Advances in genetic hearing loss: CIB2 gene.

Hearing plays a crucial role in human development. Receiving and processing sounds are essential for the advancement of the speech ability during the early childhood and for a proper functioning in the society. Hearing loss is one of the most frequent disabilities that affect human senses. It can be caused by genetic or environmental factors or both of them. Calcium- and integrin-binding protein 2 (CIB2) is one of the recently identified genes, involved in HI pathogenesis. CIB2 is widely expressed in various human and animal tissues, mainly in skeletal muscle, nervous tissue, inner ear, and retina. The CIB2 protein is responsible for maintaining Ca2+ homeostasis in cells and interacting with integrins-transmembrane receptors essential for cell adhesion, migration, and activation of signaling pathways. Calcium signaling pathway is crucial for signal transduction in the inner ear, and integrins regulate hair cell differentiation and maturation of the stereocilia. To date, mutations detected in CIB2 are causative for nonsyndromic hearing loss (DFNB48) or Usher syndrome type 1 J. Patients harboring biallelic CIB2 mutations suffer from bilateral, early onset, moderate to profound HI. In the paper, we summarize the current status of the research on CIB2.