Spermatid-specific expression of the novel X-linked gene product SPAN-X localized to the nucleus of human spermatozoa

Biol Reprod. 2000 Aug;63(2):469-81. doi: 10.1093/biolreprod/63.2.469.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Northern
  • Cell Nucleus / metabolism*
  • Chromosome Mapping
  • Genetic Linkage
  • Haploidy
  • Humans
  • In Situ Hybridization
  • Isoelectric Point
  • Male
  • Meiosis
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • RNA, Messenger / analysis
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / isolation & purification
  • Spermatids / metabolism*
  • Spermatids / ultrastructure
  • Testis / chemistry
  • Transcription, Genetic
  • X Chromosome*

Substances

  • Nuclear Proteins
  • RNA, Messenger
  • Recombinant Proteins
  • SPANXA1 protein, human
  • SPANXB1 protein, human