FMR1 and fragile X syndrome: After the seminal discovery that expansions of CGG repeats in the FMR1 gene were linked to fragile X syndrome (FXS) in 19917–10, researchers have identified approximately 60 STR loci implicated in a range of Mendelian diseases to date, including ataxias, amyotrophic lateral sclerosis, Huntington disease, frontotemporal dementia, and various neurological disorders11,12.