1
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Aldrich JC, Vanderlinden LA, Jacobsen TL, Wood C, Saba LM, Britt SG. Genome-Wide Association Study and transcriptome analysis reveals a complex gene network that regulates opsin gene expression and cell fate determination in Drosophila R7 photoreceptor cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.05.606616. [PMID: 39149333 PMCID: PMC11326169 DOI: 10.1101/2024.08.05.606616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Background An animal's ability to discriminate between differing wavelengths of light (i.e., color vision) is mediated, in part, by a subset of photoreceptor cells that express opsins with distinct absorption spectra. In Drosophila R7 photoreceptors, expression of the rhodopsin molecules, Rh3 or Rh4, is determined by a stochastic process mediated by the transcription factor spineless. The goal of this study was to identify additional factors that regulate R7 cell fate and opsin choice using a Genome Wide Association Study (GWAS) paired with transcriptome analysis via RNA-Seq. Results We examined Rh3 and Rh4 expression in a subset of fully-sequenced inbred strains from the Drosophila Genetic Reference Panel and performed a GWAS to identify 42 naturally-occurring polymorphisms-in proximity to 28 candidate genes-that significantly influence R7 opsin expression. Network analysis revealed multiple potential interactions between the associated candidate genes, spineless and its partners. GWAS candidates were further validated in a secondary RNAi screen which identified 12 lines that significantly reduce the proportion of Rh3 expressing R7 photoreceptors. Finally, using RNA-Seq, we demonstrated that all but four of the GWAS candidates are expressed in the pupal retina at a critical developmental time point and that five are among the 917 differentially expressed genes in sevenless mutants, which lack R7 cells. Conclusions Collectively, these results suggest that the relatively simple, binary cell fate decision underlying R7 opsin expression is modulated by a larger, more complex network of regulatory factors. Of particular interest are a subset of candidate genes with previously characterized neuronal functions including neurogenesis, neurodegeneration, photoreceptor development, axon growth and guidance, synaptogenesis, and synaptic function.
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Affiliation(s)
- John C. Aldrich
- Department of Neurology, Department of Ophthalmology, Dell Medical School; University of Texas at Austin, Austin, TX 78712
- Department of Psychology, University of Texas at Austin, Austin, TX 78712
| | - Lauren A. Vanderlinden
- Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Thomas L. Jacobsen
- Department of Neurology, Department of Ophthalmology, Dell Medical School; University of Texas at Austin, Austin, TX 78712
| | - Cheyret Wood
- Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Laura M. Saba
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Steven G. Britt
- Department of Neurology, Department of Ophthalmology, Dell Medical School; University of Texas at Austin, Austin, TX 78712
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2
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Sui L, Dahmann C. A cellular tilting mechanism important for dynamic tissue shape changes and cell differentiation in Drosophila. Dev Cell 2024; 59:1794-1808.e5. [PMID: 38692272 DOI: 10.1016/j.devcel.2024.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 12/15/2023] [Accepted: 04/11/2024] [Indexed: 05/03/2024]
Abstract
Dynamic changes in three-dimensional cell shape are important for tissue form and function. In the developing Drosophila eye, photoreceptor differentiation requires the progression across the tissue of an epithelial fold known as the morphogenetic furrow. Morphogenetic furrow progression involves apical cell constriction and movement of apical cell edges. Here, we show that cells progressing through the morphogenetic furrow move their basal edges in opposite direction to their apical edges, resulting in a cellular tilting movement. We further demonstrate that cells generate, at their basal side, oriented, force-generating protrusions. Knockdown of the protein kinase Src42A or photoactivation of a dominant-negative form of the small GTPase Rac1 reduces protrusion formation. Impaired protrusion formation stalls basal cell movement and slows down morphogenetic furrow progression and photoreceptor differentiation. This work identifies a cellular tilting mechanism important for the generation of dynamic tissue shape changes and cell differentiation.
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Affiliation(s)
- Liyuan Sui
- School of Science, Technische Universität Dresden, 01062 Dresden, Germany
| | - Christian Dahmann
- School of Science, Technische Universität Dresden, 01062 Dresden, Germany; Cluster of Excellence Physics of Life, Technische Universität Dresden, 01062 Dresden, Germany.
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3
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Sabin KZ, Chen S, Hill EM, Weaver KJ, Yonke J, Kirkman M, Redwine WB, Klompen AML, Zhao X, Guo F, McKinney MC, Dewey JL, Gibson MC. Graded FGF activity patterns distinct cell types within the apical sensory organ of the sea anemone Nematostella vectensis. Dev Biol 2024; 510:50-65. [PMID: 38521499 DOI: 10.1016/j.ydbio.2024.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 02/26/2024] [Accepted: 02/28/2024] [Indexed: 03/25/2024]
Abstract
Bilaterian animals have evolved complex sensory organs comprised of distinct cell types that function coordinately to sense the environment. Each sensory unit has a defined architecture built from component cell types, including sensory cells, non-sensory support cells, and dedicated sensory neurons. Whether this characteristic cellular composition is present in the sensory organs of non-bilaterian animals is unknown. Here, we interrogate the cell type composition and gene regulatory networks controlling development of the larval apical sensory organ in the sea anemone Nematostella vectensis. Using single cell RNA sequencing and imaging approaches, we reveal two unique cell types in the Nematostella apical sensory organ, GABAergic sensory cells and a putative non-sensory support cell population. Further, we identify the paired-like (PRD) homeodomain gene prd146 as a specific sensory cell marker and show that Prd146+ sensory cells become post-mitotic after gastrulation. Genetic loss of function approaches show that Prd146 is essential for apical sensory organ development. Using a candidate gene knockdown approach, we place prd146 downstream of FGF signaling in the apical sensory organ gene regulatory network. Further, we demonstrate that an aboral FGF activity gradient coordinately regulates the specification of both sensory and support cells. Collectively, these experiments define the genetic basis for apical sensory organ development in a non-bilaterian animal and reveal an unanticipated degree of complexity in a prototypic sensory structure.
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Affiliation(s)
- Keith Z Sabin
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Shiyuan Chen
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Eric M Hill
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Kyle J Weaver
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Jacob Yonke
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | | | | | | | - Xia Zhao
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Fengli Guo
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | | | | | - Matthew C Gibson
- Stowers Institute for Medical Research, Kansas City, MO, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA.
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4
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Zhang T, Zhou Q, Jusić N, Lu W, Pignoni F, Neal SJ. Mitf, with Yki and STRIPAK-PP2A, is a key determinant of form and fate in the progenitor epithelium of the Drosophila eye. Eur J Cell Biol 2024; 103:151421. [PMID: 38776620 PMCID: PMC11229422 DOI: 10.1016/j.ejcb.2024.151421] [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: 11/30/2023] [Revised: 04/30/2024] [Accepted: 05/10/2024] [Indexed: 05/25/2024] Open
Abstract
The Microphthalmia-associated Transcription Factor (MITF) governs numerous cellular and developmental processes. In mice, it promotes specification and differentiation of the retinal pigmented epithelium (RPE), and in humans, some mutations in MITF induce congenital eye malformations. Herein, we explore the function and regulation of Mitf in Drosophila eye development and uncover two roles. We find that knockdown of Mitf results in retinal displacement (RDis), a phenotype associated with abnormal eye formation. Mitf functions in the peripodial epithelium (PE), a retinal support tissue akin to the RPE, to suppress RDis, via the Hippo pathway effector Yorkie (Yki). Yki physically interacts with Mitf and can modify its transcriptional activity in vitro. Severe loss of Mitf, instead, results in the de-repression of retinogenesis in the PE, precluding its development. This activity of Mitf requires the protein phosphatase 2 A holoenzyme STRIPAK-PP2A, but not Yki; Mitf transcriptional activity is potentiated by STRIPAK-PP2A in vitro and in vivo. Knockdown of STRIPAK-PP2A results in cytoplasmic retention of Mitf in vivo and in its decreased stability in vitro, highlighting two potential mechanisms for the control of Mitf function by STRIPAK-PP2A. Thus, Mitf functions in a context-dependent manner as a key determinant of form and fate in the Drosophila eye progenitor epithelium.
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Affiliation(s)
- Tianyi Zhang
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA
| | - Qingxiang Zhou
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA
| | - Nisveta Jusić
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA
| | - Wenwen Lu
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA
| | - Francesca Pignoni
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA; Department of Ophthalmology and Visual Sciences; Department of Biochemistry and Molecular Biology; Department of Cell and Developmental Biology, USA.
| | - Scott J Neal
- Department of Neuroscience & Physiology, Upstate Medical University, 505 Irving Avenue, NRB 4601, Syracuse, NY 13210, USA.
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5
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Kittelmann M, McGregor AP. Looking across the gap: Understanding the evolution of eyes and vision among insects. Bioessays 2024; 46:e2300240. [PMID: 38593308 DOI: 10.1002/bies.202300240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 02/29/2024] [Accepted: 03/05/2024] [Indexed: 04/11/2024]
Abstract
The compound eyes of insects exhibit stunning variation in size, structure, and function, which has allowed these animals to use their vision to adapt to a huge range of different environments and lifestyles, and evolve complex behaviors. Much of our knowledge of eye development has been learned from Drosophila, while visual adaptations and behaviors are often more striking and better understood from studies of other insects. However, recent studies in Drosophila and other insects, including bees, beetles, and butterflies, have begun to address this gap by revealing the genetic and developmental bases of differences in eye morphology and key new aspects of compound eye structure and function. Furthermore, technical advances have facilitated the generation of high-resolution connectomic data from different insect species that enhances our understanding of visual information processing, and the impact of changes in these processes on the evolution of vision and behavior. Here, we review these recent breakthroughs and propose that future integrated research from the development to function of visual systems within and among insect species represents a great opportunity to understand the remarkable diversification of insect eyes and vision.
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Affiliation(s)
- Maike Kittelmann
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
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6
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Simon F, Holguera I, Chen YC, Malin J, Valentino P, Erclik T, Desplan C. High-throughput identification of the spatial origins of Drosophila optic lobe neurons using single-cell mRNA-sequencing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.05.578975. [PMID: 38370610 PMCID: PMC10871188 DOI: 10.1101/2024.02.05.578975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
The medulla is the largest neuropil of the Drosophila optic lobe. It contains about 100 neuronal types that have been comprehensively characterized morphologically and molecularly. These neuronal types are specified from a larval neuroepithelium called the Outer Proliferation Center (OPC) via the integration of temporal, spatial, and Notch-driven mechanisms. Although we recently characterized the temporal windows of origin of all medulla neurons, as well as their Notch status, their spatial origins remained unknown. Here, we isolated cells from different OPC spatial domains and performed single-cell mRNA-sequencing to identify the neuronal types produced in these domains. This allowed us to characterize in a high-throughput manner the spatial origins of all medulla neurons and to identify two new spatial subdivisions of the OPC. Moreover, our work shows that the most abundant neuronal types are produced from epithelial domains of different sizes despite being present in a similar number of copies. Combined with our previously published scRNA-seq developmental atlas of the optic lobe, our work opens the door for further studies on how specification factor expression in progenitors impacts gene expression in developing and adult neurons.
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Affiliation(s)
- Félix Simon
- Department of Biology, New York University, New York, NY 10003, USA
| | - Isabel Holguera
- Department of Biology, New York University, New York, NY 10003, USA
| | - Yen-Chung Chen
- Department of Biology, New York University, New York, NY 10003, USA
| | - Jennifer Malin
- Department of Biology, New York University, New York, NY 10003, USA
| | - Priscilla Valentino
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Ted Erclik
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA
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7
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GReNaDIne: A Data-Driven Python Library to Infer Gene Regulatory Networks from Gene Expression Data. Genes (Basel) 2023; 14:genes14020269. [PMID: 36833196 PMCID: PMC9957546 DOI: 10.3390/genes14020269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/09/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
Context: Inferring gene regulatory networks (GRN) from high-throughput gene expression data is a challenging task for which different strategies have been developed. Nevertheless, no ever-winning method exists, and each method has its advantages, intrinsic biases, and application domains. Thus, in order to analyze a dataset, users should be able to test different techniques and choose the most appropriate one. This step can be particularly difficult and time consuming, since most methods' implementations are made available independently, possibly in different programming languages. The implementation of an open-source library containing different inference methods within a common framework is expected to be a valuable toolkit for the systems biology community. Results: In this work, we introduce GReNaDIne (Gene Regulatory Network Data-driven Inference), a Python package that implements 18 machine learning data-driven gene regulatory network inference methods. It also includes eight generalist preprocessing techniques, suitable for both RNA-seq and microarray dataset analysis, as well as four normalization techniques dedicated to RNA-seq. In addition, this package implements the possibility to combine the results of different inference tools to form robust and efficient ensembles. This package has been successfully assessed under the DREAM5 challenge benchmark dataset. The open-source GReNaDIne Python package is made freely available in a dedicated GitLab repository, as well as in the official third-party software repository PyPI Python Package Index. The latest documentation on the GReNaDIne library is also available at Read the Docs, an open-source software documentation hosting platform. Contribution: The GReNaDIne tool represents a technological contribution to the field of systems biology. This package can be used to infer gene regulatory networks from high-throughput gene expression data using different algorithms within the same framework. In order to analyze their datasets, users can apply a battery of preprocessing and postprocessing tools and choose the most adapted inference method from the GReNaDIne library and even combine the output of different methods to obtain more robust results. The results format provided by GReNaDIne is compatible with well-known complementary refinement tools such as PYSCENIC.
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8
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Li VJ, Chorghay Z, Ruthazer ES. A Guide for the Multiplexed: The Development of Visual Feature Maps in the Brain. Neuroscience 2023; 508:62-75. [PMID: 35952996 DOI: 10.1016/j.neuroscience.2022.07.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 07/21/2022] [Accepted: 07/27/2022] [Indexed: 01/17/2023]
Abstract
Neural maps are found ubiquitously in the brain, where they encode a wide range of behaviourally relevant features into neural space. Developmental studies have shown that animals devote a great deal of resources to establish consistently patterned organization in neural circuits throughout the nervous system, but what purposes maps serve beneath their often intricate appearance and composition is a topic of active debate and exploration. In this article, we review the general mechanisms of map formation, with a focus on the visual system, and then survey notable organizational properties of neural maps: the multiplexing of feature representations through a nested architecture, the interspersing of fine-scale heterogeneity within a globally smooth organization, and the complex integration at the microcircuit level that enables a high dimensionality of information encoding. Finally, we discuss the roles of maps in cortical functions, including input segregation, feature extraction and routing of circuit outputs for higher order processing, as well as the evolutionary basis for the properties we observe in neural maps.
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Affiliation(s)
- Vanessa J Li
- Montreal Neurological Institute-Hospital, McGill University, 3801 University St. Montreal, Quebec H3A 2B4, Canada
| | - Zahraa Chorghay
- Montreal Neurological Institute-Hospital, McGill University, 3801 University St. Montreal, Quebec H3A 2B4, Canada
| | - Edward S Ruthazer
- Montreal Neurological Institute-Hospital, McGill University, 3801 University St. Montreal, Quebec H3A 2B4, Canada
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9
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Napoli FR, Daly CM, Neal S, McCulloch KJ, Zaloga AR, Liu A, Koenig KM. Cephalopod retinal development shows vertebrate-like mechanisms of neurogenesis. Curr Biol 2022; 32:5045-5056.e3. [PMID: 36356573 PMCID: PMC9729453 DOI: 10.1016/j.cub.2022.10.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 09/30/2022] [Accepted: 10/14/2022] [Indexed: 11/10/2022]
Abstract
Coleoid cephalopods, including squid, cuttlefish, and octopus, have large and complex nervous systems and high-acuity, camera-type eyes. These traits are comparable only to features that are independently evolved in the vertebrate lineage. The size of animal nervous systems and the diversity of their constituent cell types is a result of the tight regulation of cellular proliferation and differentiation in development. Changes in the process of development during evolution that result in a diversity of neural cell types and variable nervous system size are not well understood. Here, we have pioneered live-imaging techniques and performed functional interrogation to show that the squid Doryteuthis pealeii utilizes mechanisms during retinal neurogenesis that are hallmarks of vertebrate processes. We find that retinal progenitor cells in the squid undergo nuclear migration until they exit the cell cycle. We identify retinal organization corresponding to progenitor, post-mitotic, and differentiated cells. Finally, we find that Notch signaling may regulate both retinal cell cycle and cell fate. Given the convergent evolution of elaborate visual systems in cephalopods and vertebrates, these results reveal common mechanisms that underlie the growth of highly proliferative neurogenic primordia. This work highlights mechanisms that may alter ontogenetic allometry and contribute to the evolution of complexity and growth in animal nervous systems.
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Affiliation(s)
- Francesca R Napoli
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Christina M Daly
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Stephanie Neal
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Kyle J McCulloch
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Alexandra R Zaloga
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Alicia Liu
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA
| | - Kristen M Koenig
- John Harvard Distinguished Science Fellowship Program, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Harvard University, Cambridge, MA 02138, USA.
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10
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Rylee J, Mahato S, Aldrich J, Bergh E, Sizemore B, Feder LE, Grega S, Helms K, Maar M, Britt SG, Zelhof AC. A TRiP RNAi screen to identify molecules necessary for Drosophila photoreceptor differentiation. G3 GENES|GENOMES|GENETICS 2022; 12:6758253. [DOI: 10.1093/g3journal/jkac257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/15/2022] [Indexed: 11/06/2022]
Abstract
Abstract
Drosophila rhabdomeric terminal photoreceptor differentiation is an extended process taking several days to complete. Following ommatidial patterning by the morphogenetic furrow, photoreceptors are sequentially recruited and specified, and terminal differentiation begins. Key events of terminal differentiation include the establishment of apical and basolateral domains, rhabdomere and stalk formation, inter-rhabdomeral space formation, and expression of phototransduction machinery. While many key regulators of these processes have been identified, the complete network of transcription factors to downstream effector molecules necessary for regulating each of these major events remains incomplete. Here, we report an RNAi screen to identify additional molecules and cellular pathways required for photoreceptor terminal differentiation. First, we tested several eye-specific GAL4 drivers for correct spatial and temporal specificity and identified Pph13-GAL4 as the most appropriate GAL4 line for our screen. We screened lines available through the Transgenic RNAi Project and isolated lines that when combined with Pph13-GAL4 resulted in the loss of the deep pseudopupil, as a readout for abnormal differentiation. In the end, we screened 6,189 lines, representing 3,971 genes, and have identified 64 genes, illuminating potential new regulatory molecules and cellular pathways for the differentiation and organization of Drosophila rhabdomeric photoreceptors.
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Affiliation(s)
- Johnathan Rylee
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Simpla Mahato
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - John Aldrich
- Department of Neurology and Ophthalmology, Dell Medical School, University of Texas , Austin, TX 78712, USA
| | - Emma Bergh
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Brandon Sizemore
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Lauren E Feder
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Shaun Grega
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Kennedy Helms
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Megan Maar
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
| | - Steven G Britt
- Department of Neurology and Ophthalmology, Dell Medical School, University of Texas , Austin, TX 78712, USA
| | - Andrew C Zelhof
- Department of Biology, Indiana University , Bloomington, IN 47405, USA
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11
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Minelli A, Valero-Gracia A. Spatially and Temporally Distributed Complexity-A Refreshed Framework for the Study of GRN Evolution. Cells 2022; 11:cells11111790. [PMID: 35681485 PMCID: PMC9179533 DOI: 10.3390/cells11111790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/24/2022] [Accepted: 05/28/2022] [Indexed: 11/16/2022] Open
Abstract
Irrespective of the heuristic value of interpretations of developmental processes in terms of gene regulatory networks (GRNs), larger-angle views often suffer from: (i) an inadequate understanding of the relationship between genotype and phenotype; (ii) a predominantly zoocentric vision; and (iii) overconfidence in a putatively hierarchical organization of animal body plans. Here, we constructively criticize these assumptions. First, developmental biology is pervaded by adultocentrism, but development is not necessarily egg to adult. Second, during development, many unicells undergo transcriptomic profile transitions that are comparable to those recorded in pluricellular organisms; thus, their study should not be neglected from the GRN perspective. Third, the putatively hierarchical nature of the animal body is mirrored in the GRN logic, but in relating genotype to phenotype, independent assessments of the dynamics of the regulatory machinery and the animal’s architecture are required, better served by a combinatorial than by a hierarchical approach. The trade-offs between spatial and temporal aspects of regulation, as well as their evolutionary consequences, are also discussed. Multicellularity may derive from a unicell’s sequential phenotypes turned into different but coexisting, spatially arranged cell types. In turn, polyphenism may have been a crucial mechanism involved in the origin of complex life cycles.
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Affiliation(s)
- Alessandro Minelli
- Department of Biology, University of Padova, Via U. Bassi 58B, 35132 Padova, Italy
- Correspondence:
| | - Alberto Valero-Gracia
- Natural History Museum, University of Oslo, Blindern, P.O. Box 1172, 0318 Oslo, Norway;
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12
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Gallagher KD, Mani M, Carthew RW. Emergence of a geometric pattern of cell fates from tissue-scale mechanics in the Drosophila eye. eLife 2022; 11:72806. [PMID: 35037852 PMCID: PMC8863370 DOI: 10.7554/elife.72806] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 01/15/2022] [Indexed: 12/02/2022] Open
Abstract
Pattern formation of biological structures involves the arrangement of different types of cells in an ordered spatial configuration. In this study, we investigate the mechanism of patterning the Drosophila eye epithelium into a precise triangular grid of photoreceptor clusters called ommatidia. Previous studies had led to a long-standing biochemical model whereby a reaction-diffusion process is templated by recently formed ommatidia to propagate a molecular prepattern across the eye. Here, we find that the templating mechanism is instead, mechanochemical in origin; newly born columns of differentiating ommatidia serve as a template to spatially pattern flows that move epithelial cells into position to form each new column of ommatidia. Cell flow is generated by a source and sink, corresponding to narrow zones of cell dilation and contraction respectively, that straddle the growing wavefront of ommatidia. The newly formed lattice grid of ommatidia cells are immobile, deflecting, and focusing the flow of other cells. Thus, the self-organization of a regular pattern of cell fates in an epithelium is mechanically driven.
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Affiliation(s)
- Kevin D Gallagher
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States,NSF Simons Center for Quantitative Biology, Northwestern UniversityEvanstonUnited States
| | - Madhav Mani
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States,NSF Simons Center for Quantitative Biology, Northwestern UniversityEvanstonUnited States,Department of Engineering Sciences and Applied Mathematics, Northwestern UniversityEvanstonUnited States
| | - Richard W Carthew
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States,NSF Simons Center for Quantitative Biology, Northwestern UniversityEvanstonUnited States
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13
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Summers JA, Schaeffel F, Marcos S, Wu H, Tkatchenko AV. Functional integration of eye tissues and refractive eye development: Mechanisms and pathways. Exp Eye Res 2021; 209:108693. [PMID: 34228967 DOI: 10.1016/j.exer.2021.108693] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 06/28/2021] [Accepted: 06/30/2021] [Indexed: 12/16/2022]
Abstract
Refractive eye development is a tightly coordinated developmental process. The general layout of the eye and its various components are established during embryonic development, which involves a complex cross-tissue signaling. The eye then undergoes a refinement process during the postnatal emmetropization process, which relies heavily on the integration of environmental and genetic factors and is controlled by an elaborate genetic network. This genetic network encodes a multilayered signaling cascade, which converts visual stimuli into molecular signals that guide the postnatal growth of the eye. The signaling cascade underlying refractive eye development spans across all ocular tissues and comprises multiple signaling pathways. Notably, tissue-tissue interaction plays a key role in both embryonic eye development and postnatal eye emmetropization. Recent advances in eye biometry, physiological optics and systems genetics of refractive error have significantly advanced our understanding of the biological processes involved in refractive eye development and provided a framework for the development of new treatment options for myopia. In this review, we summarize the recent data on the mechanisms and signaling pathways underlying refractive eye development and discuss new evidence suggesting a wide-spread signal integration across different tissues and ocular components involved in visually guided eye growth.
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Affiliation(s)
- Jody A Summers
- Department of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Frank Schaeffel
- Section of Neurobiology of the Eye, Ophthalmic Research Institute, University of Tuebingen, Tuebingen, Germany; Myopia Research Group, Institute of Molecular and Clinical Ophthalmology Basel (IOB), Basel, Switzerland
| | - Susana Marcos
- Instituto de Óptica "Daza de Valdés", Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Hao Wu
- Department of Ophthalmology, Columbia University, New York, USA
| | - Andrei V Tkatchenko
- Department of Ophthalmology, Columbia University, New York, USA; Department of Pathology and Cell Biology, Columbia University, New York, USA.
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Neural specification, targeting, and circuit formation during visual system assembly. Proc Natl Acad Sci U S A 2021; 118:2101823118. [PMID: 34183440 DOI: 10.1073/pnas.2101823118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Like other sensory systems, the visual system is topographically organized: Its sensory neurons, the photoreceptors, and their targets maintain point-to-point correspondence in physical space, forming a retinotopic map. The iterative wiring of circuits in the visual system conveniently facilitates the study of its development. Over the past few decades, experiments in Drosophila have shed light on the principles that guide the specification and connectivity of visual system neurons. In this review, we describe the main findings unearthed by the study of the Drosophila visual system and compare them with similar events in mammals. We focus on how temporal and spatial patterning generates diverse cell types, how guidance molecules distribute the axons and dendrites of neurons within the correct target regions, how vertebrates and invertebrates generate their retinotopic map, and the molecules and mechanisms required for neuronal migration. We suggest that basic principles used to wire the fly visual system are broadly applicable to other systems and highlight its importance as a model to study nervous system development.
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15
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Choi BJ, Chen YCD, Desplan C. Building a circuit through correlated spontaneous neuronal activity in the developing vertebrate and invertebrate visual systems. Genes Dev 2021; 35:677-691. [PMID: 33888564 PMCID: PMC8091978 DOI: 10.1101/gad.348241.121] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
During the development of the vertebrate nervous systems, genetic programs assemble an immature circuit that is subsequently refined by neuronal activity evoked by external stimuli. However, prior to sensory experience, the intrinsic property of the developing nervous system also triggers correlated network-level neuronal activity, with retinal waves in the developing vertebrate retina being the best documented example. Spontaneous activity has also been found in the visual system of Drosophila Here, we compare the spontaneous activity of the developing visual system between mammalian and Drosophila and suggest that Drosophila is an emerging model for mechanistic and functional studies of correlated spontaneous activity.
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Affiliation(s)
- Ben Jiwon Choi
- Department of Biology, New York University, New York, New York 10003, USA
| | | | - Claude Desplan
- Department of Biology, New York University, New York, New York 10003, USA
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