Fig. 1. ExE/ChE microdissection. ExRs were microdissected from the conceptus and extra-embryonic visceral endoderm and extra-embryonic mesoderm were removed by trypsin/pancreatin treatment. Proximal and distal are as indicated. ExEs and ChEs were microdissected into fractions perpendicular to the proximodistal axis with a glass needle. Individual ExE/ChE fractions were explanted into separate TSC culture wells following dissociation with pronase, while EPC/ExE transition tissues were explanted as whole, loosely dissociated masses.