Cardiovascular disease is one of the main causes of premature death in humans, and it was reported to be the primary cause of death in the U.S. during 2018. It has been well established that cardiovascular events have a specific temporal pattern, and that the circadian rhythm can influence heart function. For example, death caused by acute myocardial infarction peaks in morning and late afternoon, rather than being spread evenly throughout the day/night. Thus, the development of novel chronotherapies might help to alleviate the progression and consequences of heart disease. Zebrafish have multiple advantages for studying heart development and function, as well as the circadian clock. For example, they can survive without a functional cardiovascular system during early developmen...[ Read more ]

Cardiovascular disease is one of the main causes of premature death in humans, and it was reported to be the primary cause of death in the U.S. during 2018. It has been well established that cardiovascular events have a specific temporal pattern, and that the circadian rhythm can influence heart function. For example, death caused by acute myocardial infarction peaks in morning and late afternoon, rather than being spread evenly throughout the day/night. Thus, the development of novel chronotherapies might help to alleviate the progression and consequences of heart disease. Zebrafish have multiple advantages for studying heart development and function, as well as the circadian clock. For example, they can survive without a functional cardiovascular system during early development, thus allowing extensive experimental intervention. Moreover, the endogenous circadian clock of the zebrafish heart is directly light‐responsive. Currently, little is known regarding the regulation of the zebrafish embryonic heart beat rate by the circadian clock. In this project, AB wild‐type, as well as transgenic Tg ((gal4)cmlc2:GFP) and Tg (per3:luc) lines of zebrafish were raised under three distinct lighting conditions: constant light (LL), constant darkness (DD), and a normal 12‐h light/12‐h dark (LD) cycle, and the heart beat rate was measured both in vivo and in vitro from 3 days post‐fertilization (dpf) to 5 dpf. Furthermore, daily changes in the expression of the clock protein Period 3 (Per3), were also characterized. Heart beat rate rhythmicity was observed following light entrainment, and this was found to be correlated with the timing of Per3 expression. Furthermore, the rhythmicity of the larval heart beat rate following injury was also investigated. Together, the data collected demonstrate that the circadian clock plays a role in regulating the function of the larval zebrafish heart, and it has a clear impact on daily changes in the heart beat rate.