A 3-week-old neonate presents with severe jaundice (total bilirubin 22 mg/dL) and anemia (hemoglobin 8.0 g/dL), requiring exchange transfusion. The direct antiglobulin (Coombs) test is negative. The peripheral smear shows numerous spherocytes. The parents are healthy and have no history of anemia. Which of the following is the most likely underlying genetic basis for this severe neonatal presentation of hereditary spherocytosis?