TEAD switches interacting partners along neural progenitor lineage progression to execute distinct functions

The TEAD family of transcription factors is best known as the DNA-binding factor in the Hippo pathway, where these factors act by interacting with transcriptional coactivators YAP and TAZ (YAP/TAZ). Despite the importance of the Hippo pathway, the in vivo functions of TEAD in mammals have not been well established. By comparing mouse mutants lacking TEAD1 and TEAD2 (TEAD1/2) with those lacking YAP/TAZ, we found that TEAD1/2 have both YAP/TAZ-dependent and YAP/TAZ-independent functions during ventral telencephalon development. TEAD1/2 loss and YAP/TAZ loss similarly disrupt neuroepithelial apical junctions. However, the impacts of their losses on progenitor lineage progression are essentially opposite: YAP/TAZ loss depletes early progenitors and increases later progenitors, consistent with their established function in promoting progenitor self-renewal and proliferation, whereas TEAD1/2 loss expands early progenitors and reduces late progenitors, indicating that TEAD1/2 promote lineage progression. We further show that TEAD1/2 promote neural progenitor lineage progression by at least in part inhibiting Notch signaling and by cooperating with insulinoma-associated 1 (INSM1). Orthologs of TEAD and INSM1 have been shown to cooperatively regulate neuronal cell fate decisions in worms and flies. Our study reveals a remarkable evolutionary conservation of the function of this transcription factor complex during metazoan neural development.