Multiple mechanisms mediate motor neuron migration in the zebrafish hindbrain

Area of Science:

• Developmental Neuroscience
• Molecular Biology
• Genetics

Background:

• Van Gogh-like 2 (Vangl2) is crucial for tangential migration of facial branchiomotor neurons (FBMNs) via the Wnt/Planar Cell Polarity (PCP) pathway.
• Vangl2 expression in the zebrafish hindbrain suggests potential roles in motor neuron migration beyond FBMNs.

Purpose of the Study:

• To investigate if Vangl2 regulates motor neuron migration in anterior hindbrain rhombomeres (r2-r3).
• To determine if motor neuron migration in r2/r3 is dependent on Vangl2 and prickle1b (pk1b) functions.

Main Methods:

• Utilized ectopic hoxb1b expression to transform r2 into an 'r4-like' compartment in zebrafish embryos.
• Employed time-lapse imaging to track GFP-expressing motor neurons in wild-type and vangl2(-) (trilobite) mutant embryos.
• Analyzed gene expression of pk1b and observed migration in pk1b morphants and tri; val double mutants.

Main Results:

• Ectopic hoxb1b expression induced migration of motor neurons in r2/r3 along the anterior-posterior axis in wild-type embryos.
• These migrating r2/r3 motor neurons expressed pk1b.
• Motor neuron migration in r2/r3 persisted in vangl2(-) mutants and pk1b morphants, despite failed FBMN migration in r4. Valentino mutation partially rescued the trilobite migration defect.

Conclusions:

• Tangentially migrating motor neurons in the anterior hindbrain (r1-r3) utilize Vangl2- and pk1b-independent mechanisms.
• Multiple regulatory mechanisms govern motor neuron migration along the anterior-posterior axis of the zebrafish hindbrain.
• The valentino mutation suggests involvement of other Vangl2-independent factors in neuronal migration.