A Screen for Genes Induced in the Suprachiasmatic Nucleus by Light

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Science  06 Mar 1998:
Vol. 279, Issue 5356, pp. 1544-1547
DOI: 10.1126/science.279.5356.1544

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The mechanism by which mammalian circadian clocks are entrained to light-dark cycles is unknown. The clock that drives behavioral rhythms is located in the suprachiasmatic nucleus (SCN) of the brain, and entrainment is thought to require induction of genes in the SCN by light. A complementary DNA subtraction method based on genomic representational difference analysis was developed to identify such genes without making assumptions about their nature. Four clones corresponded to genes induced specifically in the SCN by light, all of which showed gating of induction by the circadian clock. Among these genes are c-fos and nur77, two of the five early-response genes known to be induced in the SCN by light, andegr-3, a zinc finger transcription factor not previously identified in the SCN. In contrast to known examples, egr-3induction by light is restricted to the ventral SCN, a structure implicated in entrainment.

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