Cyclic Hair Loss and Regrowth in Transgenic Mice Overexpressing an Intermediate Filament Gene

The study involved creating transgenic mice with up to 250 copies of a sheep wool intermediate filament keratin gene to observe its effects on hair structure and development. In one transgenic line with 250 transgenes, a stable pattern of cyclic hair loss and regrowth was observed, mimicking the natural mouse hair cycle. The sheep transgenes were expressed at the correct stage of hair development and at high levels. This led to an increased level of intermediate filament keratin protein and a decreased level of filament-associated proteins, disrupting the normal protein array in hair cortex cells. This imbalance resulted in weakened hair fibers that were prematurely lost.