SLC6A1 and Neurodevelopmental delay: The phenotypic spectrum of SLC6A1-related neurodevelopmental disorders (SLC6A1-NDD) includes intellectual disability (ID), autistic spectrum disorders (ASD), epilepsy, developmental delay, beginning from early infancy or after seizure onset, and neurological features such as hypotonia and movement disorders (Goodspeed et al., 1993; Carvill et al., 2015; Johannesen et al., 2018; Mattison et al., 2018; Cai et al., 2019; Devries et al., 2020; Goodspeed et al., 2020; Kahen et al., 2022).