The ability of inner-cell-mass cells to self-renew as embryonic stem cells is acquired following epiblast specification

The authors show that mouse ICM cells from early blastocysts can progress to ERK independence if provided with a specific laminin substrate. We show by RNA sequencing that Laminin-511 is expressed in the early ICM, as is B1-integrin, which mediates laminin binding in ESCs. No expression of Laminin-521 in mouse ICM. Single ESC derivation in 2i-LIF on a fibronectin-LN511 mix and clonal ESC lines expansion on LN511.