Sex bias and dosage compensation in the zebra finch versus chicken genomes: General and specialized patterns among birds
- Yuichiro Itoh1,
- Kirstin Replogle2,
- Yong-Hwan Kim1,
- Juli Wade3,
- David F. Clayton2 and
- Arthur P. Arnold1,4
- 1 Department of Integrative Biology and Physiology and Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, California 90095-1606, USA;
- 2 Institute for Genomic Biology, University of Illinois, Urbana–Champaign, Urbana, Illinois 61801, USA;
- 3 Departments of Psychology and Zoology, Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA
Abstract
We compared global patterns of gene expression between two bird species, the chicken and zebra finch, with regard to sex bias of autosomal versus Z chromosome genes, dosage compensation, and evolution of sex bias. Both species appear to lack a Z chromosome–wide mechanism of dosage compensation, because both have a similar pattern of significantly higher expression of Z genes in males relative to females. Unlike the chicken Z chromosome, which has female-specific expression of the noncoding RNA MHM (male hypermethylated) and acetylation of histone 4 lysine 16 (H4K16) near MHM, the zebra finch Z chromosome appears to lack the MHM sequence and acetylation of H4K16. The zebra finch also does not show the reduced male-to-female (M:F) ratio of gene expression near MHM similar to that found in the chicken. Although the M:F ratios of Z chromosome gene expression are similar across tissues and ages within each species, they differ between the two species. Z genes showing the greatest species difference in M:F ratio were concentrated near the MHM region of the chicken Z chromosome. This study shows that the zebra finch differs from the chicken because it lacks a specialized region of greater dosage compensation along the Z chromosome, and shows other differences in sex bias. These patterns suggest that different avian taxa may have evolved specific compensatory mechanisms.
Footnotes
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↵4 Corresponding author.
E-mail arnold{at}ucla.edu.
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[Supplemental material is available online at http://www.genome.org.]
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Article published online before print. Article and publication date are at http://www.genome.org/cgi/doi/10.1101/gr.102343.109.
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- Received October 25, 2009.
- Accepted February 11, 2010.
- Copyright © 2010 by Cold Spring Harbor Laboratory Press
