Disrupted glial-mediated synaptic refinement in Fragile X syndrome

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Fragile X syndrome (FXS) is a leading inherited cause of intellectual disability and autism.
• Loss of fragile X mental retardation protein (FMRP) causes FXS, but its role in glial cells during neural development is unclear.

Purpose of the Study:

• Investigate the role of FMRP in glial cells during early neural circuit development in FXS.
• Identify cellular and molecular mechanisms underlying synaptic abnormalities in FXS models.

Main Methods:

• Applied a multi-omic framework including single-cell transcriptomics, computational modeling, and lipidomics in Fmr1 knockout mice.
• Utilized glial engulfment assays and analyzed the retinogeniculate pathway at postnatal day 7.

Main Results:

• FXS model mice showed altered synaptic pruning, accelerated eye-specific segregation, and coordinated gene expression changes in microglia, astrocytes, and neurons.
• Enhanced astrocyte-microglia signaling via Ephrin A and semaphorin pathways was observed.
• FXS glial cells exhibited over-engulfment of synaptic material, linked to reduced EphA-associated lipids.

Conclusions:

• Impaired glial-driven synaptic refinement is an early pathogenic mechanism in Fragile X syndrome.
• Specific genes and pathways involved in glial synaptic pruning present potential therapeutic targets for FXS circuit development.