Seminar: A Synthetic XY System in Xenopus laevis Reveals Evolutionary Pathways for Sex Chromosome Turnover

Titel: A Synthetic XY System in Xenopus laevis Reveals Evolutionary Pathways for Sex Chromosome Turnover

Kurzinhalt:
Evolutionary transitions from female (ZW) to male (XY) heterogamy are generally expected to retain the female-determining function of the ancestral W chromosome, either as a new autosome or a revamped X chromosome alongside a new Y chromosome. To test the prediction of this transition, we used CRISPR/Cas9 to generate a null mutation in the androgen receptor gene (ar) of the African clawed frog, Xenopus laevis. We found that homozygous ar knockouts (ar -/-) develop into fertile phenotypic females, irrespective of their genetic sex, which in wildtype individuals is determined by the presence or absence of a female determining gene called dm-w that is located on the W chromosome. However, genetic males that are heterozygous for the wildtype and null alleles (ar +/-) developed into fertile phenotypic males, demonstrating haplosufficiency of the wildtype ar + allele. The ar - and the haplosufficient ar + alleles are thus synthetic X and Y chromosomes, respectively, that allow for an unbiased sex ratio, and with females (ar -/-) and males (ar +/-) in a population that lacks the ancestral W chromosome. These findings offer new perspectives into sexual differentiation, while demonstrating how developmental systems drift may be realized in ways that completely abandon key components of ancestral genetic networks. We also provide a mechanistic model for how sex-determining systems can undergo radical turnover.

Das Seminar findet in hybrider Form statt:

• Seminarraum „Drachenwand“ 2. Stock
• Webconference UIBK-Link: https://webconference.uibk.ac.at/rooms/qc6-5hp-jl3 “Martin Knytl”