FGF5 is a crucial regulator of hair length in humans

In the study, researchers investigated the genetic basis of familial trichomegaly, a condition characterized by abnormally long eyelashes, by examining two Pakistani families with the disorder. They utilized whole exome sequencing and homozygosity mapping to identify mutations in the fibroblast growth factor 5 (FGF5) gene as the cause of the condition. Additional mutations in FGF5 were found upon sequencing the gene in other families with trichomegaly. The study also revealed that forearm hair from affected individuals was significantly longer and more likely to be in the anagen (growth) phase compared to controls. In vitro experiments with hair follicle organ cultures showed that FGF5 can induce the regression of the human hair follicle. This research established FGF5 as a key regulator of hair growth in humans and suggested a potential target for controlling eyelash growth therapeutically.