TCF4 and Cognitive impairment: Tcf4 knock-out mice suffer from severe brain defects (Flora et al., 2007; Li et al., 2019), whereas moderately modulating the expression of long Tcf4 isoforms in gain and loss of function mouse models is known to cause cognitive impairments (Brzózka et al., 2010; Brzózka and Rossner, 2013; Quednow et al., 2014; Badowska et al., 2020).