GJB2 is a gene located on chromosome 13 that provides instructions for making a protein called connexin 26. This protein is essential for the proper functioning of cells in the inner ear, where it helps to form gap junctions. These junctions allow for communication between cells, which is crucial for hearing. Mutations in the GJB2 gene are one of the most common causes of inherited hearing loss. When the gene is altered, it can disrupt the formation of connexin 26, leading to problems in the auditory system. This can result in varying degrees of hearing impairment, often present at birth or developing in early childhood.