Ontogeny of vasotocin-expressing cells in zebrafish: Selective requirement for the transcriptional regulators orthopedia and single-minded 1 in the preoptic area

The neurohypophysial peptide arginine vasotocin, and its mammalian ortholog arginine vasopressin, influence a wide range of physiological and behavioral responses, including aspects of sexual and social behaviors, osmoregulation, stress response, metabolism, blood pressure, and circadian rhythms. Here, we demonstrate that, in zebrafish (Danio rerio), the vasotocin precursor gene arginine vasotocin-neurophysin (avt) is expressed in two domains in the developing embryo: the dorsal preoptic area and the ventral hypothalamus. In the dorsal preoptic area, avt-expressing cells are intermingled with isotocin-neurophysin (ist) -expressing cells, and these neurons project to the neurohypophysis (posterior pituitary). In the dorsal preoptic area, the transcriptional regulators orthopedia b (otpb) and simple-minded 1 (siml) are required for expression of both avt and ist. In contrast, olp and siml are not required for avt expression in the ventral hypothalamus. Thus, the development of these two avt expression domains is influenced by separate gene regulatory networks.