BACKGROUND: In mammals, two possible clock genes (Clock, @entity14733 ) have very recently been reported. @entity14733 (the first identified @entity19 period gene), in particular, shows a circadian expression in suprachiasmatic nuclei (SCN), the @entity1 circadian centre. However, only @entity14733 and Clock as clock components may not be sufficient to understand all the events in circadian oscillation and entrainment. RESULTS: A @entity1 period complementary DNA, @entity17989 , has been isolated from the @entity19 brain. The @entity535 sequence of @entity17989 is similar to @entity14733 and @entity238 Period ( @entity69563 ), indicating that @entity17989 is a member of the family which contains @entity14733 , itself a homologue of @entity69563 . @entity17989 mRNA is predominantly expressed in SCN. A robust circadian rhythmic expression in the SCN supports the view that @entity17989 is a clock gene. @entity17989 is strongly expressed at the subjective afternoon in constant darkness, distinct from a morning-phase clock @entity14733 . Our precise quantitative in situ hybridizations have revealed that the peak expression of @entity17989 transcripts is delayed by 8 h in LD (light-dark) or 4 h in @entity400 ( @entity400 ) conditions when compared to @entity14733 . A short brief light exposure at the early subjective night, prompting a phase-shift in locomotor rhythms, induces a transient increase of @entity17989 transcripts with delayed onset, as compared to @entity14733 mRNA induction. Furthermore, @entity17989 is co-expressed with @entity14733 in single SCN cells. CONCLUSIONS: @entity1 period genes show molecular heterogeneity, each of which is composed of a different oscillator, and may serve to establish stable circadian rhythms in @entity1 oscillating cells.

A new XXXX period gene predominantly expressed in the suprachiasmatic nucleus.

@entity1 :: ('9606', 'Species') :: ['mammalian', 'Mammalian'] @entity17989 :: ('18627(Tax:10090)', 'Gene') :: ['mPer2'] @entity14733 :: ('18626(Tax:10090)', 'Gene') :: ['Per1', 'mPer1'] @entity19 :: ('10090', 'Species') :: ['mouse'] @entity535 :: ('CHEBI:33704', 'Chemical') :: ['amino acid'] @entity69563 :: ('31251(Tax:7227)', 'Gene') :: ['dPer'] @entity400 :: ('MESH:D014202', 'Disease') :: ['DD', 'dark-dark'] @entity238 :: ('7227', 'Species') :: ['Drosophila']
@entity1 :: (9606,Species) :: ['mammalian']
