Fig. 2.

Specification of tissues involved in patterning the anterior forebrain in the post-implantation mouse embryo and establishment of the anterio-posterior axis. AVE cells are induced to form by signals from the epiblast acting on VE at the distal tip of the embryo by 5.5 dpc. AVE cells migrate anteriorly at 5.5 dpc, reach the boundary between the epiblast and extra-embryonic ectoderm in approximately 5–6 h and then start to move laterally. At 6.5 dpc, the PS elongates and the anterior movements of the ADE/AME displace and intermingle with the AVE. The forebrain domain including future anterior and posterior forebrain is patterned within the anterior portion of the presumptive neural ectoderm that overlies AVE and ADE/AME tissues. By 7.5 dpc, the prospective anterior forebrain neural ectoderm overlies the ADE/AME and posterior neural tissue is underlied by the notochordal plate. VE visceral endoderm, AVE anterior visceral endoderm, ADE anterior definitive endoderm, AME anterior mesendoderm, np notochordal plate, PS primitive streak, AF anterior forebrain primordium, Ec neural ectoderm