Karyotype — Beckwith-Wiedemann 11p15.5 Imprinting Defect

A 2-week-old male infant born at 38 weeks presents with macrosomia (birth weight 4.8 kg, >97th percentile), macroglossia causing feeding difficulty, and a small omphalocele. On day 3 of life, he developed symptomatic hypoglycemia (blood glucose 35 mg/dL) requiring IV dextrose. Methylation-specific MLPA of chromosome 11 reveals loss of methylation at the maternal ICR2 (KvDMR1) region. The imprinting defect marked **A** in the diagram results in silencing of which tumor suppressor gene, and what is the recommended surveillance protocol for this patient?