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Copley RR, Buttin J, Arguel MJ, Williaume G, Lebrigand K, Barbry P, Hudson C, Yasuo H. Early transcriptional similarities between two distinct neural lineages during ascidian embryogenesis. Dev Biol 2024; 514:1-11. [PMID: 38878991 DOI: 10.1016/j.ydbio.2024.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 05/31/2024] [Accepted: 06/12/2024] [Indexed: 06/20/2024]
Abstract
In chordates, the central nervous system arises from precursors that have distinct developmental and transcriptional trajectories. Anterior nervous systems are ontogenically associated with ectodermal lineages while posterior nervous systems are associated with mesoderm. Taking advantage of the well-documented cell lineage of ascidian embryos, we asked to what extent the transcriptional states of the different neural lineages become similar during the course of progressive lineage restriction. We performed single-cell RNA sequencing (scRNA-seq) analyses on hand-dissected neural precursor cells of the two distinct lineages, together with those of their sister cell lineages, with a high temporal resolution covering five successive cell cycles from the 16-cell to neural plate stages. A transcription factor binding site enrichment analysis of neural specific genes at the neural plate stage revealed limited evidence for shared transcriptional control between the two neural lineages, consistent with their different ontogenies. Nevertheless, PCA analysis and hierarchical clustering showed that, by neural plate stages, the two neural lineages cluster together. Consistent with this, we identified a set of genes enriched in both neural lineages at the neural plate stage, including miR-124, Celf3.a, Zic.r-b, and Ets1/2. Altogether, the current study has revealed genome-wide transcriptional dynamics of neural progenitor cells of two distinct developmental origins. Our scRNA-seq dataset is unique and provides a valuable resource for future analyses, enabling a precise temporal resolution of cell types not previously described from dissociated embryos.
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Affiliation(s)
- Richard R Copley
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS UMR7009, 06230, Villefranche-sur-mer, France.
| | - Julia Buttin
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS UMR7009, 06230, Villefranche-sur-mer, France
| | - Marie-Jeanne Arguel
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur, CNRS UMR 7275, 06560, Sophia Antipolis, France
| | - Géraldine Williaume
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS UMR7009, 06230, Villefranche-sur-mer, France
| | - Kevin Lebrigand
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur, CNRS UMR 7275, 06560, Sophia Antipolis, France
| | - Pascal Barbry
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur, CNRS UMR 7275, 06560, Sophia Antipolis, France
| | - Clare Hudson
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS UMR7009, 06230, Villefranche-sur-mer, France
| | - Hitoyoshi Yasuo
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS UMR7009, 06230, Villefranche-sur-mer, France.
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2
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Frese AN, Mariossi A, Levine MS, Wühr M. Quantitative proteome dynamics across embryogenesis in a model chordate. iScience 2024; 27:109355. [PMID: 38510129 PMCID: PMC10951915 DOI: 10.1016/j.isci.2024.109355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/11/2023] [Accepted: 02/23/2024] [Indexed: 03/22/2024] Open
Abstract
The evolution of gene expression programs underlying the development of vertebrates remains poorly characterized. Here, we present a comprehensive proteome atlas of the model chordate Ciona, covering eight developmental stages and ∼7,000 translated genes, accompanied by a multi-omics analysis of co-evolution with the vertebrate Xenopus. Quantitative proteome comparisons argue against the widely held hourglass model, based solely on transcriptomic profiles, whereby peak conservation is observed during mid-developmental stages. Our analysis reveals maximal divergence at these stages, particularly gastrulation and neurulation. Together, our work provides a valuable resource for evaluating conservation and divergence of multi-omics profiles underlying the diversification of vertebrates.
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Affiliation(s)
- Alexander N. Frese
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Andrea Mariossi
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Michael S. Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Martin Wühr
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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3
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Wei J, Zhang W, Jiang A, Peng H, Zhang Q, Li Y, Bi J, Wang L, Liu P, Wang J, Ge Y, Zhang L, Yu H, Li L, Wang S, Leng L, Chen K, Dong B. Temporospatial hierarchy and allele-specific expression of zygotic genome activation revealed by distant interspecific urochordate hybrids. Nat Commun 2024; 15:2395. [PMID: 38493164 PMCID: PMC10944513 DOI: 10.1038/s41467-024-46780-0] [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: 01/27/2023] [Accepted: 03/06/2024] [Indexed: 03/18/2024] Open
Abstract
Zygotic genome activation (ZGA) is a universal process in early embryogenesis of metazoan, when the quiescent zygotic nucleus initiates global transcription. However, the mechanisms related to massive genome activation and allele-specific expression (ASE) remain not well understood. Here, we develop hybrids from two deeply diverged (120 Mya) ascidian species to symmetrically document the dynamics of ZGA. We identify two coordinated ZGA waves represent early developmental and housekeeping gene reactivation, respectively. Single-cell RNA sequencing reveals that the major expression wave exhibits spatial heterogeneity and significantly correlates with cell fate. Moreover, allele-specific expression occurs in a species- rather than parent-related manner, demonstrating the divergence of cis-regulatory elements between the two species. These findings provide insights into ZGA in chordates.
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Affiliation(s)
- Jiankai Wei
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, 266237, China
- MoE Key Laboratory of Evolution and Marine Biodiversity, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Wei Zhang
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - An Jiang
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Hongzhe Peng
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Quanyong Zhang
- State Key Laboratory of Primate Biomedical Research and Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan, 650500, China
| | - Yuting Li
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Jianqing Bi
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Linting Wang
- National Center of Mathematics and Interdisciplinary Sciences, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing, 100190, China
| | - Penghui Liu
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Jing Wang
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Yonghang Ge
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Liya Zhang
- State Key Laboratory of Primate Biomedical Research and Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan, 650500, China
| | - Haiyan Yu
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
| | - Lei Li
- National Center of Mathematics and Interdisciplinary Sciences, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing, 100190, China
| | - Shi Wang
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, 266237, China
| | - Liang Leng
- Institute of Herbgenomics, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, China.
| | - Kai Chen
- State Key Laboratory of Primate Biomedical Research and Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming, Yunnan, 650500, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), No. 1119 Haibin Rd, Nansha Dist., Guangzhou, 511458, China.
| | - Bo Dong
- Fang Zongxi Center for Marine EvoDevo, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, 266237, China.
- MoE Key Laboratory of Evolution and Marine Biodiversity, Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.
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Bump P, Lubeck L. Marine Invertebrates One Cell at A Time: Insights from Single-Cell Analysis. Integr Comp Biol 2023; 63:999-1009. [PMID: 37188638 PMCID: PMC10714908 DOI: 10.1093/icb/icad034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 04/25/2023] [Accepted: 05/05/2023] [Indexed: 05/17/2023] Open
Abstract
Over the past decade, single-cell RNA-sequencing (scRNA-seq) has made it possible to study the cellular diversity of a broad range of organisms. Technological advances in single-cell isolation and sequencing have expanded rapidly, allowing the transcriptomic profile of individual cells to be captured. As a result, there has been an explosion of cell type atlases created for many different marine invertebrate species from across the tree of life. Our focus in this review is to synthesize current literature on marine invertebrate scRNA-seq. Specifically, we provide perspectives on key insights from scRNA-seq studies, including descriptive studies of cell type composition, how cells respond in dynamic processes such as development and regeneration, and the evolution of new cell types. Despite these tremendous advances, there also lie several challenges ahead. We discuss the important considerations that are essential when making comparisons between experiments, or between datasets from different species. Finally, we address the future of single-cell analyses in marine invertebrates, including combining scRNA-seq data with other 'omics methods to get a fuller understanding of cellular complexities. The full diversity of cell types across marine invertebrates remains unknown and understanding this diversity and evolution will provide rich areas for future study.
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Affiliation(s)
- Paul Bump
- Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA
| | - Lauren Lubeck
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA
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5
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Abstract
Dimensionality reduction is standard practice for filtering noise and identifying relevant features in large-scale data analyses. In biology, single-cell genomics studies typically begin with reduction to 2 or 3 dimensions to produce "all-in-one" visuals of the data that are amenable to the human eye, and these are subsequently used for qualitative and quantitative exploratory analysis. However, there is little theoretical support for this practice, and we show that extreme dimension reduction, from hundreds or thousands of dimensions to 2, inevitably induces significant distortion of high-dimensional datasets. We therefore examine the practical implications of low-dimensional embedding of single-cell data and find that extensive distortions and inconsistent practices make such embeddings counter-productive for exploratory, biological analyses. In lieu of this, we discuss alternative approaches for conducting targeted embedding and feature exploration to enable hypothesis-driven biological discovery.
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Affiliation(s)
- Tara Chari
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - Lior Pachter
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, United States of America
- Department of Computing and Mathematical Sciences, California Institute of Technology, Pasadena, California, United States of America
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6
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Scully T, Klein A. A mannitol-based buffer improves single-cell RNA sequencing of high-salt marine cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.26.538465. [PMID: 37163054 PMCID: PMC10168337 DOI: 10.1101/2023.04.26.538465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Single-cell RNA sequencing (scRNA-seq) enables discovery of novel cell states by transcriptomic profiling with minimal prior knowledge, making it useful for studying non-model organisms. For most marine organisms, however, cells are viable at a higher salinity than is compatible with scRNA-seq, impacting data quality and cell representation. We show that a low-salinity phosphate buffer supplemented with D-mannitol (PBS-M) enables higher-quality scRNA-seq of blood cells from the tunicate Ciona robusta. Using PBS-M reduces cell death and ambient mRNA, revealing cell states not otherwise detected. This simple protocol modification could enable or improve scRNA-seq for the majority of marine organisms.
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Affiliation(s)
- Tal Scully
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Allon Klein
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
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7
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Xu Y, Zhang T, Zhou Q, Hu M, Qi Y, Xue Y, Nie Y, Wang L, Bao Z, Shi W. A single-cell transcriptome atlas profiles early organogenesis in human embryos. Nat Cell Biol 2023; 25:604-615. [PMID: 36928764 DOI: 10.1038/s41556-023-01108-w] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/16/2023] [Indexed: 03/18/2023]
Abstract
The early window of human embryogenesis is largely a black box for developmental biologists. Here we probed the cellular diversity of 4-6 week human embryos when essentially all organs are just laid out. On the basis of over 180,000 single-cell transcriptomes, we generated a comprehensive atlas of 313 clusters in 18 developmental systems, which were annotated with a collection of ontology and markers from 157 publications. Together with spatial transcriptome on embryonic sections, we characterized the molecule and spatial architecture of previously unappreciated cell types. Combined with data from other vertebrates, the rich information shed light on spatial patterning of axes, systemic temporal regulation of developmental progression and potential human-specific regulation. Our study provides a compendium of early progenitor cells of human organs, which can serve as the root of lineage analysis in organogenesis.
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Affiliation(s)
- Yichi Xu
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Tengjiao Zhang
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
- Institute for Regenerative Medicine, Shanghai East Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Qin Zhou
- Traditional Chinese Medicine Hospital of Kunshan, Suzhou, China
| | - Mengzhu Hu
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Yao Qi
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Yifang Xue
- Traditional Chinese Medicine Hospital of Kunshan, Suzhou, China
| | - Yuxiao Nie
- School of Pharmacy, Fudan University, Shanghai, China
| | - Lihui Wang
- Traditional Chinese Medicine Hospital of Kunshan, Suzhou, China
| | - Zhirong Bao
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.
| | - Weiyang Shi
- Ministry of Education Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China.
- Institute for Regenerative Medicine, Shanghai East Hospital, Tongji University, Shanghai, China.
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8
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Sun X, Zhang X, Yang L, Dong B. A microRNA Cluster-Lefty Pathway is Required for Cellulose Synthesis During Ascidian Larval Metamorphosis. Front Cell Dev Biol 2022; 10:835906. [PMID: 35372357 PMCID: PMC8965075 DOI: 10.3389/fcell.2022.835906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
Synthesis of cellulose and formation of tunic structure are unique traits in the tunicate animal group. However, the regulatory mechanism of tunic formation remains obscure. Here, we identified a novel microRNA cluster of three microRNAs, including miR4018a, miR4000f, and miR4018b in Ciona savignyi. In situ hybridization and promoter assays showed that miR4018a/4000f/4018b cluster was expressed in the mesenchymal cells in the larval trunk, and the expression levels were downregulated during the later tailbud stage and larval metamorphosis. Importantly, overexpression of miR4018a/4000f/4018b cluster in mesenchymal cells abolished the cellulose synthesis in Ciona larvae and caused the loss of tunic cells in metamorphic larvae, indicating the regulatory roles of miR4018a/4000f/4018b cluster in cellulose synthesis and mesenchymal cell differentiation into tunic cells. To elucidate the molecular mechanism, we further identified the target genes of miR4018a/4000f/4018b cluster using the combination approaches of TargetScan prediction and RNA-seq data. Left-right determination factor (Lefty) was confirmed as one of the target genes after narrow-down screening and an experimental luciferase assay. Furthermore, we showed that Lefty was expressed in the mesenchymal and tunic cells, indicating its potentially regulatory roles in mesenchymal cell differentiation and tunic formation. Notably, the defects in tunic formation and loss of tunic cells caused by overexpression of miR4018a/4000f/4018b cluster could be restored when Lefty was overexpressed in Ciona larvae, suggesting that miR4018a/4000f/4018b regulated the differentiation of mesenchymal cells into tunic cells through the Lefty signaling pathway during ascidian metamorphosis. Our findings, thus, reveal a novel microRNA-Lefty molecular pathway that regulates mesenchymal cells differentiating into tunic cells required for the tunic formation in tunicate species.
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Affiliation(s)
- Xueping Sun
- Sars Fang Centre, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Xiaoming Zhang
- Sars Fang Centre, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Likun Yang
- Sars Fang Centre, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Bo Dong
- Sars Fang Centre, MoE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China
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9
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Shimai K, Veeman M. Quantitative Dissection of the Proximal Ciona brachyury Enhancer. Front Cell Dev Biol 2022; 9:804032. [PMID: 35127721 PMCID: PMC8814421 DOI: 10.3389/fcell.2021.804032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
A major goal in biology is to understand the rules by which cis-regulatory sequences control spatially and temporally precise expression patterns. Here we present a systematic dissection of the proximal enhancer for the notochord-specific transcription factor brachyury in the ascidian chordate Ciona. The study uses a quantitative image-based reporter assay that incorporates a dual-reporter strategy to control for variable electroporation efficiency. We identified and mutated multiple predicted transcription factor binding sites of interest based on statistical matches to the JASPAR binding motif database. Most sites (Zic, Ets, FoxA, RBPJ) were selected based on prior knowledge of cell fate specification in both the primary and secondary notochord. We also mutated predicted Brachyury sites to investigate potential autoregulation as well as Fos/Jun (AP1) sites that had very strong matches to JASPAR. Our goal was to quantitatively define the relative importance of these different sites, to explore the importance of predicted high-affinity versus low-affinity motifs, and to attempt to design mutant enhancers that were specifically expressed in only the primary or secondary notochord lineages. We found that the mutation of all predicted high-affinity sites for Zic, FoxA or Ets led to quantifiably distinct effects. The FoxA construct caused a severe loss of reporter expression whereas the Ets construct had little effect. A strong Ets phenotype was only seen when much lower-scoring binding sites were also mutated. This supports the enhancer suboptimization hypothesis proposed by Farley and Levine but suggests that it may only apply to some but not all transcription factor families. We quantified reporter expression separately in the two notochord lineages with the expectation that Ets mutations and RBPJ mutations would have distinct effects given that primary notochord is induced by Ets-mediated FGF signaling whereas secondary notochord is induced by RBPJ/Su(H)-mediated Notch/Delta signaling. We found, however, that ETS mutations affected primary and secondary notochord expression relatively equally and that RBPJ mutations were only moderately more severe in their effect on secondary versus primary notochord. Our results point to the promise of quantitative reporter assays for understanding cis-regulatory logic but also highlight the challenge of arbitrary statistical thresholds for predicting potentially important sites.
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10
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Winkley KM, Reeves WM, Veeman MT. Single-cell analysis of cell fate bifurcation in the chordate Ciona. BMC Biol 2021; 19:180. [PMID: 34465302 PMCID: PMC8408944 DOI: 10.1186/s12915-021-01122-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 08/12/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Inductive signaling interactions between different cell types are a major mechanism for the further diversification of embryonic cell fates. Most blastomeres in the model chordate Ciona robusta become restricted to a single predominant fate between the 64-cell and mid-gastrula stages. The deeply stereotyped and well-characterized Ciona embryonic cell lineages allow the transcriptomic analysis of newly established cell types very early in their divergence from sibling cell states without the pseudotime inference needed in the analysis of less synchronized cell populations. This is the first ascidian study to use droplet scRNAseq with large numbers of analyzed cells as early as the 64-cell stage when major lineages such as primary notochord first become fate restricted. RESULTS AND CONCLUSIONS We identify 59 distinct cell states, including new subregions of the b-line neural lineage and the early induction of the tail tip epidermis. We find that 34 of these cell states are directly or indirectly dependent on MAPK-mediated signaling critical to early Ciona patterning. Most of the MAPK-dependent bifurcations are canalized with the signal-induced cell fate lost upon MAPK inhibition, but the posterior endoderm is unique in being transformed into a novel state expressing some but not all markers of both endoderm and muscle. Divergent gene expression between newly bifurcated sibling cell types is dominated by upregulation in the induced cell type. The Ets family transcription factor Elk1/3/4 is uniquely upregulated in nearly all the putatively direct inductions. Elk1/3/4 upregulation together with Ets transcription factor binding site enrichment analysis enables inferences about which bifurcations are directly versus indirectly controlled by MAPK signaling. We examine notochord induction in detail and find that the transition between a Zic/Ets-mediated regulatory state and a Brachyury/FoxA-mediated regulatory state is unexpectedly late. This supports a "broad-hourglass" model of cell fate specification in which many early tissue-specific genes are induced in parallel to key tissue-specific transcriptional regulators via the same set of transcriptional inputs.
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Affiliation(s)
- Konner M Winkley
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Wendy M Reeves
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Michael T Veeman
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
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11
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Fiuza UM, Lemaire P. Mechanical and genetic control of ascidian endoderm invagination during gastrulation. Semin Cell Dev Biol 2021; 120:108-118. [PMID: 34393069 DOI: 10.1016/j.semcdb.2021.08.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 07/26/2021] [Accepted: 08/02/2021] [Indexed: 10/20/2022]
Abstract
Gastrulation is a near universal developmental process of animal embryogenesis, during which dramatic morphogenetic events take place: the mesodermal and endodermal tissues are internalized, the ectoderm spreads to cover the embryo surface, and the animal body plan and germ layers are established. Morphogenesis during gastrulation has long been considered the result of spatio-temporally localised forces driven by the transcriptional programme of the embryo. Recent work has shown that tissue rheological properties, which define the mechanical response of tissues to internally-generated or external forces, are also important dynamic regulators of gastrulation. Here, we first introduce how embryonic mechanics can be represented, before outlining current knowledge of the mechanical and genetic control of gastrulation in ascidians, invertebrate marine chordates which develop with invariant cell lineages and a solid-like rheological behaviour until the neurula stages. We discuss the potential of these organisms for the experimental and computational whole-embryo characterisation of the mechanisms shaping gastrulation, and how they may inform the more complex tissue internalization strategies used by other model organisms.
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Affiliation(s)
- Ulla-Maj Fiuza
- Systems Bioengineering, DCEXS, Universidad Pompeu Fabra, Doctor Aiguader, 88, 08003 Barcelona, Spain.
| | - Patrick Lemaire
- Centre de Recherches de Biologie cellulaire de Montpellier, CRBM, Université de Montpellier, CNRS, 1919 route de Mende, Montpellier, France.
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