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Neal SJ, Rajasekaran A, Jusić N, Taylor L, Read M, Alfandari D, Pignoni F, Moody SA. Using Xenopus to discover new candidate genes involved in BOR and other congenital hearing loss syndromes. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2024; 342:212-240. [PMID: 37830236 PMCID: PMC11014897 DOI: 10.1002/jez.b.23222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/15/2023] [Accepted: 09/14/2023] [Indexed: 10/14/2023]
Abstract
Hearing in infants is essential for brain development, acquisition of verbal language skills, and development of social interactions. Therefore, it is important to diagnose hearing loss soon after birth so that interventions can be provided as early as possible. Most newborns in the United States are screened for hearing deficits and commercially available next-generation sequencing hearing loss panels often can identify the causative gene, which may also identify congenital defects in other organs. One of the most prevalent autosomal dominant congenital hearing loss syndromes is branchio-oto-renal syndrome (BOR), which also presents with defects in craniofacial structures and the kidney. Currently, mutations in three genes, SIX1, SIX5, and EYA1, are known to be causative in about half of the BOR patients that have been tested. To uncover new candidate genes that could be added to congenital hearing loss genetic screens, we have combined the power of Drosophila mutants and protein biochemical assays with the embryological advantages of Xenopus, a key aquatic animal model with a high level of genomic similarity to human, to identify potential Six1 transcriptional targets and interacting proteins that play a role during otic development. We review our transcriptomic, yeast 2-hybrid, and proteomic approaches that have revealed a large number of new candidates. We also discuss how we have begun to identify how Six1 and co-factors interact to direct developmental events necessary for normal otic development.
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Affiliation(s)
- Scott J. Neal
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Anindita Rajasekaran
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Nisveta Jusić
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Louis Taylor
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Mai Read
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Francesca Pignoni
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Sally A. Moody
- Department of Anatomy and Cell Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
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2
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Drewell RA, Klonaros D, Dresch JM. Transcription factor expression landscape in Drosophila embryonic cell lines. BMC Genomics 2024; 25:307. [PMID: 38521929 PMCID: PMC10960990 DOI: 10.1186/s12864-024-10241-1] [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: 01/26/2024] [Accepted: 03/19/2024] [Indexed: 03/25/2024] Open
Abstract
BACKGROUND Transcription factor (TF) proteins are a key component of the gene regulatory networks that control cellular fates and function. TFs bind DNA regulatory elements in a sequence-specific manner and modulate target gene expression through combinatorial interactions with each other, cofactors, and chromatin-modifying proteins. Large-scale studies over the last two decades have helped shed light on the complex network of TFs that regulate development in Drosophila melanogaster. RESULTS Here, we present a detailed characterization of expression of all known and predicted Drosophila TFs in two well-established embryonic cell lines, Kc167 and S2 cells. Using deep coverage RNA sequencing approaches we investigate the transcriptional profile of all 707 TF coding genes in both cell types. Only 103 TFs have no detectable expression in either cell line and 493 TFs have a read count of 5 or greater in at least one of the cell lines. The 493 TFs belong to 54 different DNA-binding domain families, with significant enrichment of those in the zf-C2H2 family. We identified 123 differentially expressed genes, with 57 expressed at significantly higher levels in Kc167 cells than S2 cells, and 66 expressed at significantly lower levels in Kc167 cells than S2 cells. Network mapping reveals that many of these TFs are crucial components of regulatory networks involved in cell proliferation, cell-cell signaling pathways, and eye development. CONCLUSIONS We produced a reference TF coding gene expression dataset in the extensively studied Drosophila Kc167 and S2 embryonic cell lines, and gained insight into the TF regulatory networks that control the activity of these cells.
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Affiliation(s)
- Robert A Drewell
- Biology Department, Clark University, 950 Main Street, Worcester, MA, 01610, USA.
| | - Daniel Klonaros
- Biology Department, Clark University, 950 Main Street, Worcester, MA, 01610, USA
| | - Jacqueline M Dresch
- Biology Department, Clark University, 950 Main Street, Worcester, MA, 01610, USA
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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.
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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.
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Ordway AJ, Teeters GM, Weasner BM, Weasner BP, Policastro R, Kumar JP. A multi-gene knockdown approach reveals a new role for Pax6 in controlling organ number in Drosophila. Development 2021; 148:263924. [PMID: 33982759 DOI: 10.1242/dev.198796] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 04/07/2021] [Indexed: 11/20/2022]
Abstract
Genetic screens are designed to target individual genes for the practical reason of establishing a clear association between a mutant phenotype and a single genetic locus. This allows for a developmental or physiological role to be assigned to the wild-type gene. We previously observed that the concurrent loss of Pax6 and Polycomb epigenetic repressors in Drosophila leads the eye to transform into a wing. This fate change is not seen when either factor is disrupted separately. An implication of this finding is that standard screens may miss the roles that combinations of genes play in development. Here, we show that this phenomenon is not limited to Pax6 and Polycomb but rather applies more generally. We demonstrate that in the Drosophila eye-antennal disc, the simultaneous downregulation of Pax6 with either the NURF nucleosome remodeling complex or the Pointed transcription factor transforms the head epidermis into an antenna. This is a previously unidentified fate change that is also not observed with the loss of individual genes. We propose that the use of multi-gene knockdowns is an essential tool for unraveling the complexity of development.
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Affiliation(s)
- Alison J Ordway
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Gary M Teeters
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Bonnie M Weasner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Brandon P Weasner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Robert Policastro
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Justin P Kumar
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Gao Y, Zhang X, Zhang X, Yuan J, Xiang J, Li F. CRISPR/Cas9-mediated mutation reveals Pax6 is essential for development of the compound eye in Decapoda Exopalaemon carinicauda. Dev Biol 2020; 465:157-167. [PMID: 32702356 DOI: 10.1016/j.ydbio.2020.07.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 07/03/2020] [Accepted: 07/04/2020] [Indexed: 12/01/2022]
Abstract
The compound eye in crustaceans is a main eye type in the animal kingdom, knowledge about the mechanism to determine the development of compound eye is very limited. Paired box protein 6 (Pax6) is generally regarded as a master regulator for eye development. In the present study, a genome-based analysis of the Pax6 gene in the ridge tail white prawn Exopalaemon carinicauda was performed and two members of Pax6 homologs, named Ec-Eyeless (EcEy) and Ec-Twin of eyeless (EcToy) were identified. To understand the function of these two homologs of Pax6 gene in the prawn, the CRISPR/Cas9 genome editing technique was applied to generate EcEy and EcToy knock-out (KO) prawns and their phenotypes were analyzed. The surviving EcEy-KO embryos and larvae exhibited severe abnormal eye morphology, suggesting that EcEy is necessary for the compound eye development in prawn, while no mutant phenotype was found in EcToy-KO individuals. These findings highlighted the conservative role of Pax6 gene in the compound eye formation, and the functional differentiation between EcEy and EcToy gene may reveal a novel regulating mechanism of Pax6 on the compound eye development in the decapods. These data will provide important information for understanding the regulation mechanism for crustacean compound eye development.
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Affiliation(s)
- Yi Gao
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Xiaoxi Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaojun Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Jianbo Yuan
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Jianhai Xiang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266237, China
| | - Fuhua Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071, China.
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7
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Bravo González‐Blas C, Quan X, Duran‐Romaña R, Taskiran II, Koldere D, Davie K, Christiaens V, Makhzami S, Hulselmans G, de Waegeneer M, Mauduit D, Poovathingal S, Aibar S, Aerts S. Identification of genomic enhancers through spatial integration of single-cell transcriptomics and epigenomics. Mol Syst Biol 2020; 16:e9438. [PMID: 32431014 PMCID: PMC7237818 DOI: 10.15252/msb.20209438] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 03/13/2020] [Accepted: 03/18/2020] [Indexed: 01/02/2023] Open
Abstract
Single-cell technologies allow measuring chromatin accessibility and gene expression in each cell, but jointly utilizing both layers to map bona fide gene regulatory networks and enhancers remains challenging. Here, we generate independent single-cell RNA-seq and single-cell ATAC-seq atlases of the Drosophila eye-antennal disc and spatially integrate the data into a virtual latent space that mimics the organization of the 2D tissue using ScoMAP (Single-Cell Omics Mapping into spatial Axes using Pseudotime ordering). To validate spatially predicted enhancers, we use a large collection of enhancer-reporter lines and identify ~ 85% of enhancers in which chromatin accessibility and enhancer activity are coupled. Next, we infer enhancer-to-gene relationships in the virtual space, finding that genes are mostly regulated by multiple, often redundant, enhancers. Exploiting cell type-specific enhancers, we deconvolute cell type-specific effects of bulk-derived chromatin accessibility QTLs. Finally, we discover that Prospero drives neuronal differentiation through the binding of a GGG motif. In summary, we provide a comprehensive spatial characterization of gene regulation in a 2D tissue.
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Affiliation(s)
| | - Xiao‐Jiang Quan
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | | | - Ibrahim Ihsan Taskiran
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - Duygu Koldere
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | | | - Valerie Christiaens
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - Samira Makhzami
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - Gert Hulselmans
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - Maxime de Waegeneer
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - David Mauduit
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | | | - Sara Aibar
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
| | - Stein Aerts
- VIB Center for Brain & Disease ResearchLeuvenBelgium
- Department of Human GeneticsKU LeuvenLeuvenBelgium
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8
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Abstract
Molecules of the hedgehog (hh) family are involved in the specification and patterning of eyes in vertebrates and invertebrates. These organs, though, are of very different sizes, raising the question of how Hh molecules operate at such different scales. In this paper we discuss the strategies used by Hh to control the development of the two eye types in Drosophila: the large compound eye and the small ocellus. We first describe the distinct ways in which these two eyes develop and the evidence for the key role played by Hh in both; then we consider the potential for variation in the range of action of a "typical" morphogen and measure this range ("characteristic length") for Hh in different organs, including the compound eye and the ocellus. Finally, we describe how different feedback mechanisms are used to extend the Hh range of action to pattern the large and even the small eye. In the ocellus, the basic Hh signaling pathway adds to its dynamics the attenuation of its receptor as cell differentiate. This sole regulatory change can result in the decoding of the Hh gradient by receiving cells as a wave of constant speed. Therefore, in the fly ocellus, the Hh morphogen adds to its spatial patterning role a novel one: patterning along a time axis.
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9
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Magri MS, Domínguez-Cejudo MA, Casares F. Wnt controls the medial-lateral subdivision of the Drosophila head. Biol Lett 2019; 14:rsbl.2018.0258. [PMID: 30045903 PMCID: PMC6083221 DOI: 10.1098/rsbl.2018.0258] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/02/2018] [Indexed: 12/28/2022] Open
Abstract
In insects, the subdivision of the head into a lateral region, harbouring the compound eyes (CEs), and a dorsal (medial) region, where the ocelli localize, is conserved. This organization might have been already present in the insects' euarthropodan ancestors. In Drosophila, the Wnt-1 homologue wingless (wg) plays a major role in the genetic subdivision of the head. To analyse specifically the role of wg signalling in the development of the dorsal head, we attenuated this pathway specifically in this region by genetic means. We find that loss of wg signalling transforms the dorsal/medial head into lateral head structures, including the development of ectopic CEs. Our genetic analysis further suggests that wg signalling organizes the dorsal head medial–lateral axis by controlling, at least in part, the expression domains of the transcription factors Otd and Ey/Pax6.
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Affiliation(s)
- M S Magri
- GEM-DMC2 María de Maeztu Unit of Excellence, The CABD (CSIC-UPO-JA), 41013 Seville, Spain
| | - M A Domínguez-Cejudo
- GEM-DMC2 María de Maeztu Unit of Excellence, The CABD (CSIC-UPO-JA), 41013 Seville, Spain
| | - F Casares
- GEM-DMC2 María de Maeztu Unit of Excellence, The CABD (CSIC-UPO-JA), 41013 Seville, Spain
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10
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Rass M, Oestreich S, Guetter S, Fischer S, Schneuwly S. The Drosophila fussel gene is required for bitter gustatory neuron differentiation acting within an Rpd3 dependent chromatin modifying complex. PLoS Genet 2019; 15:e1007940. [PMID: 30730884 PMCID: PMC6382215 DOI: 10.1371/journal.pgen.1007940] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 02/20/2019] [Accepted: 01/07/2019] [Indexed: 01/14/2023] Open
Abstract
Members of the Ski/Sno protein family are classified as proto-oncogenes and act as negative regulators of the TGF-ß/BMP-pathways in vertebrates and invertebrates. A newly identified member of this protein family is fussel (fuss), the Drosophila homologue of the human functional Smad suppressing elements (fussel-15 and fussel-18). We and others have shown that Fuss interacts with SMAD4 and that overexpression leads to a strong inhibition of Dpp signaling. However, to be able to characterize the endogenous Fuss function in Drosophila melanogaster, we have generated a number of state of the art tools including anti-Fuss antibodies, specific fuss-Gal4 lines and fuss mutant fly lines via the CRISPR/Cas9 system. Fuss is a predominantly nuclear, postmitotic protein, mainly expressed in interneurons and fuss mutants are fully viable without any obvious developmental phenotype. To identify potential target genes or cells affected in fuss mutants, we conducted targeted DamID experiments in adult flies, which revealed the function of fuss in bitter gustatory neurons. We fully characterized fuss expression in the adult proboscis and by using food choice assays we were able to show that fuss mutants display defects in detecting bitter compounds. This correlated with a reduction of gustatory receptor gene expression (Gr33a, Gr66a, Gr93a) providing a molecular link to the behavioral phenotype. In addition, Fuss interacts with Rpd3, and downregulation of rpd3 in gustatory neurons phenocopies the loss of Fuss expression. Surprisingly, there is no colocalization of Fuss with phosphorylated Mad in the larval central nervous system, excluding a direct involvement of Fuss in Dpp/BMP signaling. Here we provide a first and exciting link of Fuss function in gustatory bitter neurons. Although gustatory receptors have been well characterized, little is known regarding the differentiation and maturation of gustatory neurons. This work therefore reveals Fuss as a pivotal element for the proper differentiation of bitter gustatory neurons acting within a chromatin modifying complex.
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Affiliation(s)
- Mathias Rass
- Department of Developmental Biology, Institute of Zoology, University of Regensburg, Regensburg, Bavaria, Germany
| | - Svenja Oestreich
- Department of Developmental Biology, Institute of Zoology, University of Regensburg, Regensburg, Bavaria, Germany
| | - Severin Guetter
- Department of Developmental Biology, Institute of Zoology, University of Regensburg, Regensburg, Bavaria, Germany
| | - Susanne Fischer
- Department of Developmental Biology, Institute of Zoology, University of Regensburg, Regensburg, Bavaria, Germany
| | - Stephan Schneuwly
- Department of Developmental Biology, Institute of Zoology, University of Regensburg, Regensburg, Bavaria, Germany
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11
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Baker LR, Weasner BM, Nagel A, Neuman SD, Bashirullah A, Kumar JP. Eyeless/Pax6 initiates eye formation non-autonomously from the peripodial epithelium. Development 2018; 145:dev.163329. [PMID: 29980566 DOI: 10.1242/dev.163329] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 06/27/2018] [Indexed: 01/08/2023]
Abstract
The transcription factor Pax6 is considered the master control gene for eye formation because (1) it is present within the genomes and retina/lens of all animals with a visual system; (2) severe retinal defects accompany its loss; (3) Pax6 genes have the ability to substitute for one another across the animal kingdom; and (4) Pax6 genes are capable of inducing ectopic eye/lens in flies and mammals. Many roles of Pax6 were first elucidated in Drosophila through studies of the gene eyeless (ey), which controls both growth of the entire eye-antennal imaginal disc and fate specification of the eye. We show that Ey also plays a surprising role within cells of the peripodial epithelium to control pattern formation. It regulates the expression of decapentaplegic (dpp), which is required for initiation of the morphogenetic furrow in the eye itself. Loss of Ey within the peripodial epithelium leads to the loss of dpp expression within the eye, failure of the furrow to initiate, and abrogation of retinal development. These findings reveal an unexpected mechanism for how Pax6 controls eye development in Drosophila.
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Affiliation(s)
- Luke R Baker
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Bonnie M Weasner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Athena Nagel
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Sarah D Neuman
- Department of Pharmaceutical Sciences, University of Wisconsin, Madison, WI 53705, USA
| | - Arash Bashirullah
- Department of Pharmaceutical Sciences, University of Wisconsin, Madison, WI 53705, USA
| | - Justin P Kumar
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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12
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Drosophila Pax6 promotes development of the entire eye-antennal disc, thereby ensuring proper adult head formation. Proc Natl Acad Sci U S A 2018; 114:5846-5853. [PMID: 28584125 DOI: 10.1073/pnas.1610614114] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Paired box 6 (Pax6) is considered to be the master control gene for eye development in all seeing animals studied so far. In vertebrates, it is required not only for lens/retina formation but also for the development of the CNS, olfactory system, and pancreas. Although Pax6 plays important roles in cell differentiation, proliferation, and patterning during the development of these systems, the underlying mechanism remains poorly understood. In the fruit fly, Drosophila melanogaster, Pax6 also functions in a range of tissues, including the eye and brain. In this report, we describe the function of Pax6 in Drosophila eye-antennal disc development. Previous studies have suggested that the two fly Pax6 genes, eyeless (ey) and twin of eyeless (toy), initiate eye specification, whereas eyegone (eyg) and the Notch (N) pathway independently regulate cell proliferation. Here, we show that Pax6 controls eye progenitor cell survival and proliferation through the activation of teashirt (tsh) and eyg, thereby indicating that Pax6 initiates both eye specification and proliferation. Although simultaneous loss of ey and toy during early eye-antennal disc development disrupts the development of all head structures derived from the eye-antennal disc, overexpression of N or tsh in the absence of Pax6 rescues only antennal and head epidermis development. Furthermore, overexpression of tsh induces a homeotic transformation of the fly head into thoracic structures. Taking these data together, we demonstrate that Pax6 promotes development of the entire eye-antennal disc and that the retinal determination network works to repress alternative tissue fates, which ensures proper development of adult head structures.
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13
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Davis TL, Rebay I. Pleiotropy in Drosophila organogenesis: Mechanistic insights from Combgap and the retinal determination gene network. Fly (Austin) 2018; 12:62-70. [PMID: 29125381 DOI: 10.1080/19336934.2017.1402994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Master regulatory transcription factors cooperate in networks to shepherd cells through organogenesis. In the Drosophila eye, a collection of master control proteins known as the retinal determination gene network (RDGN) switches the direction and targets of its output to choreograph developmental transitions, but the molecular partners that enable such regulatory flexibility are not known. We recently showed that two RDGN members, Eyes absent (Eya) and Sine oculis (So), promote exit from the terminal cell cycle known as the second mitotic wave (SMW) to permit differentiation. A search for co-factors identified the ubiquitously expressed Combgap (Cg) as a novel transcriptional partner that impedes cell cycle exit and interferes with Eya-So activity specifically in this context. Here, we argue that Cg acts as a flexible transcriptional platform that contributes to numerous gene expression outcomes by a variety of mechanisms. For example, Cg provides repressive activities that dampen Eya-So output, but not by recruiting Polycomb chromatin-remodeling complexes as it does in other contexts. We propose that master regulators depend on both specifically expressed co-factors that assemble the combinatorial code and broadly expressed partners like Cg that recruit the diverse molecular activities needed to appropriately regulate their target enhancers.
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Affiliation(s)
- Trevor L Davis
- a Committee on Development, Regeneration, and Stem Cell Biology , University of Chicago , Chicago , IL , USA
| | - Ilaria Rebay
- a Committee on Development, Regeneration, and Stem Cell Biology , University of Chicago , Chicago , IL , USA.,b Ben May Department for Cancer Research , University of Chicago , Chicago , IL , USA
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Development of functional ectopic compound eyes in scarabaeid beetles by knockdown of orthodenticle. Proc Natl Acad Sci U S A 2017; 114:12021-12026. [PMID: 29078401 DOI: 10.1073/pnas.1714895114] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Complex traits like limbs, brains, or eyes form through coordinated integration of diverse cell fates across developmental space and time, yet understanding how complexity and integration emerge from uniform, undifferentiated precursor tissues remains limited. Here, we use ectopic eye formation as a paradigm to investigate the emergence and integration of novel complex structures following massive ontogenetic perturbation. We show that down-regulation via RNAi of a single head patterning gene-orthodenticle-induces ectopic structures externally resembling compound eyes at the middorsal adult head of both basal and derived scarabaeid beetle species (Onthophagini and Oniticellini). Scanning electron microscopy documents ommatidial organization of these induced structures, while immunohistochemistry reveals the presence of rudimentary ommatidial lenses, crystalline cones, and associated neural-like tissue within them. Further, RNA-sequencing experiments show that after orthodenticle down-regulation, the transcriptional signature of the middorsal head-the location of ectopic eye induction-converges onto that of regular compound eyes, including up-regulation of several retina-specific genes. Finally, a light-aversion behavioral assay to assess functionality reveals that ectopic compound eyes can rescue the ability to respond to visual stimuli when wild-type eyes are surgically removed. Combined, our results show that knockdown of a single gene is sufficient for the middorsal head to acquire the competence to ectopically generate a functional compound eye-like structure. These findings highlight the buffering capacity of developmental systems, allowing massive genetic perturbations to be channeled toward orderly and functional developmental outcomes, and render ectopic eye formation a widely accessible paradigm to study the evolution of complex systems.
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Friedrich M. Ancient genetic redundancy of eyeless and twin of eyeless in the arthropod ocular segment. Dev Biol 2017; 432:192-200. [PMID: 28993201 DOI: 10.1016/j.ydbio.2017.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 10/02/2017] [Accepted: 10/03/2017] [Indexed: 01/28/2023]
Abstract
Pax6 transcription factors are essential upstream regulators in the developing anterior brain and peripheral visual system of most bilaterian animals. While a single homolog is in charge of these functions in vertebrates, two Pax6 genes are in Drosophila: eyeless (ey) and twin of eyeless (toy). At first glance, their co-existence seems sufficiently explained by their differential involvement in the specification of two types of insect visual organs: the lateral compound eyes (ey) and the dorsal ocelli (toy). Less straightforward to understand, however, is their genetic redundancy in promoting defined early and late growth phases of the precursor tissue to these organs: the eye-antennal imaginal disc. Drawing on comparative sequence, expression, and gene function evidence, I here conclude that this gene regulatory network module dates back to the dawn of arthropod evolution, securing the embryonic development of the ocular head segment. Thus, ey and toy constitute a paradigm to explore the organization and functional significance of longterm conserved genetic redundancy of duplicated genes. Indeed, as first steps in this direction, recent studies uncovered the shared use of binding sites in shared enhancers of target genes that are under redundant (string) and, strikingly, even subfunctionalized control by ey and toy (atonal). Equally significant, the evolutionarily recent and paralog-specific function of ey to repress the transcription of the antenna fate regulator Distal-less offers a functionally and phylogenetically well-defined opportunity to study the reconciliation of shared, partitioned, and newly acquired functions in a duplicated developmental gene pair.
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Affiliation(s)
- Markus Friedrich
- Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA; Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, 540 East Canfield Avenue, Detroit, MI 48201,USA.
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16
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Neilson KM, Abbruzzesse G, Kenyon K, Bartolo V, Krohn P, Alfandari D, Moody SA. Pa2G4 is a novel Six1 co-factor that is required for neural crest and otic development. Dev Biol 2017; 421:171-182. [PMID: 27940157 PMCID: PMC5221411 DOI: 10.1016/j.ydbio.2016.11.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 11/15/2016] [Accepted: 11/28/2016] [Indexed: 11/29/2022]
Abstract
Mutations in SIX1 and in its co-factor, EYA1, underlie Branchiootorenal Spectrum disorder (BOS), which is characterized by variable branchial arch, otic and kidney malformations. However, mutations in these two genes are identified in only half of patients. We screened for other potential co-factors, and herein characterize one of them, Pa2G4 (aka Ebp1/Plfap). In human embryonic kidney cells, Pa2G4 binds to Six1 and interferes with the Six1-Eya1 complex. In Xenopus embryos, knock-down of Pa2G4 leads to down-regulation of neural border zone, neural crest and cranial placode genes, and concomitant expansion of neural plate genes. Gain-of-function leads to a broader neural border zone, expanded neural crest and altered cranial placode domains. In loss-of-function assays, the later developing otocyst is reduced in size, which impacts gene expression. In contrast, the size of the otocyst in gain-of-function assays is not changed but the expression domains of several otocyst genes are reduced. Together these findings establish an interaction between Pa2G4 and Six1, and demonstrate that it has an important role in the development of tissues affected in BOS. Thereby, we suggest that pa2g4 is a potential candidate gene for BOS.
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Affiliation(s)
- Karen M Neilson
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Genevieve Abbruzzesse
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Kristy Kenyon
- Department of Biology, Hobart and William Smith Colleges, Geneva, NY, USA
| | - Vanessa Bartolo
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Patrick Krohn
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Sally A Moody
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA.
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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.
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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.
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18
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Skottheim Honn J, Johansson L, Rasmuson Lestander Å. Regulation of twin of eyeless during Drosophila development. Gene Expr Patterns 2016; 20:120-9. [PMID: 26976323 DOI: 10.1016/j.gep.2016.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 03/07/2016] [Accepted: 03/07/2016] [Indexed: 10/22/2022]
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Moody SA, Neilson KM, Kenyon KL, Alfandari D, Pignoni F. Using Xenopus to discover new genes involved in branchiootorenal spectrum disorders. Comp Biochem Physiol C Toxicol Pharmacol 2015; 178:16-24. [PMID: 26117063 PMCID: PMC4662879 DOI: 10.1016/j.cbpc.2015.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 06/16/2015] [Accepted: 06/17/2015] [Indexed: 12/14/2022]
Abstract
Congenital hearing loss is an important clinical problem because, without early intervention, affected children do not properly acquire language and consequently have difficulties developing social skills. Although most newborns in the US are screened for hearing deficits, even earlier diagnosis can be made with prenatal genetic screening. Genetic screening that identifies the relevant mutated gene can also warn about potential congenital defects in organs not related to hearing. We will discuss efforts to identify new candidate genes that underlie the Branchiootorenal spectrum disorders in which affected children have hearing deficits and are also at risk for kidney defects. Mutations in two genes, SIX1 and EYA1, have been identified in about half of the patients tested. To uncover new candidate genes, we have used the aquatic animal model, Xenopus laevis, to identify genes that are part of the developmental genetic pathway of Six1 during otic and kidney development. We have already identified a large number of potential Six1 transcriptional targets and candidate co-factor proteins that are expressed at the right time and in the correct tissues to interact with Six1 during development. We discuss the advantages of using this system for gene discovery in a human congenital hearing loss syndrome.
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Affiliation(s)
- Sally A Moody
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA.
| | - Karen M Neilson
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Kristy L Kenyon
- Department of Biology, Hobart and William Smith Colleges, Geneva, NY, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Francesca Pignoni
- Department of Ophthalmology, Upstate Medical University, Syracuse, NY, USA
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Meinhardt H. Models for patterning primary embryonic body axes: The role of space and time. Semin Cell Dev Biol 2015; 42:103-17. [PMID: 26126935 DOI: 10.1016/j.semcdb.2015.06.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 06/23/2015] [Indexed: 11/19/2022]
Abstract
Models for the generation and interpretation of spatial patterns are discussed. Crucial for these processes is an intimate link between self-enhancing and antagonistic reactions. For spatial patterning, long-ranging antagonistic reactions are required that restrict the self-enhancing reactions to generate organizing regions. Self-enhancement is also required for a permanent switch-like activation of genes. This self-enhancement is antagonized by the mutual repression of genes, making sure that in a particular cell only one gene of a set of possible genes become activated - a long range inhibition in the 'gene space'. The understanding how the main body axes are initiated becomes more straightforward if the evolutionary ancestral head/brain pattern and the trunk pattern is considered separately. To activate a specific gene at particular concentration of morphogenetic gradient, observations are compatible with a systematic and time-requiring 'promotion' from one gene to the next until the local concentration is insufficient to accomplish a further promotion. The achieved determination is stable against a fading of the morphogen, as required to allow substantial growth. Minor modifications lead to a purely time-dependent activation of genes; both mechanisms are involved to pattern the anteroposterior axis. A mutual activation of cell states that locally exclude each other accounts for many features of the segmental patterning of the trunk. A possible scenario for the evolutionary invention of segmentation is discussed that is based on a reemployment of interactions involved in asexual reproduction.
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Affiliation(s)
- Hans Meinhardt
- Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35, D-72076 Tübingen, Germany.
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21
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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.
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22
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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.
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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
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23
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Glossop NRJ, Gummadova JO, Ghangrekar I, Hardin PE, Coutts GA. Effects of TWIN-OF-EYELESS on Clock Gene Expression and Central-Pacemaker Neuron Development in Drosophila. J Biol Rhythms 2014; 29:151-166. [PMID: 24916389 PMCID: PMC4262727 DOI: 10.1177/0748730414534819] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Circadian oscillators are autonomous molecular rhythms that reside in cells to align whole-organism physiology and behavior to the 24-h day. In flies, as in mammals, the oscillator operates in cells that coexpress CLOCK (CLK) and CYCLE (CYC). Recent work in Drosophila has shown that CLK is unique in its ability to generate heterologous oscillators, indicating that Clk gene expression defines the circadian cell fate. Here, using standard in vitro and in vivo techniques, we show that TWIN-OF-EYELESS (TOY; dPax6) regulates Clk expression in small ventrolateral neurons (s-LNvs) that coordinate sleep-wake cycles. Crucially, toy binds multiple sites at the Clk locus, is expressed independent of CLK-CYC in LNvs, regulates CLK protein levels under optimal photoperiodic conditions, and sets clock-speed during endogenous free-run. Furthermore, TOY is necessary for the onset of Clk expression in LNvs during embryogenesis. We propose that TOY contributes to a transcription complex that functions upstream of the oscillator to promote Clk expression in s-LNvs.
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Affiliation(s)
| | | | - Indrayani Ghangrekar
- Faculty of Life Sciences, University of Manchester, Manchester, UK Cancer Research UK, London, UK
| | | | - Graham A Coutts
- Faculty of Life Sciences, University of Manchester, Manchester, UK
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Blaquiere JA, Lee W, Verheyen EM. Hipk promotes photoreceptor differentiation through the repression of Twin of eyeless and Eyeless expression. Dev Biol 2014; 390:14-25. [PMID: 24631217 DOI: 10.1016/j.ydbio.2014.02.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 02/26/2014] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
Abstract
Organogenesis is a complex developmental process, which requires tight regulation of selector gene expression to specify individual organ types. The Pax6 homolog Eyeless (Ey) is an example of such a factor and its expression pattern reveals it is dynamically controlled during development. Ey׳s paralog Twin of eyeless (Toy) induces its expression during embryogenesis, and the two genes are expressed in nearly identical patterns during the larval stages of development. While Ey must be expressed to initiate retinal specification, it must subsequently be repressed behind the morphogenetic furrow to allow for neuronal differentiation. Thus far, a few factors have been implicated in this repression including the signaling pathways Hedgehog (Hh) and Decapentaplegic (Dpp), and more recently downstream components of the retinal determination gene network (RDGN) Sine oculis (So), Eyes absent (Eya), and Dachshund (Dac). Homeodomain-interacting protein kinase (Hipk), a conserved serine-threonine kinase, regulates numerous factors during tissue patterning and development, including the Hh pathway. Using genetic analyses we identify Hipk as a repressor of both Toy and Ey and show that it may do so, in part, through Hh signaling. We also provide evidence that Ey repression is a critical step in ectopic eye development and that Hipk plays an important role in this process. Because Ey repression within the retinal field is a critical step in eye development, we propose that Hipk is a key link between eye specification and patterning.
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Affiliation(s)
- Jessica A Blaquiere
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A1S6
| | - Wendy Lee
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A1S6; Department of Dermatology and Cell Biology, NYU Langone Medical Center and School of Medicine, New York University, New York, NY 10016, USA
| | - Esther M Verheyen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A1S6.
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Aguilar-Hidalgo D, Domínguez-Cejudo MA, Amore G, Brockmann A, Lemos MC, Córdoba A, Casares F. A Hh-driven gene network controls specification, pattern and size of the Drosophila simple eyes. Development 2012; 140:82-92. [PMID: 23154412 DOI: 10.1242/dev.082172] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During development, extracellular signaling molecules interact with intracellular gene networks to control the specification, pattern and size of organs. One such signaling molecule is Hedgehog (Hh). Hh is known to act as a morphogen, instructing different fates depending on the distance to its source. However, how Hh, when signaling across a cell field, impacts organ-specific transcriptional networks is still poorly understood. Here, we investigate this issue during the development of the Drosophila ocellar complex. The development of this sensory structure, which is composed of three simple eyes (or ocelli) located at the vertices of a triangular patch of cuticle on the dorsal head, depends on Hh signaling and on the definition of three domains: two areas of eya and so expression--the prospective anterior and posterior ocelli--and the intervening interocellar domain. Our results highlight the role of the homeodomain transcription factor engrailed (en) both as a target and as a transcriptional repressor of hh signaling in the prospective interocellar region. Furthermore, we identify a requirement for the Notch pathway in the establishment of en maintenance in a Hh-independent manner. Therefore, hh signals transiently during the specification of the interocellar domain, with en being required here for hh signaling attenuation. Computational analysis further suggests that this network design confers robustness to signaling noise and constrains phenotypic variation. In summary, using genetics and modeling we have expanded the ocellar gene network to explain how the interaction between the Hh gradient and this gene network results in the generation of stable mutually exclusive gene expression domains. In addition, we discuss some general implications our model may have in some Hh-driven gene networks.
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Justice ED, Macedonia NJ, Hamilton C, Condron B. The simple fly larval visual system can process complex images. Nat Commun 2012; 3:1156. [DOI: 10.1038/ncomms2174] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/27/2012] [Indexed: 11/09/2022] Open
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27
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Brockmann A, Domínguez-Cejudo MA, Amore G, Casares F. Regulation of ocellar specification and size by twin of eyeless and homothorax. Dev Dyn 2011; 240:75-85. [PMID: 21104743 DOI: 10.1002/dvdy.22494] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The retinal determination gene network (RDGN) constitutes a paradigm of a gene network controlling organ specification and growth. In this study, we probed the RDGN in the Drosophila ocelli, a set of simple eyes located on the fly's dorsal head, by studying the expression, regulation, and function of toy, hth, eya, and so, members of the Pax6, Meis, Eya, and Six gene families. Our results highlight the role of the pax6 gene toy, together with the hh signaling pathway, in the initiation of eya and so expression; the engagement of eya and so in a feedback loop necessary for their full expression; and the interplay between hh signaling and hth as a mechanism of organ size control, as general regulatory steps in the specification of visual organs.
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Affiliation(s)
- Anette Brockmann
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-UPO, Seville, Spain
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