The Subcommissural Organ and the Development of the Posterior Commissure

Grondona, Jesús M.; Hoyo-Becerra, Carolina; Visser, Rick; Fernández-Llébrez, Pedro; López-Ávalos, María Dolores

doi:10.1016/b978-0-12-394307-1.00002-3

Cited by 24 publications

(22 citation statements)

References 328 publications

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“…The subcommissural organ, a specialized neuroepithelium located at the dorsal midline underneath the posterior commissure, releases the subcommissural organ spondin, a large glycoprotein belonging to the thrombospondin superfamily that shares molecular domains with axonal path-finding molecules. The subcommissural organ is thought to be involved in the development of the posterior commissure (3,12). In our anatomical study, we observed the posterior commissure but we could not distinctly identify the subcommissural organ.…”

Section: Discussioncontrasting

confidence: 66%

“…Some fibers are believed to be derived from the posterior part of the thalamus and from the superior colliculus and to continue directly to the medial longitudinal fasciculus. Fibers from the thalamic, pretectal, tectal region, fibers from the superior colliculus and the habenular nuclei are known to connect with the posterior commissure, but they have not been shown anatomically (3)(4)(5)12).…”

Section: Introductionmentioning

confidence: 99%

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The anatomy of the posterior commissure

Özdemir¹

2015

Turkish Neurosurgery

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AIm: The connections of posterior commissure are defined. Its fibers mediate the consensual light reflex by interconnecting the pretectal nuclei. The fiber connections from the thalamic, pretectal, superior colliculus and the habenular nuclei are known, but they have not been shown anatomically. The present study is a fiber dissection study to define the anatomy of the posterior commissure. mAterIAl and methOds: Twenty formalin-fixed sheep heads were used in the study. The specimens were fixed in 10% formalin solution for 3 weeks. The arachnoidal and vascular structures were removed by using a surgical microscope magnification (x6-x40) and brains were again fixed for 4 weeks at -20°C. The fiber dissections were performed at Marmara University, Rhoton Laboratory. Also, a radiological tractographic study was carried on five healthy volunteers to see the posterior commissure cortical connections. results:In fifteen sheep brains, the dimensions of the posterior commissure were measured as 1.36 mm (range 0.5-2.5 mm) width, and as 4.6 mm (range 3-6 mm) length. In the dissection study, a frontotemporooccipital fascicle was observed to connect with the fibers of the posterior commissure. Diffusion tensor imaging scans showed the frontotemporooccipital tract to extend to posterior commissural region.COnClusIOn: To our knowledge, this is the first anatomical and tractographic study regarding the posterior commissure. However, further human cadaveric studies are necessary. BulGulAr: On beş koyun beyninde posterior komissür'ün ortalama kalınlığı 1,36 mm (0,5-2,5 mm), uzunluğu 4,6 mm (3-6 mm) olarak bulundu. Posterior komissür'ün her iki tarafta superior ve inferior kolikulusları bağladığı; habenula, pretektal, tektal ve periakuaduktal bölgeden kısa liflerle bağlantı kurduğu görüldü. Bazı spesimenlerde hipokampal komissür liflerinin splenial bölgede bu liflere eşlik ettiği izlendi. Talamik diseksiyondan sonra gözlenen frontotemporooksipital fasikülün posterior komissür'e uzandığı saptandı. sOnuÇ: Çalışmada diseksiyonla posterior komissür'ün frontotemporooksipitopontin bağlantısı gösterilmiştir. Araştırma posterior komissür'ün lif bağlantılarını ortaya koyacak insan kadavra çalışmalarıyla desteklenmelidir.

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Section: Discussioncontrasting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

The anatomy of the posterior commissure

Özdemir¹

2015

Turkish Neurosurgery

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“…The following previous lines of evidence have led some authors to propose that SCO-spondin contributes to the PC development (Meiniel et al, 2008; Caprile et al, 2009; Hoyo-Becerra et al, 2010; Stanic et al, 2010; Grondona et al, 2012): (1) the concomitant formation of SCO and PC, (2) the similarity of SCO-spondin with other molecules involved in axonal guidance, (3) the early secretion of this protein toward the extracellular matrix surrounding the PC axons, and (4) in vitro experiments where the addition of SCO-spondin or peptides derived from its sequence increase neurite length and fasciculation. Here, we provide direct in vivo evidence that SCO-spondin is crucial for PC formation, as its loss of function either causes a marked decrease in the number of axons (animals with total inhibition), a moderate diminution in the number of axons (inhibition at the caudal region), or axonal defasciculation (animals with cephalic inhibition).…”

Section: Discussionmentioning

confidence: 99%

SCO-spondin from embryonic cerebrospinal fluid is required for neurogenesis during early brain development

Vera-Montecinos¹,

Stanic²,

Montecinos³

et al. 2013

Front. Cell. Neurosci.

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The central nervous system (CNS) develops from the neural tube, a hollow structure filled with embryonic cerebrospinal fluid (eCSF) and surrounded by neuroepithelial cells. Several lines of evidence suggest that the eCSF contains diffusible factors regulating the survival, proliferation, and differentiation of the neuroepithelium, although these factors are only beginning to be uncovered. One possible candidate as eCSF morphogenetic molecule is SCO-spondin, a large glycoprotein whose secretion by the diencephalic roof plate starts at early developmental stages. In vitro, SCO-spondin promotes neuronal survival and differentiation, but its in vivo function still remains to be elucidated. Here we performed in vivo loss of function experiments for SCO-spondin during early brain development by injecting and electroporating a specific shRNA expression vector into the neural tube of chick embryos. We show that SCO-spondin knock down induces an increase in neuroepithelial cells proliferation concomitantly with a decrease in cellular differentiation toward neuronal lineages, leading to hyperplasia in both the diencephalon and the mesencephalon. In addition, SCO-spondin is required for the correct morphogenesis of the posterior commissure and pineal gland. Because SCO-spondin is secreted by the diencephalon, we sought to corroborate the long-range function of this protein in vitro by performing gain and loss of function experiments on mesencephalic explants. We find that culture medium enriched in SCO-spondin causes an increased neurodifferentiation of explanted mesencephalic region. Conversely, inhibitory antibodies against SCO-spondin cause a reduction in neurodifferentiation and an increase of mitosis when such explants are cultured in eCSF. Our results suggest that SCO-spondin is a crucial eCSF diffusible factor regulating the balance between proliferation and differentiation of the brain neuroepithelial cells.

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“…Its formation is closely linked to that of the posterior commissure, and there is evidence that the SCO is required for proper pathfinding of commissural axons (Grondona et al. ). Genes that specifically affect the SCO have not yet been discovered, but both SCO and pineal development are affected in Pax6 mutants (see above) (Estivill‐Torrus et al.…”

Section: The Subcommissural Organ (Sco)mentioning

confidence: 99%

The origins of the circumventricular organs

Kiecker

2017

Journal of Anatomy

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The circumventricular organs (CVOs) are specialised neuroepithelial structures found in the midline of the brain, grouped around the third and fourth ventricles. They mediate the communication between the brain and the periphery by performing sensory and secretory roles, facilitated by increased vascularisation and the absence of a blood-brain barrier. Surprisingly little is known about the origins of the CVOs (both developmental and evolutionary), but their functional and organisational similarities raise the question of the extent of their relationship. Here, I review our current knowledge of the embryonic development of the seven major CVOs (area postrema, median eminence, neurohypophysis, organum vasculosum of the lamina terminalis, pineal organ, subcommissural organ, subfornical organ) in embryos of different vertebrate species. Although there are conspicuous similarities between subsets of CVOs, no unifying feature characteristic of their development has been identified. Cross-species comparisons suggest that CVOs also display a high degree of evolutionary flexibility. Thus, the term 'CVO' is merely a functional definition, and features shared by multiple CVOs may be the result of homoplasy rather than ontogenetic or phylogenetic relationships.

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The Subcommissural Organ and the Development of the Posterior Commissure

Cited by 24 publications

References 328 publications

The anatomy of the posterior commissure

The anatomy of the posterior commissure

SCO-spondin from embryonic cerebrospinal fluid is required for neurogenesis during early brain development

The origins of the circumventricular organs

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