The Lee lab studies a cellular process called X-chromosome inactivation. In mammals, including humans, males receive one copy of the X chromosome, whereas females possess two. To avoid producing a “double dose” of the proteins and RNAs encoded by genes on the X chromosome, all female cells randomly select one of the X chromosomes per cell and permanently silence all of its genes. In some instances, reactivation of these silenced genes could be therapeutically beneficial, for example, in the case of X-linked genetic diseases. Combining techniques in cell and molecular biology with a unique drug-discovery system, I will screen for drugs that can regulate the activation of genes on the X chromosome by binding to newly discovered regulatory molecules that initiate X inactivation. These findings could open up a new approach to switching on specific X-linked genes, work that has direct therapeutic relevance for diseases, such as Fragile X syndrome, that are caused by mutations in genes on the X chromosome.