TCF4 and Pitt-Hopkins syndrome: For instance, a recent study reported reduced upper GI and distal colonic transit velocities in mice heterozygous for the deletion of Transcription factor 4 (TCF4) (Grubišić et al., 2015), emulating symptoms, i.e., gastroesophageal reflux and constipation, of patients with the Pitt-Hopkins Syndrome (PTHS) (Whalen et al., 2012), a very rare ASD (Sweatt, 2013), caused by the haplo-insufficiency of the TCF4 gene (Amiel et al., 2007; Brockschmidt et al., 2007; Zweier et al., 2007).