Developmental stage-specific regulation of the circadian clock by temperature in zebrafish.

The circadian clock enables animals to adapt their physiology and behaviour in anticipation of the day-night cycle. Light and temperature represent two key environmental timing cues (zeitgebers) able to reset this mechanism and so maintain its synchronization with the environmental cycle. One key challenge is to unravel how the regulation of the clock by zeitgebers matures during early development.

Differential maturation of rhythmic clock gene expression during early development in medaka (Oryzias latipes).

One key challenge for the field of chronobiology is to identify how circadian clock function emerges during early embryonic development. Teleosts such as the zebrafish are ideal models for studying circadian clock ontogeny since the entire process of development occurs ex utero in an optically transparent chorion. Medaka (Oryzias latipes) represents another powerful fish model for exploring early clock function with, like the zebrafish, many tools available for detailed genetic analysis.

The light responsive transcriptome of the zebrafish: function and regulation.

Most organisms possess circadian clocks that are able to anticipate the day/night cycle and are reset or "entrained" by the ambient light. In the zebrafish, many organs and even cultured cell lines are directly light responsive, allowing for direct entrainment of the clock by light. Here, we have characterized light induced gene transcription in the zebrafish at several organizational levels.

Light directs zebrafish period2 expression via conserved D and E boxes.

For most species, light represents the principal environmental signal for entraining the endogenous circadian clock. The zebrafish is a fascinating vertebrate model for studying this process since unlike mammals, direct exposure of most of its tissues to light leads to local clock entrainment. Importantly, light induces the expression of a set of genes including certain clock genes in most zebrafish cell types in vivo and in vitro.

Zebrafish cell clocks feel the heat and see the light!

The zebrafish has rapidly become established as one of the most valuable vertebrate models for studying circadian clock function. A major initial attraction was its utility in large-scale genetic screens. It subsequently emerged that most zebrafish cells possess circadian clocks that can be entrained directly by exposure to temperature or light dark cycles, a property shared by several zebrafish cell lines.

Transgenesis in fish: efficient selection of transgenic fish by co-injection with a fluorescent reporter construct.

Small fish are a popular laboratory model for studying gene expression and function by transgenesis. If, however, the transgenes are not readily detectable by visual inspection, a large number of embryos must be injected, raised and screened to identify positive founder fish. Here, we describe a strategy to efficiently generate and preselect transgenic lines harbouring any transgene of interest.

Glucocorticoids play a key role in circadian cell cycle rhythms.

Clock output pathways play a pivotal role by relaying timing information from the circadian clock to a diversity of physiological systems. Both cell-autonomous and systemic mechanisms have been implicated as clock outputs; however, the relative importance and interplay between these mechanisms are poorly understood. The cell cycle represents a highly conserved regulatory target of the circadian timing system.

Start the clock! Circadian rhythms and development.

The contribution of timing cues from the environment to the coordination of early developmental processes is poorly understood. The day-night cycle represents one of the most important, regular environmental changes that animals are exposed to. A key adaptation that allows animals to anticipate daily environmental changes is the circadian clock.

Temperature regulates transcription in the zebrafish circadian clock.

It has been well-documented that temperature influences key aspects of the circadian clock. Temperature cycles entrain the clock, while the period length of the circadian cycle is adjusted so that it remains relatively constant over a wide range of temperatures (temperature compensation). In vertebrates, the molecular basis of these properties is poorly understood.