Light and melatonin schedule neuronal differentiation in the habenular nuclei

• Published in: Developmental biology Vol. 358; no. 1; pp. 251 - 261
• Main Authors: de Borsetti, Nancy Hernandez, Dean, Benjamin J., Bain, Emily J., Clanton, Joshua A., Taylor, Robert W., Gamse, Joshua T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2011
• Subjects: Animals; Brain; Cell Differentiation - physiology; Cell migration; Circadian rhythm; Cloning, Molecular; Danio rerio; Differentiation; Embryos; Enzyme-Linked Immunosorbent Assay; Epithalamus; Fluorescent Antibody Technique; Gene Expression Regulation - radiation effects; Habenula - cytology; Habenula - physiology; Hormones; In Situ Hybridization; Light; Light effects; Melatonin; Melatonin - metabolism; Melatonin receptors; Neural stem cells; Neurogenesis; Neurogenesis - physiology; neurons; Neurons - physiology; Neuropil; Photoperiod; Photoperiods; Pineal gland; Pineal organ; receptors; Receptors, Melatonin - genetics; Receptors, Melatonin - metabolism; Zebrafish; Zebrafish - embryology; Pineal organ; Zebrafish; Epithalamus; Photoperiod; Neuropil; Circadian rhythm; Neurogenesis
• ISSN: 0012-1606; 1095-564X; 1095-564X
• DOI: 10.1016/j.ydbio.2011.07.038

The formation of the embryonic brain requires the production, migration, and differentiation of neurons to be timely and coordinated. Coupling to the photoperiod could synchronize the development of neurons in the embryo. Here, we consider the effect of light and melatonin on the differentiation of embryonic neurons in zebrafish. We examine the formation of neurons in the habenular nuclei, a paired structure found near the dorsal surface of the brain adjacent to the pineal organ. Keeping embryos in constant darkness causes a temporary accumulation of habenular precursor cells, resulting in late differentiation and a long-lasting reduction in neuronal processes (neuropil). Because constant darkness delays the accumulation of the neurendocrine hormone melatonin in embryos, we looked for a link between melatonin signaling and habenular neurogenesis. A pharmacological block of melatonin receptors delays neurogenesis and reduces neuropil similarly to constant darkness, while addition of melatonin to embryos in constant darkness restores timely neurogenesis and neuropil. We conclude that light and melatonin schedule the differentiation of neurons and the formation of neural processes in the habenular nuclei. ► Constant darkness delays neurogenesis in the habenular nuclei. ► Constant darkness delays melatonin production. ► Blocking melatonin signaling also delays neurogenesis in the habenular nuclei. ► Neural processes in the habenular nuclei are reduced when neurogenesis is delayed.