Mediolateral intercalation in the formation of the primitive streak (Cellular Dance Mechanism) cells came down the sides of the epiblast to undergo a medially directed intercalation of cells in the posterior margin

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#Unit 5. Developmental Biology

The anterior neural plate produce the next signals, that promotes the synthesis of the Pax6 transcription factor in the anterior ectoderm.

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#Unit 5. Developmental Biology

Expression of Pax6 protein constitute the competence of the surface ectoderm to respond to the optic vesicle.

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#Id: 169

#Unit 5. Developmental Biology

The optic vesicle secrete two paracrine factors:

 BMP4

 FGF8

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#Id: 170

#Unit 5. Developmental Biology

BMP4 

A protein that is received by the lens cells and induces the production of the Sox transcription factors.

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#Id: 171

#Unit 5. Developmental Biology

FGF8 

A secreted signal that is received by the lens cells and induces the production of the L-Maf transcription factor.

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#Id: 172

#Unit 5. Developmental Biology

Combination of Pax6, Sox2, and L-Maf in the ectoderm is needed for the production of the lens and the activation of lens-specific genes i.e. δ-crystallin.