Mouse models of alopecia: identifying structural genes that are baldly needed

The mature hair follicle undergoes a unique developmental cycle, in which phases of growth are interspersed with phases of involution and rest. The main effectors of this cycle are skin epithelial stem cells that reside in a specialized compartment of the follicle. Defects in this cycle, or in the structure of the hair produced, often result in alopecia (partial or complete hair loss), a condition that affects a significant fraction of the population. Here we discuss transgenic mouse models that exhibit alopecia as a primary phenotype, resulting from the inactivation of genes encoding structural proteins.