The infundibular organ of the lancelet (Branchiostoma lanceolatum, Acrania): an immunocytochemical study

Olsson, Ragnar; Yulis, Roberto; Rodr�guez, Est�ban M.

doi:10.1007/s004410050137

Cited by 19 publications

(29 citation statements)

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“…At the cellular level, the cerebral vesicle has counterparts with several diencephalic structures. Most striking perhaps is the lamellar body of amphioxus as compared to the pineal gland in the vertebrate diencephalon [Ruiz and Anadon, 1991;Lacalli et al, 1994;Olsson et al, 1994]. The lamellar body, which is a ciliary photoreceptor with the ciliary membrane modified into large whorls, strikingly resembles photoreceptor cells in the lamprey pineal complex [Meiniel, 1980;Cole and Youson, 1982].…”

Section: The Amphioxus Cns Shares Key Domains With the Vertebrate Cnsmentioning

confidence: 98%

“…The lamellar body, which is a ciliary photoreceptor with the ciliary membrane modified into large whorls, strikingly resembles photoreceptor cells in the lamprey pineal complex [Meiniel, 1980;Cole and Youson, 1982]. In addition, it has been argued that the anterior photoreceptor of amphioxus is homologous to the vertebrate paired eyes [Lacalli, 1996] and that the amphioxus infundibular organ, which secretes an extracellular fiber that extends posteriorly in the lumen of the CNS, is homologous to the vertebrate subcommissural organ, which secretes Reissner's fiber [Olsson et al, 1994]. Additional correspondences of gene expression support the homology of the amphioxus cerebral vesicle and vertebrate diencephalon.…”

Section: The Amphioxus Cns Shares Key Domains With the Vertebrate Cnsmentioning

confidence: 99%

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Gene Duplication, Co-Option and Recruitment during the Origin of the Vertebrate Brain from the Invertebrate Chordate Brain

Holland

Short

2008

Brain Behav Evol

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The brain of the basal chordate amphioxus has been compared to the vertebrate diencephalic forebrain, midbrain, hindbrain and spinal cord on the basis of the cell architecture from serial electron micrographs and patterns of developmental gene expression. In addition, genes specifying the neural plate and neural plate border as well as Gbx and Otx, that position the midbrain/hindbrain boundary (MHB), are expressed in comparable patterns in amphioxus and vertebrates. However, migratory neural crest is lacking in amphioxus, and although it has homologs of the genes that specify neural crest, they are not expressed at the edges of the amphioxus neural plate. Similarly, amphioxus has the genes that specify organizer properties of the MHB, but they are not expressed at the Gbx/Otx boundary as in vertebrates. Thus, the genetic machinery that created migratory neural crest and an MHB organizer was present in the ancestral chordate, but only co-opted for these new roles in vertebrates. Analyses with the amphioxus genome project strongly support the idea of two rounds of whole genome duplication with subsequent gene losses in the vertebrate lineage. Duplicates of developmental genes were preferentially retained. Although some genes apparently acquired roles in neural crest prior to these genome duplications, other key genes (e.g., FoxD3 in neural crest and Wnt1 at the MHB) were recruited into the respective gene networks after one or both genome duplications, suggesting that such an expansion of the genetic toolkit was critical for the evolution of these structures. The toolkit has also increased by alternative splicing. Contrary to the general rule, for at least one gene family with key roles in neural crest and the MHB, namely Pax genes, alternative splicing has not decreased subsequent to gene duplication. Thus, vertebrates have a much larger number of proteins available for mediating new functions in these tissues. The creation of new splice forms typically changes protein structure more than evolution of the protein after gene duplication. The functions of particular isoforms of key proteins expressed at the MHB and in neural crest have only just begun to be studied. Their roles in modulating gene networks may turn out to rival gene duplication for facilitating the evolution of structures such as neural crest and the MHB.

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Section: The Amphioxus Cns Shares Key Domains With the Vertebrate Cnsmentioning

confidence: 98%

Section: The Amphioxus Cns Shares Key Domains With the Vertebrate Cnsmentioning

confidence: 99%

Gene Duplication, Co-Option and Recruitment during the Origin of the Vertebrate Brain from the Invertebrate Chordate Brain

Holland

Short

2008

Brain Behav Evol

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“…A landmark comes from the origin of Reissner's fiber, which is present in all chordate groups (Olsson, 1993). In amphioxus Reissner's fiber is produced by the infundibular organ that locates ventrocaudally in the brain vesicle (Olsson, 1955;Sterba et al, 1983;Olsson et al, 1994). Although in all adult vertebrates Reissner's fiber is produced by the subcommissural organ (i.e., dorsally), the homologue of the amphioxus infundibular organ may be the flexural organ, a transient early ventral secretory ependyma between the hindbrain and the midbrain (Olsson et al, 1994).…”

Section: Brainmentioning

confidence: 99%

“…In amphioxus Reissner's fiber is produced by the infundibular organ that locates ventrocaudally in the brain vesicle (Olsson, 1955;Sterba et al, 1983;Olsson et al, 1994). Although in all adult vertebrates Reissner's fiber is produced by the subcommissural organ (i.e., dorsally), the homologue of the amphioxus infundibular organ may be the flexural organ, a transient early ventral secretory ependyma between the hindbrain and the midbrain (Olsson et al, 1994). Comparison of the anterior limit of expression of the AmphiHox3 gene in the amphioxus nerve cord (Holland et al, 1992) with that of its homologue HoxB3 in the chick (Lumsden, 1990) also suggests that most amphioxus brain corresponds to the vertebrate hindbrain.…”

Section: Brainmentioning

confidence: 99%

Distribution of GABA immunoreactivity in the central and peripheral nervous system of amphioxus (Branchiostoma lanceolatum pallas)

1998

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On the basis of labeling with an anti-gamma-aminobutyric acid (GABA) antibody, we report for the first time the presence and distribution of GABA-immunoreactive cells in the central and peripheral nervous system of amphioxus. In the nerve cord, there is a large dorsorostral group of cerebrospinal-fluid-contacting (CSFc) cells at the caudal end of the brain vesicle that gives rise to a large ventral commissure and neuropilar region. In the middle and caudal region of the brain, numerous commissural and CSFc neurons are situated below the region of large dorsal cells. In the spinal cord, several types of GABA-immunoreactive neurons of different size, appearance, and distribution were observed. In the dorsalmost region, very small commissural cells are scattered regularly along the cord. More ventrally in the cord, GABAergic neurons, both of commissural and CSFc cell types, form segmental groups, but scattered cells are observed throughout. These cells give rise to dense longitudinal fascicles of GABAergic fibers and to scattered commissural fibers. The caudal ampulla lacks GABAergic cells and fibers. Some of the fibers of the most rostral and caudal peripheral (sensory) nerves, as well as some sensory cells of the rostral and caudal epidermis, are GABA immunoreactive. The significance of these results for the understanding of the evolution of GABAergic systems of vertebrates is discussed.

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“…Evidence that amphioxus has a homologue of the vertebrate diencephalon is strong. Based on fine structure and histology, there is an infundibulum [26,27]. Additional evidence for a diencephalic homologue is the presence of the lamellar body, which has the same fine structure as the pineal in a larval lamprey [28,29].…”

Section: Introductionmentioning

confidence: 99%

The origin and evolution of chordate nervous systems

Holland

2015

Phil. Trans. R. Soc. B

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One contribution of 16 to a discussion meeting issue 'Origin and evolution of the nervous system'. In the past 40 years, comparisons of developmental gene expression and mechanisms of development (evodevo) joined comparative morphology as tools for reconstructing long-extinct ancestral forms. Unfortunately, both approaches typically give congruent answers only with closely related organisms. Chordate nervous systems are good examples. Classical studies alone left open whether the vertebrate brain was a new structure or evolved from the anterior end of an ancestral nerve cord like that of modern amphioxus. Evodevo plus electron microscopy showed that the amphioxus brain has a diencephalic forebrain, small midbrain, hindbrain and spinal cord with parts of the genetic mechanisms for the midbrain/hindbrain boundary, zona limitans intrathalamica and neural crest. Evodevo also showed how extra genes resulting from whole-genome duplications in vertebrates facilitated evolution of new structures like neural crest. Understanding how the chordate central nervous system (CNS) evolved from that of the ancestral deuterostome has been truly challenging. The majority view is that this ancestor had a CNS with a brain that gave rise to the chordate CNS and, with loss of a discrete brain, to one of the two hemichordate nerve cords. The minority view is that this ancestor had no nerve cord; those in chordates and hemichordates evolved independently. New techniques such as phylostratigraphy may help resolve this conundrum.

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The infundibular organ of the lancelet (Branchiostoma lanceolatum, Acrania): an immunocytochemical study

Cited by 19 publications

References 0 publications

Gene Duplication, Co-Option and Recruitment during the Origin of the Vertebrate Brain from the Invertebrate Chordate Brain

Gene Duplication, Co-Option and Recruitment during the Origin of the Vertebrate Brain from the Invertebrate Chordate Brain

Distribution of GABA immunoreactivity in the central and peripheral nervous system of amphioxus (Branchiostoma lanceolatum pallas)

The origin and evolution of chordate nervous systems

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