Defects in the acid phosphatase ACPT cause recessive hypoplastic amelogenesis imperfecta

We identified two homozygous missense variants (c.428C>T, p.(T143M) and c.746C>T, p.(P249L)) in ACPT, the gene encoding Acid Phosphatase, Testicular, which segregate with hypoplastic Amelogenesis imperfecta (AI) in two unrelated families. ACPT is reported to play a role in odontoblast differentiation and mineralisation by supplying phosphate during dentine formation. Analysis by computerised tomography and scanning electron microscopy of a primary molar tooth from an individual homozygous for the c.746C>T variant, revealed an enamel layer that was hypoplastic but mineralised with prismatic architecture. These findings implicate variants in ACPT as a cause of early failure of amelogenesis during the secretory phase.