FXS is caused by an abnormal expansion of CGG trinucleotide repeats in the fragile X mental retardation 1 (FMR1) gene, which results in the transcriptional silencing of FMR1 gene and consequent reduction in the levels of the fragile X mental retardation protein (FMRP), an RNA-binding protein essential for synaptic plasticity and neuronal cytoarchitecture (Zalfa et al., 2006; Soden and Chen, 2010; Kute et al., 2019). Here, FMR1 is linked to fragile X syndrome.