title: Polar nuclear localization of H1T2, a histone H1 variant, required for spermatid elongation and DNA condensation during spermiogenesis.
abstract: Spermiogenesis entails a major biochemical and morphological restructuring of the germ cell involving replacement of the somatic histones by protamines packing the DNA into the condensed spermatid nucleus and elimination of the cytoplasm during the elongation phase. We describe H1T2, an histone H1 variant selectively and transiently expressed in male haploid germ cells during spermiogenesis. In round and elongating spermatids, H1T2 specifically localizes to a chromatin domain at the apical pole, revealing a polarity in the spermatid nucleus. Inactivation by homologous recombination shows that H1T2 is critical for spermiogenesis as male H1t2(-/-) mice have greatly reduced fertility. Analysis of spermiogenesis in H1t2 mutant mice shows delayed nuclear condensation and aberrant elongation. As a result, mutant spermatids are characterized by the presence of residual cytoplasm, acrosome detachment, and fragmented DNA. Hence, H1T2 is a protein required for proper cell restructuring and DNA condensation during the elongation phase of spermiogenesis.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, and Université Louis Pasteur, 1 Rue Laurent Fries, 67404 Illkirch Cédex, France.
authors.forename: Igor
authors.initials: I
authors.lastname: Martianov
authors.forename: Stefano
authors.initials: S
authors.lastname: Brancorsini
authors.forename: Raffaella
authors.initials: R
authors.lastname: Catena
authors.forename: Anne
authors.initials: A
authors.lastname: Gansmuller
authors.forename: Noora
authors.initials: N
authors.lastname: Kotaja
authors.forename: Martti
authors.initials: M
authors.lastname: Parvinen
authors.forename: Paolo
authors.initials: P
authors.lastname: Sassone-Corsi
authors.forename: Irwin
authors.initials: I
authors.lastname: Davidson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry*; D016764:Cell Polarity; D004247:DNA / Q000378:metabolism*; D005298:Fertility; D006657:Histones / Q000032:analysis* / Q000502:physiology; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D013087:Spermatids / Q000737:chemistry / Q000502:physiology*; D013091:Spermatogenesis
chemical_list: D006657:Histones; D004247:DNA