RIMS2 (regulating synaptic membrane exocytosis 2) is a presynaptic scaffold protein that plays a critical role in calcium-regulated neurotransmitter release and synaptic vesicle exocytosis 1. The protein localizes to presynaptic active zones and functions as a Rab effector involved in synaptic vesicle docking and priming 1. RIMS2 shows predominant expression in rod photoreceptors within the outer plexiform layer of the retina, as well as in Purkinje cells and pancreatic islets 1. Loss-of-function mutations in RIMS2 cause a syndromic congenital cone-rod synaptic disorder characterized by night blindness, photophobia, nystagmus, and distinctive electroretinographic abnormalities 1. Beyond retinal dysfunction, RIMS2 deficiency is associated with neurodevelopmental impairments and abnormal glucose homeostasis, likely due to impaired insulin secretion from pancreatic beta cells 1. The circular RNA form of RIMS2 (circRIMS2) is highly expressed in neural tissues and plays important roles in maintaining retinal structure and function, with deficiency leading to retinal degeneration and neuroinflammation 2. Additionally, circRIMS2 has been implicated in synaptic dysfunction associated with Alzheimer's disease through regulation of NMDA receptor degradation 3.