An early Sox2-dependent gene expression programme required for hippocampal dentate gyrus development

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• The hippocampus is vital for cognitive functions.
• SOX2 gene mutations cause neurodevelopmental disorders, including intellectual disability and seizures.
• These disorders are often associated with hippocampal abnormalities.

Purpose of the Study:

• To investigate the role of the SOX2 transcription factor in hippocampal development.
• To determine the effects of SOX2 deletion at different embryonic stages on hippocampal formation.
• To elucidate the molecular mechanisms underlying SOX2-dependent hippocampal development.

Main Methods:

• Generation of a conditional Sox2 mutation mouse model with deletions at distinct developmental time points (E9.5, E10.5, E11.5).
• Analysis of hippocampal morphology and gene expression patterns in Sox2 mutant mice.
• Electrophysiological recordings in specific hippocampal subregions (CA1, CA3).

Main Results:

• Early Sox2 deletion (E9.5) resulted in near-complete absence of the dentate gyrus (DG).
• Later Sox2 deletion (E10.5) significantly reduced the DG size.
• Downregulation of key developmental genes (Gli3, Wnt3a, Cxcr4, p73, Tbr2) was observed in early mutants, with SOX2 directly regulating Gli3 and Cxcr4.
• Electrophysiology revealed impaired excitatory transmission in CA1 and CA3 regions in the Emx1-Cre model.

Conclusions:

• SOX2 is essential for proper hippocampal development, particularly the formation of the dentate gyrus.
• SOX2 regulates a network of genes critical for hippocampal embryogenesis.
• Disruption of SOX2 function leads to molecular and functional deficits in the hippocampus, contributing to neurodevelopmental abnormalities.