{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,8]],"date-time":"2026-10-08T22:09:31Z","timestamp":1791497371950,"version":"4.3.4"},"reference-count":42,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2022,3,25]],"date-time":"2022-03-25T00:00:00Z","timestamp":1648166400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cells"],"abstract":"<jats:p>The conspicuous colour sexual dimorphism of guppies has made them paradigmatic study objects for sex-linked traits and sex chromosome evolution. Both the X- and Y-chromosomes of the common guppy (Poecilia reticulata) are genetically active and homomorphic, with a large homologous part and a small sex specific region. This feature is considered to emulate the initial stage of sex chromosome evolution. A similar situation has been documented in the related Endler\u2019s and Oropuche guppies (P. wingei, P. obscura) indicating a common origin of the Y in this group. A recent molecular study in the swamp guppy (Micropoecilia. picta) reported a low SNP density on the Y, indicating Y-chromosome deterioration. We performed a series of cytological studies on M. picta to show that the Y-chromosome is quite small compared to the X and has accumulated a high content of heterochromatin. Furthermore, the Y-chromosome stands out in displaying CpG clusters around the centromeric region. These cytological findings evidently illustrate that the Y-chromosome in M. picta is indeed highly degenerated. Immunostaining for SYCP3 and MLH1 in pachytene meiocytes revealed that a substantial part of the Y remains associated with the X. A specific MLH1 hotspot site was persistently marked at the distal end of the associated XY structure. These results unveil a landmark of a recombining pseudoautosomal region on the otherwise strongly degenerated Y chromosome of M. picta. Hormone treatments of females revealed that, unexpectedly, no sexually antagonistic color gene is Y-linked in M. picta. All these differences to the Poecilia group of guppies indicate that the trajectories associated with the evolution of sex chromosomes are not in parallel.<\/jats:p>","DOI":"10.3390\/cells11071118","type":"journal-article","created":{"date-parts":[[2022,3,25]],"date-time":"2022-03-25T15:31:21Z","timestamp":1648222281000},"page":"1118","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Evolution of the Degenerated Y-Chromosome of the Swamp Guppy, Micropoecilia picta"],"prefix":"10.3390","volume":"11","author":[{"given":"Indrajit","family":"Nanda","sequence":"first","affiliation":[{"name":"Department of Human Genetics, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Susanne","family":"Schories","sequence":"additional","affiliation":[{"name":"Developmental Biochemistry, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ivan","family":"Simeonov","sequence":"additional","affiliation":[{"name":"Developmental Biochemistry, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mateus Contar","family":"Adolfi","sequence":"additional","affiliation":[{"name":"Developmental Biochemistry, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1497-8945","authenticated-orcid":false,"given":"Kang","family":"Du","sequence":"additional","affiliation":[{"name":"Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX 78666, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Claus","family":"Steinlein","sequence":"additional","affiliation":[{"name":"Department of Human Genetics, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manfred","family":"Alsheimer","sequence":"additional","affiliation":[{"name":"Department of Cell and Developmental Biology, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0737-0763","authenticated-orcid":false,"given":"Thomas","family":"Haaf","sequence":"additional","affiliation":[{"name":"Department of Human Genetics, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9882-5948","authenticated-orcid":false,"given":"Manfred","family":"Schartl","sequence":"additional","affiliation":[{"name":"Developmental Biochemistry, University of W\u00fcrzburg Biocenter, 97074 W\u00fcrzburg, Germany"},{"name":"Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX 78666, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"634","DOI":"10.1016\/j.gde.2004.09.005","article-title":"Sex chromosome evolution in non-mammalian vertebrates","volume":"14","author":"Schartl","year":"2004","journal-title":"Curr. 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