IgSF11 homophilic adhesion proteins promote layer-specific synaptic assembly of the cortical interneuron subtype

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Mammalian neocortical circuits exhibit a distinct layer-based organization of cell types and synaptic inputs.
• Cortical inhibitory interneurons (INs) play a key role in shaping network activity through subtype-specific laminar targeting.
• The molecular mechanisms governing this precise synaptic targeting remain largely unknown.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the layer-specific synaptic connectivity of cortical inhibitory interneurons.
• To determine the role of Immunoglobulin Superfamily member 11 (IgSF11) in the development of chandelier cell (ChC) synapses.

Main Methods:

• Utilized loss-of-function experiments in ChCs and postsynaptic cells.
• Examined the effects of IgSF11 expression levels on ChC presynaptic bouton morphology and synaptic targeting.
• Investigated IgSF11 localization in relation to synaptic partners.

Main Results:

• IgSF11 is preferentially expressed in ChCs and their specific synaptic targets.
• Loss of IgSF11 function disrupts ChC synaptic development in the target layer.
• IgSF11 overexpression in ChCs enlarges presynaptic boutons, while expression in non-target layers induces ectopic ChC synapses.

Conclusions:

• IgSF11 acts as a synapse-promoting adhesion protein essential for layer-specific ChC connectivity.
• Highly localized IgSF11 expression between synaptic partners dictates precise neocortical circuit wiring.
• This study elucidates a key molecular mechanism for establishing subtype-specific IN synaptic specificity.