{"entity": "publication", "iuid": "e243a6cb61c644a0b4a59b07ec18fbc1", "timestamp": "2026-09-24T14:45:08.781Z", "links": {"self": {"href": "https://publications-affiliated.scilifelab.se/publication/e243a6cb61c644a0b4a59b07ec18fbc1.json"}, "display": {"href": "https://publications-affiliated.scilifelab.se/publication/e243a6cb61c644a0b4a59b07ec18fbc1"}}, "title": "The avian W chromosome is a refugium for endogenous retroviruses with likely effects on female-biased mutational load and genetic incompatibilities.", "authors": [{"family": "Peona", "given": "Valentina", "initials": "V"}, {"family": "Palacios-Gimenez", "given": "Octavio M", "initials": "OM"}, {"family": "Blommaert", "given": "Julie", "initials": "J"}, {"family": "Liu", "given": "Jing", "initials": "J"}, {"family": "Haryoko", "given": "Tri", "initials": "T"}, {"family": "J\u00f8nsson", "given": "Knud A", "initials": "KA"}, {"family": "Irestedt", "given": "Martin", "initials": "M"}, {"family": "Zhou", "given": "Qi", "initials": "Q"}, {"family": "Jern", "given": "Patric", "initials": "P"}, {"family": "Suh", "given": "Alexander", "initials": "A"}], "type": "journal article", "published": "2021-09-13", "journal": {"title": "Philos. Trans. R. Soc. Lond., B, Biol. Sci.", "issn": "1471-2970", "volume": "376", "issue": "1833", "pages": "20200186", "issn-l": "0962-8436"}, "abstract": "It is a broadly observed pattern that the non-recombining regions of sex-limited chromosomes (Y and W) accumulate more repeats than the rest of the genome, even in species like birds with a low genome-wide repeat content. Here, we show that in birds with highly heteromorphic sex chromosomes, the W chromosome has a transposable element (TE) density of greater than 55% compared to the genome-wide density of less than 10%, and contains over half of all full-length (thus potentially active) endogenous retroviruses (ERVs) of the entire genome. Using RNA-seq and protein mass spectrometry data, we were able to detect signatures of female-specific ERV expression. We hypothesize that the avian W chromosome acts as a refugium for active ERVs, probably leading to female-biased mutational load that may influence female physiology similar to the 'toxic-Y' effect in Drosophila males. Furthermore, Haldane's rule predicts that the heterogametic sex has reduced fertility in hybrids. We propose that the excess of W-linked active ERVs over the rest of the genome may be an additional explanatory variable for Haldane's rule, with consequences for genetic incompatibilities between species through TE/repressor mismatches in hybrids. Together, our results suggest that the sequence content of female-specific W chromosomes can have effects far beyond sex determination and gene dosage. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.", "doi": "10.1098/rstb.2020.0186", "pmid": "34304594", "labels": [], "xrefs": [{"db": "pmc", "key": "PMC8310711"}, {"db": "figshare", "key": "10.6084/m9.figshare.c.5450746"}], "notes": [], "created": "2026-09-23T07:45:29.860Z", "modified": "2026-09-23T07:45:29.889Z"}