Brain development is a multi-level regulated process--the case of the OTX2 gene.

The OTX2 gene encodes a key transcription factor in developmental processes. In particular, it is required for the early specification of the brain and the embryonic development of sensory organs, including the pituitary gland, pineal gland, inner part of the ear, eyes, and optic nerve. In later stages, it is important for maintaining intact retina and brain function. Overexpression of OTX2 was found in medulloblastoma, a malignant brain tumor that occurs mainly in childhood. OTX2 mutations are associated with severe ocular phenotypes and central nervous system abnormalities such as seizures, short stature and developmental delay, combined pituitary hormone deficiency (CPHD), structural abnormalities of the pituitary gland and early onset retinal dystrophy. There is no genotype-phenotype correlation and the severity of the disease varies not only by the specific OTX2 mutations but also among individuals harboring the same mutation, suggesting the involvement of multiple levels of regulation.