Loss, Gain and Altered Function of GlyR α2 Subunit Mutations in Neurodevelopmental Disorders.

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Glycine receptors (GlyRs) with the α2 subunit are crucial for early brain development, regulating cell fate, neuronal migration, and synaptogenesis.
• Mutations in the X-linked GLRA2 gene, encoding the GlyR α2 subunit, are associated with autism spectrum disorder (ASD), often causing loss-of-function.
• While some GLRA2 variants lead to loss-of-function, others, like p.R323L, exhibit gain-of-function properties.

Purpose of the Study:

• To functionally characterize four novel GLRA2 missense variants (p.V-22L, p.N38K, p.K213E, p.T269M) associated with ASD or developmental disorders.
• To elucidate the impact of these variants on GlyR α2 function, including cell-surface expression, glycine sensitivity, and channel activity.

Main Methods:

• Bioinformatics analysis and molecular dynamics simulations.
• Cellular models to assess GlyR α2 trafficking and cell-surface expression.
• Electrophysiology using artificial synapses to measure synaptic currents and glycine sensitivity.

Main Results:

• GlyR α2^V-22L and GlyR α2^N38K variants exhibited reduced cell-surface expression and impaired glycine binding, suggesting partial loss-of-function.
• GlyR α2^K213E displayed enhanced channel activity (gain-of-function) with larger and faster synaptic currents.
• GlyR α2^T269M showed increased glycine sensitivity and a significant leak current, indicating an altered function that enhances glycinergic signaling.

Conclusions:

• Missense variants in GLRA2 can result in diverse functional outcomes: loss-of-function, gain-of-function, or altered function.
• These functional changes in GlyR α2 likely contribute to the heterogeneous clinical phenotypes observed in individuals with GLRA2 mutations.
• The study highlights the complex role of GlyR α2 variants in regulating neural development and their potential impact on cognition, learning, and memory.