Different responses of two key body clock genes, mper1 and mper2, to light

A second mammalian gene, mper2, has been isolated with properties expected of a circadian clock gene.

• mper2 shows greater similarity to the Drosophila period gene compared to mper1.
• Both mper1 and mper2 are expressed in the suprachiasmatic nucleus in a circadian pattern.
• mper1 maintains its circadian expression pattern in constant darkness and can adjust to new light/dark cycles.
• The expression of mper1 occurs rapidly after light exposure at CT22, indicating its role as a light-responsive pacemaker component.
• mper1 and mper2 expression overlaps but is asynchronous by 4 hours.

Simplified