Differential regulation of two period genes in the Xenopus eye.
The recent identification and analysis of mammalian homologues of the well characterized Drosophila circadian clock gene, Period (Per), has led to the idea that key features of vertebrate circadian rhythmicity are conserved at the molecular level. The Xenopus laevis retina contains a circadian clock mechanism that can be studied in vitro. To study the rhythmic expression of Per in the Xenopus retina, we used a degenerate RT-PCR strategy to obtain cDNA clones covering the entire 1427 amino acid coding region of a Xenopus homologue of Per2 and a partial cDNA sequence for a Xenopus homologue of Per1. Northern blot analysis shows that xPer1 and xPer2 transcripts are expressed most abundantly in the eye and the brain. However, rhythmic expression of xPer2 transcripts in the retina and retinal pigment epithelium (RPE) is light dependent and occurs only under 12 h light/12 h dark (LD) conditions, not in constant dark (DD). In contrast, xPer1 mRNA accumulation is rhythmic under both LD and DD conditions. Light dependent regulation of xPer2 mRNA and circadian regulation of xPer1 mRNA in the Xenopus retina differs from that in Drosophila and mammals. Light dependence of xPer2 mRNA levels and the offset phase relationship of the xPer2 rhythm to that for xPer1 suggests a role for xPer2 in circadian entrainment.
Zhuang
M
M
Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Wang
Y
Y
Steenhard
B M
BM
Besharse
J C
JC
D000595:Amino Acid Sequence; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology; D019143:Evolution, Molecular; D005123:Eye / Q000378:metabolism*; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D008027:Light; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D009928:Organ Specificity; D056950:Period Circadian Proteins; D017440:Photoperiod; D010802:Phylogeny; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D051381:Rats; D012160:Retina / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000235:genetics*
D029721:Drosophila Proteins; D005136:Eye Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; C539022:PER1 protein, human; C539025:Per1 protein, Xenopus; C539023:Per1 protein, mouse; C539024:Per1 protein, rat; C498845:Per2 protein, Xenopus; D056950:Period Circadian Proteins; D011506:Proteins; D029867:Xenopus Proteins