Expression of the Hippo pathway effector, TEAD1, within the developing murine forebrain.

The Hippo pathway is a critical regulator of animal development. Activation of the Hippo pathway causes a cascade of phosphorylation events that culminate in the phosphorylation of the transcriptional co-factors YAP and TAZ, which limits their entry into the nucleus. When the Hippo pathway is 'off', however, YAP and TAZ can enter the nucleus, where they interact with the transcription factors of the TEA Domain (TEAD) family to regulate transcriptional activity. Despite the importance of the Hippo pathway for development, including within the nervous system, the expression of the TEAD family remains poorly defined in mammals. Here, we mapped the expression of TEAD1 in the developing mouse brain. We find that TEAD1 expression is confined to progenitor cells during embryonic development, namely radial glia and intermediate progenitor cells. TEAD1 expression is not evident in post-mitotic neurons of the cortical plate. We also identify expression of TEAD1 in developing and mature ependymal cells of the lateral and third ventricle, including within the subcommissural organ, as well as by cells within the choroid plexuses and the forebrain neurogenic niches. Finally, we find that adult mice conditionally heterozygous for Tead1 in the central nervous system exhibit a significantly smaller brain. Collectively, these findings reveal a specific pattern of expression for TEAD1 during telencephalic development and implicate this factor in regulating neural progenitor cell proliferation.