BSX (brain-specific homeobox) is a transcriptional regulator essential for postnatal development and neuroendocrine function. As a DNA-binding protein, BSX functions as a transcription factor with sequence-specific activity toward double-stranded DNA 1. The gene exhibits restricted expression in key hypothalamic and pineal structures, including the arcuate nucleus, mammillary bodies, septum, and pineal gland 1. BSX is critical for normal postnatal growth and lactation; homozygous mutant mice display impaired growth and nursing defects due to rapid involution of mammary glands after parturition, suggesting BSX's role in suppressing apoptosis of postpartum mammary epithelial cells 2. In the pineal gland, BSX exhibits circadian regulation with nighttime peaks controlled by sympathetic adrenergic signaling and cAMP second messengers, functioning as a negative regulator of other developmental homeobox genes like Pax4 3. BSX is essential for energy balance regulation, as BSX-expressing hypothalamic neurons regulate neuropeptide Y and agouti-related peptide signaling that control locomotory behavior and feeding 4. Clinically, deletions encompassing BSX on chromosome 11 in Jacobsen syndrome correlate with cognitive impairment and neurobehavioral deficits, implicating BSX in auditory attention and intellectual function 4.