Genes are distributed non-randomly across the genome. One intriguing pattern to emerge from genome-wide expression profiling is that genes with sex-biased expression that is, genes that are differentially expressed between the sexes show a biased distribution on sex chromosomes. In particular, male-biased genes are depleted from the Drosophila X chromosome, such that the X has become demasculinized. The deficiency of male-biased genes can partly be explained by movement of male genes off the X chromosome. The evolutionary forces underlying these patterns are controversial and may involve male germline X inactivation, sexual antagonism, or dosage compensation mechanisms. Drosophila miranda - a species for which we recently generated a de novo genome sequence assembly - has a newly formed sex chromosome system. Its neo-Y chromosome is in transition from an ordinary autosome to a degenerate Y. In response, the neo-X is evolving the stereotypical properties of a differentiated X, including the acquisition of partial dosage compensation and - as suggested by preliminary data - an excess of gene translocations originating from its neo-X. D. Miranda therefore provides a unique system to study the mechanisms of gene trafficking on an evolving X chromosome and its evolutionary causes in action using a comparative and functional genomics approach.

Public Health Relevance

Evidence for the importance of genetic factors in male fertility is accumulating, and is often associated with genes that are expressed in testis. Comparative genome analysis has shown that testis genes show rapid turnover between species (that is, many novel genes unique to humans show testis-specific expression) and often avoiding linkage to sex chromosomes. We will use the model species Drosophila to investigate the underlying causes for the rapid evolution of testis genes and their biased distribution in the genome, which will help to understand male infertility associated with defects in testis genes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM093182-01
Application #
7866777
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Eckstrand, Irene A
Project Start
2010-03-01
Project End
2014-02-28
Budget Start
2010-03-01
Budget End
2011-02-28
Support Year
1
Fiscal Year
2010
Total Cost
$295,063
Indirect Cost
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
Wong Miller, Karen M; Bracewell, Ryan R; Eisen, Michael B et al. (2017) Patterns of Genome-Wide Diversity and Population Structure in the Drosophila athabasca Species Complex. Mol Biol Evol 34:1912-1923
Mahajan, Shivani; Bachtrog, Doris (2017) Convergent evolution of Y chromosome gene content in flies. Nat Commun 8:785
Blackmon, Heath; Ross, Laura; Bachtrog, Doris (2017) Sex Determination, Sex Chromosomes, and Karyotype Evolution in Insects. J Hered 108:78-93
Zhou, Qi; Bachtrog, Doris (2015) Ancestral Chromatin Configuration Constrains Chromatin Evolution on Differentiating Sex Chromosomes in Drosophila. PLoS Genet 11:e1005331
Ellison, Christopher E; Bachtrog, Doris (2015) Non-allelic gene conversion enables rapid evolutionary change at multiple regulatory sites encoded by transposable elements. Elife 4:
Mahajan, Shivani; Bachtrog, Doris (2015) Partial dosage compensation in Strepsiptera, a sister group of beetles. Genome Biol Evol 7:591-600
Vicoso, Beatriz; Bachtrog, Doris (2015) Numerous transitions of sex chromosomes in Diptera. PLoS Biol 13:e1002078
Assis, Raquel; Bachtrog, Doris (2015) Rapid divergence and diversification of mammalian duplicate gene functions. BMC Evol Biol 15:138
Brown, Emily J; Bachtrog, Doris (2014) The chromatin landscape of Drosophila: comparisons between species, sexes, and chromosomes. Genome Res 24:1125-37
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

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