TCF4 and microcephaly: A recent study using brain organoids derived from individuals with Pitt–Hopkins syndrome carrying TCF4 mutations (Papes et al., 2022) demonstrated that neural progenitors bearing these mutations have reduced proliferation and impaired capacity to differentiate into neurons (Papes et al., 2022), providing clear evidence for the role of TCF4 in neural proliferation and differentiation and ultimately microcephaly.