The gene encoding murine alpha 1,3-galactosyltransferase is expressed in female germ cells but not in male germ cells.
An essential step in murine fertilization is the binding of acrosome-intact sperm to specific O-linked glycans on zona pellucida glycoprotein 3 (ZP3). While there is agreement on the primary role of O-linked glycans in sperm-ZP3 binding, there is a striking lack of consensus on both the terminal monosaccharide(s) required for a functional binding site and the cognate protein on the sperm cell surface that recognizes this glycan. Much current debate centers on the essential role of nonreducing terminal N-acetyl-glucosaminyl or alternatively, alpha-galactosyl residues, to form a functional sperm binding ligand. Relevant to this debate, we demonstrated that alpha 1,3-galactosyltransferase (alpha 3-GT), which adds nonreducing terminal alpha-galactosyl residues to glycans, is not expressed in murine spermatocytes or spermatids. The objectives of this study were to determine whether alpha 3-GT is expressed in female germ cells and to compare the pattern of expression of two other terminal glycosyltransferases, beta 1,4-galactosyltransferase (beta 4-GT) and alpha 2,6-sialyltransferase (alpha 6-ST), between male and female germ cells. Total RNA was isolated from growing oocytes obtained from 15-day-old animals, fully grown oocytes, and eggs as well as spermatogonia, spermatocytes, and spermatids. The presence of alpha 3-GT, beta 4-GT, and alpha 6-ST mRNAs was analyzed by an RT-PCR-based assay. Our data demonstrate that the alpha 3-GT gene is expressed in female germ cells, but not in male germ cells. In contrast, both beta 4-GT and alpha 6-ST are expressed during oogenesis and spermatogenesis. This differential expression of alpha 3-GT in female germ cells is consistent with the model of sperm-egg binding in which a nonreducing terminal alpha-galactosyl residue is required for a functional determinant on ZP3 and with our hypothesis that the biological significance for the suppression of alpha 3-GT expression in male germ cells is to prevent sperm-sperm aggregation.
Johnston
D S
DS
Department of Population Dynamics, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205-2179, USA.
Shaper
J H
JH
Shaper
N L
NL
Joziasse
D H
DH
Wright
W W
WW
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D005260:Female; D005700:Galactosyltransferases / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D008297:Male; D008540:Meiosis / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009237:N-Acetyllactosamine Synthase / Q000235:genetics; D009865:Oocytes / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D012727:Sex Characteristics; D012799:Sialyltransferases / Q000235:genetics; D013090:Spermatocytes / Q000201:enzymology*; D014158:Transcription, Genetic
D017931:DNA Primers; D005700:Galactosyltransferases; C037959:beta-D-galactosyl-N-acetylglucosaminylglycopeptide alpha-1,3-galactosyltransferase; D009237:N-Acetyllactosamine Synthase; D012799:Sialyltransferases