User:Aj.blackford77/sandbox

Retina and anterior neural fold homeobox (RAX), is a transcription factor that is involved in the early formation events of the eye. Towards the end of late gastrulation a single eye field has formed and splits into bilateral fields via action by the signaling molecule, sonic hedgehog (Shh) secreted from the forebrain. Rax and Six-3 (also a transcription factor) maintain the forebrain's ability to secrete Shh by inhibiting activity of the signaling molecule Wnt. Individuals who have a mutation in the RAX gene fail to develop ocular structures, referred to as anophthalmia. RAX mutant individuals can also have micropthalmia, where one or both of the eyes is smaller than normal. Xenopus tropicalis rax mutant frogs are eyeless where the future retinal tissue instead has diencephalon and telencephalon features. Also, RAX knockout mice have no eyes and abnormal forebrain formation.The RAX gene is located on chromosome 18 in humans, mice, and rats.