Brain-specific homeobox

Brain-specific homeobox is a protein that in humans is encoded by the BSX gene.^[1]

Structure and expression pattern

Bsx is an evolutionarily highly-conserved homeodomain-containing transcription factor that belongs to the ANTP-class.^[2] In mouse it has been shown to be expressed in the telencephalic septum, pineal gland, the mammillary bodies and arcuate nucleus.^[3]

Function in the hypothalamus

In the hypothalamic arcuate nucleus, Bsx has been demonstrated to be necessary for normal expression levels of the two orexigenic neuropeptides Agouti-related peptide and Neuropeptide Y.^[4]

Function in the pineal gland

In the pineal gland of the clawed frog Xenopus, Bsx is expressed following the circadian rhythm and controls photoreceptor cell differentiation.^[5] In zebrafish Bsx is required for normal development of all cell types within the pineal gland, including melatonin-releasing pinealocytes, photoreceptor cells and leftwards migrating parapineal cells,^[6] which in zebrafish are crucial for the establishment of brain asymmetry.^[7]