Primitive Pit 

A funnel-shaped depression at the center of Hensen’s node through which cells migrate to form the notochord and prechordal plate.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Wnt = wingless + integrated

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Wnt proteins are modified by linkage of a monounsaturated fatty acid, palmitoleic acid, to a serine in the middle of the protein.

TLS Online TPP Program

#Id: 9961

#Unit 4. Cell Communication and Cell Signaling

Lipid modifications of Wnt are catalyzed by the 

O-acetyltransferase Porcupine.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Principal signaling receptor is Frizzled (Fz), contains 

7 TM α helices.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

The palmitoleate attached to the Wnt protein binds to a specific site on the Fz extracellular domain and stabilizes the Wnt-Fz complex.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Wnt signal transduction pathways classify into:

1. Canonical wnt pathway (β-catenin dependent)

2. Noncanonical wnt pathways (β-catenin independent)