--- _id: '1991' abstract: - lang: eng text: Although transitions of sex-determination mechanisms are frequent in species with homomorphic sex chromosomes, heteromorphic sex chromosomes are thought to represent a terminal evolutionary stage owing to chromosome-specific adaptations such as dosage compensation or an accumulation of sex-specific mutations. Here we show that an autosome of Drosophila, the dot chromosome, was ancestrally a differentiated X chromosome. We analyse the whole genome of true fruitflies (Tephritidae), flesh flies (Sarcophagidae) and soldier flies (Stratiomyidae) to show that genes located on the dot chromosome of Drosophila are X-linked in outgroup species, whereas Drosophila X-linked genes are autosomal. We date this chromosomal transition to early drosophilid evolution by sequencing the genome of other Drosophilidae. Our results reveal several puzzling aspects of Drosophila dot chromosome biology to be possible remnants of its former life as a sex chromosome, such as its minor feminizing role in sex determination or its targeting by a chromosome-specific regulatory mechanism. We also show that patterns of biased gene expression of the dot chromosome during early embryogenesis, oogenesis and spermatogenesis resemble that of the current X chromosome. Thus, although sex chromosomes are not necessarily evolutionary end points and can revert back to an autosomal inheritance, the highly specialized genome architecture of this former X chromosome suggests that severe fitness costs must be overcome for such a turnover to occur. acknowledgement: Funded by National Institutes of Health grants (R01GM076007 and R01GM093182) and a Packard Fellowship to D.B. author: - first_name: Beatriz full_name: Beatriz Vicoso id: 49E1C5C6-F248-11E8-B48F-1D18A9856A87 last_name: Vicoso orcid: 0000-0002-4579-8306 - first_name: Doris full_name: Bachtrog, Doris last_name: Bachtrog citation: ama: Vicoso B, Bachtrog D. Reversal of an ancient sex chromosome to an autosome in Drosophila. Nature. 2013;499(7458):332-335. doi:10.1038/nature12235 apa: Vicoso, B., & Bachtrog, D. (2013). Reversal of an ancient sex chromosome to an autosome in Drosophila. Nature. Nature Publishing Group. https://doi.org/10.1038/nature12235 chicago: Vicoso, Beatriz, and Doris Bachtrog. “Reversal of an Ancient Sex Chromosome to an Autosome in Drosophila.” Nature. Nature Publishing Group, 2013. https://doi.org/10.1038/nature12235. ieee: B. Vicoso and D. Bachtrog, “Reversal of an ancient sex chromosome to an autosome in Drosophila,” Nature, vol. 499, no. 7458. Nature Publishing Group, pp. 332–335, 2013. ista: Vicoso B, Bachtrog D. 2013. Reversal of an ancient sex chromosome to an autosome in Drosophila. Nature. 499(7458), 332–335. mla: Vicoso, Beatriz, and Doris Bachtrog. “Reversal of an Ancient Sex Chromosome to an Autosome in Drosophila.” Nature, vol. 499, no. 7458, Nature Publishing Group, 2013, pp. 332–35, doi:10.1038/nature12235. short: B. Vicoso, D. Bachtrog, Nature 499 (2013) 332–335. date_created: 2018-12-11T11:55:05Z date_published: 2013-07-18T00:00:00Z date_updated: 2021-01-12T06:54:33Z day: '18' doi: 10.1038/nature12235 extern: 1 intvolume: ' 499' issue: '7458' month: '07' page: 332 - 335 publication: Nature publication_status: published publisher: Nature Publishing Group publist_id: '5092' quality_controlled: 0 status: public title: Reversal of an ancient sex chromosome to an autosome in Drosophila type: journal_article volume: 499 year: '2013' ...