passages.id: split_6_test_1206_passage
passages.type: progene_text
passages.text: It is expressed in migrating neural crest cells of the trunk and a subset of cells in the diencephalon in close proximity to the expression domain of the Nodal - related protein Cyclops / Ndr2 / Znr1 , a potential signal upstream of Smad2 / 3 required for eye - field separation and floor plate specification .