PTBP1 and fragile X syndrome: The FMR1 locus encodes the Fragile X Mental Retardation Protein (FMRP), a neuronally enriched RNA-binding protein whose dysregulation through compromised transcription or translation leads to neurodevelopmental disorders, including Fragile X Syndrome (FXS) and Fragile X-associated tremor/ataxia syndrome (FXTAS) [81,82].