CRYBB3 encodes crystallin beta B3, a dominant structural protein essential for lens transparency and light refraction in the vertebrate eye 1. The protein is a member of the beta/gamma-crystallin superfamily characterized by four Greek key motifs, with CRYBB3 organized as a duplet gene alongside CRYBB2 on chromosome 22 1. During lens fiber cell differentiation, CRYBB3 exhibits spatially and temporally regulated expression, with spliced transcripts transiently accumulating in early differentiating lens fiber cell nuclei, potentially reflecting a developmentally specific regulatory mechanism 2. Mutations in CRYBB3 cause congenital cataracts, often with associated microphthalmia. Pathogenic variants include missense mutations at position 156 (p.Gly156Glu and p.Gly156Arg) and p.Gly165Arg, which segregate with autosomal dominant and recessive inheritance patterns 3 4. A common ancestral p.Gly165Arg mutation was identified across four consanguineous Pakistani families with nuclear cataracts 4. Loss-of-function studies reveal that CRYBB3 depletion disrupts lens morphology and alters the lens proteome, with downregulation of multiple proteins including Smarcc1/Baf155 and reduced expression of protective and structural components 5. The CRYBB3 promoter contains binding sites for transcription factors AP-2α, c-Jun, c-Maf, Etv5, and Pax6, with FGF2 activation identified in lens cell cultures 5. CRYBB3 mutations account for a minority of inherited cataracts but represent an important diagnostic target in pediatric ophthalmology.