In this study, we used these tools, together with efficient (Rosa26-lox-stop-lox TdTomato) and inefficient (Brainbow2.1/+ confetti) lineage tracing, 5-ethynyl-2′-deoxyuridine (EdU) labeling and genetic deletion of Ect2 (which inhibits cytokinesis and migration) and Esco2 (which impairs chromatin cohesion and thus leads to the death of proliferating cells) to directly examine the extent, functional consequence, and molecular characteristics of fibroblast proliferation in 2 distinct models of PF induced by silica or bleomycin. The gene discussed is ECT2; the disease is pemphigus foliaceus.