EvSex Presentation - Melissa Wilson Sayres

Evolution of dosage compensation - Melissa A. Wilson Sayres

School of Life Sciences
Arizona State University
Evolution of dosage compensation

In species with highly heteromorphic sex chromosomes, the degradation of one of the sex chromosomes will result in unequal gene expression between the sexes (e.g., between XX females and XY males) and between the sex chromosomes and the autosomes. Dosage compensation is a process whereby genes on the sex chromosomes achieve equal gene expression. We study dosage compensation in a range of species, and find evidence for independent and convergent mechanisms. In humans, we find evidence that gene-by-gene dosage compensation on the human X chromosome likely evolved in response to gene loss on the Y chromosome (with both up regulation in males and down regulation in females, the X-inactivation that is often observed). Alternatively, in the green anole, we find evidence for up regulation in males only. We are now working new methods to accurately infer biased allele expression to investigate variable levels of dosage compensation between individuals, and between tissues in the same individual. Our results from the green anole support the hypothesis that chromosome-wide dosage compensation may be a universal feature of XX/XY sex determination systems.