Filaggrin is a structural protein that is crucial for in the development and maintenance of the skin barrier. This gene encodes a retroviral-like protease involved in profilaggrin-to-filaggrin processing. Expression is found primarily in the epidermis and inner root sheath of hair follicles. [provided by RefSeq, May 2017] see less Filaggrin is a structural protein that is crucial for in the development and maintenance of the skin barrier. This gene encodes a retroviral-like protease involved in profilaggrin-to-filaggrin processing. Expression is found primarily in the epidermis and inner root sheath of hair follicles. [provided by RefSeq, May 2017]