Figure 4. A unique cell lineage expressing Krt4 and Krt10. Horizontal sections of eyelids double stained with keratin 4 (Krt4; red) and Krt10 (green) at P4 (A, B), P11 (C, D), and adult (E, F). Regions of colocalization were determined using the Coloc 2 plug-in for the Fiji software package. Colocalized regions are shown in white at P4 (B), P11 (D) and adult (F). At P4, colocalization of Krt4 and Krt10 is found in the developing central duct as well as the distal gland region. By P11, the colocalization region is restricted to the central duct and is absent from the acini. In the fully developed meibomian gland (adult), areas of colocalization are found within the central duct near the ductule openings. EP = epidermis; MCJ = mucocutaneous junction; CJ = conjunctiva; AC = acinus; asterisk = central duct.