Changes in the cortical GABAergic inhibitory system in a Spinal Muscular Atrophy mouse model

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Excitatory-inhibitory (E/I) imbalance in the motor cortex is implicated in neurodegenerative movement disorders.
• Spinal Muscular Atrophy (SMA) involves lower motor neuron degeneration due to SMN protein deficiency, but upper motor neuron vulnerability suggests broader cortical involvement.
• Preclinical studies are essential to understand SMA's complex cortical mechanisms due to limited access to early-stage human brain tissue.

Purpose of the Study:

• To investigate the role of GABAergic signaling, metabolism, and interneuron function in the sensorimotor cortex of a severe SMA mouse model.
• To assess the impact of SMN deficiency on GABA levels, its precursor glutamine, synthetic enzymes (GAD65/67), and Parvalbumin-positive interneuron density.
• To explore the age-dependent modulation of neurotransmitter pathways and their correlation with SMA progression.

Main Methods:

• Electrophysiological characterization of cortical inhibitory neurotransmission.
• Imaging and molecular techniques in SMA mouse sensorimotor cortex and primary neuron-astrocyte co-cultures.
• Bioinformatic analyses and biochemical assays to quantify metabolites and assess neurotransmitter pathways.

Main Results:

• SMN deficiency is significantly associated with impaired density, morphology, and signaling of GABAergic Parvalbumin-positive interneurons in the late-stage SMA mouse sensorimotor cortex.
• Evidence of E/I imbalance in the motor cortex of SMA mice, potentially contributing to upper motor neuron vulnerability.
• SMN's role in pre-mRNA splicing impacts neuronal-astrocyte interactions regulating GABA metabolism, release, and reuptake.

Conclusions:

• Altered motor cortical GABAergic neurotransmission plays a role in SMA progression.
• Findings offer a new perspective for developing comprehensive therapeutic strategies for SMA.
• Targeting GABAergic pathways may be a promising avenue for future SMA treatments.