Isthmic organizer

[3] These two homeodomain transcription factors are activated by Irx1 and then cross inhibit one another in the developing central nervous system (CNS).

[3] This leads to the creation of a defined boundary that becomes the isthmic organizer region after the neural tube closes.

[2] The usual combined expression pattern of all involved signaling molecules is necessary for the formation and maintenance of the MHB as well as the development of the midbrain and cerebellum.

Fgf8 was shown to be an organizing molecule in the MHB through an experiment where an Fgf8-loaded bead was placed on a more anterior region of the neural tube.

[5] Once the midbrain/hindbrain boundary has formed, Wnt1 expression localizes to the roof plate of the neural tube and to the posterior region of the midbrain.