TCF4 and Pitt-Hopkins syndrome: As a next step of this study, a similar TCF4 protein expression analysis should be done for human brain regions with a focus on the hippocampus and cerebral cortex, as studies of structural brain anomalies in PTHS-patients and Tcf4-heterozygous mice have shown hypoplasia of these brain regions (Marangi and Zollino, 2015).