1. Neurulation: formation of the neural tube
Embryology 4.
Neurulation: formation of the neural tube
Dr. Nandor Nagy
Semmelweis University

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3. Neural Induction and Neurulation - specification of neural fate and formation of the neural tube.
NEURAL INDUCTION : the delineation of ectodermal cells to the neural fate.
NEURULATION: the process in which the ectoderm of the future brain and spinal cord - the neural plate - develops folds (neural folds) and forms the neural tube.

5. Figure 5-12 Relationships between the neural plate and primitive streak. A, Day 15. B, Day 18. C, Day 19. D, Days 20 to 21.
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© 2005 Elsevier

6. Induction Inductive effects
The Nobel Prize in Physiology or Medicine 1935 was awarded to Hans Spemann "for his discovery of the organizer effect in embryonic development".

7. Induction of the Neural Tube
epiblast
inhibition of default
inhibition of default
BMP-2
BMP-4
activin
mesoderm
epidermis
follistatin
chordin
noggin (BMP-inhibition)
default pathway
E-cadherin
neural tube
N-Cadherin
Numerous signal proteins inhibit the activity of BMP/Activin, thereby maintaining the default mechanism (- neural tube).

11. Closure of the neural tube in a „zip-lock” like manner
Figure 6-1 Early stages in the formation of the human central nervous system. A, At 18 days. B, At 20 days. C, At 22 days. D, At 23 days.
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© 2005 Elsevier

12. neuroporus anterior
Neural tube
3week old human
embryo (2mm)

13. Secondary neurulation
Condensing
mesenchymal
cells
cavitation
Neural tube
Tail bud
vulnerable target for neural tube defects !

14. (NTD, neural tube defects)
Aproximately 1:1000 infants with spina bifida occure

15. Non-closure of neural tube anomalies: spina bifida
Hair
Open neural tube
Meninx
Meninx
Skin
Transverse process
Rachischisis
Spina bifida occulta (skin-covered NTDs)
Spinal cord
Meninx
Meningocele
Meningomyelocele

16. Meningomyelokele, spina bifida (neuroporus posterior is open) :Open NTDs occur in about 0.1% of all live births

17. Non-Closure of Neural Tube
Anencephalia
Hole on cranial bone
Meninges
Ventricle
Bulging brain tissue
teratogenic effects
e.g.: maternal diabetes
hyperthermia
Pax3
sonic hedgehog
openbrain
protective factors
Folic acid, B12

18. Folic-acid receptor expression in human embryo
-Folate acid (vitamin B9) supplementation (400 micrograms of synthetic folic acid per day in a prenatal multivitamin) can reduce the incidence of NTDs by up to 75%.
devbio8e-fig jpg
Folic-acid receptor expression in human embryo

19. Neural crest cells are a unique population of cells that arise from the dorsal part of the forming neural tube during neurulation and gives rise to a diverse cell lineage including : myofibroblasts, fibroblasts, cartilage, bone, melanocytes, endocrine cells, peripheral neurons, glial cells .
3 weeks old human embryo 19

20. The NC cells undergo an epithelial-to-mesenchymal transformation as they detach from the neural tube.

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