The fact that both downregulation and upregulation of HOXC13 affect the regular expression of hard keratins specific to the hair and led to hair loss, as illustrated both by the brittle hair resulting in the alopecia phenotype, displayed by mice lacking the function of HOXC13, and by the hairless phenotype of mouse models overexpressing HOXC13, resembling ichthyosis, further highlights the vital regulatory role of HOXC13 expression levels over various keratin genes [51, 52, 53, 54, 55]. This evidence concerns the gene HOXC13 and alopecia.