and Drosophila cells, and it increases mortality from bacterial infections in both mice and Drosophila. However, the molecular mediators of hypercapnic immune suppression are undefined. In this study, we report a genome-wide RNA interference screen in Drosophila S2* cells stimulated with bacterial peptidoglycan. The screen identified 16 genes with human orthologs whose knockdown reduced hypercapnic suppression of the gene encoding the antimicrobial peptide Diptericin (Dipt), but did not increase Dipt mRNA levels in air. In vivo tests of one of the strongest screen hits, zinc finger homeodomain 2 (Zfh2; mammalian orthologs ZFHX3/ATBF1 and ZFHX4), demonstrate that reducing zfh2 function using a mutation or RNA interference improves survival of flies exposed to elevated CO2 and infected with Staphylococcus aureus. Tissue-specific knockdown of zfh2 in the fat body, the major immune and metabolic organ of the fly, mitigates hypercapnia-induced reductions in Dipt and other antimicrobial peptides and improves resistance of CO2-exposed flies to infection. Zfh2 mutations also partially rescue hypercapnia-induced delays in egg hatching, suggesting that Zfh2's role in mediating responses to hypercapnia extends beyond the immune system. Taken together, to our knowledge, these results identify Zfh2 as the first in vivo mediator of hypercapnic immune suppression.
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Affiliation(s)
- Iiro Taneli Helenius
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.,Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Ryan J Haake
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Yong-Jae Kwon
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Jennifer A Hu
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Thomas Krupinski
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - S Marina Casalino-Matsuda
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Peter H S Sporn
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.,Jesse Brown Veterans Affairs Medical Center, Chicago, IL 60612, USA
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Greg J Beitel
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
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18
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Vega‐López GA, Bonano M, Tríbulo C, Fernández JP, Agüero TH, Aybar MJ. Functional analysis of
Hairy
genes in
Xenopus
neural crest initial specification and cell migration. Dev Dyn 2015; 244:988-1013. [DOI: 10.1002/dvdy.24295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 04/25/2015] [Accepted: 05/14/2015] [Indexed: 01/28/2023] Open
Affiliation(s)
| | - Marcela Bonano
- Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET‐UNT
| | - Celeste Tríbulo
- Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET‐UNT
- Instituto de Biología “Dr. Francisco D. Barbieri”, Facultad de Bioquímica, Química y FarmaciaUniversidad Nacional de TucumánChacabuco San Miguel de Tucumán Argentina
| | - Juan P. Fernández
- Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET‐UNT
| | - Tristán H. Agüero
- Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET‐UNT
| | - Manuel J. Aybar
- Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET‐UNT
- Instituto de Biología “Dr. Francisco D. Barbieri”, Facultad de Bioquímica, Química y FarmaciaUniversidad Nacional de TucumánChacabuco San Miguel de Tucumán Argentina
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19
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A conserved regulatory logic controls temporal identity in mouse neural progenitors. Neuron 2015; 85:497-504. [PMID: 25654255 DOI: 10.1016/j.neuron.2014.12.052] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 12/12/2014] [Accepted: 12/17/2014] [Indexed: 11/23/2022]
Abstract
Neural progenitors alter their output over time to generate different types of neurons and glia in specific chronological sequences, but this process remains poorly understood in vertebrates. Here we show that Casz1, the vertebrate ortholog of the Drosophila temporal identity factor castor, controls the production of mid-/late-born neurons in the murine retina. Casz1 is expressed from mid/late stages in retinal progenitor cells (RPCs), and conditional deletion of Casz1 increases production of early-born retinal neurons at the expense of later-born fates, whereas precocious misexpression of Casz1 has the opposite effect. In both cases, cell proliferation is unaffected, indicating that Casz1 does not control the timing of cell birth but instead biases RPC output directly. Just as Drosophila castor lies downstream of the early temporal identity factor hunchback, we find that the hunchback ortholog Ikzf1 represses Casz1. These results uncover a conserved strategy regulating temporal identity transitions from flies to mammals.
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20
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Konstantinides N, Rossi AM, Desplan C. Common temporal identity factors regulate neuronal diversity in fly ventral nerve cord and mouse retina. Neuron 2015; 85:447-9. [PMID: 25654249 DOI: 10.1016/j.neuron.2015.01.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Temporal sequences of transcription factors (tTFs) in Drosophila neural progenitors generate neuronal diversity. Mattar et al. (2015) identify Casz1/Castor as a late temporal identity factor in mouse retinal progenitors that is regulated by the early factor Ikzf1/Hunchback, thus generalizing the notion of tTFs.
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Affiliation(s)
- Nikolaos Konstantinides
- Department of Biology, New York University, 1009 Silver Center, 100 Washington Square East, New York, NY 10003, USA
| | - Anthony M Rossi
- Department of Biology, New York University, 1009 Silver Center, 100 Washington Square East, New York, NY 10003, USA
| | - Claude Desplan
- Department of Biology, New York University, 1009 Silver Center, 100 Washington Square East, New York, NY 10003, USA.
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21
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Moris-Sanz M, Estacio-Gómez A, Álvarez-Rivero J, Díaz-Benjumea FJ. Specification of neuronal subtypes by different levels of Hunchback. Development 2014; 141:4366-74. [DOI: 10.1242/dev.113381] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
During the development of the central nervous system, neural progenitors generate an enormous number of distinct types of neuron and glial cells by asymmetric division. Intrinsic genetic programs define the combinations of transcription factors that determine the fate of each cell, but the precise mechanisms by which all these factors are integrated at the level of individual cells are poorly understood. Here, we analyzed the specification of the neurons in the ventral nerve cord of Drosophila that express Crustacean cardioactive peptide (CCAP). There are two types of CCAP neurons: interneurons and efferent neurons. We found that both are specified during the Hunchback temporal window of neuroblast 3-5, but are not sibling cells. Further, this temporal window generates two ganglion mother cells that give rise to four neurons, which can be identified by the expression of empty spiracles. We show that the expression of Hunchback in the neuroblast increases over time and provide evidence that the absolute levels of Hunchback expression specify the two different CCAP neuronal fates.
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Affiliation(s)
- Marta Moris-Sanz
- Centro de Biología Molecular-Severo Ochoa (CSIC-UAM), c./Nicolás Cabrera 1, Universidad Autónoma, Madrid 28049, Spain
| | - Alicia Estacio-Gómez
- Centro de Biología Molecular-Severo Ochoa (CSIC-UAM), c./Nicolás Cabrera 1, Universidad Autónoma, Madrid 28049, Spain
| | - Javier Álvarez-Rivero
- Centro de Biología Molecular-Severo Ochoa (CSIC-UAM), c./Nicolás Cabrera 1, Universidad Autónoma, Madrid 28049, Spain
| | - Fernando J. Díaz-Benjumea
- Centro de Biología Molecular-Severo Ochoa (CSIC-UAM), c./Nicolás Cabrera 1, Universidad Autónoma, Madrid 28049, Spain
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22
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Cell-specific fine-tuning of neuronal excitability by differential expression of modulator protein isoforms. J Neurosci 2013; 33:16767-77. [PMID: 24133277 DOI: 10.1523/jneurosci.1001-13.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
SLOB (SLOWPOKE-binding protein) modulates the Drosophila SLOWPOKE calcium-activated potassium channel. We have shown previously that SLOB deletion or RNAi knockdown decreases excitability of neurosecretory pars intercerebralis (PI) neurons in the adult Drosophila brain. In contrast, we found that SLOB deletion/knockdown enhances neurotransmitter release from motor neurons at the fly larval neuromuscular junction, suggesting an increase in excitability. Because two prominent SLOB isoforms, SLOB57 and SLOB71, modulate SLOWPOKE channels in opposite directions in vitro, we investigated whether divergent expression patterns of these two isoforms might underlie the differential modulation of excitability in PI and motor neurons. By performing detailed in vitro and in vivo analysis, we found strikingly different modes of regulatory control by the slob57 and slob71 promoters. The slob71, but not slob57, promoter contains binding sites for the Hunchback and Mirror transcriptional repressors. Furthermore, several core promoter elements that are absent in the slob57 promoter coordinately drive robust expression of a luciferase vector by the slob71 promoter in vitro. In addition, we visualized the expression patterns of the slob57 and slob71 promoters in vivo and found clear spatiotemporal differences in promoter activity. SLOB57 is expressed prominently in adult PI neurons, whereas larval motor neurons exclusively express SLOB71. In contrast, at the larval neuromuscular junction, SLOB57 expression appears to be restricted mainly to a subset of glial cells. Our results illustrate how the use of alternative transcriptional start sites within an ion channel modulator locus coupled with functionally relevant alternative splicing can be used to fine-tune neuronal excitability in a cell-specific manner.
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23
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Setting appropriate boundaries: fate, patterning and competence at the neural plate border. Dev Biol 2013; 389:2-12. [PMID: 24321819 DOI: 10.1016/j.ydbio.2013.11.027] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 11/26/2013] [Accepted: 11/27/2013] [Indexed: 11/20/2022]
Abstract
The neural crest and craniofacial placodes are two distinct progenitor populations that arise at the border of the vertebrate neural plate. This border region develops through a series of inductive interactions that begins before gastrulation and progressively divide embryonic ectoderm into neural and non-neural regions, followed by the emergence of neural crest and placodal progenitors. In this review, we describe how a limited repertoire of inductive signals-principally FGFs, Wnts and BMPs-set up domains of transcription factors in the border region which establish these progenitor territories by both cross-inhibitory and cross-autoregulatory interactions. The gradual assembly of different cohorts of transcription factors that results from these interactions is one mechanism to provide the competence to respond to inductive signals in different ways, ultimately generating the neural crest and cranial placodes.
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24
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The zinc finger homeodomain-2 gene of Drosophila controls Notch targets and regulates apoptosis in the tarsal segments. Dev Biol 2013; 385:350-65. [PMID: 24144920 DOI: 10.1016/j.ydbio.2013.10.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 10/06/2013] [Accepted: 10/12/2013] [Indexed: 12/19/2022]
Abstract
The development of the Drosophila leg is a good model to study processes of pattern formation, cell death and segmentation. Such processes require the coordinate activity of different genes and signaling pathways that progressively subdivide the leg territory into smaller domains. One of the main pathways needed for leg development is the Notch pathway, required for determining the proximo-distal axis of the leg and for the formation of the joints that separate different leg segments. The mechanisms required to coordinate such events are largely unknown. We describe here that the zinc finger homeodomain-2 (zfh-2) gene is highly expressed in cells that will form the leg joints and needed to establish a correct size and pattern in the distal leg. There is an early requirement of zfh-2 to establish the correct proximo-distal axis, but zfh-2 is also needed at late third instar to form the joint between the fourth and fifth tarsal segments. The expression of zfh-2 requires Notch activity but zfh-2 is necessary, in turn, to activate Notch targets such as Enhancer of split and big brain. zfh-2 is controlled by the Drosophila activator protein 2 gene and regulates the late expression of tarsal-less. In the absence of zfh-2 many cells ectopically express the pro-apoptotic gene head involution defective, activate caspase-3 and are positive for acridine orange, indicating they undergo apoptosis. Our results demonstrate the key role of zfh-2 in the control of cell death and Notch signaling during leg development.
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25
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Tran KD, Rodriguez-Contreras D, Vieira DP, Yates PA, David L, Beatty W, Elferich J, Landfear SM. KHARON1 mediates flagellar targeting of a glucose transporter in Leishmania mexicana and is critical for viability of infectious intracellular amastigotes. J Biol Chem 2013; 288:22721-33. [PMID: 23766511 PMCID: PMC3829357 DOI: 10.1074/jbc.m113.483461] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 06/12/2012] [Indexed: 01/05/2023] Open
Abstract
The LmxGT1 glucose transporter is selectively targeted to the flagellum of the kinetoplastid parasite Leishmania mexicana, but the mechanism for targeting this and other flagella-specific membrane proteins among the Kinetoplastida is unknown. To address the mechanism of flagellar targeting, we employed in vivo cross-linking, tandem affinity purification, and mass spectrometry to identify a novel protein, KHARON1 (KH1), which is important for the flagellar trafficking of LmxGT1. Kh1 null mutant parasites are strongly impaired in flagellar targeting of LmxGT1, and trafficking of the permease was arrested in the flagellar pocket. Immunolocalization revealed that KH1 is located at the base of the flagellum, within the flagellar pocket, where it associates with the proximal segment of the flagellar axoneme. We propose that KH1 mediates transit of LmxGT1 from the flagellar pocket into the flagellar membrane via interaction with the proximal portion of the flagellar axoneme. KH1 represents the first component involved in flagellar trafficking of integral membrane proteins among parasitic protozoa. Of considerable interest, Kh1 null mutants are strongly compromised for growth as amastigotes within host macrophages. Thus, KH1 is also important for the disease causing stage of the parasite life cycle.
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Affiliation(s)
- Khoa D. Tran
- From the Departments of Molecular Microbiology and Immunology
| | | | | | | | - Larry David
- Proteomics Shared Resource, Oregon Health & Science University, Portland, Oregon 97239 and
| | - Wandy Beatty
- the Molecular Microbiology Imaging Facility, Washington University School of Medicine, St. Louis, Missouri 63110
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26
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Abstract
Drosophila has recently become a powerful model system to understand the mechanisms of temporal patterning of neural progenitors called neuroblasts (NBs). Two different temporal sequences of transcription factors (TFs) have been found to be sequentially expressed in NBs of two different systems: the Hunchback, Krüppel, Pdm1/Pdm2, Castor, and Grainyhead sequence in the Drosophila ventral nerve cord; and the Homothorax, Klumpfuss, Eyeless, Sloppy-paired, Dichaete, and Tailless sequence that patterns medulla NBs. In addition, the intermediate neural progenitors of type II NB lineages are patterned by a different sequence: Dichaete, Grainyhead, and Eyeless. These three examples suggest that temporal patterning of neural precursors by sequences of TFs is a common theme to generate neural diversity. Cross-regulations, including negative feedback regulation and positive feedforward regulation among the temporal factors, can facilitate the progression of the sequence. However, there are many remaining questions to understand the mechanism of temporal transitions. The temporal sequence progression is intimately linked to the progressive restriction of NB competence, and eventually determines the end of neurogenesis. Temporal identity has to be integrated with spatial identity information, as well as with the Notch-dependent binary fate choices, in order to generate specific neuron fates.
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Affiliation(s)
- Xin Li
- Department of Biology, New York University, New York, New York, USA
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27
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Manning L, Heckscher ES, Purice MD, Roberts J, Bennett AL, Kroll JR, Pollard JL, Strader ME, Lupton JR, Dyukareva AV, Doan PN, Bauer DM, Wilbur AN, Tanner S, Kelly JJ, Lai SL, Tran KD, Kohwi M, Laverty TR, Pearson JC, Crews ST, Rubin GM, Doe CQ. A resource for manipulating gene expression and analyzing cis-regulatory modules in the Drosophila CNS. Cell Rep 2012; 2:1002-13. [PMID: 23063363 PMCID: PMC3523218 DOI: 10.1016/j.celrep.2012.09.009] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 09/11/2012] [Accepted: 09/17/2012] [Indexed: 01/03/2023] Open
Abstract
Here, we describe the embryonic central nervous system expression of 5,000 GAL4 lines made using molecularly defined cis-regulatory DNA inserted into a single attP genomic location. We document and annotate the patterns in early embryos when neurogenesis is at its peak, and in older embryos where there is maximal neuronal diversity and the first neural circuits are established. We note expression in other tissues, such as the lateral body wall (muscle, sensory neurons, and trachea) and viscera. Companion papers report on the adult brain and larval imaginal discs, and the integrated data sets are available online (http://www.janelia.org/gal4-gen1). This collection of embryonically expressed GAL4 lines will be valuable for determining neuronal morphology and function. The 1,862 lines expressed in small subsets of neurons (<20/segment) will be especially valuable for characterizing interneuronal diversity and function, because although interneurons comprise the majority of all central nervous system neurons, their gene expression profile and function remain virtually unexplored.
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Affiliation(s)
- Laurina Manning
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Ellie S. Heckscher
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Maria D. Purice
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Jourdain Roberts
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Alysha L. Bennett
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Jason R. Kroll
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Jill L. Pollard
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Marie E. Strader
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Josh R. Lupton
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Anna V. Dyukareva
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Phuong Nam Doan
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - David M. Bauer
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Allison N. Wilbur
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Stephanie Tanner
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Jimmy J. Kelly
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Sen-Lin Lai
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Khoa D. Tran
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Minoree Kohwi
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Todd R. Laverty
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn VA 20147
| | - Joseph C. Pearson
- Program in Molecular Biology and Biophysics, Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Stephen T. Crews
- Program in Molecular Biology and Biophysics, Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Gerald M. Rubin
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn VA 20147
| | - Chris Q. Doe
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
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Yáñez-Cuna JO, Dinh HQ, Kvon EZ, Shlyueva D, Stark A. Uncovering cis-regulatory sequence requirements for context-specific transcription factor binding. Genome Res 2012; 22:2018-30. [PMID: 22534400 PMCID: PMC3460196 DOI: 10.1101/gr.132811.111] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The regulation of gene expression is mediated at the transcriptional level by enhancer regions that are bound by sequence-specific transcription factors (TFs). Recent studies have shown that the in vivo binding sites of single TFs differ between developmental or cellular contexts. How this context-specific binding is encoded in the cis-regulatory DNA sequence has, however, remained unclear. We computationally dissect context-specific TF binding sites in Drosophila, Caenorhabditis elegans, mouse, and human and find distinct combinations of sequence motifs for partner factors, which are predictive and reveal specific motif requirements of individual binding sites. We predict that TF binding in the early Drosophila embryo depends on motifs for the early zygotic TFs Vielfaltig (also known as Zelda) and Tramtrack. We validate experimentally that the activity of Twist-bound enhancers and Twist binding itself depend on Vielfaltig motifs, suggesting that Vielfaltig is more generally important for early transcription. Our finding that the motif content can predict context-specific binding and that the predictions work across different Drosophila species suggests that characteristic motif combinations are shared between sites, revealing context-specific motif codes (cis-regulatory signatures), which appear to be conserved during evolution. Taken together, this study establishes a novel approach to derive predictive cis-regulatory motif requirements for individual TF binding sites and enhancers. Importantly, the method is generally applicable across different cell types and organisms to elucidate cis-regulatory sequence determinants and the corresponding trans-acting factors from the increasing number of tissue- and cell-type-specific TF binding studies.
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Touma JJ, Weckerle FF, Cleary MD. Drosophila Polycomb complexes restrict neuroblast competence to generate motoneurons. Development 2012; 139:657-66. [DOI: 10.1242/dev.071589] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Similar to mammalian neural progenitors, Drosophila neuroblasts progressively lose competence to make early-born neurons. In neuroblast 7-1 (NB7-1), Kruppel (Kr) specifies the third-born U3 motoneuron and Kr misexpression induces ectopic U3 cells. However, competence to generate U3 cells is limited to early divisions, when the Eve+ U motoneurons are produced, and competence is lost when NB7-1 transitions to making interneurons. We have found that Polycomb repressor complexes (PRCs) are necessary and sufficient to restrict competence in NB7-1. PRC loss of function extends the ability of Kr to induce U3 fates and PRC gain of function causes precocious loss of competence to make motoneurons. PRCs also restrict competence to make HB9+ Islet+ motoneurons in another neuroblast that undergoes a motoneuron-to-interneuron transition, NB3-1. In contrast to the regulation of motoneuron competence, PRC activity does not affect the production of Eve+ interneurons by NB3-3, HB9+ Islet+ interneurons by NB7-3, or Dbx+ interneurons by multiple neuroblasts. These findings support a model in which PRCs establish motoneuron-specific competence windows in neuroblasts that transition from motoneuron to interneuron production.
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Affiliation(s)
- Johnny J. Touma
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
| | - Frank F. Weckerle
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
| | - Michael D. Cleary
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
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31
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Whole-embryo modeling of early segmentation in Drosophila identifies robust and fragile expression domains. Biophys J 2011; 101:287-96. [PMID: 21767480 DOI: 10.1016/j.bpj.2011.05.060] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 05/03/2011] [Accepted: 05/19/2011] [Indexed: 11/24/2022] Open
Abstract
Segmentation of the Drosophila melanogaster embryo results from the dynamic establishment of spatial mRNA and protein patterns. Here, we exploit recent temporal mRNA and protein expression measurements on the full surface of the blastoderm to calibrate a dynamical model of the gap gene network on the entire embryo cortex. We model the early mRNA and protein dynamics of the gap genes hunchback, Kruppel, giant, and knirps, taking as regulatory inputs the maternal Bicoid and Caudal gradients, plus the zygotic Tailless and Huckebein proteins. The model captures the expression patterns faithfully, and its predictions are assessed from gap gene mutants. The inferred network shows an architecture based on reciprocal repression between gap genes that can stably pattern the embryo on a realistic geometry but requires complex regulations such as those involving the Hunchback monomer and dimers. Sensitivity analysis identifies the posterior domain of giant as among the most fragile features of an otherwise robust network, and hints at redundant regulations by Bicoid and Hunchback, possibly reflecting recent evolutionary changes in the gap-gene network in insects.
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Hirono K, Margolis JS, Posakony JW, Doe CQ. Identification of hunchback cis-regulatory DNA conferring temporal expression in neuroblasts and neurons. Gene Expr Patterns 2011; 12:11-7. [PMID: 22033538 DOI: 10.1016/j.gep.2011.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 10/03/2011] [Accepted: 10/05/2011] [Indexed: 02/04/2023]
Abstract
The specification of temporal identity within single progenitor lineages is essential to generate functional neuronal diversity in Drosophila and mammals. In Drosophila, four transcription factors are sequentially expressed in neural progenitors (neuroblasts) and each regulates the temporal identity of the progeny produced during its expression window. The first temporal identity is established by the Ikaros-family zinc finger transcription factor Hunchback (Hb). Hb is detected in young (newly-formed) neuroblasts for about an hour and is maintained in the early-born neurons produced during this interval. Hb is necessary and sufficient to specify early-born neuronal or glial identity in multiple neuroblast lineages. The timing of hb expression in neuroblasts is regulated at the transcriptional level. Here we identify cis-regulatory elements that confer proper hb expression in "young" neuroblasts and early-born neurons. We show that the neuroblast element contains clusters of predicted binding sites for the Seven-up transcription factor, which is known to limit hb neuroblast expression. We identify highly conserved sequences in the neuronal element that are good candidates for maintaining Hb transcription in neurons. Our results provide the necessary foundation for identifying trans-acting factors that establish the Hb early temporal expression domain.
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Affiliation(s)
- Keiko Hirono
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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Abstract
Neural circuit mapping and manipulation are facilitated by independent control of gene expression in pre- and post-synaptic neurons. The GAL4/UAS and Q binary transcription systems have the potential to provide this capability. Of particular use in neural circuit mapping would be GAL4 and QF drivers specific for neurotransmitters and neurotransmitter receptors. Recently available Drosophila genomic BAC libraries make recombineering large genes including those specific for neurotransmitters and neurotransmitter receptors feasible. Here the functionality of cassettes that allow efficient recombineering of GAL4 and QF drivers based on kanamycin selection is demonstrated in Drosophila. The cassettes should, however, be generalizable for recombineering in other species.
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Affiliation(s)
- R Steven Stowers
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, USA.
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Sexually dimorphic shaping of interneuron dendrites involves the hunchback transcription factor. J Neurosci 2011; 31:5454-9. [PMID: 21471381 DOI: 10.1523/jneurosci.4861-10.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Sexual dimorphism of the brain has been well characterized anatomically in Drosophila melanogaster at the single neuron level, yet little is known about the molecular mechanism whereby cellular sex differences are generated except that the neural sex determination gene fruitless (fru) plays a key role. The fru-expressing mAL interneuron cluster is sexually dimorphic in three aspects: the number of cells composing the cluster is 5 in females and 30 in males; the ipsilateral neurite is absent in females and present in males; the contralateral neurite forms Y-shaped branches in the subesophageal ganglion in females while it ends with a simple horsetail-like structure in males. By screens in the compound eye for modifiers of roughness induced by fru(+) overexpression, we identified a loss-of-function allele of hunchback (hb) to be a suppressor of this phenotype. Hb was expressed in most of the fru-expressing neurons in the pupal and adult stages. Knocking down hb in mAL MARCM (Mosaic Analysis with a Repressible Cell Marker) clones in the male brain resulted in partial demasculinization of the branching pattern of the contralateral neurites without affecting the cell number and the ipsilateral neurite formation. The present results suggest that Hb is essential for male-typical shaping of the contralateral neurites by Fru.
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Kohwi M, Hiebert LS, Doe CQ. The pipsqueak-domain proteins Distal antenna and Distal antenna-related restrict Hunchback neuroblast expression and early-born neuronal identity. Development 2011; 138:1727-35. [PMID: 21429984 DOI: 10.1242/dev.061499] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A fundamental question in brain development is how precursor cells generate a diverse group of neural progeny in an ordered manner. Drosophila neuroblasts sequentially express the transcription factors Hunchback (Hb), Krüppel (Kr), Pdm1/Pdm2 (Pdm) and Castor (Cas). Hb is necessary and sufficient to specify early-born temporal identity and, thus, Hb downregulation is essential for specification of later-born progeny. Here, we show that distal antenna (dan) and distal antenna-related (danr), encoding pipsqueak motif DNA-binding domain protein family members, are detected in all neuroblasts during the Hb-to-Cas expression window. Dan and Danr are required for timely downregulation of Hb in neuroblasts and for limiting the number of early-born neurons. Dan and Danr function independently of Seven-up (Svp), an orphan nuclear receptor known to repress Hb expression in neuroblasts, because Dan, Danr and Svp do not regulate each other and dan danr svp triple mutants have increased early-born neurons compared with either dan danr or svp mutants. Interestingly, misexpression of Hb can induce Dan and Svp expression in neuroblasts, suggesting that Hb might activate a negative feedback loop to limit its own expression. We conclude that Dan/Danr and Svp act in parallel pathways to limit Hb expression and allow neuroblasts to transition from making early-born neurons to late-born neurons at the proper time.
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Affiliation(s)
- Minoree Kohwi
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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