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Juárez-Morales JL, Weierud F, England SJ, Demby C, Santos N, Grieb G, Mazan S, Lewis KE. Evolution of lbx spinal cord expression and function. Evol Dev 2021; 23:404-422. [PMID: 34411410 DOI: 10.1111/ede.12387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 06/04/2021] [Accepted: 06/21/2021] [Indexed: 11/29/2022]
Abstract
Ladybird homeobox (Lbx) transcription factors have crucial functions in muscle and nervous system development in many animals. Amniotes have two Lbx genes, but only Lbx1 is expressed in spinal cord. In contrast, teleosts have three lbx genes and we show here that zebrafish lbx1a, lbx1b, and lbx2 are expressed by distinct spinal cell types, and that lbx1a is expressed in dI4, dI5, and dI6 interneurons, as in amniotes. Our data examining lbx expression in Scyliorhinus canicula and Xenopus tropicalis suggest that the spinal interneuron expression of zebrafish lbx1a is ancestral, whereas lbx1b has acquired a new expression pattern in spinal cord progenitor cells. lbx2 spinal expression was probably acquired in the ray-finned lineage, as this gene is not expressed in the spinal cords of either amniotes or S. canicula. We also show that the spinal function of zebrafish lbx1a is conserved with mouse Lbx1. In zebrafish lbx1a mutants, there is a reduction in the number of inhibitory spinal interneurons and an increase in the number of excitatory spinal interneurons, similar to mouse Lbx1 mutants. Interestingly, the number of inhibitory spinal interneurons is also reduced in lbx1b mutants, although in this case the number of excitatory interneurons is not increased. lbx1a;lbx1b double mutants have a similar spinal interneuron phenotype to lbx1a single mutants. Taken together these data suggest that lbx1b and lbx1a may be required in succession for correct specification of dI4 and dI6 spinal interneurons, although only lbx1a is required for suppression of excitatory fates in these cells.
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Affiliation(s)
| | - Frida Weierud
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | | | - Celia Demby
- Department of Biology, Syracuse University, Syracuse, New York, USA
| | - Nicole Santos
- Department of Biology, Syracuse University, Syracuse, New York, USA
| | - Ginny Grieb
- Department of Biology, Syracuse University, Syracuse, New York, USA
| | - Sylvie Mazan
- Biologie Intégrative des Organismes Marins, UMR 7232 CNRS, Observatoire Océanologique, Sorbonne Université, Banyuls-sur-Mer, France
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Treffkorn S, Kahnke L, Hering L, Mayer G. Expression of NK cluster genes in the onychophoran Euperipatoides rowelli: implications for the evolution of NK family genes in nephrozoans. EvoDevo 2018; 9:17. [PMID: 30026904 PMCID: PMC6050708 DOI: 10.1186/s13227-018-0105-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 07/06/2018] [Indexed: 02/05/2023] Open
Abstract
Background Understanding the evolution and development of morphological traits of the last common bilaterian ancestor is a major goal of the evo-devo discipline. The reconstruction of this "urbilaterian" is mainly based on comparative studies of common molecular patterning mechanisms in recent model organisms. The NK homeobox genes are key players in many of these molecular pathways, including processes regulating mesoderm, heart and neural development. Shared features seen in the expression patterns of NK genes have been used to determine the ancestral bilaterian characters. However, the commonly used model organisms provide only a limited view on the evolution of these molecular pathways. To further investigate the ancestral roles of NK cluster genes, we analyzed their expression patterns in the onychophoran Euperipatoides rowelli. Results We identified nine transcripts of NK cluster genes in E. rowelli, including single copies of NK1, NK3, NK4, NK5, Msx, Lbx and Tlx, and two copies of NK6. All of these genes except for NK6.1 and NK6.2 are expressed in different mesodermal organs and tissues in embryos of E. rowelli, including the anlagen of somatic musculature and the heart. Furthermore, we found distinct expression patterns of NK3, NK5, NK6, Lbx and Msx in the developing nervous system. The same holds true for the NKL gene NK2.2, which does not belong to the NK cluster but is a related gene playing a role in neural patterning. Surprisingly, NK1, Msx and Lbx are additionally expressed in a segment polarity-like pattern early in development-a feature that has been otherwise reported only from annelids. Conclusion Our results indicate that the NK cluster genes were involved in mesoderm and neural development in the last common ancestor of bilaterians or at least nephrozoans (i.e., bilaterians to the exclusion of xenacoelomorphs). By comparing our data from an onychophoran to those from other bilaterians, we critically review the hypothesis of a complex "urbilaterian" with a segmented body, a pulsatile organ or heart, and a condensed mediolaterally patterned nerve cord.
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Affiliation(s)
- Sandra Treffkorn
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Laura Kahnke
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Lars Hering
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
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Zhao Y, Gao P, Li W, Zhang Y, Xu K, Guo X, Li B, Cao G. Study on the Developmental Expression ofLbx1Gene inLongissimus Dorsiof Mashen and Large White Pigs. ITALIAN JOURNAL OF ANIMAL SCIENCE 2016. [DOI: 10.4081/ijas.2015.3720] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Wotton KR, Schubert FR, Dietrich S. Hypaxial muscle: controversial classification and controversial data? Results Probl Cell Differ 2015; 56:25-48. [PMID: 25344665 DOI: 10.1007/978-3-662-44608-9_2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypaxial muscle is the anatomical term commonly used when referring to all the ventrally located musculature in the body of vertebrates, including muscles of the body wall and the limbs. Yet these muscles had very humble beginnings when vertebrates evolved from their chordate ancestors, and complex anatomical changes and changes in underlying gene regulatory networks occurred. This review summarises the current knowledge and controversies regarding the development and evolution of hypaxial muscles.
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Affiliation(s)
- Karl R Wotton
- EMBL/CRG Systems Biology Research Unit, Centre for Genomic Regulation (CRG), Dr. Aiguader 88, 08003, Barcelona, Spain
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Balakirev ES, Anisimova M, Ayala FJ. Complex interplay of evolutionary forces in the ladybird homeobox genes of Drosophila melanogaster. PLoS One 2011; 6:e22613. [PMID: 21799919 PMCID: PMC3142176 DOI: 10.1371/journal.pone.0022613] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 06/29/2011] [Indexed: 11/19/2022] Open
Abstract
Tandemly arranged paralogous genes lbe and lbl are members of the Drosophila NK homeobox family. We analyzed population samples of Drosophila melanogaster from Africa, Europe, North and South America, and single strains of D. sechellia, D. simulans, and D. yakuba within two linked regions encompassing partial sequences of lbe and lbl. The evolution of lbe and lbl is highly constrained due to their important regulatory functions. Despite this, a variety of forces have shaped the patterns of variation in lb genes: recombination, intragenic gene conversion and natural selection strongly influence background variation created by linkage disequilibrium and dimorphic haplotype structure. The two genes exhibited similar levels of nucleotide diversity and positive selection was detected in the noncoding regions of both genes. However, synonymous variability was significantly higher for lbe: no nonsynonymous changes were observed in this gene. We argue that balancing selection impacts some synonymous sites of the lbe gene. Stability of mRNA secondary structure was significantly different between the lbe (but not lbl) haplotype groups and may represent a driving force of balancing selection in epistatically interacting synonymous sites. Balancing selection on synonymous sites may be the first, or one of a few such observations, in Drosophila. In contrast, recurrent positive selection on lbl at the protein level influenced evolution at three codon sites. Transcription factor binding-site profiles were different for lbe and lbl, suggesting that their developmental functions are not redundant. Combined with our previous results on nucleotide variation in esterase and other homeobox genes, these results suggest that interplay of balancing and directional selection may be a general feature of molecular evolution in Drosophila and other eukaryote genomes.
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Affiliation(s)
- Evgeniy S Balakirev
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, California, United States of America.
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Moisan V, Robert NM, Tremblay JJ. Expression of ladybird-like homeobox 2 (LBX2) during ovarian development and folliculogenesis in the mouse. J Mol Histol 2010; 41:289-94. [PMID: 20820887 DOI: 10.1007/s10735-010-9291-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Accepted: 08/26/2010] [Indexed: 01/16/2023]
Abstract
The Ladybird-like homeobox gene 2 (Lbx2) belongs to the homeodomain-containing family of transcription factor that are known to play crucial role in various developmental processes. During early mouse embryogenesis, Lbx2 was shown to be expressed in the developing eye, brain and urogenital system. Although Lbx2 was detected in the testis and epididymis throughout development, no data was available regarding its expression in the female gonad. Here we have determined Lbx2 expression throughout mouse ovarian development by in situ hybridization. In contrast to the strong expression in the male fetal gonad, no Lbx2 signal could be detected in the fetal ovary. Soon after birth, however, Lbx2 expression was detected at different levels in various ovarian compartments (oocyte, granulosa cells, theca cells) where its expression was highly dynamic depending on the stage of follicular maturation. Our data would be consistent with a role for LBX2 in ovarian maturation and folliculogenesis.
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Affiliation(s)
- Vanessa Moisan
- Reproduction, Perinatal and Child Health, CHUQ Research Centre, CHUL Room T1-49, 2705 Laurier Blvd, Quebec City, QC G1V 4G2, Canada.
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Wotton KR, Weierud FK, Juárez-Morales JL, Alvares LE, Dietrich S, Lewis KE. Conservation of gene linkage in dispersed vertebrate NK homeobox clusters. Dev Genes Evol 2010; 219:481-96. [PMID: 20112453 DOI: 10.1007/s00427-009-0311-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nk homeobox genes are important regulators of many different developmental processes including muscle, heart, central nervous system and sensory organ development. They are thought to have arisen as part of the ANTP megacluster, which also gave rise to Hox and ParaHox genes, and at least some NK genes remain tightly linked in all animals examined so far. The protostome-deuterostome ancestor probably contained a cluster of nine Nk genes: (Msx)-(Nk4/tinman)-(Nk3/bagpipe)-(Lbx/ladybird)-(Tlx/c15)-(Nk7)-(Nk6/hgtx)-(Nk1/slouch)-(Nk5/Hmx). Of these genes, only NKX2.6-NKX3.1, LBX1-TLX1 and LBX2-TLX2 remain tightly linked in humans. However, it is currently unclear whether this is unique to the human genome as we do not know which of these Nk genes are clustered in other vertebrates. This makes it difficult to assess whether the remaining linkages are due to selective pressures or because chance rearrangements have "missed" certain genes. In this paper, we identify all of the paralogs of these ancestrally clustered NK genes in several distinct vertebrates. We demonstrate that tight linkages of Lbx1-Tlx1, Lbx2-Tlx2 and Nkx3.1-Nkx2.6 have been widely maintained in both the ray-finned and lobe-finned fish lineages. Moreover, the recently duplicated Hmx2-Hmx3 genes are also tightly linked. Finally, we show that Lbx1-Tlx1 and Hmx2-Hmx3 are flanked by highly conserved noncoding elements, suggesting that shared regulatory regions may have resulted in evolutionary pressure to maintain these linkages. Consistent with this, these pairs of genes have overlapping expression domains. In contrast, Lbx2-Tlx2 and Nkx3.1-Nkx2.6, which do not seem to be coexpressed, are also not associated with conserved noncoding sequences, suggesting that an alternative mechanism may be responsible for the continued clustering of these genes.
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Affiliation(s)
- Karl R Wotton
- Department of Craniofacial Development, King's College London, Floor 27 Guy's Tower, Guy's Hospital, London Bridge, London, SE1 9RT, UK
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Wotton KR, Weierud FK, Dietrich S, Lewis KE. Comparative genomics of Lbx loci reveals conservation of identical Lbx ohnologs in bony vertebrates. BMC Evol Biol 2008; 8:171. [PMID: 18541024 PMCID: PMC2446394 DOI: 10.1186/1471-2148-8-171] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 06/09/2008] [Indexed: 01/07/2023] Open
Abstract
Background Lbx/ladybird genes originated as part of the metazoan cluster of Nk homeobox genes. In all animals investigated so far, both the protostome genes and the vertebrate Lbx1 genes were found to play crucial roles in neural and muscle development. Recently however, additional Lbx genes with divergent expression patterns were discovered in amniotes. Early in the evolution of vertebrates, two rounds of whole genome duplication are thought to have occurred, during which 4 Lbx genes were generated. Which of these genes were maintained in extant vertebrates, and how these genes and their functions evolved, is not known. Results Here we searched vertebrate genomes for Lbx genes and discovered novel members of this gene family. We also identified signature genes linked to particular Lbx loci and traced the remnants of 4 Lbx paralogons (two of which retain Lbx genes) in amniotes. In teleosts, that have undergone an additional genome duplication, 8 Lbx paralogons (three of which retain Lbx genes) were found. Phylogenetic analyses of Lbx and Lbx-associated genes show that in extant, bony vertebrates only Lbx1- and Lbx2-type genes are maintained. Of these, some Lbx2 sequences evolved faster and were probably subject to neofunctionalisation, while Lbx1 genes may have retained more features of the ancestral Lbx gene. Genes at Lbx1 and former Lbx4 loci are more closely related, as are genes at Lbx2 and former Lbx3 loci. This suggests that during the second vertebrate genome duplication, Lbx1/4 and Lbx2/3 paralogons were generated from the duplicated Lbx loci created during the first duplication event. Conclusion Our study establishes for the first time the evolutionary history of Lbx genes in bony vertebrates, including the order of gene duplication events, gene loss and phylogenetic relationships. Moreover, we identified genetic hallmarks for each of the Lbx paralogons that can be used to trace Lbx genes as other vertebrate genomes become available. Significantly, we show that bony vertebrates only retained copies of Lbx1 and Lbx2 genes, with some Lbx2 genes being highly divergent. Thus, we have established a base on which the evolution of Lbx gene function in vertebrate development can be evaluated.
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Affiliation(s)
- Karl R Wotton
- King's College London, Department of Craniofacial Development, Floor 27 Guy's Tower, Guy's Hospital, London Bridge, London, SE1 9RT, UK.
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Moisan V, Bomgardner D, Tremblay JJ. Expression of the Ladybird-like homeobox 2 transcription factor in the developing mouse testis and epididymis. BMC DEVELOPMENTAL BIOLOGY 2008; 8:22. [PMID: 18304314 PMCID: PMC2277406 DOI: 10.1186/1471-213x-8-22] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Accepted: 02/27/2008] [Indexed: 02/04/2023]
Abstract
BACKGROUND Homeoproteins are a class of transcription factors that are well-known regulators of organogenesis and cell differentiation in numerous tissues, including the male reproductive system. Indeed, a handful of homeoproteins have so far been identified in the testis and epididymis where a few were shown to play important developmental roles. Through a degenerate PCR approach aimed at identifying novel homeoproteins expressed in the male reproductive system, we have detected several homeoproteins most of which had never been described before in this tissue. One of these homeoproteins is Ladybird-like homeobox 2 (Lbx2), a homeobox factor mostly known to be expressed in the nervous system. RESULTS To better define the expression profile of Lbx2 in the male reproductive system, we have performed in situ hybridization throughout testicular and epididymal development and into adulthood. Lbx2 expression was also confirmed by real time RT-PCR in those tissues and in several testicular and epididymal cell lines. In the epididymis, a highly segmented tissue, Lbx2 shows a regionalized expression profile, being more expressed in proximal segments of the caput epididymis than any other segment. In the testis, we found that Lbx2 is constitutively expressed at high levels in Sertoli cells. In interstitial cells, Lbx2 is weakly expressed during fetal and early postnatal life, highly expressed around P32-P36, and absent in adult animals. Finally, Lbx2 can also be detected in a population of germ cells in adults. CONCLUSION Altogether, our data suggest that the homeoprotein Lbx2 might be involved in the regulation of male reproductive system development and cell differentiation as well as in male epididymal segmentation.
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Affiliation(s)
- Vanessa Moisan
- Ontogeny-Reproduction Research Unit, CHUQ Research Centre (CHUL), Québec City, Québec, Canada.
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Saudemont A, Dray N, Hudry B, Le Gouar M, Vervoort M, Balavoine G. Complementary striped expression patterns of NK homeobox genes during segment formation in the annelid Platynereis. Dev Biol 2008; 317:430-43. [PMID: 18343360 DOI: 10.1016/j.ydbio.2008.02.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Revised: 01/31/2008] [Accepted: 02/05/2008] [Indexed: 11/18/2022]
Abstract
NK genes are related pan-metazoan homeobox genes. In the fruitfly, NK genes are clustered and involved in patterning various mesodermal derivatives during embryogenesis. It was therefore suggested that the NK cluster emerged in evolution as an ancestral mesodermal patterning cluster. To test this hypothesis, we cloned and analysed the expression patterns of the homologues of NK cluster genes Msx, NK4, NK3, Lbx, Tlx, NK1 and NK5 in the marine annelid Platynereis dumerilii, a representative of trochozoans, the third great branch of bilaterian animals alongside deuterostomes and ecdysozoans. We found that most of these genes are involved, as they are in the fly, in the specification of distinct mesodermal derivatives, notably subsets of muscle precursors. The expression of the homologue of NK4/tinman in the pulsatile dorsal vessel of Platynereis strongly supports the hypothesis that the vertebrate heart derived from a dorsal vessel relocated to a ventral position by D/V axis inversion in a chordate ancestor. Additionally and more surprisingly, NK4, Lbx, Msx, Tlx and NK1 orthologues are expressed in complementary sets of stripes in the ectoderm and/or mesoderm of forming segments, suggesting an involvement in the segment formation process. A potentially ancient role of the NK cluster genes in segment formation, unsuspected from vertebrate and fruitfly studies so far, now deserves to be investigated in other bilaterian species, especially non-insect arthropods and onychophorans.
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Affiliation(s)
- Alexandra Saudemont
- Centre de Génétique Moléculaire, CNRS UPR 2167, 1 avenue de la terrasse, 91198 Gif-sur-Yvette, France
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Wei K, Chen J, Akrami K, Sekhon R, Chen F. Generation of mice deficient for Lbx2, a gene expressed in the urogenital system, nervous system, and Pax3 dependent tissues. Genesis 2007; 45:361-8. [PMID: 17492753 DOI: 10.1002/dvg.20302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Lbx2 is a member of the ladybird family of homeobox genes. The first murine ortholog identified, Lbx1, is required for hypaxial musculature and dorsal spinal cord neuron development. The second murine ortholog, Lbx2, is expressed in the developing urogenital and nervous systems. To elucidate the function of Lbx2, we generated a gene-targeted allele of Lbx2 in mice. Lbx2 deficiency did not impair mouse development, and Lbx2 null mice appeared healthy and fertile. Replacement of Lbx2 by the lacZ gene provides a valuable histological marker for Lbx2-expressing cells. Given the important role of Pax3 in neural crest, we intercrossed our Lbx2 deficient mice with Splotch Pax3 mutant mice to determine if Pax3 affects Lbx2 expression. There was reduced Lbx2 expression in dorsal root ganglia and cranial nerve ganglia with Pax3 deficiency, but not in the genital tubercle. This suggested that Pax3 is required for Lbx2 expression in affected neural crest-derived tissues.
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Affiliation(s)
- Ke Wei
- Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
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