Phylogenetic Origins of Brain Organisers
The regionalisation of the nervous system begins early in embryogenesis, concomitant with the establishment of the anteroposterior (AP) and dorsoventral (DV) body axes. The molecular mechanisms that drive axis induction appear to be conserved throughout the animal kingdom and may be phylogenetically...
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Wiley
2012-01-01
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| Series: | Scientifica |
| Online Access: | http://dx.doi.org/10.6064/2012/475017 |
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| author | Ellen Robertshaw Clemens Kiecker |
| author_facet | Ellen Robertshaw Clemens Kiecker |
| author_sort | Ellen Robertshaw |
| collection | DOAJ |
| description | The regionalisation of the nervous system begins early in embryogenesis, concomitant with the establishment of the anteroposterior (AP) and dorsoventral (DV) body axes. The molecular mechanisms that drive axis induction appear to be conserved throughout the animal kingdom and may be phylogenetically older than the emergence of bilateral symmetry. As a result of this process, groups of patterning genes that are equally well conserved are expressed at specific AP and DV coordinates of the embryo. In the emerging nervous system of vertebrate embryos, this initial pattern is refined by local signalling centres, secondary organisers, that regulate patterning, proliferation, and axonal pathfinding in adjacent neuroepithelium. The main secondary organisers for the AP neuraxis are the midbrain-hindbrain boundary, zona limitans intrathalamica, and anterior neural ridge and for the DV neuraxis the notochord, floor plate, and roof plate. A search for homologous secondary organisers in nonvertebrate lineages has led to controversy over their phylogenetic origins. Based on a recent study in hemichordates, it has been suggested that the AP secondary organisers evolved at the base of the deuterostome superphylum, earlier than previously thought. According to this view, the lack of signalling centres in some deuterostome lineages is likely to reflect a secondary loss due to adaptive processes. We propose that the relative evolutionary flexibility of secondary organisers has contributed to a broader morphological complexity of nervous systems in different clades. |
| format | Article |
| id | doaj-art-4e94639a1dee435791a4882422d56199 |
| institution | Kabale University |
| issn | 2090-908X |
| language | English |
| publishDate | 2012-01-01 |
| publisher | Wiley |
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| series | Scientifica |
| spelling | doaj-art-4e94639a1dee435791a4882422d561992025-08-20T03:36:34ZengWileyScientifica2090-908X2012-01-01201210.6064/2012/475017475017Phylogenetic Origins of Brain OrganisersEllen Robertshaw0Clemens Kiecker1MRC Centre for Developmental Neurobiology, King's College London, 4th Floor, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UKMRC Centre for Developmental Neurobiology, King's College London, 4th Floor, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UKThe regionalisation of the nervous system begins early in embryogenesis, concomitant with the establishment of the anteroposterior (AP) and dorsoventral (DV) body axes. The molecular mechanisms that drive axis induction appear to be conserved throughout the animal kingdom and may be phylogenetically older than the emergence of bilateral symmetry. As a result of this process, groups of patterning genes that are equally well conserved are expressed at specific AP and DV coordinates of the embryo. In the emerging nervous system of vertebrate embryos, this initial pattern is refined by local signalling centres, secondary organisers, that regulate patterning, proliferation, and axonal pathfinding in adjacent neuroepithelium. The main secondary organisers for the AP neuraxis are the midbrain-hindbrain boundary, zona limitans intrathalamica, and anterior neural ridge and for the DV neuraxis the notochord, floor plate, and roof plate. A search for homologous secondary organisers in nonvertebrate lineages has led to controversy over their phylogenetic origins. Based on a recent study in hemichordates, it has been suggested that the AP secondary organisers evolved at the base of the deuterostome superphylum, earlier than previously thought. According to this view, the lack of signalling centres in some deuterostome lineages is likely to reflect a secondary loss due to adaptive processes. We propose that the relative evolutionary flexibility of secondary organisers has contributed to a broader morphological complexity of nervous systems in different clades.http://dx.doi.org/10.6064/2012/475017 |
| spellingShingle | Ellen Robertshaw Clemens Kiecker Phylogenetic Origins of Brain Organisers Scientifica |
| title | Phylogenetic Origins of Brain Organisers |
| title_full | Phylogenetic Origins of Brain Organisers |
| title_fullStr | Phylogenetic Origins of Brain Organisers |
| title_full_unstemmed | Phylogenetic Origins of Brain Organisers |
| title_short | Phylogenetic Origins of Brain Organisers |
| title_sort | phylogenetic origins of brain organisers |
| url | http://dx.doi.org/10.6064/2012/475017 |
| work_keys_str_mv | AT ellenrobertshaw phylogeneticoriginsofbrainorganisers AT clemenskiecker phylogeneticoriginsofbrainorganisers |