TAC3 (Neurokinin B, Tachykinin-3, NKB) is a secreted neuropeptide expressed in the nervous system where it functions as a neurotransmitter. It is involved in regulating the expression of luteinizing hormone and gonadotropin-releasing hormone. It is thought to play a role in modulating the reproductive axis, as expression is associated with pregnancy and adult maturation and some common allele variants in TAC3 are correlated with precocious puberty. Additionally, certain pathogenic TAC3 mutations are correlated with hypogonadism. In immunohistochemistry, TAC3 has cytoplasmic positivity in neurons throughout the nervous system, high levels of expression in placental extracellular deposits, and some limited expression in the gastrointestinal tract. References: Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID: 26553804; J Pediatr Endocrinol Metab. 2015 Jan;28(1-2):65-71, PMID: 25153567; Endocrinology. 151 (8): 3479–3489, PMID: 20501670;