PTPN11 Mutations in the Ras-MAPK Signaling Pathway Affect Human White Matter Microstructure

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Germline activating PTPN11 gene mutations overactivate the Ras-Mitogen-Activated Protein Kinase pathway.
• These mutations cause Noonan syndrome (NS), a disorder linked to cognitive deficits in attention, executive function, and memory.
• While mouse models show PTPN11 mutations impair white matter, their impact on human brain development is less understood.

Purpose of the Study:

• To investigate the effects of PTPN11 mutations on white matter connectivity in the developing human brain.
• To correlate white matter alterations with cognitive phenotypes in children with Noonan syndrome.

Main Methods:

• Diffusion imaging and structural MRI were used to assess white matter connectivity and brain morphology in 17 children with NS and 17 age/sex-matched controls.
• Analysis focused on fractional anisotropy (FA) and radial diffusivity (RD) to quantify white matter integrity.

Main Results:

• Children with NS exhibited widespread reductions in FA and increases in RD, indicating decreased white matter connectivity.
• Specific white matter tracts, including the posterior thalamic radiation and genu of the corpus callosum, showed correlations with inhibition and auditory attention, respectively.
• Memory performance was associated with connectivity in the cingulum hippocampus and cingulum cingulate gyrus.

Conclusions:

• PTPN11 mutations significantly impact white matter connectivity in children with Noonan syndrome.
• These findings elucidate the neural underpinnings of NS-related cognitive deficits.
• Altered white matter connectivity may serve as a brain-based biomarker for Noonan syndrome.