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PLoS One. January 1, 2014; 9 (9): e108266.

Circadian genes, xBmal1 and xNocturnin, modulate the timing and differentiation of somites in Xenopus laevis.

Curran KL , Allen L , Porter BB , Dodge J , Lope C , Willadsen G , Fisher R , Johnson N , Campbell E , VonBergen B , Winfrey D , Hadley M , Kerndt T .

We have been investigating whether xBmal1 and xNocturnin play a role in somitogenesis, a cyclic developmental process with an ultradian period. Previous work from our lab shows that circadian genes (xPeriod1, xPeriod2, xBmal1, and xNocturnin) are expressed in developing somites. Somites eventually form the vertebrae, muscles of the back, and dermis. In Xenopus, a pair of somites is formed about every 50 minutes from anterior to posterior. We were intrigued by the co-localization of circadian genes in an embryonic tissue known to be regulated by an ultradian clock. Cyclic expression of genes involved in Notch signaling has been implicated in the somite clock. Disruption of Notch signaling in humans has been linked to skeletal defects in the vertebral column. We found that both depletion (morpholino) and overexpression (mRNA) of xBMAL1 protein (bHLH transcription factor) or xNOCTURNIN protein (deadenylase) on one side of the developing embryo led to a significant decrease in somite number with respect to the untreated side (p<0.001). These manipulations also significantly affect expression of a somite clock component (xESR9; p<0.05). We observed opposing effects on somite size. Depletion of xBMAL1 or xNOCTURNIN caused a statistically significant decrease in somite area (quantified using NIH ImageJ; p<0.002), while overexpression of these proteins caused a significant dose dependent increase in somite area (p<0.02; p<0.001, respectively). We speculate that circadian genes may play two separate roles during somitogenesis. Depletion and overexpression of xBMAL1 and NOCTURNIN both decrease somite number and influence expression of a somite clock component, suggesting that these proteins may modulate the timing of the somite clock in the undifferentiated presomitic mesoderm. The dosage dependent effects on somite area suggest that xBMAL1 and xNOCTURNIN may also act during somite differentiation to promote myogenesis.

PubMed ID: 25238599
PMC ID: PMC4169625
Article link: PLoS One.

Genes referenced: act3 arntl axin2 clock creb1 cry1 cry2 csnk1e dkk1 dll1 egfr hes1 hes6.2 hes9.1 myod1 noct notch1 per1 rora sp5 tnfrsf9

Antibodies referenced: Arntl Ab1 Noct Ab1 Somite Ab3 Tuba4b Ab15
Morpholinos referenced: arntl MO1 noct MO1

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Andrews, 2010, Pubmed [+]

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