The early cortical primordium develops from a sheet of neuroepithelium that is flanked by distinct signaling centers. Of these, the hem and the antihem are positioned as longitudinal stripes, running rostro-caudally along the medial and lateral faces, respectively, of each telencepahlic hemisphere.
Therefore, these two structures are separated by the expanse cortical neuroepithelium except at the extreme caudal pole of the telencephalon, where they almost meet, separated by a small domain of cortical neuroepithelium
The hem expresses signaling molecules of the Wnt family, Wnt2b, 3a, and 5a. Several members of the Bmp gene family are expressed in broader domains that include the adjacent choroid plexus and/or hippocampal primordium .
The antihem expresses epidermal growth factor (EGF) family members, a fibroblast growth factor Fgf7, as well as a Wnt signaling inhibitor Sfrp2 . Of the several EGF family members, ligands Tgfα, Nrg1 and Nrg3 are concentrated at the antihem. Egf is itself expressed throughout the ventral neuroepithelium, but is not concentrated at the PSB . Sfrp2 is intensely expressed in the antihem, and more weakly in the rest of the telencephalic neuroepithelium. Members of this family bind directly to Wnts and act as Wnt antagonists
Lef1 only express in medial pallium.
Lmx1a express in hem and choroid plexus, whereas Lhx2 express in medial pallium and dorsolateral pallium. (Lhx2 <-> Lmx1a)
Foxg1 and Pax6 only express in MP and DP.
TTR only express in choroid plexus.
FoxG1 is expressed in neocortex and medial pallium, but not in cortical hem and choroid plexus.
Cortical hem is the organizor of hippocamous in the fulture.
