title: Spermatid-specific expression of the novel X-linked gene product SPAN-X localized to the nucleus of human spermatozoa.
abstract: Formation of mature spermatozoa involves a series of dramatic molecular and morphological changes in the male germ cell lineage. These changes result from the temporally regulated transcription and translation of several testis-specific gene products. Here, we describe a novel, testis-specific protein designated SPAN-X for sperm protein associated with the nucleus on the X chromosome. SPAN-X sequences showed no significant similarity with known cDNA or peptide sequences. The SPAN-X peptide sequences contained three overlapping consensus nuclear localization signals, a high percentage (33%-37%) of charged amino acid residues, and a relatively acidic isoelectric point (pI; 4.88-6.05). Northern analysis of mRNA from multiple human tissues identified a SPAN-X transcript exclusively in the testis. In situ hybridization of human testes sections showed SPAN-X mRNA expression in haploid, round, and elongating spermatids. The SPANX gene was mapped to chromosome Xq27. 1 by fluorescence in situ hybridization and by Southern blot analysis of human/mouse somatic cell hybrids. On Western blots of human sperm proteins, antirecombinant SPAN-X antibodies reacted with broad bands migrating between 15-20 kDa. Immunofluorescent labeling of human spermatozoa demonstrated SPAN-X localization to nuclear craters and cytoplasmic droplets. Expression of SPAN-X, an X-linked gene product, exclusively in haploid spermatids leads to interesting questions regarding the transcription of sex-linked genes during spermiogenesis.
authors.affiliation: Departments of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: V A
authors.initials: VA
authors.lastname: Westbrook
authors.forename: A B
authors.initials: AB
authors.lastname: Diekman
authors.forename: K L
authors.initials: KL
authors.lastname: Klotz
authors.forename: V V
authors.initials: VV
authors.lastname: Khole
authors.forename: C
authors.initials: C
authors.lastname: von Kap-Herr
authors.forename: W L
authors.initials: WL
authors.lastname: Golden
authors.forename: R L
authors.initials: RL
authors.lastname: Eddy
authors.forename: T B
authors.initials: TB
authors.lastname: Shows
authors.forename: M H
authors.initials: MH
authors.lastname: Stoler
authors.forename: C Y
authors.initials: CY
authors.lastname: Lee
authors.forename: C J
authors.initials: CJ
authors.lastname: Flickinger
authors.forename: J C
authors.initials: JC
authors.lastname: Herr
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism*; D002874:Chromosome Mapping; D008040:Genetic Linkage; D006238:Haploidy; D006801:Humans; D017403:In Situ Hybridization; D007526:Isoelectric Point; D008297:Male; D008540:Meiosis; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D013087:Spermatids / Q000378:metabolism* / Q000648:ultrastructure; D013737:Testis / Q000737:chemistry; D014158:Transcription, Genetic; D014960:X Chromosome
chemical_list: D009687:Nuclear Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C414403:SPANXA1 protein, human; C518957:SPANXB1 protein, human