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Mol. Cells 2009; 27(5): 497-502

Published online May 31, 2009

https://doi.org/10.1007/s10059-009-0068-1

© The Korean Society for Molecular and Cellular Biology

Rhythmic Gene Expression in Somite Formation and Neural Development

Ryoichiro Kageyama, Yasutaka Niwa, and Hiromi Shimojo

Received: March 17, 2009; Accepted: March 20, 2009

Abstract

In mouse embryos, somite formation occurs every two hours, and this periodic event is regulated by a biological clock called the segmentation clock, which involves cyclic expression of the basic helix-loop-helix gene Hes7. Hes7 expression oscillates by negative feedback and is cooperatively regulated by Fgf and Notch signaling. Both loss of expression and sustained expression of Hes7 result in severe somite fusion, suggesting that Hes7 oscillation is required for proper somite segmentation. Expression of a related gene, Hes1, also oscillates by negative feedback with a period of about two hours in many cell types such as neural progenitor cells. Hes1 is required for maintenance of neural progenitor cells, but persistent Hes1 expression inhibits proliferation and differentiation of these cells, suggesting that Hes1 oscillation is required for their proper activities. Hes1 oscillation regulates cyclic expression of the proneural gene Neurogenin2 (Ngn2) and the Notch ligand Delta1, which in turn lead to maintenance of neural progenitor cells by mutual activation of Notch signaling. Taken together, these results suggest that oscillatory expression with short periods (ultradian oscillation) plays an important role in many biological events.

Keywords biological clock, negative feedback, segmentation clock, ultradian oscillation

Article

Minireview

Mol. Cells 2009; 27(5): 497-502

Published online May 31, 2009 https://doi.org/10.1007/s10059-009-0068-1

Copyright © The Korean Society for Molecular and Cellular Biology.

Rhythmic Gene Expression in Somite Formation and Neural Development

Ryoichiro Kageyama, Yasutaka Niwa, and Hiromi Shimojo

Received: March 17, 2009; Accepted: March 20, 2009

Abstract

In mouse embryos, somite formation occurs every two hours, and this periodic event is regulated by a biological clock called the segmentation clock, which involves cyclic expression of the basic helix-loop-helix gene Hes7. Hes7 expression oscillates by negative feedback and is cooperatively regulated by Fgf and Notch signaling. Both loss of expression and sustained expression of Hes7 result in severe somite fusion, suggesting that Hes7 oscillation is required for proper somite segmentation. Expression of a related gene, Hes1, also oscillates by negative feedback with a period of about two hours in many cell types such as neural progenitor cells. Hes1 is required for maintenance of neural progenitor cells, but persistent Hes1 expression inhibits proliferation and differentiation of these cells, suggesting that Hes1 oscillation is required for their proper activities. Hes1 oscillation regulates cyclic expression of the proneural gene Neurogenin2 (Ngn2) and the Notch ligand Delta1, which in turn lead to maintenance of neural progenitor cells by mutual activation of Notch signaling. Taken together, these results suggest that oscillatory expression with short periods (ultradian oscillation) plays an important role in many biological events.

Keywords: biological clock, negative feedback, segmentation clock, ultradian oscillation

Mol. Cells
Sep 30, 2022 Vol.45 No.9, pp. 603~672
COVER PICTURE
The Target of Rapamycin Complex (TORC) is a central regulatory hub in eukaryotes, which is well conserved in diverse plant species, including tomato (Solanum lycopersicum). Inhibition of TORC genes (SlTOR, SlLST8, and SlRAPTOR) by VIGS (virus-induced gene silencing) results in early fruit ripening in tomato. The red/ orange tomatoes are early-ripened TORC-silenced fruits, while the green tomato is a control fruit. Top, left, control fruit (TRV2-myc); top, right, TRV2-SlLST8; bottom, left, TRV2-SlTOR; bottom, right, TRV2-SlRAPTOR(Choi et al., pp. 660-672).

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