Evolution of sex chromosomes
The widespread presence of independently derived sex chromosomes with shared characteristics across plants, animals and even fungi is striking and suggests that a common set of evolutionary forces select for their formation. In some groups, closely related species have different sex chromosomes, suggesting that they can evolve rapidly. These observations have stimulated much theoretical work to investigate both why and how sex chromosomes evolve. Despite this large body of theory, relatively few empirical studies have put these theoretical predictions to the test, due to the fact that most empirical studies thus far have focused on old and degenerate sex chromosomes (e.g. mammals, fruit flies) that tell us little about the mechanisms that drive the earliest stages of sex chromosome evolution or that lead to the rapid turnover of sex chromosomes among closely related species.
Our work on the diversity of young sex chromosomes found in sticklebacks has contributed to a paradigm shift away from studying old and degenerate sex chromosomes, to using young sex chromosomes like those in sticklebacks to understand how and why these unique regions of the genome evolve. Our work on stickleback sex chromosomes has made it one of the preeminent model systems for studying the early stages of Y chromosome degeneration, the rapid turnover of sex chromosomes within and between species, and the role of sex chromosome turnover in speciation.
Ongoing research directions
Currently, we are performing large-scale genomic studies to analyze patterns of degeneration on the young threespine stickleback Y chromosome. In the future, I am particularly interested in investigating the evolutionary forces that underlie both the degeneration of sex chromosomes and the rapid turnover of sex chromosome systems found in many systems.
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White MA, Kitano J, Peichel CL (2015) Purifying selection maintains dosage sensitive genes during degeneration of the threespine stickleback Y chromosome. Molecular Biology and Evolution 32: 1981-1995. 10.1093/molbev/msv078
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Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto SP, Ashman T-L, Hahn MW, Kitano J, Mayrose I, Ming R, Perrin N, Ross L, Valenzuela N, Vamosi J; Tree of Sex Consortium (2014) Sex determination – why so many ways of doing it? PLoS Biology 12: e1001899. 10.1371/journal.pbio.1001899
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Urton JR, McCann SM, Peichel CL (2011) Karyotype differentiation between two stickleback species (Gasterosteidae). Cytogenetic and Genome Research 135: 150-159. 10.1159/000331232
Kitano J, Ross JA, Mori S, Kume M, Jones FC, Chan YF, Absher DM, Grimwood J, Schmutz J, Myers RM, Kingsley DM, Peichel CL (2009) A role for a neo-sex chromosome in stickleback speciation. Nature 461: 1079-1083. 10.1038/nature08441
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Ross JA, Peichel CL (2008) Molecular cytogenetic evidence of rearrangements on the Y chromosome of the threespine stickleback fish. Genetics 179: 2173-2182. 10.1534/genetics.108.088559
Peichel CL, Ross JA, Matson CK, Dickson M, Grimwood J, Schmutz J, Myers R, Mori S, Schluter D, Kingsley DM (2004) The master sex-determination locus in threespine sticklebacks is on a nascent Y chromosome. Current Biology 14: 1416-1424. 10.1016/j.cub.2004.08.030