A 13 year old male patient complains about the discoloration of his teeth. His mother shows a similar discoloration of her teeth. Clinical findings reveal teeth with mottled, opaque white brown yellowish discoloration. Snowcapped appearance of teeth is appreciable. OPG reveals a thin layer of enamel over the cusp tips and interproximal surfaces. Probe test is positive. Based on the Pedigree chart for the inheritance of this disorder, which of the following gene may be affected?

A complex inheritance pattern gives rise to amelogenesis imperfecta (AI), a structural defect of the tooth enamel. It may be differentiated into three main groups: hypoplastic (HP), hypocalcified (HC), and hypomature (HM), depending on the clinical presentation of the defects and the likely stage of enamel formation that is primarily affected. Each main clinical group of AI may be further divided into several subgroups depending on the mode of inheritance, as well as the clinical appearance of the defective enamel, although in some cases, overlapping clinical features may make distinction difficult.  Note: ENAM gene has autosomal dominant inheritance. AMELX has an X-linked recessive inheritance.