Fragile X cortex is characterized by decreased parvalbumin-expressing interneurons

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Fragile X syndrome (FXS) is a genetic neurodevelopmental disorder linked to FMR1 gene mutations.
• FXS frequently co-occurs with autism spectrum disorder (ASD), accounting for up to 5% of ASD cases.
• The specific cellular alterations in the FXS cortex remain incompletely understood.

Purpose of the Study:

• To investigate alterations in specific interneuron populations within the FXS cortex.
• To compare the number of Calbindin (CB+), Calretinin (CR+), and Parvalbumin (PV+) interneurons in multiple cortical regions between FXS and neurotypical brains.

Main Methods:

• Quantitative analysis of interneuron populations (CB+, CR+, PV+) in five cortical areas (BA46, BA3, BA4, BA22, BA24).
• Comparison of interneuron counts between post-mortem brain tissue from individuals with FXS and neurotypical controls.

Main Results:

• Fragile X syndrome brains exhibited a significant reduction in PV+ interneurons across all examined cortical areas.
• A significant decrease in CR+ interneurons was observed in the superior temporal cortex (BA22) and primary somatosensory cortex (BA3) of FXS brains.
• No significant difference was found in the number of CB+ interneurons between FXS and neurotypical brains.

Conclusions:

• These findings represent the first evidence of widespread PV+ interneuron deficits in the FXS cortex.
• These interneuron deficits may disrupt cortical network balance, contributing to clinical manifestations in FXS.
• Understanding these cellular changes could guide the development of targeted therapies for FXS and related neurodevelopmental disorders like ASD.