Dosage compensation is the process by which the expression of X-linked genes is altered in one sex to counterbalance the difference in X-chromosome and autosome number in the heterogametic sex. Degeneration of the non-recombining Y chromosome is a general facet of sex chromosome evolution. Selective pressure to equalize expression levels of X- linked genes in males accompanies Y-chromosome degeneration, thus driving the evolution of dosage compensation. Drosophila miranda - a species for which we recently generated a de novo genome sequence assembly - has three sex chromosomes of different age and at different stages of transition from ordinary autosomes into heteromorphic sex chromosomes. Specifically, X-L is the ancestral sex chromosome of the genus Drosophila and >60MY old, X-R is shared by members of the D. pseudoobscura subgroup and >10MY old, while its neo-sex chromosome (about 1MY old) still largely resembles an autosome, but the neo-X is evolving partial dosage compensation. D. miranda therefore provides a unique system to study the evolution of dosage compensation in action using a comparative and functional genomics approach. We will use ChIP-seq techniques together with whole-genome population analysis to functionally characterize the targeting of the dosage compensation complex to the X chromosome, and how it evolves.

Public Health Relevance

Expression networks are often fine-tuned, and chromosomal aneuploidy and changes in gene dosage can disturb the overall balance of gene expression networks, and are associated with several known human diseases and birth defects (Down syndrome results from an extra copy of Chromosome 21), and chromosomal aneuploidies are also frequent in cancer cells. Sex chromosomes, in contrast, provide systems of naturally occurring aneuploidy, with females having two X chromosomes and males having one X and a Y, resulting in X monosomy in males, and unique gene regulation strategies have evolved to compensate for this gene-dose deficiency in males. We will use the model species Drosophila to investigate evolutionary and functional aspects of dosage compensation, which will help to understand the effects of aneuploidy on gene expression and the mechanisms that alleviate aneuploidy-induced expression imbalances of the genome.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM076007-08
Application #
8446473
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Eckstrand, Irene A
Project Start
2006-04-01
Project End
2016-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
8
Fiscal Year
2013
Total Cost
$292,037
Indirect Cost
$99,037
Name
University of California Berkeley
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Kaiser, Vera B; Bachtrog, Doris (2014) De novo transcriptome assembly reveals sex-specific selection acting on evolving neo-sex chromosomes in Drosophila miranda. BMC Genomics 15:241
Lott, Susan E; Villalta, Jacqueline E; Zhou, Qi et al. (2014) Sex-specific embryonic gene expression in species with newly evolved sex chromosomes. PLoS Genet 10:e1004159
Brown, Emily J; Bachtrog, Doris (2014) The chromatin landscape of Drosophila: comparisons between species, sexes, and chromosomes. Genome Res 24:1125-37
Boussau, Bastien; Walton, Zaak; Delgado, Juan A et al. (2014) Strepsiptera, phylogenomics and the long branch attraction problem. PLoS One 9:e107709
Zhou, Qi; Zhang, Jilin; Bachtrog, Doris et al. (2014) Complex evolutionary trajectories of sex chromosomes across bird taxa. Science 346:1246338
Vicoso, Beatriz; Bachtrog, Doris (2013) Reversal of an ancient sex chromosome to an autosome in Drosophila. Nature 499:332-5
Alekseyenko, Artyom A; Ellison, Christopher E; Gorchakov, Andrey A et al. (2013) Conservation and de novo acquisition of dosage compensation on newly evolved sex chromosomes in Drosophila. Genes Dev 27:853-8
Vicoso, Beatriz; Emerson, J J; Zektser, Yulia et al. (2013) Comparative sex chromosome genomics in snakes: differentiation, evolutionary strata, and lack of global dosage compensation. PLoS Biol 11:e1001643
Vicoso, Beatriz; Kaiser, Vera B; Bachtrog, Doris (2013) Sex-biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution. Proc Natl Acad Sci U S A 110:6453-8
Bachtrog, Doris (2013) Y-chromosome evolution: emerging insights into processes of Y-chromosome degeneration. Nat Rev Genet 14:113-24

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