Changes in circadian period and morphology of the hypothalamic suprachiasmatic nucleus in fyn kinase-deficient mice

Protein tyrosine phosphorylation is involved in intracellular signal transd uction and plays important roles in various physiological events. To unders tand the role of Fyn, a non-receptor type tyrosine kinase of Src family kin ases, in the mechanism of circadian rhythms, we analyzed the circadian loco motor behavior and morphology of the hypothalamic suprachiasmatic nucleus ( SCN), a master circadian oscillator in Fyn mutant mice, because Fyn-like im munoreactive substance was observed in the SCN. Under constant dark (DD) co ndition the Fyn (-/-) mutant mice showed a free-running circadian rhythm, a nd the period of the circadian rhythm of the locomotor activity was signifi cantly longer than that of the control mice. Fyn (-/-) mutant mice had abno rmal distribution of neurons containing vasoactive intestinal polypeptide ( VIP)-like immunoreactive substance in the SCN. These findings suggest that Fyn is involved in the mechanism of circadian oscillation and morphological formation of the SCN. The mechanism of the implication of Fyn discussed wi th the Fyn's roles in neural network formation and cellular signal transduc tion pathway. (C) 2000 Elsevier Science B.V. All rights reserved.