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Mulley JF. Regulation of posterior Hox genes by sex steroids explains vertebral variation in inbred mouse strains. J Anat 2022; 240:735-745. [PMID: 34747015 PMCID: PMC8930804 DOI: 10.1111/joa.13580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/08/2021] [Accepted: 10/21/2021] [Indexed: 11/29/2022] Open
Abstract
A series of elegant embryo transfer experiments in the 1950s demonstrated that the uterine environment could alter vertebral patterning in inbred mouse strains. In the intervening decades, attention has tended to focus on the technical achievements involved and neglected the underlying biological question: how can genetically homogenous individuals have a heterogenous number of vertebrae? Here I revisit these experiments and, with the benefit of knowledge of the molecular-level processes of vertebral patterning gained over the intervening decades, suggest a novel hypothesis for homeotic transformation of the last lumbar vertebra to the adjacent sacral type through regulation of Hox genes by sex steroids. Hox genes are involved in both axial patterning and development of male and female reproductive systems and have been shown to be sensitive to sex steroids in vitro and in vivo. Regulation of these genes by sex steroids and resulting alterations to vertebral patterning may hint at a deep evolutionary link between the ribless lumbar region of mammals and the switch from egg-laying to embryo implantation. An appreciation of the impact of sex steroids on Hox genes may explain some puzzling aspects of human disease, and highlights the spine as a neglected target for in utero exposure to endocrine disruptors.
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2
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Sefton EM, Bhullar BAS, Mohaddes Z, Hanken J. Evolution of the head-trunk interface in tetrapod vertebrates. eLife 2016; 5:e09972. [PMID: 27090084 PMCID: PMC4841772 DOI: 10.7554/elife.09972] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 03/16/2016] [Indexed: 12/15/2022] Open
Abstract
Vertebrate neck musculature spans the transition zone between head and trunk. The extent to which the cucullaris muscle is a cranial muscle allied with the gill levators of anamniotes or is instead a trunk muscle is an ongoing debate. Novel computed tomography datasets reveal broad conservation of the cucullaris in gnathostomes, including coelacanth and caecilian, two sarcopterygians previously thought to lack it. In chicken, lateral plate mesoderm (LPM) adjacent to occipital somites is a recently identified embryonic source of cervical musculature. We fate-map this mesoderm in the axolotl (Ambystoma mexicanum), which retains external gills, and demonstrate its contribution to posterior gill-levator muscles and the cucullaris. Accordingly, LPM adjacent to the occipital somites should be regarded as posterior cranial mesoderm. The axial position of the head-trunk border in axolotl is congruent between LPM and somitic mesoderm, unlike in chicken and possibly other amniotes.
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Affiliation(s)
- Elizabeth M Sefton
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.,Museum of Comparative Zoology, Harvard University, Cambridge, United States
| | - Bhart-Anjan S Bhullar
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.,Museum of Comparative Zoology, Harvard University, Cambridge, United States.,Department of Organismal Biology and Anatomy, University of Chicago, Chicago, United States.,Department of Geology and Geophysics, Yale University, New Haven, United States.,Yale Peabody Museum of Natural History, Yale University, New Haven, United States
| | - Zahra Mohaddes
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.,Museum of Comparative Zoology, Harvard University, Cambridge, United States
| | - James Hanken
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.,Museum of Comparative Zoology, Harvard University, Cambridge, United States
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3
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Meyer MR, Williams SA, Smith MP, Sawyer GJ. Lucy's back: Reassessment of fossils associated with the A.L. 288-1 vertebral column. J Hum Evol 2015; 85:174-80. [DOI: 10.1016/j.jhevol.2015.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 05/10/2015] [Accepted: 05/13/2015] [Indexed: 10/23/2022]
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4
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Krück S, Nesemann J, Scaal M. Development of somites, muscle, and skeleton is independent of signals from the wolffian duct. Dev Dyn 2013; 242:941-8. [DOI: 10.1002/dvdy.23986] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/16/2013] [Accepted: 05/01/2013] [Indexed: 11/09/2022] Open
Affiliation(s)
| | - Johanna Nesemann
- Institute of Anatomy and Cell Biology; Department of Molecular Embryology; University of Freiburg; Freiburg; Germany
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5
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Pu Q, Bai Z, Haque Z, Wang J, Huang R. Occipital somites guide motor axons of the accessory nerve in the avian embryo. Neuroscience 2013; 246:22-7. [PMID: 23632169 DOI: 10.1016/j.neuroscience.2013.04.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 04/04/2013] [Accepted: 04/18/2013] [Indexed: 10/26/2022]
Abstract
The accessory nerve (nervus accessorius) displays a unique organization in that its axons ascend along the rostrocaudal axis after exiting the cervical spinal cord and medulla oblongata and thereafter project ventrally into the periphery at the first somite level. Little is known about how this organization is achieved. We have investigated the role of somites in the guidance of motor axons of the accessory nerve using heterotopic transplantations of somites in avian embryos. The formation of not only accessory nerve but also the vagal nerve was affected, when a more caudal occipital somite (somites 2-4) was grafted to the position of the first occipital somite. Our study reveals that only the first occipital somite permits the development of ventral projection of accessory axons, a process that is inhibited by more caudal occipital somites.
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Affiliation(s)
- Q Pu
- Department of Neuroanatomy, Institute of Anatomy, University of Bonn, Germany
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6
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Guinard G, Marchand D. Modularity and Complete Natural Homeoses in Cervical Vertebrae of Extant and Extinct Penguins (Aves: Sphenisciformes). Evol Biol 2010. [DOI: 10.1007/s11692-010-9097-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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7
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Wang B, Pu Q, De R, Patel K, Christ B, Wilting J, Huang R. Commitment of chondrogenic precursors of the avian scapula takes place after epithelial-mesenchymal transition of the dermomyotome. BMC DEVELOPMENTAL BIOLOGY 2010; 10:91. [PMID: 20807426 PMCID: PMC2936895 DOI: 10.1186/1471-213x-10-91] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 08/31/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Cells of the epithelially organised dermomyotome are traditionally believed to give rise to skeletal muscle and dermis. We have previously shown that the dermomyotome can undergo epithelial-mesenchymal transition (EMT) and give rise to chondrogenic cells, which go on to form the scapula blade in birds. At present we have little understanding regarding the issue of when the chondrogenic fate of dermomyotomal cells is determined. Using quail-chick grafting experiments, we investigated whether scapula precursor cells are committed to a chondrogenic fate while in an epithelial state or whether commitment is established after EMT. RESULTS We show that the hypaxial dermomyotome, which normally forms the scapula, does not generate cartilaginous tissue after it is grafted to the epaxial domain. In contrast engraftment of the epaxial dermomyotome to the hypaxial domain gives rise to scapula-like cartilage. However, the hypaxial sub-ectodermal mesenchyme (SEM), which originates from the hypaxial dermomyotome after EMT, generates cartilaginous elements in the epaxial domain, whereas in reciprocal grafting experiments, the epaxial SEM cannot form cartilage in the hypaxial domain. CONCLUSIONS We suggest that the epithelial cells of the dermomyotome are not committed to the chondrogenic lineage. Commitment to this lineage occurs after it has undergone EMT to form the sub-ectodermal mesenchyme.
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Affiliation(s)
- Baigang Wang
- Department of Anatomy and Cell Biology, University of Goettingen, Kreuzbergring 36, 37075 Goettingen, Germany.
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8
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Geetha-Loganathan P, Nimmagadda S, Christ B, Huang R, Scaal M. Ectodermal Wnt6 is an early negative regulator of limb chondrogenesis in the chicken embryo. BMC DEVELOPMENTAL BIOLOGY 2010; 10:32. [PMID: 20334703 PMCID: PMC2859743 DOI: 10.1186/1471-213x-10-32] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 03/25/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Pattern formation of the limb skeleton is regulated by a complex interplay of signaling centers located in the ectodermal sheath and mesenchymal core of the limb anlagen, which results, in the forelimb, in the coordinate array of humerus, radius, ulna, carpals, metacarpals and digits. Much less understood is why skeletal elements form only in the central mesenchyme of the limb, whereas muscle anlagen develop in the peripheral mesenchyme ensheathing the chondrogenic center. Classical studies have suggested a role of the limb ectoderm as a negative regulator of limb chondrogenesis. RESULTS In this paper, we investigated the molecular nature of the inhibitory influence of the ectoderm on limb chondrogenesis in the avian embryo in vivo. We show that ectoderm ablation in the early limb bud leads to increased and ectopic expression of early chondrogenic marker genes like Sox9 and Collagen II, indicating that the limb ectoderm inhibits limb chondrogenesis at an early stage of the chondrogenic cascade. To investigate the molecular nature of the inhibitory influence of the ectoderm, we ectopically expressed Wnt6, which is presently the only known Wnt expressed throughout the avian limb ectoderm, and found that Wnt6 overexpression leads to reduced expression of the early chondrogenic marker genes Sox9 and Collagen II. CONCLUSION Our results suggest that the inhibitory influence of the ectoderm on limb chondrogenesis acts on an early stage of chondrogenesis upsteam of Sox9 and Collagen II. We identify Wnt6 as a candidate mediator of ectodermal chondrogenic inhibition in vivo. We propose a model of Wnt-mediated centripetal patterning of the limb by the surface ectoderm.
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Affiliation(s)
- Poongodi Geetha-Loganathan
- Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Freiburg, Germany.
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9
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Rustamzadeh E, Graupman PC, Lam CH. Basicranial diplomyelia: an extension of the split cord malformation theory. Case report. J Neurosurg 2006; 104:362-5. [PMID: 16848097 DOI: 10.3171/ped.2006.104.5.362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Basicranial diastematomyelia is an extremely rare congenital disorder. A review of the literature indicates only one reported case of basicranial diastematomyelia in which an osseous peg divided the brainstem in two. The authors present the first reported case of basicranial diplomyelia split by a fibrous band and correlate its pathogenesis with that of split cord malformation (SCM). The patient described in the present report had a fibrous stalk dividing the brainstem, and therefore the condition was categorized as a diplomyelia, or SCM Type II. Because the occipital dermatomes behave similarly to the spinal dermatomes early in development, they may be subject to the same embryonic error that results in SCM. The authors propose that the mechanism leading to SCM is the same as that found in basicranial split malformations and that the theory explaining it be modified to include the posterior fossa.
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Affiliation(s)
- Edward Rustamzadeh
- Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota 55455, USA
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10
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Abstract
Unraveling the complex tissue interactions necessary to generate the structural and functional diversity present among craniofacial muscles is challenging. These muscles initiate their development within a mesenchymal population bounded by the brain, pharyngeal endoderm, surface ectoderm, and neural crest cells. This set of spatial relations, and in particular the segmental properties of these adjacent tissues, are unique to the head. Additionally, the lack of early epithelialization in head mesoderm necessitates strategies for generating discrete myogenic foci that may differ from those operating in the trunk. Molecular data indeed indicate dissimilar methods of regulation, yet transplantation studies suggest that some head and trunk myogenic populations are interchangeable. The first goal of this review is to present key features of these diversities, identifying and comparing tissue and molecular interactions regulating myogenesis in the head and trunk. Our second focus is on the diverse morphogenetic movements exhibited by craniofacial muscles. Precursors of tongue muscles partly mimic migrations of appendicular myoblasts, whereas myoblasts destined to form extraocular muscles condense within paraxial mesoderm, then as large cohorts they cross the mesoderm:neural crest interface en route to periocular regions. Branchial muscle precursors exhibit yet another strategy, establishing contacts with neural crest populations before branchial arch formation and maintaining these relations through subsequent stages of morphogenesis. With many of the prerequisite stepping-stones in our knowledge of craniofacial myogenesis now in place, discovering the cellular and molecular interactions necessary to initiate and sustain the differentiation and morphogenesis of these neglected craniofacial muscles is now an attainable goal.
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Affiliation(s)
- Drew M Noden
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
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11
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Adham IM, Gille M, Gamel AJ, Reis A, Dressel R, Steding G, Brand-Saberi B, Engel W. The scoliosis (sco) mouse: a new allele of Pax1. Cytogenet Genome Res 2005; 111:16-26. [PMID: 16093716 DOI: 10.1159/000085665] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Accepted: 12/20/2004] [Indexed: 11/19/2022] Open
Abstract
We describe the spontaneous mutant mouse scoliosis (sco) that carries a new allele of Pax1 (un-i, undulated intermediate). The Pax1(un-i) allele is lacking the 5'-flanking region and exon 1 to 4 which is mapped to nt -2636 to -640 and -272 to 4271 of the Pax1 gene. Homozygous mice show a mild form of the known phenotypes of other Pax1 mutants. Adult mice have a lumbar scoliosis and kinky tails. In homozygous embryos the skeleton ossifies early, ossification centers of the vertebral bodies are fused with the ossification centers of the pedicles. Neural arches and spinous processes are underdeveloped but the pedicles and transverse processes are overdeveloped which is in contrast to other Pax1 mutants. In the scapula, the acromion is missing and the deltoid tuberosity of the proximal humerus is shortened and thickened. Among the inner organs the thymus development is affected. In late embryos, the thymus is small and thymocyte numbers are reduced. T-cell development from CD4- and CD8- double negative (DN) to CD4+ and CD8+ double positive (DP) is decelerated. The percentage of CD90+ cells is also reduced but in contrast to other Pax1 mutants no alteration of the expression level of the CD90 (Thy-1) could be found.
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Affiliation(s)
- I M Adham
- Institute of Human Genetics, University of Göttingen, Göttingen, Germany
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12
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Wang B, He L, Ehehalt F, Geetha-Loganathan P, Nimmagadda S, Christ B, Scaal M, Huang R. The formation of the avian scapula blade takes place in the hypaxial domain of the somites and requires somatopleure-derived BMP signals. Dev Biol 2005; 287:11-8. [PMID: 16202988 DOI: 10.1016/j.ydbio.2005.08.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 07/26/2005] [Accepted: 08/09/2005] [Indexed: 12/21/2022]
Abstract
The avian scapula is a long bone located dorsally on the thorax. The cranial part that articulates with the upper limb is derived from the somatopleure of the forelimb field, while the caudal part, the scapula blade, originates from the dermomyotomes of brachial and thoracic somites. In previous studies, we have shown that scapula blade formation is intrinsically controlled by segment-specific information as well as extrinsically by ectoderm-derived signals. Here, we addressed the role of signals derived from the lateral plate mesoderm on scapula development. Chick-quail chimera experiments revealed that scapula precursor cells are located within the hypaxial domain of the dermomyotome adjacent to somatopleural cells. Barrier implantation between these two cell populations inhibited scapula blade formation. Furthermore, we identified BMPs as scapula-inducing signals from the somatopleure using injection of Noggin-producing cells into the hypaxial domain of scapula-forming dermomyotomes. We found that inhibition of BMP activity interfered with scapula-specific Pax1 expression and scapula blade formation. Taken together, we demonstrate that the scapula-forming cells located within the hypaxial somitic domain require BMP signals derived from the somatopleure for their specification and differentiation.
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Affiliation(s)
- Baigang Wang
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Albert-Ludwigs-University Freiburg, D-79001 Freiburg, Germany
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13
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Malashichev Y, Borkhvardt V, Christ B, Scaal M. Differential regulation of avian pelvic girdle development by the limb field ectoderm. ACTA ACUST UNITED AC 2005; 210:187-97. [PMID: 16170541 DOI: 10.1007/s00429-005-0014-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2005] [Indexed: 10/25/2022]
Abstract
Although limb development has been a subject of intense research over the last decades, development of the girdles has been poorly investigated. Particularly, a detailed analysis of pelvic girdle development including functional data is not available to date. Here, we describe the early steps of the formation of mesenchymal and cartilaginous anlagen of the pelvic elements using alcian blue staining in whole mount embryos and serial histological sections, and the expression pattern of several marker genes to provide an operative basis for further research in pelvis development. Moreover, we describe pelvis development after unilateral hindlimb bud amputation and somatopleural ectoderm extirpation. We show for the first time, that ectodermal signals at pre-limb bud stages are required for pelvis formation. We present evidence suggesting that the regulation of ilium development is different from the development of ischium and pubis.
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Affiliation(s)
- Yegor Malashichev
- Department of Vertebrate Zoology, St. Petersburg State University, Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia.
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14
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Liu J, Chen D, Goldstein RS, Cui S. Effects of male and female sex steroids on the development of normal and the transient Froriep's dorsal root ganglia of the chick embryo. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 155:14-25. [PMID: 15763271 DOI: 10.1016/j.devbrainres.2004.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 12/08/2004] [Accepted: 12/09/2004] [Indexed: 11/16/2022]
Abstract
Sex steroids can influence developmental processes and support the survival of neurons in the embryonic central nervous system. Recent studies have shown that estrogen receptors are also expressed in the peripheral nervous system, in the dorsal root ganglia (DRG) of chick embryos. However, no studies have examined the effects of sex steroids on development of embryonic DRG. In the present study, 0.2 microg, 1.0 microg, 5.0 microg 10 microg, 20 microg, 25 microg, and 40 microg doses of testosterone or estradiol were delivered to chick embryos at Hamburger and Hamilton stage 18 (E3). The actions of these doses of sex steroids on the development of the C5DRG (fifth cervical ganglion, a "normal" DRG) and C2DRG (a transient ganglion known as a "Froriep's DRG") were then evaluated by quantifying ganglionic volumes, cell number, proliferation, and apoptosis after 1 day of growth to stage 23. We found that both testosterone and estradiol promoted proliferation of cells in both normal DRG and the Froriep's ganglia. By contrast, estradiol significantly increased the number of apoptotic cells, while testosterone strongly inhibited apoptosis. These actions of sex steroids on DRG development were dose-dependent, and C5DRG and C2DRG showed different sensitivities to the applied sex steroids. In addition, the present results demonstrated that specific ER and AR inhibitors (tamoxifen and flutamide) did not influence the effects of 5 microg E2 and 5 microg T on C2 and C5DRG significantly. These results demonstrate that male and female sex steroids can modulate DRG development through an epigenetic mechanism, as had been shown for the central nervous system.
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Affiliation(s)
- Jiali Liu
- College of Biological Sciences, China Agricultural University, Beijing, 100094, PR China
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15
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Fomenou MD, Scaal M, Stockdale FE, Christ B, Huang R. Cells of all somitic compartments are determined with respect to segmental identity. Dev Dyn 2005; 233:1386-93. [PMID: 15973735 DOI: 10.1002/dvdy.20464] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Development of somite cells is orchestrated by two regulatory processes. Differentiation of cells from the various somitic compartments into different anlagen and tissues is regulated by extrinsic signals from neighboring structures such as the notochord, neural tube, and surface ectoderm. Morphogenesis of these anlagen to form specific structures according to the segmental identity of each somite is specified by segment-specific positional information, based on the Hox-code. It has been shown that following experimental rotation of presomitic mesoderm or newly formed somites, paraxial mesodermal cells adapt to the altered signaling environment and differentiate according to their new orientation. In contrast, presomitic mesoderm or newly formed somites transplanted to different segmental levels keep their primordial segmental identity and form ectopic structures according to their original position. To determine whether all cells of a segment, including the dorsal and ventral compartment, share the same segmental identity, presomitic mesoderm or newly formed somites were rotated and transplanted from thoracic to cervical level. These experiments show that cells from all compartments of a segment are able to interpret extrinsic local signals correctly, but form structures according to their original positional information and maintain their original Hox expression in the new environment.
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Affiliation(s)
- Marlyse Dieuguie Fomenou
- Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Freiburg, Germany
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16
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Mittapalli VR, Huang R, Patel K, Christ B, Scaal M. Arthrotome: A specific joint forming compartment in the avian somite. Dev Dyn 2005; 234:48-53. [PMID: 16028274 DOI: 10.1002/dvdy.20502] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Somitocoele cells previously have been shown to form the proximal part of the ribs, the intervertebral discs, and the intervertebral joints (synovial joints). To determine whether the somitocoele cells are necessary for the development of axial skeleton joints, we microsurgically ablated the somitocoele cells in epithelial somites of 2-day-old chick embryos. The operated embryos were analyzed after whole-mount skeletal preparations and in sections. Removal of the somitocoele cells led to two major outcomes: (1) Intervertebral joints failed to develop and resulted in the fusion of the superior articular process and the inferior articular process; (2) Adjacent vertebral bodies fused and lacked the intervertebral disc. These results demonstrate that somitocoele cells specifically give rise to intervertebral joints and discs. Furthermore, these results suggest that neighboring sclerotome cells cannot adapt to form vertebral joints in the absence of the somitocoele compartment. Thus, we provide for the first time experimental evidence for the existence of a joint forming compartment in the somites, which we term the "arthrotome."
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Affiliation(s)
- Venugopal Rao Mittapalli
- Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Germany
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17
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Ferguson CA, Graham A. Redefining the head–trunk interface for the neural crest. Dev Biol 2004; 269:70-80. [PMID: 15081358 DOI: 10.1016/j.ydbio.2004.01.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Revised: 12/16/2003] [Accepted: 01/08/2004] [Indexed: 11/12/2022]
Abstract
The head-trunk interface lies at the occipito-cervical boundary, which corresponds to the somite 5/6 level. Previous studies have demonstrated that neural crest cells also behave differently either side of this boundary and that this may be due to intrinsic differences between cranial and trunk crest. However, it is also possible that some of the observed differences between cranial and trunk crest are assigned by environmental cues. We have therefore scrutinised the behaviour of the neural crest cells generated either side of the occipito-cervical boundary in chick and, interestingly, find that both behave in a truncal fashion by traversing the anterior half of their adjacent somites. Furthermore, although not previously described, we find that transient DRGs form opposite somites 4 and 5. Crest cells produced anterior of the somite 3/4 boundary avoid the somites and behave in a non-truncal fashion; these cells populate the pharyngeal arches, and thus contribute to the developing head. We have further shown, via somite transplantations, that differential behaviour of the posterior versus anterior occipital crest is assigned by the somites. If somites 1 to 3 are replaced by trunk somites, then the anterior occipital crest will behave in a truncal fashion by invading the somites. Correspondingly, if these anterior occipital somites are transplanted in place of trunk somites, they perturb the migration of trunk crest. Thus, for the neural crest, the head-trunk interface does not lie at the occipito-cervical boundary, but rather lies at the somite 3/4 level and is defined by the somites. The fact that this boundary lies at the somite 3/4 level in chick is significant as it reflects the more ancient posterior occipital boundary; in fish, only the first three somites contribute to the occipital bone.
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Affiliation(s)
- Christine A Ferguson
- MRC Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
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18
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Avivi C, Goldstein RS. Differing patterns of neurotrophin-receptor expressing neurons allow distinction of the transient Frorieps' ganglia from normal DRG before morphological differences appear. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2003; 145:49-59. [PMID: 14519493 DOI: 10.1016/s0165-3806(03)00212-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The Frorieps' ganglia are dorsal root ganglia (DRG) that form and then degenerate during normal embryonic development of amniotes. Their degeneration or survival has been shown to be modulated by modifying expression of Hox-family and other genes involved in pattern formation, and by the mesodermal microenvironment of the cranial somites in which they develop. In ovo application of the neurotrophin NGF partially rescues DRG2 from degeneration. To further examine the potential role of neurotrophins in the life cycle of Frorieps' DRG we have now quantified the numbers of neurons expressing neurotrophin receptors trkA and trkC in avian Frorieps' ganglia (DRG2) and normal cervical DRG (DRG5). We have found that the Frorieps' DRG are different from normal DRG in terms of the numbers of neurons expressing these receptors. trkC-expressing neurons are generally lacking in DRG2, this is the earliest (St 18, E2.5) described difference between DRG2 and normal DRG, preceding morphological differences between these ganglia that appear at St 20. The difference between DRG2 and DRG5 in terms of numbers of trkA-expressing neurons is evident only at later embryonic stages, where DRG2 contains a higher proportion of trkA neurons than normal cervical DRG. The few trkC+ neurons present late in DRG2 development are not concentrated in the VL portion of the ganglion, the zone where trkC+ neurons are generally found in normal DRG. We also find that DRG2 neurons are smaller than those of normal DRG, this is true for both trkA+ and trkC+ populations. These data together therefore suggest that the neurons that survive in the Frorieps' ganglia at later stages belong almost exclusively to the trkA-expressing DM class DRG neurons. We further find that the differences in the populations of trkA/trkC between DRG2 and DRG5 result from signals from the mesodermal microenvironment, since DRG arising in cranial somites transplanted caudally contain few trkC+ neurons and a higher proportion of trkA+ cells than contralateral controls.
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Affiliation(s)
- Camila Avivi
- Faculty of Life Sciences, Gonda Research Center, Bar-Ilan University, 52900 Ramat-Gan, Israel
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Omelchenko N, Lance-Jones C. Programming neural Hoxd10: in vivo evidence that early node-associated signals predominate over paraxial mesoderm signals at posterior spinal levels. Dev Biol 2003; 261:99-115. [PMID: 12941623 DOI: 10.1016/s0012-1606(03)00280-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Studies of the programming of Hox patterns at anterior spinal levels suggest that these events are accomplished through an integration of Hensen's node-derived and paraxial mesoderm signaling. We have used in vivo tissue manipulation in the avian embryo to examine the respective roles of node- derived and other local signals in the programming of a Hox pattern at posterior spinal levels. Hoxd10 is highly expressed in the lumbosacral (LS) spinal cord and adjacent paraxial mesoderm. At stages of LS neural tube formation (stages 12-14), the tailbud contains the remnants of Hensen's node and the primitive streak. Hoxd10 expression was analyzed after transposition of LS neural segments with and without the tailbud, after isolation of normally positioned LS segments from the stage 13 tailbud, and after axial displacement of posterior paraxial mesoderm. Data suggest that inductive signals from the tailbud are primarily responsible for the programming of Hoxd10 at neural plate and the earliest neural tube stages. After these stages, the LS neural tube appears to differ from more anterior neural segments in its lack of dependence on Hox-inductive signals from local tissues, including paraxial mesoderm. Our data also suggest that a graded system of repressive signals for posterior Hox genes is present at cervical and thoracic levels and likely to originate from paraxial mesoderm.
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Affiliation(s)
- Natalia Omelchenko
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Avivi C, Cui S, Goren S, Goldstein RS. Differences in neuronal differentiation between the transient cranial (Frorieps') and normal dorsal root ganglia. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2002; 135:19-28. [PMID: 11978389 DOI: 10.1016/s0165-3806(02)00272-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Frorieps' ganglia are dorsal root ganglia (DRG) that form, grow slowly compared to normal DRG, and then degenerate during normal embryonic development of amniotes. Their fate has been shown to be regulated by the Hox family and other genes involved in pattern formation, and by the mesodermal microenvironment of the cranial somites in which they develop. Neurons are known to differentiate within the Frorieps' DRG in the course of their short life span. In this study, we compared several aspects of neural differentiation between the longest-lived Frorieps' ganglia, DRG2, and normal trunk DRG in chick embryos. The expression of transcription factor Islet-1 and the RNA-binding protein Hu differ between normal and Frorieps' DRG at St. 23 (embryonic day 4). Islet-1 is expressed in a higher proportion of cells in DRG2 than DRG5, suggesting that cells in DRG2 differentiate more rapidly into neurons than in normal DRG. This molecular difference appears at the same developmental stage as overt morphological differences between DRG2 and normal DRG. Other LIM-homeobox proteins (Lim-1, -2 and -3 and Islet-2) are not expressed either in normal or Frorieps' DRG at early stages of development. Somite-grafting experiments reveal that the increased proportion of Isl-1(+) in DRG2 is due to the special microenvironment of the cranial somites. In contrast to Islet-1, the Hu antigen is expressed in a slightly lower proportion of cells in DRG2 at St. 23. At St. 28, there is a significant population of neurons in DRG2 that are Isl-1(+)/Hu(-). Since Islet-1 is normally expressed before Hu in DRG cells, it is possible that the reduced growth rate of the DRG2 ganglion may partially result from the inability of precociously differentiating Islet-1(+) neurons to further mature, as reflected by Hu antigen expression. In contrast to the neuronal markers examined, the satellite cell marker 7B3 is expressed at similar levels in DRG2 and DRG5.
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Affiliation(s)
- Camila Avivi
- Faculty of Life Sciences, Gonda Research Center, Bar-Ilan University, 52900 Ramat-Gan, Israel
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Galis F, Metz JA. Testing the vulnerability of the phylotypic stage: on modularity and evolutionary conservation. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2001; 291:195-204. [PMID: 11479918 DOI: 10.1002/jez.1069] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The phylotypic stage is the developmental stage at which vertebrates most resemble each other. In this study we test the plausibility of the hypotheses of Sander [1983, Development and Evolution, Cambridge University Press] and Raff [1994, Early Life on Earth, Columbia University Press; 1996, The Shape of Life, University of Chicago Press] that the phylotypic stage is conserved due to the intense and global interactivity occurring during that stage. First, we test the prediction that the phylotypic stage is much more vulnerable than any other stage. A search of the teratological literature shows that disturbances at this stage lead to a much higher mortality than in other stages, in accordance with the prediction. Second, we test whether that vulnerability is indeed caused by the interactiveness and lack of modularity of the inductions or, alternatively, is caused by some particularly vulnerable process going on at that time. From the pattern of multiple induced anomalies we conclude that it is indeed the interactiveness that is the root cause of the vulnerability. Together these results support the hypotheses of Sander and Raff. We end by presenting an argument on why the absence of modularity in the inductive interactions may also be the root cause of the conservation of the much discussed temporal and spatial colinearity of the Hox genes. J. Exp. Zool. (Mol. Dev. Evol.) 291:195-204, 2001.
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Affiliation(s)
- F Galis
- Institute of Evolutionary and Ecological Sciences (EEW), Section Theoretical Evolutionary Biology, Leiden University, Kaiserstraat 63, 2311 GP Leiden, The Netherlands
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Abstract
Brn3a/Brn-3.0 is a POU-domain transcription factor expressed in primary sensory neurons of the cranial and dorsal root ganglia and in specific neurons in the caudal CNS. Mice lacking Brn3a undergo extensive sensory neural death late in gestation and die at birth. To further examine Brn3a expression and the abnormalities that accompany its absence, we constructed a transgene containing 11 kb of Brn3a upstream regulatory sequence linked to a LacZ reporter. Here we show that these regulatory sequences direct transgene expression specifically to Brn3a peripheral sensory neurons of the cranial and dorsal root ganglia. Furthermore, expression of the 11 kb/LacZ reporter in the sensory neurons of the mesencephalic trigeminal, but not other Brn3a midbrain neurons, demonstrates that cell-specific transgene expression is targeted to a functional class of neurons rather than to an anatomical region. We then interbred the 11 kb/LacZ reporter strain with mice carrying a null mutant allele of Brn3a to generate 11 kb/LacZ, Brn3a knock-out mice. beta-Galactosidase expression in these mice reveals significant axonal growth defects, including excessive and premature branching of the major divisions of the trigeminal nerve and a failure to correctly innervate whisker follicles, all of which precede sensory neural death in these mice. These defects in Brn3a(-/-) mice resemble strongly those seen in mice lacking the mediators of sensory pathfinding semaphorin 3A and neuropilin-1. Here we show, however, that sensory neurons are able to express neuropilin-1 in the absence of Brn3a.
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Nowicki JL, Burke AC. Hox genes and morphological identity: axial versus lateral patterning in the vertebrate mesoderm. Development 2000; 127:4265-75. [PMID: 10976057 DOI: 10.1242/dev.127.19.4265] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The successful organization of the vertebrate body requires that local information in the embryo be translated into a functional, global pattern. Somite cells form the bulk of the musculoskeletal system. Heterotopic transplants of segmental plate along the axis from quail to chick were performed to test the correlation between autonomous morphological patterning and Hox gene expression in somite subpopulations. The data presented strengthen the correlation of Hox gene expression with axial specification and focus on the significance of Hox genes in specific derivatives of the somites. We have defined two anatomical compartments of the body based on the embryonic origin of the cells making up contributing structures: the dorsal compartment, formed from purely somitic cell populations; and the ventral compartment comprising cells from somites and lateral plate. The boundary between these anatomical compartments is termed the somitic frontier. Somitic tissue transplanted between axial levels retains both original Hox expression and morphological identity in the dorsal compartment. In contrast, migrating lateral somitic cells crossing the somitic frontier do not maintain donor Hox expression but apparently adopt the Hox expression of the lateral plate and participate in the morphology appropriate to the host level. Dorsal and ventral compartments, as defined here, have relevance for experimental manipulations that influence somite cell behavior. The correlation of Hox expression profiles and patterning behavior of cells in these two compartments supports the hypothesis of independent Hox codes in paraxial and lateral plate mesoderm.
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Affiliation(s)
- J L Nowicki
- University of North Carolina, Department of Biology, Chapel Hill, NC 27599, USA
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