Premature Termination of Hair Follicle Morphogenesis and Accelerated Hair Follicle Cycling in Iasi Congenital Atrichia (fzica) Mice Points to Fuzzy as a Key Element of Hair Cycle Control

The study analyzed the skin phenotype of mice homozygous for the Iasi congenital atrichia (fzica/fzica) mutation, which is allelic to the fuzzy (fz) mutation. These mice exhibited a sparse hair coat after birth and lost all hair by postnatal day 120. While early and mid-stages of hair follicle morphogenesis were normal, late stages showed cell degeneration in the Huxley layer of the inner root sheath and a lack of hair shaft medulla. Hair follicle development was prematurely terminated, leading to an accelerated hair cycle with shortened telogen and premature anagen phases. The findings suggested that the fuzzy gene played a crucial role in hair shaft integrity, inner root sheath and medulla differentiation, and the control of hair follicle cycling, making it a significant target for studying the mechanisms driving hair follicle cycling.