Genotype and brain pathology phenotype in children with tuberous sclerosis complex

Area of Science:

• Neurogenetics
• Developmental Neuroscience
• Medical Imaging

Background:

• Tuberous Sclerosis Complex (TSC) is a genetic disorder characterized by benign tumor formation in multiple organs, including the brain.
• Brain malformations in TSC are associated with disease severity and can be visualized using magnetic resonance imaging (MRI).
• TSC is caused by inactivating mutations in either the TSC1 or TSC2 genes.

Purpose of the Study:

• To investigate the association between specific inactivating TSC1 and TSC2 variants and TSC-related brain pathology.
• To evaluate the prognostic value of subdividing TSC2 variants based on their predicted impact on TSC2 protein expression.

Main Methods:

• Genotype-phenotype association study of 64 children (1.4-17.9 years) with TSC.
• Brain abnormalities assessed via MRI.
• Participants grouped by TSC1 or TSC2 variant, with TSC2 group further subdivided based on predicted protein expression impact (TSC2p vs. TSC2x).

Main Results:

• The TSC2 variant group exhibited more numerous and larger tubers, increased radial migration lines, and more subependymal nodules compared to the TSC1 group.
• Subependymal nodules were more frequently calcified in the TSC2 group.
• Subdivision of TSC2 variants showed a trend towards more temporal lobe tubers and a higher proportion of cystic tubers in the TSC2x subgroup, but did not substantially alter overall prediction.

Conclusions:

• Inactivating TSC2 variants are associated with more severe brain pathology in TSC compared to TSC1 variants.
• While TSC2 variants influence brain pathology severity, subdividing them based on predicted expression effects did not significantly improve prognostic prediction in this cohort.
• Larger studies may be needed to identify specific TSC2 variants with clear prognostic value.