Useful markers of epithelial differentiation are: (A) Fillagrin, (B) Loricin, (C) Both, (D) None
Answer is C. 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.