<prompt> Useful markers of epithelial differentiation areFillagrinLoricinBothNone  <response>: The protein making the bulk of keratohyalin granules is fillagrin. Also sulfur-rich protein loricin is present. Fillagrin and loricin are useful markers of epithelial differentiation. Involucrin contributes to the Cornified cell envelope in the cell membrane of keratohyalin cells. 