A retinal diffusible factor modulates the pineal gland clock in zebrafish

HERNANDEZ DE BORSETTI N.E; BORSETTI H.M. ; CAHILL G.M.

California

Conferencia; Gordon Research Conference, Pineal Cell Biology; 2006

A retinal diffusible factor modulates the pineal gland clock in zebrafish Hernandez de Borsetti N.E.*, Borsetti H.M. and Cahill G.M. Department of Biology and Biochemistry, Science and Research Building II, University of Houston, Houston, Tx 77204, U.S.A. Two photoreceptive organs that secret melatonin rhythmically, pineal gland and eyes, were originally described in teleost. Several reports demonstrated a clock responsive to light controlling melatonin levels at about 24 hours postfertilization, while retina is not yet differentiated, suggesting pineal gland as a candidate for an early clock structure in embryos. The larval pineal gland can function as an input structure and also as an oscillator when it secretes melatonin. However, little is known about how both structures interact in adult zebrafish. Considering that both structures posses an intrinsic clock responsive to light regulating their melatonin secretion communication between them is to be expected. We approached that possible communication by co-culturing pineal glands from adult Per-3-Luc transgenic zebrafish with retina from adult wild type zebrafish. The rhythmic expression of pineal gland Per-3-luc was measured during 7 days by topcount scintillation. As a result of the co-culture pineal gland exhibit an about 1hr shorter period of Per-3-luc rhythmicity when compared with the rhythmicity of pineal gland alone. The experiment was repeated using for co-cultures retinas from cryptocrome2a (cry2a) mutant zebrafish. Cryptochrome2a (Cry2a) protein is highly expressed in retina and the mutation results in a truncated Cry2a protein lacking its C-terminal. Retinas from cry2a zebrafish failed to induce the shortening of Per-3-luc pineal gland period remaining unaffected We conclude that retina can modulate the pineal gland intrinsic clock through a diffusible factor which is absent in retinas deficient in cry2a. Then, the C-terminal of Cry2a is required for the production or release of that diffusible factor.