Linx mediates interaxonal interactions and formation of the internal capsule

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Forebrain connectivity development involves complex axon guidance.
• The molecular mechanisms underlying internal capsule (IC) formation are not fully understood.
• Identifying guidance cues is critical for understanding brain development.

Purpose of the Study:

• To identify molecular cues involved in internal capsule (IC) formation.
• To elucidate the role of the transmembrane protein Linx in forebrain axon guidance.
• To understand how Linx mediates interactions between thalamocortical and corticofugal axons.

Main Methods:

• Generated and analyzed mice with a null mutation of Linx.
• Performed regional inactivation of Linx in specific brain areas (prethalamus, LGE, neocortex).
• Investigated Linx expression patterns and its binding interactions with axons.

Main Results:

• Linx knockout mice completely lack the internal capsule (IC).
• Regional Linx inactivation in the prethalamus/LGE or neocortex prevents IC formation.
• Linx is expressed on corticofugal axons and in the guiding corridor, but not on thalamocortical axons.
• Linx binds to thalamocortical projections and promotes their outgrowth.

Conclusions:

• Linx is essential for the formation of the internal capsule (IC).
• Linx acts as a guidance cue for thalamocortical axons in the ventral forebrain.
• Linx mediates reciprocal interactions between different axon populations to establish forebrain connectivity.