ASD CGG Repeat Expansion Disease CRISPR 3 DNA instability DNA methylation FMR1 FMR1 gene FMRP Fmr1 Fmr1 KO mouse Fragile X Fragile X Syndrome Fragile X syndrome 1 Fragile X-associated Tremor/Ataxia Syndrome 2 Fxr2 Gene editing Non-homologous end-joining (NHEJ) PRC2 Q1-390 QH301-705.5 RNA:DNA hybrid Trinucleotide Repeat 4 X chromosome adeno-associated virus anxiety attention autism spectrum disorders automated vocal analysis avoidance base excision repair (BER)