FIGURE 2.

Somatic MTOR variant was detected in dysplastic cortex and basal ganglia. Immunostaining of phosphorylated S6 protein (Ser235/236) revealed (A–C) dysmorphic neurons and (D) balloon cells with mTOR pathway hyperactivation in cortical specimens. (E, F) Hematoxylin and eosin staining of basal ganglia biopsies showed dysmorphic neuron morphology with cytomegaly, irregular cytoplasmic outlines, and prominent nucleoli. (G) Droplet digital PCR confirmed the MTOR NM_004958.4:c.4375G > C (p.Ala1459Pro) variant in 12 frozen cortical specimens from three epilepsy surgeries (white bars), and two FFPE basal ganglia specimens from biopsy at age 2.6 years (gray bars), with mean VAF between 0.4% and 5.4%. Error bars represent standard deviation, n = 3 independent experiments. (H) Approximate locations of cortical specimens in which VAF was determined, taken from operative photographs and notes. Hatched line indicates location deep to the cortical surface. (A–F): ×400 magnification, (E): ×200 magnification, scale bars = 20 μm