A DIFFERENTIAL RESPONSE OF 2 PUTATIVE MAMMALIAN CIRCADIAN REGULATORS,MPER1 AND MPER2, TO LIGHT

A mouse gene, mper1, having all the properties expected of a circadian clock gene, was reported recently. This gene is expressed in a circad ian pattern in the suprachiasmatic nucleus (SCN). mper1 maintains this pattern of circadian expression in constant darkness and can be entra ined to a new light/dark cycle. Here we report the isolation of a seco nd mammalian gene, mper2, which also has these properties and greater homology to Drosophila period. Expression of mper1 and mper2 is overla pping but asynchronous by 4 hr. mper1, unlike period and mper2, is exp ressed rapidly after exposure to light at CT22. It appears that mper1 is the pacemaker component which responds to light and thus mediates p hotic entrainment.