A C>T mutation was engineered in the highly conserved Fmr1 cis-regulatory element (CRE) using an sgRNA (targeting ACCTTGTGTCTATGACTATTTGG) and a ssODN template (TAAGATGGATTCATATTAGGGCTCAAATGCATTGATAGCATTCTACATATTTTTATCCATTTTTATTCCAAGCTACTTTTATCCAAATAGTTATAGACACAAGGTTATTGCAAATTGTATTTGTCTGCTGCCATAGT GCTTTCTATTTTAGAGGAGTAGAAGTAACTATCTCCTTAACAA) with CRISPR/Cas9 technology. The mutation mimics one found in some families with individuals presenting with X-linked intellectual disability (XLID). (J:308813)