Cyclopia is a part of holoprosencephaly disorders which result from the failure of the forebrain to develop properly. Cyclopia presents as alobar holoprosencephaly which is the most severe form and one characterization of such a disorder is the lack of midline structures. The lack or abundance of tissue in the midface, prevents the two nasal primordia from joining the midline. When shh is expressed by the prechordal plate and ventral midline of the diencephalon, it causes Pax-6 expression in the midline to become repressed causing the single eye field to split into two separate eye fields on either side of the diencephalon. Rax a retina and anterior neural fold homeobox and Six-3, another important transcription factor, protect the ability of the forebrain to express shh by suppressing Wnt signaling. When Wnt is active and not suppressed, it enabled the anterior region of the brain that is developing to become posteriorized and unable to secrete shh. The lack of Six-3 expression results in a loss of shh secretion which then stops the splitting of the eye fields causing one
Cyclopia is a part of holoprosencephaly disorders which result from the failure of the forebrain to develop properly. Cyclopia presents as alobar holoprosencephaly which is the most severe form and one characterization of such a disorder is the lack of midline structures. The lack or abundance of tissue in the midface, prevents the two nasal primordia from joining the midline. When shh is expressed by the prechordal plate and ventral midline of the diencephalon, it causes Pax-6 expression in the midline to become repressed causing the single eye field to split into two separate eye fields on either side of the diencephalon. Rax a retina and anterior neural fold homeobox and Six-3, another important transcription factor, protect the ability of the forebrain to express shh by suppressing Wnt signaling. When Wnt is active and not suppressed, it enabled the anterior region of the brain that is developing to become posteriorized and unable to secrete shh. The lack of Six-3 expression results in a loss of shh secretion which then stops the splitting of the eye fields causing one