A murine gene with circadian expression revealed by transposon insertion: self-sustained rhythmicity in the liver and the photoreceptors.
We have previously identified in some mouse strains (e.g. BALB/c, DBA/2) a murine Intracisternal A-particle (IAP) transposable element specifically expressed in the liver. This IAP sequence is inserted within a gene, mCCR4/m. nocturnin, the sequence of which is related to the circadian Xenopus nocturnin gene. Here we show, using real-time quantitative RT-PCR, that both the IAP sequence and the m. nocturnin gene display strong circadian expression in the liver, with peak abundance after dusk. Circadian oscillations of m. nocturnin RNA are maintained in mice without the IAP insertion (e.g. CBA/J, 129/sv), are free-running under constant light and dark conditions, and persist upon food and water privation, demonstrating that m. nocturnin is a circadian gene. In situ hybridization analyses (in 129/sv mice) further show circadian expression of m. nocturnin also in the retina, precisely at the level of the photoreceptors, a result consistent with the previously described circadian expression of the Xenopus gene. These results strengthen the strong conservation of the nocturnin gene with the identification of a functional mouse ortholog of the Xenopus gene, and demonstrate the reciprocal influence of nearby genes on the expression of transposable elements via "position effects".
Barbot
Willy
W
Unité des Rétrovirus Endogènes et Eléments Rétroïdes des Eucaryotes Supérieurs, UMR 1573 CNRS, Institut Gustave Roussy, 39 rue Camille Desmoulins, 94805 Villejuif Cedex, France.
Wasowicz
Marguerite
M
Dupressoir
Anne
A
Versaux-Botteri
Claudine
C
Heidmann
Thierry
T
D000818:Animals; D002940:Circadian Rhythm; D004251:DNA Transposable Elements; D004326:Drinking; D004435:Eating; D015870:Gene Expression; D007426:Genes, Intracisternal A-Particle; D017403:In Situ Hybridization; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D009687:Nuclear Proteins; D010786:Photoreceptor Cells / Q000378:metabolism*; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors
D004251:DNA Transposable Elements; D009687:Nuclear Proteins; D011506:Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C102804:nocturnin