This gene encodes subunit a, one of two subunits of alpha-crystallin, which is a high molecular weight, soluble aggregate and is a member of the small heat shock protein (sHSP) family. The encoded protein has been identified as a moonlighting protein based on its ability to perform mechanistically distinct functions. It acts as a molecular chaperone and is the major protein in the eye lens, maintaining the transparency and refractive index of the lens. In mouse, deficiency in this gene is associated with smaller lenses and eyes and with increasing lens opacity with age. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]