Inhibitory CCK+ basket synapse defects in mouse models of dystroglycanopathy

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Dystroglycan (Dag1) is crucial for linking the extracellular matrix to the cytoskeleton.
• Mutations in Dag1 or its glycosylation genes cause dystroglycanopathy, a congenital muscular dystrophy with neurological defects.
• The role of Dag1 in neuronal development and synaptic function remains incompletely understood.

Purpose of the Study:

• To investigate interneuron (IN) development, synaptic function, and seizure susceptibility in mouse models of dystroglycanopathy.
• To elucidate the specific roles of Dystroglycan in organizing inhibitory synapses.
• To correlate specific Dag1-related defects with neuropathological phenotypes.

Main Methods:

• Utilized multiple mouse models with varying degrees of Dystroglycan deficiency (forebrain deletion, intracellular domain absence, partial glycosylation reduction).
• Examined the development and targeting of CCK+/CB1R+ interneurons in the hippocampus.
• Assessed synaptic function and seizure susceptibility using electrophysiological and behavioral analyses.

Main Results:

• Severe Dag1 deficiency impaired CCK+/CB1R+ IN development and axonal targeting, causing synaptic defects and increased seizures.
• Absence of the intracellular Dystroglycan domain led to altered inhibitory synaptic function, indicating a postsynaptic role.
• Mild Dystroglycan reduction did not affect IN synaptic function or seizure susceptibility.

Conclusions:

• Inhibitory synaptic dysfunction and heightened seizure susceptibility are key features of severe dystroglycanopathy.
• Dystroglycan is essential for the proper assembly of functional inhibitory synapses.
• The severity of Dystroglycan defects dictates the extent of neuropathological consequences.