Calretinin is a calcium-binding protein involved in calcium signaling. Calretinin belongs to the troponin C superfamily. This protein plays a role in diverse cellular functions, including message targeting and intracellular calcium buffering. Calretinin is abundantly expressed in neurons including retina and cortical interneurons. Calretinin has an important role as a modulator of neuronal excitability including the induction of long-term potentiation. Loss of expression of calretinin in hippocampal interneurons has been suggested to be relevant in temporal lobe epilepsy. It is expressed in a number of other locations including hair follicles. Calretinin is a diagnostic marker for some human diseases, including Hirschsprung disease and some cancers.