Dual effects of ARX poly-alanine mutations in human cortical and interneuron development

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Infantile spasms are a severe childhood epilepsy linked to intellectual disability.
• Mutations in the Aristaless-related homeobox (ARX) gene are found in approximately 5% of affected males.
• Existing animal models do not fully replicate human infantile spasms, highlighting the need for human-specific models.

Purpose of the Study:

• To investigate the impact of Aristaless-related homeobox (ARX) gene mutations, specifically the PAE mutation, on human brain development using organoid models.
• To understand the cellular and molecular mechanisms underlying ARX-related infantile spasms and developmental epilepsies.

Main Methods:

• Utilized human cortical organoids (COs) and ganglionic eminence organoids (GEOs) to model cortical and interneuron development.
• Analyzed the effects of ARX ^PAE mutations on gene expression, cell migration, and cell proliferation in organoid models.
• Investigated potential therapeutic interventions by inhibiting CXCR4 to rescue observed migration defects.

Main Results:

• ARX ^PAE mutations led to decreased ARX expression and enhanced interneuron migration in GEOs, a phenotype reversible by CXCR4 inhibition.
• Observed an initial increase in radial glia and intermediate progenitor cells, followed by a loss of cortical neurons in organoid models.
• Found ARX upregulation and altered CDKN1C expression in patient-derived COs, with ARX ^PAE assembloids exhibiting early hyperactivity.

Conclusions:

• Human brain organoid models effectively recapitulate key aspects of ARX-related infantile spasms and developmental epilepsies.
• ARX ^PAE mutations disrupt crucial developmental processes, including interneuron migration and neuronal cell populations.
• Targeting ARX ^PAE pathways in human organoids provides a promising avenue for developing novel therapeutic strategies for infantile spasms.