1
|
Molina-Gil S, Sotillos S, Espinosa-Vázquez JM, Almudi I, Hombría JCG. Interlocking of co-opted developmental gene networks in Drosophila and the evolution of pre-adaptive novelty. Nat Commun 2023; 14:5730. [PMID: 37714829 PMCID: PMC10504328 DOI: 10.1038/s41467-023-41414-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 08/30/2023] [Indexed: 09/17/2023] Open
Abstract
The re-use of genes in new organs forms the base of many evolutionary novelties. A well-characterised case is the recruitment of the posterior spiracle gene network to the Drosophila male genitalia. Here we find that this network has also been co-opted to the testis mesoderm where is required for sperm liberation, providing an example of sequentially repeated developmental co-options. Associated to this co-option event, an evolutionary expression novelty appeared, the activation of the posterior segment determinant Engrailed to the anterior A8 segment controlled by common testis and spiracle regulatory elements. Enhancer deletion shows that A8 anterior Engrailed activation is not required for spiracle development but only necessary in the testis. Our study presents an example of pre-adaptive developmental novelty: the activation of the Engrailed transcription factor in the anterior compartment of the A8 segment where, despite having no specific function, opens the possibility of this developmental factor acquiring one. We propose that recently co-opted networks become interlocked, so that any change to the network because of its function in one organ, will be mirrored by other organs even if it provides no selective advantage to them.
Collapse
Affiliation(s)
- Sara Molina-Gil
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-JA-UPO Ctra. de Utrera, km1, 41013, Seville, Spain
- Málaga Biomedical Research Institute and Andalusian Centre for Nanomedicine and Biotechnology Platform, Severo Ochoa, 35, 29590, Málaga, Spain
| | - Sol Sotillos
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-JA-UPO Ctra. de Utrera, km1, 41013, Seville, Spain
| | - José Manuel Espinosa-Vázquez
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-JA-UPO Ctra. de Utrera, km1, 41013, Seville, Spain
- Department of Food Biotechnology, Instituto de la Grasa. Campus de la Universidad Pablo de Olavide. Ctra. de Utrera, km. 1, 41013, Seville, Spain
| | - Isabel Almudi
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-JA-UPO Ctra. de Utrera, km1, 41013, Seville, Spain
- Department of Genetics, Microbiology and Statistics and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Diagonal, 643, 08028, Barcelona, Spain
| | - James C-G Hombría
- Centro Andaluz de Biología del Desarrollo (CABD), CSIC-JA-UPO Ctra. de Utrera, km1, 41013, Seville, Spain.
| |
Collapse
|
2
|
Zhang Y, Wang XX, Shen LF, Feng ZJ, Zhang SQ, Tian HG, Feng Y, Liu TX. Abdominal-B regulates structure and development of the Harmonia axyridis cremaster. INSECT SCIENCE 2021; 28:965-975. [PMID: 32452090 DOI: 10.1111/1744-7917.12821] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/26/2020] [Accepted: 05/06/2020] [Indexed: 06/11/2023]
Abstract
The ladybird Harmonia axyridis is an insect that exhibits pupal attachment to plants, which facilitates development and environmental adaptation. The cremaster is highly specialized for this behavior. However, the underlying molecular regulation of the cremaster remains unclear; therefore, we performed experiments to investigate the transcriptional regulation of cremaster development. First, we examined the morphological structure of the cremaster to reveal its function in pupal attachment of H. axyridis. Next, we analyzed the Hox gene Ha-Abd-B using RNA interference (RNAi) to determine its function in regulating cremaster formation; Ha-Abd-B up-regulation promoted effective pupal attachment, whereas successful RNAi caused severe down-regulation of this gene, and pupae were unable to attach. Furthermore, successful RNAi and subsequent Ha-Abd-B down-regulation caused phenotypic changes in cremaster structure, including its complete disappearance from some individuals. Finally, we observed unique development of the cremaster and dynamic expression of Ha-Abd-B during pre-pupal development; consequently, we hypothesized that there was specific pre-pupal development of the cremaster. Overall, based on these results, the specialized cremasteric structure located on the posterior side of H. axyridis was determined to be a key organ for pupal attachment. Cremaster identification in H. axyridis is regulated by Ha-Abd-B and exhibits preferential development. Pupal attachment of H. axyridis reveals an environmental adaptation of this species; thus, this study and future molecular studies will help determine the role of Hox genes in regulation of insect attachment and further our understanding of the multiple functions of Hox genes.
Collapse
Affiliation(s)
- Yi Zhang
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Xing-Xing Wang
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Ling-Feng Shen
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Zhu-Jun Feng
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Song-Qi Zhang
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Hong-Gang Tian
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Yi Feng
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Tong-Xian Liu
- Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| |
Collapse
|
3
|
Unpredictable Effects of the Genetic Background of Transgenic Lines in Physiological Quantitative Traits. G3-GENES GENOMES GENETICS 2019; 9:3877-3890. [PMID: 31540975 PMCID: PMC6829147 DOI: 10.1534/g3.119.400715] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Physiology, fitness and disease phenotypes are complex traits exhibiting continuous variation in natural populations. To understand complex trait gene functions transgenic lines of undefined genetic background are often combined to assess quantitative phenotypes ignoring the impact of genetic polymorphisms. Here, we used inbred wild-type strains of the Drosophila Genetics Reference Panel to assess the phenotypic variation of six physiological and fitness traits, namely, female fecundity, survival and intestinal mitosis upon oral infection, defecation rate and fecal pH upon oral infection, and terminal tracheal cell branching in hypoxia. We found continuous variation in the approximately 150 strains tested for each trait, with extreme values differing by more than four standard deviations for all traits. In addition, we assessed the effects of commonly used Drosophila UAS-RNAi transgenic strains and their backcrossed isogenized counterparts, in the same traits plus baseline intestinal mitosis and tracheal branching in normoxia, in heterozygous conditions, when only half of the genetic background was different among strains. We tested 20 non-isogenic strains (10 KK and 10 GD) from the Vienna Drosophila Resource Center and their isogenized counterparts without Gal4 induction. Survival upon infection and female fecundity exhibited differences in 50% and 40% of the tested isogenic vs. non-isogenic pairs, respectively, whereas all other traits were affected in only 10–25% of the cases. When 11 isogenic and their corresponding non-isogenic UAS-RNAi lines were expressed ubiquitously with Gal4, 4 isogenic vs. non-isogenic pairs exhibited differences in survival to infection. Furthermore, when a single UAS-RNAi line was crossed with the same Gal4 transgene inserted in different genetic backgrounds, the quantitative variations observed were unpredictable on the basis of pure line performance. Thus, irrespective of the trait of interest, the genetic background of commonly used transgenic strains needs to be considered carefully during experimentation.
Collapse
|
4
|
Matsuda R, Hosono C, Saigo K, Samakovlis C. The intersection of the extrinsic hedgehog and WNT/wingless signals with the intrinsic Hox code underpins branching pattern and tube shape diversity in the drosophila airways. PLoS Genet 2015; 11:e1004929. [PMID: 25615601 PMCID: PMC4304712 DOI: 10.1371/journal.pgen.1004929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 11/28/2014] [Indexed: 01/04/2023] Open
Abstract
The tubular networks of the Drosophila respiratory system and our vasculature show distinct branching patterns and tube shapes in different body regions. These local variations are crucial for organ function and organismal fitness. Organotypic patterns and tube geometries in branched networks are typically controlled by variations of extrinsic signaling but the impact of intrinsic factors on branch patterns and shapes is not well explored. Here, we show that the intersection of extrinsic hedgehog(hh) and WNT/wingless (wg) signaling with the tube-intrinsic Hox code of distinct segments specifies the tube pattern and shape of the Drosophila airways. In the cephalic part of the airways, hh signaling induces expression of the transcription factor (TF) knirps (kni) in the anterior dorsal trunk (DTa1). kni represses the expression of another TF spalt major (salm), making DTa1 a narrow and long tube. In DTa branches of more posterior metameres, Bithorax Complex (BX-C) Hox genes autonomously divert hh signaling from inducing kni, thereby allowing DTa branches to develop as salm-dependent thick and short tubes. Moreover, the differential expression of BX-C genes is partly responsible for the anterior-to-posterior gradual increase of the DT tube diameter through regulating the expression level of Salm, a transcriptional target of WNT/wg signaling. Thus, our results highlight how tube intrinsic differential competence can diversify tube morphology without changing availabilities of extrinsic factors. Tubes are common structural elements of many internal organs,
facilitating fluid flow and material exchange. To meet the local needs of diverse tissues, the branching patterns and tube shapes vary regionally. Diametric tapering and specialized branch targeting to the brain represent two common examples of variations with organismal benefits in the Drosophila airways and our vascular system. Several extrinsic signals instruct tube diversifications but the impact of intrinsic factors remains underexplored. Here, we show that the local, tube-intrinsic Hox code instructs the pattern and shape of the dorsal trunk (DT), the main Drosophila airway. In the cephalic part (DT1), where Bithorax Complex (BX-C) Hox genes are not expressed, the extrinsic Hedgehog signal is epistatic to WNT/Wingless signals. Hedgehog instructs anterior DT1 cells to take a long and narrow tube fate targeting the brain. In more posterior metameres, BX-C genes make the extrinsic WNT/Wingless signals epistatic over Hedgehog. There, WNT/Wingless instruct all DT cells to take the thick and short tube fate. Moreover, BX-C genes modulate the outputs of WNT/wingless signaling, making the DT tubes thicker in more posterior metameres. We provide a model for how intrinsic factors modify extrinsic signaling to control regional tube morphologies in a network.
Collapse
Affiliation(s)
- Ryo Matsuda
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Chie Hosono
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Kaoru Saigo
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | - Christos Samakovlis
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
- ECCPS, University of Giessen, Giessen, Germany
- * E-mail:
| |
Collapse
|
5
|
Sánchez-Herrero E. Hox targets and cellular functions. SCIENTIFICA 2013; 2013:738257. [PMID: 24490109 PMCID: PMC3892749 DOI: 10.1155/2013/738257] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 11/20/2013] [Indexed: 06/03/2023]
Abstract
Hox genes are a group of genes that specify structures along the anteroposterior axis in bilaterians. Although in many cases they do so by modifying a homologous structure with a different (or no) Hox input, there are also examples of Hox genes constructing new organs with no homology in other regions of the body. Hox genes determine structures though the regulation of targets implementing cellular functions and by coordinating cell behavior. The genetic organization to construct or modify a certain organ involves both a genetic cascade through intermediate transcription factors and a direct regulation of targets carrying out cellular functions. In this review I discuss new data from genome-wide techniques, as well as previous genetic and developmental information, to describe some examples of Hox regulation of different cell functions. I also discuss the organization of genetic cascades leading to the development of new organs, mainly using Drosophila melanogaster as the model to analyze Hox function.
Collapse
Affiliation(s)
- Ernesto Sánchez-Herrero
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| |
Collapse
|
6
|
Yoder JH. Abdominal segment reduction: development and evolution of a deeply fixed trait. Fly (Austin) 2012; 6:240-5. [PMID: 23026836 DOI: 10.4161/fly.22109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
When a new student first begins to push flies, an immediate skill that must be learned is sorting the sexes. In Drosophila melanogaster several sexually dimorphic characters can be used to readily distinguish males from females including abdominal pigmentation, male sex combs and genital morphology. Another, often-overlooked, sexual dimorphism is adult abdominal segment number. Externally, adult Drosophila males possess one fewer abdominal segment than females; the terminal pre-genital segment apparently either absent or fused with the next-most anterior segment. Beyond known roles for the homeotic protein Abdominal-B (Abd-B) and the sex-determining transcription factor Doublesex (Dsx) as key regulators of this trait, surprisingly little is known about either the morphogenetic processes or the downstream genetics responsible for patterning these events. We have explored both and found that rapid epithelial reorganization during pupation eliminates a nascent terminal male segment. We found this Abd-B-dependent process results from sex- and segment-specific regulation of diverse developmental targets including the wingless gene and surprisingly, dsx itself. ( 1) (,) ( 2) Here, I review our observations and discuss this trait as a model to explore both dynamics of epithelial morphogenesis as well as the evolution of developmental mechanisms.
Collapse
Affiliation(s)
- John H Yoder
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.
| |
Collapse
|
7
|
Sexually dimorphic regulation of the Wingless morphogen controls sex-specific segment number in Drosophila. Proc Natl Acad Sci U S A 2011; 108:11139-44. [PMID: 21690416 DOI: 10.1073/pnas.1108431108] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sexual dimorphism is widespread throughout the metazoa and plays important roles in mate recognition and preference, sex-based niche partitioning, and sex-specific coadaptation. One notable example of sex-specific differences in insect body morphology is presented by the higher diptera, such as Drosophila, in which males develop fewer abdominal segments than females. Because diversity in segment number is a distinguishing feature of major arthropod clades, it is of fundamental interest to understand how different numbers of segments can be generated within the same species. Here we show that sex-specific and segment-specific regulation of the Wingless (Wg) morphogen underlies the development of sexually dimorphic adult segment number in Drosophila. Wg expression is repressed in the developing terminal male abdominal segment by the combination of the Hox protein Abdominal-B (Abd-B) and the sex-determination regulator Doublesex (Dsx). The subsequent loss of the terminal male abdominal segment during pupation occurs through a combination of developmental processes including segment compartmental transformation, apoptosis, and suppression of cell proliferation. Furthermore, we show that ectopic expression of Wg is sufficient to rescue this loss. We propose that dimorphic Wg regulation, in concert with monomorphic segment-specific programmed cell death, are the principal mechanisms of sculpting the sexually dimorphic abdomen of Drosophila.
Collapse
|
8
|
Kalis AK, Murphy MW, Zarkower D. EGL-5/ABD-B plays an instructive role in male cell fate determination in the C. elegans somatic gonad. Dev Biol 2010; 344:827-35. [PMID: 20553900 DOI: 10.1016/j.ydbio.2010.05.516] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/26/2010] [Accepted: 05/28/2010] [Indexed: 01/15/2023]
Abstract
Hox genes of the Abdominal-B (Abd-B) class regulate gonadal development in diverse metazoans. Here we have investigated the role of the Abd-B homolog egl-5 in C. elegans gonadal development. Previous work showed that egl-5 is required male-specifically in the gonad and that mutant gonads are highly dysgenic and possibly feminized. We have used sex-specific gonadal reporter genes to confirm that the gonads of egl-5 males are extensively feminized. Sex-specific expression of egl-5 requires the global sex determination gene tra-1 and the gonadal masculinizing gene fkh-6, but mutagenesis of a short male gonadal enhancer element in egl-5 suggested that this regulation is indirect. Ectopic expression of EGL-5 in hermaphrodites is sufficient to induce male gonadal gene expression, indicating that EGL-5 plays an instructive role in male gonadal fate determination. EGL-5 acts in parallel with a Wnt/beta-catenin pathway to regulate male gonadal fates and can physically interact with the Wnt pathway transcription factor POP-1 and modulate activity of a POP-1 dependent reporter gene. We propose that EGL-5 imparts sex-specific function on POP-1 by recruiting it to male-specific gonadal target genes.
Collapse
Affiliation(s)
- Andrea K Kalis
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | |
Collapse
|
9
|
Maurel-Zaffran C, Pradel J, Graba Y. Reiterative use of signalling pathways controls multiple cellular events during Drosophila posterior spiracle organogenesis. Dev Biol 2010; 343:18-27. [PMID: 20403348 DOI: 10.1016/j.ydbio.2010.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 03/07/2010] [Accepted: 04/04/2010] [Indexed: 10/19/2022]
Abstract
Organogenesis proceeds in multiple steps and events that need to be coordinated in time and space. Yet the genetic and molecular control of such coordination remains poorly understood. In this study we have investigated the contribution of three signalling pathways, Wnt/Wingless (Wg), Hedgehog (Hh), and epidermal growth factor receptor (EGFR), to posterior spiracle morphogenesis, an organ that forms under Abdominal-B (AbdB) control in the eighth abdominal segment. Using targeted signalling inactivation, we show that these pathways are reiteratively used to control multiple cellular events during posterior spiracle organogenesis, including cell survival and maintenance of cell polarity and adhesion required for tissue integrity. We propose that the reiterative use of the Wg, Hh, and EGFR signalling pathways serves to coordinate in time and space the sequential deployment of events that collectively allow proper organogenesis.
Collapse
Affiliation(s)
- Corinne Maurel-Zaffran
- Institut de Biologie du Développement de Marseille Luminy, IBDML, CNRS, Université de la Méditerranée, Parc Scientifique de Luminy, Case 907 13288 Marseille Cedex 09, France.
| | | | | |
Collapse
|
10
|
Zhai Z, Fuchs AL, Lohmann I. Cellular analysis of newly identified Hox downstream genes in Drosophila. Eur J Cell Biol 2009; 89:273-8. [PMID: 20018403 DOI: 10.1016/j.ejcb.2009.11.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hox genes code for conserved homeodomain transcription factors, which act as regional regulators for the specification of segmental identities along the anterior-posterior axis in all animals studied. They execute their function mainly through the activation or repression of their downstream genes. We have recently identified a large number of genes to be directly or indirectly targeted by Hox proteins through gene expression profiling in the model organism Drosophila. However, the cell-specific regulation of these downstream genes and the functional significance of the regulation are largely unknown. We have validated and functionally studied many of the newly identified downstream genes of the Hox proteins Deformed (Dfd) and Abdominal-B (Abd-B), and provide evidence that Hox proteins regulate a diverse group of downstream genes, from transcription factors to realisators with major and minor roles during morphogenesis.
Collapse
Affiliation(s)
- Zongzhao Zhai
- BIOQUANT Center, Cluster of Excellence - CellNetworks, Heidelberg, University of Heidelberg, Im Neuenheimer Feld 267, D-69120 Heidelberg, Germany
| | | | | |
Collapse
|
11
|
Retinoic acid and Wnt/beta-catenin have complementary roles in anterior/posterior patterning embryos of the basal chordate amphioxus. Dev Biol 2009; 332:223-33. [PMID: 19497318 DOI: 10.1016/j.ydbio.2009.05.571] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 05/26/2009] [Accepted: 05/27/2009] [Indexed: 12/18/2022]
Abstract
A role for Wnt/beta-catenin signaling in axial patterning has been demonstrated in animals as basal as cnidarians, while roles in axial patterning for retinoic acid (RA) probably evolved in the deuterostomes and may be chordate-specific. In vertebrates, these two pathways interact both directly and indirectly. To investigate the evolutionary origins of interactions between these two pathways, we manipulated Wnt/beta-catenin and RA signaling in the basal chordate amphioxus during the gastrula stage, which is the RA-sensitive period for anterior/posterior (A/P) patterning. The results show that Wnt/beta-catenin and RA signaling have distinctly different roles in patterning the A/P axis of the amphioxus gastrula. Wnt/beta-catenin specifies the identity of the ends of the embryo (high Wnt = posterior; low Wnt = anterior) but not intervening positions. Thus, upregulation of Wnt/beta-catenin signaling induces ectopic expression of posterior markers at the anterior tip of the embryo. In contrast, RA specifies position along the A/P axis, but not the identity of the ends of the embryo-increased RA signaling strongly affects the domains of Hox expression along the A/P axis but has little or no effect on the expression of either anterior or posterior markers. Although the two pathways may both influence such things as specification of neuronal identity, interactions between them in A/P patterning appear to be minimal.
Collapse
|
12
|
Mann RS, Lelli KM, Joshi R. Hox specificity unique roles for cofactors and collaborators. Curr Top Dev Biol 2009; 88:63-101. [PMID: 19651302 DOI: 10.1016/s0070-2153(09)88003-4] [Citation(s) in RCA: 265] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hox proteins are well known for executing highly specific functions in vivo, but our understanding of the molecular mechanisms underlying gene regulation by these fascinating proteins has lagged behind. The premise of this review is that an understanding of gene regulation-by any transcription factor-requires the dissection of the cis-regulatory elements that they act upon. With this goal in mind, we review the concepts and ideas regarding gene regulation by Hox proteins and apply them to a curated list of directly regulated Hox cis-regulatory elements that have been validated in the literature. Our analysis of the Hox-binding sites within these elements suggests several emerging generalizations. We distinguish between Hox cofactors, proteins that bind DNA cooperatively with Hox proteins and thereby help with DNA-binding site selection, and Hox collaborators, proteins that bind in parallel to Hox-targeted cis-regulatory elements and dictate the sign and strength of gene regulation. Finally, we summarize insights that come from examining five X-ray crystal structures of Hox-cofactor-DNA complexes. Together, these analyses reveal an enormous amount of flexibility into how Hox proteins function to regulate gene expression, perhaps providing an explanation for why these factors have been central players in the evolution of morphological diversity in the animal kingdom.
Collapse
Affiliation(s)
- Richard S Mann
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | | | | |
Collapse
|
13
|
Ryan JF, Baxevanis AD. Hox, Wnt, and the evolution of the primary body axis: insights from the early-divergent phyla. Biol Direct 2007; 2:37. [PMID: 18078518 PMCID: PMC2222619 DOI: 10.1186/1745-6150-2-37] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 12/13/2007] [Indexed: 11/12/2022] Open
Abstract
The subkingdom Bilateria encompasses the overwhelming majority of animals, including all but four early-branching phyla: Porifera, Ctenophora, Placozoa, and Cnidaria. On average, these early-branching phyla have fewer cell types, tissues, and organs, and are considered to be significantly less specialized along their primary body axis. As such, they present an attractive outgroup from which to investigate how evolutionary changes in the genetic toolkit may have contributed to the emergence of the complex animal body plans of the Bilateria. This review offers an up-to-date glimpse of genome-scale comparisons between bilaterians and these early-diverging taxa. Specifically, we examine these data in the context of how they may explain the evolutionary development of primary body axes and axial symmetry across the Metazoa. Next, we re-evaluate the validity and evolutionary genomic relevance of the zootype hypothesis, which defines an animal by a specific spatial pattern of gene expression. Finally, we extend the hypothesis that Wnt genes may be the earliest primary body axis patterning mechanism by suggesting that Hox genes were co-opted into this patterning network prior to the last common ancestor of cnidarians and bilaterians.
Collapse
Affiliation(s)
- Joseph F Ryan
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Andreas D Baxevanis
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| |
Collapse
|
14
|
Takaesu NT, Bulanin DS, Johnson AN, Orenic TV, Newfeld SJ. A combinatorial enhancer recognized by Mad, TCF and Brinker first activates then represses dpp expression in the posterior spiracles of Drosophila. Dev Biol 2007; 313:829-43. [PMID: 18068697 DOI: 10.1016/j.ydbio.2007.10.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 09/28/2007] [Accepted: 10/18/2007] [Indexed: 10/22/2022]
Abstract
A previous genetic analysis of a reporter gene carrying a 375-bp region from a dpp intron (dppMX-lacZ) revealed that the Wingless and Dpp pathways are required to activate dpp expression in posterior spiracle formation. Here we report that within the dppMX region there is an enhancer with binding sites for TCF and Mad that are essential for activating dppMX expression in posterior spiracles. There is also a binding site for Brinker likely employed to repress dppMX expression. This combinatorial enhancer may be the first identified with the ability to integrate temporally distinct positive (TCF and Mad) and negative (Brinker) inputs in the same cells. Cuticle studies on a unique dpp mutant lacking this enhancer showed that it is required for viability and that the Filzkorper are U-shaped rather than straight. Together with gene expression data from these mutants and from brk mutants, our results suggest that there are two rounds of Dpp signaling in posterior spiracle development. The first round is associated with dorsal-ventral patterning and is necessary for designating the posterior spiracle field. The second is governed by the combinatorial enhancer and begins during germ band retraction. The second round appears necessary for proper spiracle internal morphology and fusion with the remainder of the tracheal system. Intriguingly, several aspects of dpp posterior spiracle expression and function are similar to demonstrated roles for Wnt and BMP signaling in proximal-distal outgrowth of the mammalian embryonic lung.
Collapse
Affiliation(s)
- Norma T Takaesu
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | | | | | | | | |
Collapse
|
15
|
Krattinger A, Gendre N, Ramaekers A, Grillenzoni N, Stocker RF. DmOAZ, the unique Drosophila melanogaster OAZ homologue is involved in posterior spiracle development. Dev Genes Evol 2007; 217:197-208. [PMID: 17323106 DOI: 10.1007/s00427-007-0134-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Accepted: 01/09/2007] [Indexed: 10/23/2022]
Abstract
In this paper, we study DmOAZ, the unique Drosophila melanogaster homologue of the OAZ zinc finger protein family. We show partial conservation of the zinc finger organization between DmOAZ and the vertebrate members of this family. We determine the exon/intron structure of the dmOAZ gene and deduce its open reading frame. Reverse transcriptase-polymerase chain reaction analysis shows that dmOAZ is transcribed throughout life. In the embryo, strongest DmOAZ expression is observed in the posterior spiracles. We suggest that dmOAZ acts as a secondary target of the Abd-B gene in posterior spiracle development, downstream of cut and ems. In a newly created loss-of-function mutant, dmOAZ ( 93 ), the "filzkörper" part of the posterior spiracles, is indeed structurally abnormal. The dmOAZ ( 93 ) mutant is a larval lethal, a phenotype that may be linked to the spiracular defect. Given the dmOAZ ( 93 ) mutant as a new tool, the fruit fly may provide an alternative model for analyzing in vivo the functions of OAZ family members.
Collapse
Affiliation(s)
- Anne Krattinger
- Department of Biology, University of Fribourg, Ch. du Musée 10, CH-1700, Fribourg, Switzerland
| | | | | | | | | |
Collapse
|
16
|
Lovegrove B, Simões S, Rivas ML, Sotillos S, Johnson K, Knust E, Jacinto A, Hombría JCG. Coordinated control of cell adhesion, polarity, and cytoskeleton underlies Hox-induced organogenesis in Drosophila. Curr Biol 2007; 16:2206-16. [PMID: 17113384 DOI: 10.1016/j.cub.2006.09.029] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 09/05/2006] [Accepted: 09/07/2006] [Indexed: 12/14/2022]
Abstract
BACKGROUND Hox genes control animal body plans by directing the morphogenesis of segment-specific structures. As transcription factors, HOX proteins achieve this through the activation of downstream target genes. Much research has been devoted to the search for these targets and the characterization of their roles in organogenesis. This has shown that the direct targets of Hox activation are often transcription factors or signaling molecules, which form hierarchical genetic networks directing the morphogenesis of particular organs. Importantly, very few of the direct Hox targets known are "realizator" genes involved directly in the cellular processes of organogenesis. RESULTS Here, we describe for the first time a complete network linking the Hox gene Abdominal-B to the realizator genes it controls during the organogenesis of the external respiratory organ of the larva. In this process, Abdominal-B induces the expression of four intermediate signaling molecules and transcription factors, and this expression results in the mosaic activation of several realizator genes. The ABD-B spiracle realizators include at least five cell-adhesion proteins, cell-polarity proteins, and GAP and GEF cytoskeleton regulators. Simultaneous ectopic expression of the Abd-B downstream targets can induce spiracle-like structure formation in the absence of ABD-B protein. CONCLUSION Hox realizators include cytoskeletal regulators and molecules required for the apico-basal cell organization. HOX-coordinated activation of these realizators in mosaic patterns confers to the organ primordium its assembling properties. We propose that during animal development, Hox-controlled genetic cascades coordinate the local cell-specific behaviors that result in organogenesis of segment-specific structures.
Collapse
Affiliation(s)
- Bridget Lovegrove
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Bondos S. Variations on a theme: Hox and Wnt combinatorial regulation during animal development. ACTA ACUST UNITED AC 2006; 2006:pe38. [PMID: 17018850 DOI: 10.1126/stke.3552006pe38] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Shockingly few transcription factors and cell signaling pathways are utilized to pattern organs and to specify the fate of a seemingly endless variety of unique cell types during animal development. This dichotomy led to the hypothesis that each factor is used in multiple tissues and that a combinatorial code of factors determines cell fate or tissue identity in a unique fashion. Two recent papers describe temporal changes in the interplay between Hox transcription factors, which specify positional identity, and Wnt signaling, which provides spatial information and promotes asymmetric cell division. These changes guide cells through a series of discrete steps, leading to unique fates. Variations between these two studies highlight the diversifying potential of combinatorial regulation, in short, that the pathways through which these molecules interact can vary even between adjacent cells. Shared features include cross-regulatory interactions to redeploy patterning genes in a tissue-specific manner for organogenesis and coregulation of common downstream targets. Identification of additional combinatorial gene targets and elucidation of their underlying molecular mechanisms are important future tasks in developmental biology and the study of evolution.
Collapse
Affiliation(s)
- Sarah Bondos
- Department of Biochemistry and Cell Biology, Rice University, 6100 South Main Street, Houston, TX 77005, USA.
| |
Collapse
|
18
|
Shippy TD, Rogers CD, Beeman RW, Brown SJ, Denell RE. The Tribolium castaneum ortholog of Sex combs reduced controls dorsal ridge development. Genetics 2006; 174:297-307. [PMID: 16849608 PMCID: PMC1569817 DOI: 10.1534/genetics.106.058610] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In insects, the boundary between the embryonic head and thorax is formed by the dorsal ridge, a fused structure composed of portions of the maxillary and labial segments. However, the mechanisms that promote development of this unusual structure remain a mystery. In Drosophila, mutations in the Hox genes Sex combs reduced and Deformed have been reported to cause abnormal dorsal ridge formation, but the significance of these abnormalities is not clear. We have identified three mutant allele classes of Cephalothorax, the Tribolium castaneum (red flour beetle) ortholog of Sex combs reduced, each of which has a different effect on dorsal ridge development. By using Engrailed expression to monitor dorsal ridge development in these mutants, we demonstrate that Cephalothorax promotes the fusion and subsequent dorsolateral extension of the maxillary and labial Engrailed stripes (posterior compartments) during dorsal ridge formation. Molecular and genetic analysis of these alleles indicates that the N terminus of Cephalothorax is important for the fusion step, but is dispensable for Engrailed stripe extension. Thus, we find that specific regions of Cephalothorax are required for discrete steps in dorsal ridge formation.
Collapse
Affiliation(s)
- Teresa D Shippy
- Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA
| | | | | | | | | |
Collapse
|
19
|
Barmina O, Gonzalo M, McIntyre LM, Kopp A. Sex- and segment-specific modulation of gene expression profiles in Drosophila. Dev Biol 2005; 288:528-44. [PMID: 16269142 DOI: 10.1016/j.ydbio.2005.09.052] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Revised: 09/28/2005] [Accepted: 09/30/2005] [Indexed: 10/25/2022]
Abstract
Homeotic and sex-determining genes control a wide range of morphological traits by regulating the expression of different target genes in different tissues. The identity of most of these target genes remains unknown, and it is not even clear what fraction of the genome is regulated in a segment- and sex-specific manner. In this report, we examine segment- and sex-specific gene expression in Drosophila pupal legs. The first and second legs in Drosophila have clearly distinguishable bristle patterns. Bristle pattern in the first leg also differs between males and females, whereas the second leg has no overt sexual dimorphism. To identify the genes responsible for these differences, we compared transcriptional profiles between male and female first and second legs during early pupal development. The extent of sexually dimorphic gene expression parallels morphological differences: over 100 genes are expressed sex specifically in the first leg, whereas no sexual differences are seen in the second leg. Segmental differences are less extensive than sexual dimorphism and involve fewer than 14 genes. We have identified a novel gene, CG13857, that is expressed exclusively in the first leg in a pattern that suggests this gene may play an important role in specifying segment- and sex-specific bristle patterns.
Collapse
Affiliation(s)
- Olga Barmina
- Section of Evolution and Ecology, Center for Genetics and Development, University of California-Davis, One Shields Ave., Davis, CA 95616, USA
| | | | | | | |
Collapse
|