Spermatid-specific expression of the novel X-linked gene product SPAN-X localized to the nucleus of human spermatozoa.
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.
Westbrook
V A
VA
Departments of Cell Biology, University of Virginia, Charlottesville, Virginia 22908, USA.
Diekman
A B
AB
Klotz
K L
KL
Khole
V V
VV
von Kap-Herr
C
C
Golden
W L
WL
Eddy
R L
RL
Shows
T B
TB
Stoler
M H
MH
Lee
C Y
CY
Flickinger
C J
CJ
Herr
J C
JC
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
D009687:Nuclear Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C414403:SPANXA1 protein, human; C518957:SPANXB1 protein, human