KRTAP4-2 encodes a keratin-associated protein that localizes to the hair cortex cytosol, where it forms an interfilamentary matrix essential for hair shaft structure. Through extensive disulfide bond cross-linking with cysteine-rich hair keratins, KRTAP4-2 contributes to forming rigid, resistant hair shafts [GO annotations: protein binding, hair cycle]. Based on limited published evidence, KRTAP4-2 has been identified as a potential biomarker in glioblastoma multiforme, with higher expression associated with disease progression 1, and as a variant detected in mature cystic teratomas of the ovary 2.