GDF7 and choroid plexus carcinoma: However other signaling pathways, most notably the Notch pathway, have been implicated in the formation of choroid plexus neoplasias, as Gdf7-Cre driven expression of the activated ligand NotchICD[10] led to persistent proliferation of hChPe cells and retrovirus-driven expression of the ligand Notch3 [54] resulted in choroid plexus papillomas.