Metastasis-associated kinase modulates Wnt signaling to regulate brain patterning and morphogenesis

Area of Science:

• Developmental Biology
• Molecular Biology
• Cell Biology

Background:

• Wnt signaling is crucial for vertebrate embryonic development, controlling cell fate, proliferation, and morphogenetic movements.
• Distinct Wnt pathway branches regulate gene expression and cytoskeletal organization through phosphorylation events.

Purpose of the Study:

• To identify novel regulators of Wnt signaling involved in embryonic development.
• To investigate the role of metastasis-associated kinase (MAK) in Xenopus embryonic development and Wnt pathway modulation.

Main Methods:

• Wnt transcriptional reporters and Jun N-terminal kinase activation assays were used.
• MAK's interaction with Frizzled 3 and Dishevelled was examined through complex formation and in vitro phosphorylation.
• Embryonic brain marker expression (Otx2, En2, Gbx2) was analyzed following MAK modulation.
• Rescue experiments involved simultaneous depletion of MAK and beta-catenin.

Main Results:

• MAK RNA injection suppressed Wnt reporters and activated Jun N-terminal kinase.
• MAK localized to the cell membrane, complexed with Dishevelled, and phosphorylated Dsh.
• MAK activity modulated regional brain markers, affecting midbrain-hindbrain boundary formation.
• Depletion of MAK caused midbrain patterning defects, rescued by beta-catenin depletion.

Conclusions:

• Metastasis-associated kinase (MAK) is a novel regulator of Wnt signaling in Xenopus embryos.
• MAK plays a role in morphogenetic movements, eye, and brain development, particularly midbrain-hindbrain boundary formation.
• MAK functions as a switch between canonical and non-canonical Wnt signaling branches during development.