Azu Cohen

All cells have the capacity to code for any protein in the body, but cells are specialized and don’t produce all the proteins they can potentially code for. As a consequence, humans don’t have features such as taste buds on their arms or hair on their eyes. Millar lab focuses on hair growth and the molecular restrictions on where and what kind of hair can grow. A central question that Millar Lab seeks to answer is: what factors and mechanisms regulate hair growth, and how can we manipulate these processes for our gain? One process that influences hair growth in mammals is the Wnt/ß-catenin signaling pathway, whose signaling inhibition permits proper patterning and development of hair follicles. Dkk2, the specific inhibitor studied in this paper, shows high levels of expression in mice plantar paw skin (the human equivalent of palms and foot soles). In contrast, Dkk2 shows little to no presence in the dorsal paw (the human equivalent of the back of the hands). To better understand these differences, Millar lab bred mice with the Dkk2 null gene, utilizing the absence of this inhibitor to observe how and where it normally functions in the dermis. The Dkk2 null mutants grew—albeit irregular—hair follicles, not just hair-like structures, in the plantar region as well as the ventral digits of their paws. Additionally, Dkk2 was overshadowed in areas such as the nail as its absence didn’t cause hair growth there, suggesting that each Wnt inhibitor holds regional control over specific sections of the mouse dermis. Nullifying Dkk2 didn’t have any effect on the mices’ overall skin development, reiterating Dkk2’s sole influence on the development of hair follicles. Alongside mice, the hair growth of rabbits was studied, revealing that Dkk2 is naturally absent in their plantar paw skin, permitting fully haired paws. This difference in Dkk2 plantar presence between mice and rabbits suggest evolutionary changes in Dkk2 expression across mammals. The hair growth upon Dkk2’s nullification prompts the start of a new era of hair replacement and regrowth technologies, using the nullification of select Wnt inhibitors to selectively manipulate hair follicle development.