Both protamine-1 to protamine-2 mRNA ratio and Bcl2 mRNA content in testicular spermatids and ejaculated spermatozoa discriminate between fertile and infertile men.
BACKGROUND
Human sperm contain similar amounts of protamine-1 (P1) and protamine-2 (P2). Although aberrant protamine ratios have been observed in infertile men, functional evidence is provided by protamine knockout mice exhibiting male infertility. As sperm DNA integrity is known to be linked with DNA fragmentation and apoptosis, we investigated whether the protamine ratio or Bcl2 content represent a reliable biomarker to discriminate fertile and infertile men.


METHODS
Real-time quantitative RT-PCR was used for P1, P2 and the apoptotic marker Bcl2 in testicular biopsies (TB; 74 infertile men versus 17 controls) and ejaculates (E; 95 infertile men versus 10 controls).


RESULTS
The P1-P2 mRNA ratio differed significantly between groups, namely 1:4 versus 1:3.2 in TB (P = 0.0038) and 1:1.7 versus 1:1 in E (P = 0.0002), for infertile men and controls, respectively. Bcl2 mRNA content was correlated with protamine mRNA ratio (P = 0.0250 for TB; P = 0.0003 for E). Infertile men exhibit a more than 10-fold (P = 0.0155 for TB; P = 7.0 x 10(-6) for E) higher Bcl2 mRNA content versus controls. No correlation was found between absolute sperm density and the protamine mRNA ratio or Bcl2 mRNA content. No significant correlation was demonstrated with fertilization rate after ICSI and either protamine ratio or Bcl2 content.


CONCLUSIONS
We found significantly aberrant protamine ratios and a higher Bcl2 content in TB and E of infertile men compared to controls, suggesting that these molecules may be useful biomarkers for predicting male infertility.
Steger
Klaus
K
Department of Urology and Pediatric Urology, University of Giessen, Germany. Klaus.Steger@chiru.med.uni-giessen.de
Wilhelm
Jochen
J
Konrad
Lutz
L
Stalf
Thomas
T
Greb
Robert
R
Diemer
Thorsten
T
Kliesch
Sabine
S
Bergmann
Martin
M
Weidner
Wolfgang
W
D000328:Adult; D004542:Ejaculation; D005260:Female; D005298:Fertility; D006801:Humans; D007248:Infertility, Male / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011479:Protamines / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D013087:Spermatids / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism*; D013737:Testis
C082073:PRM1 protein, human; D011479:Protamines; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C068621:protamine 2