Peripherin (PRPH) is a cytoskeletal intermediate filament protein found in neurons of the peripheral and central nervous systems. Peripherin functions in developmental neurite elongation and injury-related axon regeneration. Mutations in peripherin are associated with amyotrophic lateral sclerosis. Antibodies to peripherin are sometimes used in the diagnosis of Hirschsprung disease, specifically to determine the presence (peripherin positive) or absence (negative) of ganglion cells in rectal biopsies. In immunohistochemistry, peripherin stains various neurons throughout the peripheral nervous system, the enteric nervous system, the brainstem and spinal cord, as well as smaller populations of neurons in the cerebral cortex and hypothalamus. References: The Journal of Clinical Investigation. 119 (7): 1814–24, PMID: 19587456; Guidebook to the Cytoskeletal and Motor Proteins (2nd ed.). 1999. Sambrook & Tooze Partnership; BMC Neuroscience. 2008. 9: 26, PMID: 18294400; Modern Pathology. 23 (9): 1173–9, PMID: 20495540.