title: Unlocking sperm chromatin at fertilization requires a dedicated egg thioredoxin in Drosophila.
abstract: In most animals, the extreme compaction of sperm DNA is achieved after the massive replacement of histones with sperm nuclear basic proteins (SNBPs), such as protamines. In some species, the ultracompact sperm chromatin is stabilized by a network of disulfide bonds connecting cysteine residues present in SNBPs. Studies in mammals have established that the reduction of these disulfide crosslinks at fertilization is required for sperm nuclear decondensation and the formation of the male pronucleus. Here, we show that the Drosophila maternal thioredoxin Deadhead (DHD) is specifically required to unlock sperm chromatin at fertilization. In dhd mutant eggs, the sperm nucleus fails to decondense and the replacement of SNBPs with maternally-provided histones is severely delayed, thus preventing the participation of paternal chromosomes in embryo development. We demonstrate that DHD localizes to the sperm nucleus to reduce its disulfide targets and is then rapidly degraded after fertilization.
authors.affiliation: Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Villeurbanne F-69622, France.
authors.forename: Samantha
authors.initials: S
authors.lastname: Tirmarche
authors.affiliation: Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Villeurbanne F-69622, France.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Kimura
authors.affiliation: Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Villeurbanne F-69622, France.
authors.forename: Raphaëlle
authors.initials: R
authors.lastname: Dubruille
authors.affiliation: Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Villeurbanne F-69622, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Horard
authors.affiliation: Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Villeurbanne F-69622, France.
authors.forename: Benjamin
authors.identifier: http://orcid.org/0000-0002-7166-9233
authors.initials: B
authors.lastname: Loppin
mesh_terms: D000818:Animals; D002843:Chromatin / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000378:metabolism*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010063:Ovum / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; C491201:DHD protein, Drosophila; D029721:Drosophila Proteins; D008565:Membrane Proteins; D013879:Thioredoxins