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신경발생 (Development of nervous system)

Neurulation (I)

• Surface ectoderm

: Neural plate Neural fold Neural tube

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Neurulation (II)

• Neural plate (신경판)

• Neural fold (신경주름)

• Neural tube (신경관)

• Surface ectoderm

• Neural groove (신경고랑)

• Neural crest (신경능선)

• Notochord (척삭)

Neurulation in the mammalian embryo

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The neural crest

Initial migratory route of

undifferentiated neural

crest cell

1.2, senosry & autonomic ganglions

3, adrenal medulla, melanocyte

4, sensory endings

Regional specification of the developing brain

3 flexure

1. Cephalic

2. Cervical

3. Pontine

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Sequential gene expression divides the embryo into regions and segments

Bicoid: anterior pole

Kruppel: ant-post axis

Hairy: mature segmented body

Wingless: individual segment

Hox genes (from an abbreviation of homeobox) are a group of related genes that control

the body plan of the embryo along the anterior-posterior (head-tail) axis

Spinal cord

• Neuroepithelial layer

• Mantle layer

• Marginal layer

• Roof plate

• Alar plate

– Dorsal, posterior horn

• Sulcus limitans

• Basal plate

– Ventral, anterior horn

• Floor plate

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Myelencephalon (숨뇌)

Metencephalon (뒤뇌)

소뇌

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External granular layer

-발생과정의일과성층

-분열능력

-생성된세포는속질로이동

과립층형성

Cerebellum (소뇌)

Mesencephalon (중간뇌)

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Diencephalon (사이뇌)

• Basal plate: 퇴화

• Roof plate: 송과체

• Alar plate: 시상, 시상하부

Telencephalon (끝뇌)

• 대뇌반구: 가쪽벽의팽대

• 줄무늬체

: 대뇌반구의 바닥부분

• 해마: 맥락틈새의위

MGE

; medial ganglionic eminence

LGE

; Lateral Ganglionic Eminence

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Major inductive signaling pathways in vertebrate embryos

Cell lineage of developing CNS

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Neurogenesis: Where, When, and What

Where When What

Lineage

Birthdate Differentiation

brdUAcquire specific phenotypic or

molecular features

; specific identity of any

neurons

Regulation of

spinal cord development

• SHH (sonic hedgehog)

• BMP (bone morphogenetic

protein)

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Developmental property of OLG

• OLG originates in a specialized

domain of the ventral ventricular

zone (VZ) in spinal cord

– Shh (Sonic Hedgehog)

– BMP (Bone Morphogenetic

protein)

D

V

Neural precursor cells undergo mitosis within the ventricular zone

Dash line: ventricular surface

Red line: vertically oriented division

Arrows: radial process of cells

The radial processes are

retained once the cell has

divided

Symmetric division

Asymmetric division

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Generation of cortical neurons

Inside first outside last

Delta-Notch signaling leads to neuronal differentiation

Delta binding cleavage

NICD

NICD translocation to nucleus

Binds to RBP-J

Activates bHLH

A stochastic increase in Delta ligands on a

particular cell leads to downregulation of Delth

in neighboring cells, while in the Delta-

increasing cell, bHLH gene expression is also

increased, and the cell becomes primed for

neuronal differentiation

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Molecular and cellular mechanisms that guide neuronal and glial differentiation

Migration and differentiation of the neural crest relies on regulation of gene expression and cell–cell

signaling

Neural crest+ cell

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Radial glia guide migrating neurons

Radially: arrows

Non-radially: *

Mixing it up: Long-distance neuronal migration

At first: Position was destiny

Laterly: Adult brain structures might be derived from a

broad range of embryonic brain subdivision

Radial

Tangential: GABAergic interneuron

but some GABAergic interneuron also are

genereated in the cortical rudiment

Cortical migration disorders: infant spasm

1. Reelin

2. DCX (doublecortin)

3. neuregulin, NCAM, DISC1-psychiatric disease

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Radial migration in the developing cortex

Axon growth and Guidance

Grasshopper

1.Ti1 Pioneer is aided by

guidespot or stepping stone cells

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The structure and action of growth cones

F-Actin : red

Microtubule: green; Lamellipodium

Filopodium

G-actin can be incorporated into F-

actin at the leading edge of

filopodium in response to atractive

cues.

Repulsive cues support

disassembly and retrograde flow of

G-actin toward the lamellipodium

By Ca via voltage-regulated Ca

channels as well as TRP channels

Several families of ligands and receptors constitute the major classes of axon guidance molecules

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Signals provided by the embryonic environment

Chemoattraction

Chemorepulsion

Growth cone-collapsing activity of semaphorin

depends on Ca signaling

Target-derived trophic support regulates survival of related neurons

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Hebb’s postulate and the development of synaptic inputs

Strenthening of synapse

Winner-takes-all”

The human brain changes significantly during postnatal life

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Birdsong

Foreing languate

In fact, many learned behaviors

are acquired during a critical

period in early life when

experence exerts an especially

potent influence on subseqent

behavior.

The sensitive period for song

learning

In short, intrinsic factors make

the nervous system of oscine

brids especially sensitive to

songs that are species-typical.

Similar biases may influence

human language learning.

Figure 24.11 Learning language

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