Neural - Telencephalon Development

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Introduction

Stage10 sem6.jpg

Neural development is one of the earliest systems to begin and the last to be completed after birth. This development generates the most complex structure within the embryo and the long time period of development means in utero insult during pregnancy may have consequences to development of the nervous system.

The early central nervous system begins as a simple neural plate that folds to form a groove then tube, open initially at each end. Failure of these opening to close contributes a major class of neural abnormalities (neural tube defects).

Within the neural tube stem cells generate the 2 major classes of cells that make the majority of the nervous system : neurons and glia. Both these classes of cells differentiate into many different types generated with highly specialized functions and shapes. This section covers the establishment of neural populations, the inductive influences of surrounding tissues and the sequential generation of neurons establishing the layered structure seen in the brain and spinal cord.

  • Neural development beginnings quite early, therefore also look at notes covering Week 3- neural tube and Week 4-early nervous system.
  • Development of the neural crest and sensory systems (hearing/vision/smell) are only introduced in these notes and are covered in other notes sections.


Neural Links: ectoderm | neural | neural crest | ventricular | sensory | Stage 22 | gliogenesis | neural fetal | Medicine Lecture - Neural | Lecture - Ectoderm | Lecture - Neural Crest | Lab - Early Neural | neural abnormalities | folic acid | iodine deficiency | Fetal Alcohol Syndrome | neural postnatal | neural examination | Histology | Historic Neural | Category:Neural

Some Recent Findings

  • Populations of subplate and interstitial neurons in fetal and adult human telencephalonPMID20979586 "In the adult human telencephalon, subcortical (gyral) white matter contains a special population of interstitial neurons considered to be surviving descendants of fetal subplate neurons [Kostovic & Rakic (1980) Cytology and the time of origin of interstitial neurons in the white matter in infant and adult human and monkey telencephalon. J Neurocytol9, 219]. We designate this population of cells as superficial (gyral) interstitial neurons and describe their morphology and distribution in the postnatal and adult human cerebrum. Human fetal subplate neurons cannot be regarded as interstitial, because the subplate zone is an essential part of the fetal cortex, the major site of synaptogenesis and the 'waiting' compartment for growing cortical afferents, and contains both projection neurons and interneurons with distinct input-output connectivity. However, although the subplate zone is a transient fetal structure, many subplate neurons survive postnatally as superficial (gyral) interstitial neurons. The fetal white matter is represented by the intermediate zone and well-defined deep periventricular tracts of growing axons, such as the corpus callosum, anterior commissure, internal and external capsule, and the fountainhead of the corona radiata."
  • Ephrins guide migrating cortical interneurons in the basal telencephalon[1] "Cortical interneurons are born in the proliferative zones of the ganglionic eminences in the subpallium and migrate to the developing cortex along well-defined tangential routes. The mechanisms regulating interneuron migration are not completely understood. ... Together, these results suggest that ephrin-A3 acts as a repulsive cue that restricts cortical interneurons from entering inappropriate regions and thus contributes to define the migratory route of cortical interneurons."
  • FoxG1 and TLE2 act cooperatively to regulate ventral telencephalon formation[2] "FoxG1 is a conserved transcriptional repressor that plays a key role in the specification, proliferation and differentiation of the telencephalon, and is expressed from the earliest stages of telencephalic development through to the adult. ...Knocking down either FoxG1 or TLE2 disrupts the development of the ventral telencephalon, supporting the idea that endogenous TLE2 and FoxG1 work together to specify the ventral telencephalon."

Development Overview

Neuralation begins at the trilaminar embryo with formation of the notochord and somites, both of which underly the ectoderm and do not contribute to the nervous system, but are involved with patterning its initial formation. The central portion of the ectoderm then forms the neural plate that folds to form the neural tube, that will eventually form the entire central nervous system.

Early developmental sequence: Epiblast - Ectoderm - Neural Plate - Neural groove and Neural Crest - Neural Tube and Neural Crest


Neural Tube Development
Neural Tube Primary Vesicles Secondary Vesicles Adult Structures
week 3 week 4 week 5 adult
neural plate
neural groove
neural tube

Brain
prosencephalon (forebrain) telencephalon Rhinencephalon, Amygdala, hippocampus, cerebrum (cortex), hypothalamus‎, pituitary | Basal Ganglia, lateral ventricles
diencephalon epithalamus, thalamus, Subthalamus, pineal, posterior commissure, pretectum, third ventricle
mesencephalon (midbrain) mesencephalon tectum, Cerebral peduncle, cerebral aqueduct, pons
rhombencephalon (hindbrain) metencephalon cerebellum
myelencephalon medulla oblongata, isthmus
spinal cord, pyramidal decussation, central canal

Early Brain Vesicles

Primary Vesicles

CNS primary vesicles.jpg

Secondary Vesicles

CNS secondary vesicles.jpg

Molecular Development

Regulatory Networks

Telencephalon gene regulatory network.jpg

Algorithm-based gene regulatory network structure for dorsal and ventral telencephalon development.[3]

To highlight the key regulators, the nodes representing genes predicted to be the parent of at least nine other genes are largest in size (Sox9, Mef2a, Elavl4 and Pou6f1), whereas those that are predicted to regulate at least five other genes are medium in size (Ngn2, Centg3, Tef, Tcf4, Wnt7b, Pou2f1, Yy1, Dll1, E2f1, Arx, and Creb).

Netrin-1 Signaling

Telencephalon- Netrin-1 signaling thalamocortical projections.jpg Model of the Role of Netrin-1 Signaling in the Topography of Thalamocortical Projections in the Ventral Telencephalon[4]

Models summarizing previous[5] and above reference[4] findings regarding the axon guidance cues controlling the topographic sorting of thalamocortical axons in the ventral telencephalon.


Links: OMIM - NETRIN 1 | Mouse Development

References

  1. <pubmed>20473036</pubmed>
  2. <pubmed>20356955</pubmed>
  3. <pubmed>18377642</pubmed>| BMC Biol.
  4. 4.0 4.1 <pubmed>18479186</pubmed>| PMC2584572 | PLoS Biol.
  5. <pubmed>12895420</pubmed>

Reviews

<pubmed>19210541</pubmed> <pubmed>19143049</pubmed>


Articles

<pubmed>19632216</pubmed> <pubmed>18997789</pubmed> <pubmed>18682721</pubmed> <pubmed>17959802</pubmed>

Search PubMed

Search Pubmed: Telencephalon Embryology | Telencephalon Development |


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Cite this page: Hill, M.A. (2020, March 30) Embryology Neural - Telencephalon Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_-_Telencephalon_Development

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© Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G