Title: "Widespread allelic imbalance in Drosophila hybrid heads"
Speaker: Lauren McIntyre, Department of Molecular Genetics and Microbiology, University of Florida
Place: HORT 117; April 19, 2011, Tuesday, 4:30pm


Hundreds to thousands of genes are expressed differently between species, implying that differential regulation between species may be the rule rather than an exception. Unraveling how regulatory divergence contributes to species differences and to adaptation requires identifying functional, potentially adaptive, variants from among millions of genetic differences. Functional divergence of cis regulatory regions has been found in thousands of genes in multiple organisms. When functional cis regulatory divergence is coupled with signatures of adaptive evolution it suggests that the regulatory differences observed are adaptive or a direct consequence of adaptive evolution. A comprehensive assessment of cis regulatory divergence in Drosophila melanogaster-Drosophila simulans hybrid female heads identified allelic imbalance (AI) using RNA-seq technology. Critical to sound inferences was overcoming issues of map bias. Additionally, a novel Bayesian method for the analysis of these data- one that explicitly accounts for read sampling as a random variable- was developed and implemented. We found that cis regulatory divergence was widespread in the head, 41% of all genes showed significant AI. For 30% of cis regulatory divergent genes, these functional differences were coupled with adaptive evolution. While these estimates are startling, they are lower than previous analyses which failed to account for map bias and sampling variation.

Associated Reading:
Rita M. Graze, Lauren M. McIntyre, Bradley J. Main, Marta L. Wayne, and Sergey V. Nuzhdin. 2009. Regulatory Divergence in Drosophila melanogaster and D. simulans, a Genomewide Analysis of Allele-Specific Expression. Genetics. 183: 547-561.

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