EIPR1 acts as a regulator of insulin secretion and distribution of mature dense-core vesicles.28 Dense-core vesicles are regulated secretory vesicles found in neurons and endocrine cells and are involved in the modulation of neurotransmission.29 Allele-specific methylation of EIPR1 has been proposed as a mediator of psychiatric disorder susceptibility in phenotypically discordant monozygotic twins.30 Here, EIPR1 is linked to psychiatric disorder.