PTEN and fragile X syndrome: Aberrant alternative splicing has previously been studied in complex NDDs such as ASD (6–8) and other psychiatric illnesses with a neurodevelopmental trajectory including Schizophrenia (8, 9), Bipolar Disorder (8, 9), Huntington's (10), and recently in monogenic IDs such as FXS (5), PTEN (11), and RTT (12–14) (Table 1).