1
|
Jean‐Guillaume CB, Kumar JP. Development of the ocellar visual system in Drosophila melanogaster. FEBS J 2022; 289:7411-7427. [PMID: 35490409 PMCID: PMC9805374 DOI: 10.1111/febs.16468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 03/28/2022] [Accepted: 04/29/2022] [Indexed: 01/14/2023]
Abstract
The adult visual system of the fruit fly, Drosophila melanogaster, contains seven eyes-two compound eyes, a pair of Hofbauer-Buchner eyelets, and three ocelli. Each of these eye types has a specialized and essential role to play in visual and/or circadian behavior. As such, understanding how each is specified, patterned, and wired is of primary importance to vision biologists. Since the fruit fly is amenable to manipulation by an enormous array of genetic and molecular tools, its development is one of the best and most studied model systems. After more than a century of experimental investigations, our understanding of how each eye type is specified and patterned is grossly uneven. The compound eye has been the subject of several thousand studies; thus, our knowledge of its development is the deepest. By comparison, very little is known about the specification and patterning of the other two visual systems. In this Viewpoint article, we will describe what is known about the function and development of the Drosophila ocelli.
Collapse
|
2
|
Weasner BP, Kumar JP. The early history of the eye-antennal disc of Drosophila melanogaster. Genetics 2022; 221:6573236. [PMID: 35460415 PMCID: PMC9071535 DOI: 10.1093/genetics/iyac041] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 03/04/2022] [Indexed: 12/15/2022] Open
Abstract
A pair of eye-antennal imaginal discs give rise to nearly all external structures of the adult Drosophila head including the compound eyes, ocelli, antennae, maxillary palps, head epidermis, and bristles. In the earliest days of Drosophila research, investigators would examine thousands of adult flies in search of viable mutants whose appearance deviated from the norm. The compound eyes are dispensable for viability and perturbations to their structure are easy to detect. As such, the adult compound eye and the developing eye-antennal disc emerged as focal points for studies of genetics and developmental biology. Since few tools were available at the time, early researchers put an enormous amount of thought into models that would explain their experimental observations-many of these hypotheses remain to be tested. However, these "ancient" studies have been lost to time and are no longer read or incorporated into today's literature despite the abundance of field-defining discoveries that are contained therein. In this FlyBook chapter, I will bring these forgotten classics together and draw connections between them and modern studies of tissue specification and patterning. In doing so, I hope to bring a larger appreciation of the contributions that the eye-antennal disc has made to our understanding of development as well as draw the readers' attention to the earliest studies of this important imaginal disc. Armed with the today's toolkit of sophisticated genetic and molecular methods and using the old papers as a guide, we can use the eye-antennal disc to unravel the mysteries of development.
Collapse
Affiliation(s)
- Brandon P Weasner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Justin P Kumar
- Department of Biology, Indiana University, Bloomington, IN 47405, USA,Corresponding author: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
| |
Collapse
|
3
|
Regulation of Eye Determination and Regionalization in the Spider Parasteatoda tepidariorum. Cells 2022; 11:cells11040631. [PMID: 35203282 PMCID: PMC8870698 DOI: 10.3390/cells11040631] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 11/17/2022] Open
Abstract
Animal visual systems are enormously diverse, but their development appears to be controlled by a set of conserved retinal determination genes (RDGs). Spiders are particular masters of visual system innovation, and offer an excellent opportunity to study the evolution of animal eyes. Several RDGs have been identified in spider eye primordia, but their interactions and regulation remain unclear. From our knowledge of RDG network regulation in Drosophila melanogaster, we hypothesize that orthologs of Pax6, eyegone, Wnt genes, hh, dpp, and atonal could play important roles in controlling eye development in spiders. We analyzed the expression of these genes in developing embryos of the spider Parasteatodatepidariorum, both independently and in relation to the eye primordia, marked using probes for the RDG sine oculis. Our results support conserved roles for Wnt genes in restricting the size and position of the eye field, as well as for atonal initiating photoreceptor differentiation. However, we found no strong evidence for an upstream role of Pax6 in eye development, despite its label as a master regulator of animal eye development; nor do eyg, hh or dpp compensate for the absence of Pax6. Conversely, our results indicate that hh may work with Wnt signaling to restrict eye growth, a role similar to that of Sonichedgehog (Shh) in vertebrates.
Collapse
|
4
|
Sánchez-Aragón M, Cantisán-Gómez J, Luque CM, Brás-Pereira C, Lopes CS, Lemos MC, Casares F. A Toggle-Switch and a Feed-Forward Loop Engage in the Control of the Drosophila Retinal Determination Gene Network. Front Ecol Evol 2019. [DOI: 10.3389/fevo.2019.00221] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
|
5
|
Kumar JP. The fly eye: Through the looking glass. Dev Dyn 2017; 247:111-123. [PMID: 28856763 DOI: 10.1002/dvdy.24585] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 12/20/2022] Open
Abstract
The developing eye-antennal disc of Drosophila melanogaster has been studied for more than a century, and it has been used as a model system to study diverse processes, such as tissue specification, organ growth, programmed cell death, compartment boundaries, pattern formation, cell fate specification, and planar cell polarity. The findings that have come out of these studies have informed our understanding of basic developmental processes as well as human disease. For example, the isolation of a white-eyed fly ultimately led to a greater appreciation of the role that sex chromosomes play in development, sex determination, and sex linked genetic disorders. Similarly, the discovery of the Sevenless receptor tyrosine kinase pathway not only revealed how the fate of the R7 photoreceptor is selected but it also helped our understanding of how disruptions in similar biochemical pathways result in tumorigenesis and cancer onset. In this article, I will discuss some underappreciated areas of fly eye development that are fertile for investigation and are ripe for producing exciting new breakthroughs. The topics covered here include organ shape, growth control, inductive signaling, and right-left symmetry. Developmental Dynamics 247:111-123, 2018. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Justin P Kumar
- Department of Biology, Indiana University, Bloomington, Indiana
| |
Collapse
|
6
|
Teotia P, Van Hook MJ, Wichman CS, Allingham RR, Hauser MA, Ahmad I. Modeling Glaucoma: Retinal Ganglion Cells Generated from Induced Pluripotent Stem Cells of Patients with SIX6 Risk Allele Show Developmental Abnormalities. Stem Cells 2017; 35:2239-2252. [PMID: 28792678 DOI: 10.1002/stem.2675] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/14/2017] [Accepted: 07/18/2017] [Indexed: 01/01/2023]
Abstract
Glaucoma represents a group of multifactorial diseases with a unifying pathology of progressive retinal ganglion cell (RGC) degeneration, causing irreversible vision loss. To test the hypothesis that RGCs are intrinsically vulnerable in glaucoma, we have developed an in vitro model using the SIX6 risk allele carrying glaucoma patient-specific induced pluripotent stem cells (iPSCs) for generating functional RGCs. Here, we demonstrate that the efficiency of RGC generation by SIX6 risk allele iPSCs is significantly lower than iPSCs-derived from healthy, age- and sex-matched controls. The decrease in the number of RGC generation is accompanied by repressed developmental expression of RGC regulatory genes. The SIX6 risk allele RGCs display short and simple neurites, reduced expression of guidance molecules, and immature electrophysiological signature. In addition, these cells have higher expression of glaucoma-associated genes, CDKN2A and CDKN2B, suggesting an early onset of the disease phenotype. Consistent with the developmental abnormalities, the SIX6 risk allele RGCs display global dysregulation of genes which map on developmentally relevant biological processes for RGC differentiation and signaling pathways such as mammalian target of rapamycin that integrate diverse functions for differentiation, metabolism, and survival. The results suggest that SIX6 influences different stages of RGC differentiation and their survival; therefore, alteration in SIX6 function due to the risk allele may lead to cellular and molecular abnormalities. These abnormalities, if carried into adulthood, may make RGCs vulnerable in glaucoma. Stem Cells 2017;35:2239-2252.
Collapse
Affiliation(s)
- Pooja Teotia
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Matthew J Van Hook
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Christopher S Wichman
- Department of Biostatistics, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - R Rand Allingham
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Michael A Hauser
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Iqbal Ahmad
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| |
Collapse
|
7
|
Davis TL, Rebay I. Master regulators in development: Views from the Drosophila retinal determination and mammalian pluripotency gene networks. Dev Biol 2016; 421:93-107. [PMID: 27979656 DOI: 10.1016/j.ydbio.2016.12.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 12/03/2016] [Accepted: 12/03/2016] [Indexed: 02/07/2023]
Abstract
Among the mechanisms that steer cells to their correct fate during development, master regulatory networks are unique in their sufficiency to trigger a developmental program outside of its normal context. In this review we discuss the key features that underlie master regulatory potency during normal and ectopic development, focusing on two examples, the retinal determination gene network (RDGN) that directs eye development in the fruit fly and the pluripotency gene network (PGN) that maintains cell fate competency in the early mammalian embryo. In addition to the hierarchical transcriptional activation, extensive positive transcriptional feedback, and cooperative protein-protein interactions that enable master regulators to override competing cellular programs, recent evidence suggests that network topology must also be dynamic, with extensive rewiring of the interactions and feedback loops required to navigate the correct sequence of developmental transitions to reach a final fate. By synthesizing the in vivo evidence provided by the RDGN with the extensive mechanistic insight gleaned from the PGN, we highlight the unique regulatory capabilities that continual reorganization into new hierarchies confers on master control networks. We suggest that deeper understanding of such dynamics should be a priority, as accurate spatiotemporal remodeling of network topology will undoubtedly be essential for successful stem cell based therapeutic efforts.
Collapse
Affiliation(s)
- Trevor L Davis
- Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Ilaria Rebay
- Committee on Development, Regeneration, and Stem Cell Biology, University of Chicago, Chicago, IL 60637, USA; Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA.
| |
Collapse
|
8
|
Zhou Q, DeSantis DF, Friedrich M, Pignoni F. Shared and distinct mechanisms of atonal regulation in Drosophila ocelli and compound eyes. Dev Biol 2016; 418:10-16. [PMID: 27565023 DOI: 10.1016/j.ydbio.2016.08.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 01/04/2023]
Abstract
The fruit fly Drosophila melanogaster has two types of external visual organs, a pair of compound eyes and a group of three ocelli. At the time of neurogenesis, the proneural transcription factor Atonal mediates the transition from progenitor cells to differentiating photoreceptor neurons in both organs. In the developing compound eye, atonal (ato) expression is directly induced by transcriptional regulators that confer retinal identity, the Retinal Determination (RD) factors. Little is known, however, about control of ato transcription in the ocelli. Here we show that a 2kb genomic DNA fragment contains distinct and common regulatory elements necessary for ato induction in compound eyes and ocelli. The three binding sites that mediate direct regulation by the RD factors Sine oculis and Eyeless in the compound eye are also required in the ocelli. However, in the latter, these sites mediate control by Sine oculis and the other Pax6 factor of Drosophila, Twin of eyeless, which can bind the Pax6 sites in vitro. Moreover, the three sites are differentially utilized in the ocelli: all three are similarly essential for atonal induction in the posterior ocelli, but show considerable redundancy in the anterior ocellus. Strikingly, this difference parallels the distinct control of ato transcription in the posterior and anterior progenitors of the developing compound eyes. From a comparative perspective, our findings suggest that the ocelli of arthropods may have originated through spatial partitioning from the dorsal edge of an ancestral compound eye.
Collapse
Affiliation(s)
- Qingxiang Zhou
- Department of Ophthalmology and Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Dana F DeSantis
- Department of Ophthalmology and Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Markus Friedrich
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA; Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA
| | - Francesca Pignoni
- Department of Ophthalmology and Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
| |
Collapse
|
9
|
Molecular characterization and embryonic origin of the eyes in the common house spider Parasteatoda tepidariorum. EvoDevo 2015; 6:15. [PMID: 26034574 PMCID: PMC4450840 DOI: 10.1186/s13227-015-0011-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 04/10/2015] [Indexed: 01/30/2023] Open
Abstract
Background Two visual systems are present in most arthropod groups: median and lateral eyes. Most of our current knowledge about the developmental and molecular mechanisms involved in eye formation in arthropods comes from research in the model system Drosophila melanogaster. Here, a core set of retinal determination genes, namely, sine-oculis (so), eyes absent (eya), dachshund (dac), and the two pax6 orthologues eyeless (ey) and twin of eyeless (toy) govern early retinal development. By contrast, not much is known about the development of the up-to-eight eyes present in spiders. Therefore, we analyzed the embryonic expression of core retinal determination genes in the common house spider Parasteatoda tepidariorum. Results We show that the anlagen of the median and lateral eyes in P. tepidariorum originate from different regions of the non-neurogenic ectoderm in the embryonic head. The median eyes are specified as two individual anlagen in an anterior median position in the developing head and subsequently move to their final position following extensive morphogenetic movements of the non-neurogenic ectoderm. The lateral eyes develop from a more lateral position. Intriguingly, they are specified as a unique field of cells that splits into the three individual lateral eyes during late embryonic development. Using gene expression analyses, we identified a unique combination of determination gene expression in the anlagen of the lateral and median eyes, respectively. Conclusions This study of retinal determination genes in the common house spider P. tepidariorum represents the first comprehensive analysis of the well-known retinal determination genes in arthropods outside insects. The development of the individual lateral eyes via the subdivision of one single eye primordium might be the vestige of a larger composite eye anlage, and thus supports the notion that the composite eye is the plesiomorphic state of the lateral eyes in arthropods. The molecular distinction of the two visual systems is similar to the one described for compound eyes and ocelli in Drosophila, suggesting that a unique core determination network for median and lateral eyes, respectively, might have been in place already in the last common ancestor of spiders and insects. Electronic supplementary material The online version of this article (doi:10.1186/s13227-015-0011-9) contains supplementary material, which is available to authorized users.
Collapse
|
10
|
Domínguez-Cejudo MA, Casares F. Antero-posterior patterning of Drosophila ocelli requires an anti-repressor mechanism within the hh-pathway mediated by the Six3 gene Optix. Development 2015; 142:2801-9. [DOI: 10.1242/dev.125179] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 06/29/2015] [Indexed: 12/23/2022]
Abstract
In addition to the compound eyes, most insects possess a set of three dorsal ocelli that develop at the vertices of a triangular cuticle patch, forming the ocellar complex. The wingless and hedgehog signaling pathways, together with the transcription factor encoded by orthodenticle, are known to play major roles in the specification and patterning of the ocellar complex. Specifically, hedgehog is responsible for the choice between ocellus and cuticle fates within the ocellar complex primordium. However, the interaction between signals and transcription factors known to date do not fully explain how this choice is controlled. We show that this binary choice depends on dynamic changes in the domains of hedgehog signaling. In this dynamics, the restricted expression of engrailed, a hedgehog-signaling target, is key because it defines a domain within the complex where hh transcription is maintained while the pathway activity is blocked. We show that the Drosophila Six3, Optix, is expressed in and required for the development of the anterior ocellus specifically. Optix would not act as an ocellar selector, but rather as a patterning gene, limiting the en expression domain. Our results indicate that, despite their genetic and structural similarity, anterior and posterior ocelli are under different genetic control.
Collapse
Affiliation(s)
- M. A. Domínguez-Cejudo
- CABD (Andalusian Centre for Developmental Biology), CSIC-Universidad Pablo de Olavide-Junta de Andalucía. Campus UPO, Ctra. Utrera km1, 41013, Sevilla, SPAIN
| | - F. Casares
- CABD (Andalusian Centre for Developmental Biology), CSIC-Universidad Pablo de Olavide-Junta de Andalucía. Campus UPO, Ctra. Utrera km1, 41013, Sevilla, SPAIN
| |
Collapse
|
11
|
Gold KS, Brand AH. Optix defines a neuroepithelial compartment in the optic lobe of the Drosophila brain. Neural Dev 2014; 9:18. [PMID: 25074684 PMCID: PMC4127074 DOI: 10.1186/1749-8104-9-18] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/25/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND During early brain development, the organisation of neural progenitors into a neuroepithelial sheet maintains tissue integrity during growth. Neuroepithelial cohesion and patterning is essential for orderly proliferation and neural fate specification. Neuroepithelia are regionalised by the expression of transcription factors and signalling molecules, resulting in the formation of distinct developmental, and ultimately functional, domains. RESULTS We have discovered that the Six3/6 family orthologue Optix is an essential regulator of neuroepithelial maintenance and patterning in the Drosophila brain. Six3 and Six6 are required for mammalian eye and forebrain development, and mutations in humans are associated with severe eye and brain malformation. In Drosophila, Optix is expressed in a sharply defined region of the larval optic lobe, and its expression is reciprocal to that of the transcription factor Vsx1. Optix gain- and loss-of-function affects neuroepithelial adhesion, integrity and polarity. We find restricted cell lineage boundaries that correspond to transcription factor expression domains. CONCLUSION We propose that the optic lobe is compartmentalised by expression of Optix and Vsx1. Our findings provide insight into the spatial patterning of a complex region of the brain, and suggest an evolutionarily conserved principle of visual system development.
Collapse
Affiliation(s)
| | - Andrea H Brand
- The Gurdon Institute and Department of Physiology, Development & Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
| |
Collapse
|
12
|
Drosophila eyes absent is required for normal cone and pigment cell development. PLoS One 2014; 9:e102143. [PMID: 25057928 PMCID: PMC4109927 DOI: 10.1371/journal.pone.0102143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 06/14/2014] [Indexed: 11/19/2022] Open
Abstract
In Drosophila, development of the compound eye is orchestrated by a network of highly conserved transcriptional regulators known as the retinal determination (RD) network. The retinal determination gene eyes absent (eya) is expressed in most cells within the developing eye field, from undifferentiated retinal progenitors to photoreceptor cells whose differentiation begins at the morphogenetic furrow (MF). Loss of eya expression leads to an early block in retinal development, making it impossible to study the role of eya expression during later steps of retinal differentiation. We have identified two new regulatory regions that control eya expression during retinal development. These two enhancers are necessary to maintain eya expression anterior to the MF (eya-IAM) and in photoreceptors (eya-PSE), respectively. We find that deleting these enhancers affects developmental events anterior to the MF as well as retinal differentiation posterior to the MF. In line with previous results, we find that reducing eya expression anterior to the MF affects several early steps during early retinal differentiation, including cell cycle arrest and expression of the proneural gene ato. Consistent with previous observations that suggest a role for eya in cell proliferation during early development we find that deletion of eya-IAM leads to a marked reduction in the size of the adult retinal field. On the other hand, deletion of eya-PSE leads to defects in cone and pigment cell development. In addition we find that eya expression is necessary to activate expression of the cone cell marker Cut and to regulate levels of the Hedgehog pathway effector Ci. In summary, our study uncovers novel aspects of eya-mediated regulation of eye development. The genetic tools generated in this study will allow for a detailed study of how the RD network regulates key steps in eye formation.
Collapse
|