In a subset of the NDD mouse models, adult gene reinstatement rescues some but not all behavioral deficits (e.g. upon reinstatement of Shank3 (Mei et al., 2016)), rescues observed phenotypes partially (e.g. upon reinstatement of Mecp2 or Grin1 (Lang et al., 2014; Mielnik et al., 2020)), or only rescues the behavioral deficits if reinstated at a juvenile age (e.g. upon reinstatement of Ube3a or Syngap1 (Aceti et al., 2015; Silva-Santos et al., 2015)). The gene discussed is GRIN1; the disease is Neurodevelopmental delay.