A 14-month-old girl presents with developmental delay, severe growth failure, and recurrent seizures since 9 months of age. On examination, she has a distinctive facial appearance with a broad prominent glabella continuous with the nasal bridge, marked hypertelorism, highly arched eyebrows, downturned mouth, and a short philtrum with a vertical midline groove. Her parents report normal karyotypes. High-resolution karyotype was normal, but chromosomal microarray reveals the deletion marked **A** in the diagram. Which of the following best explains the pathogenesis of her seizure disorder in this condition?