NF2 Bilateral Vestibular Schwannomas

An 18-year-old college student presents with a two-year history of bilateral progressive sensorineural hearing loss and tinnitus. MRI of the brain reveals bilateral enhancing masses centered on both internal auditory canals with classic ice-cream cone morphology. The structure marked **A** (right vestibular schwannoma at the right internal auditory canal) measures 2.2 cm with both intracanalicular and cisternal components. Additional imaging reveals meningiomas, an intramedullary ependymoma, and a peripheral nerve sheath tumor in the calf. Genetic testing confirms a heterozygous truncating mutation in the NF2 gene on chromosome 22q12. Which of the following best describes the molecular consequence of this NF2 mutation affecting the structure marked **A**?