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X-chromosome-counting mechanisms that determine nematode sex

Nature volume 388, pages 200–204 (1997)Cite this article

Abstract

Sex is determined in Caenorhabditis elegans by an X-chromosome-counting mechanism that reliably distinguishes the twofold difference in X-chromosome dose between males (1X) and hermaphrodites (2X)1,2. This small quantitative difference is translated into the ‘;on/off’ response of the target gene, xol-1, a switch that specifies the male fate when active and the hermaphrodite fate when inactive3. Specific regions of X contain counted signal elements whose combined dose sets the activity of xol-1 (ref. 4). Here we ascribe the dose effects of one region to a discrete, protein-encoding gene, fox-1. We demonstrate that the dose-sensitive signal elements on chromosome X control xol-1 through two different molecular mechanisms. One involves the transcriptional repression of xol-1 in XX animals. The other uses the putative RNA-binding protein encoded by fox-1 to reduce the level of xol-1 protein. These two mechanisms of repression act together to ensure the fidelity of the X-chromosome counting process.

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Figure 1: xol-1 is transcriptionally regulated.
Figure 2: The putative RNA binding protein, FOX-1, is a signal element.
Figure 3: fox-1 represses xol-1.

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Acknowledgements

We thank I. Carmi, T. Cline, J. Rine, H. Dawes for discussions and critical comments on the manuscript, A. Fire for reporter gene vectors and Y. Jin for the gfp coding sequences. M.N. is a National Science Foundation predoctoral fellow. C.C.A. was an American Cancer Society postdoctoral fellow. This work was supported by a grant from the National Institutes of Health to B.J.M.

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  1. Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, 94720-3204, California, USA

    Monique Nicoll, Chantal C. Akerib & Barbara J. Meyer

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  1. Monique Nicoll
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  2. Chantal C. Akerib
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  3. Barbara J. Meyer
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Correspondence to Barbara J. Meyer.

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Nicoll, M., Akerib, C. & Meyer, B. X-chromosome-counting mechanisms that determine nematode sex. Nature 388, 200–204 (1997). https://doi.org/10.1038/40669

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