title: Frequent polymorphism of the mitochondrial DNA polymerase gamma gene (POLG) in patients with normal spermiograms and unexplained subfertility.
abstract: BACKGROUND
  Male fertility largely depends on the quality of sperm production, which may be affected by environmental and genetic factors. In this study, we explored a possible role of the polymerase gamma (POLG) gene polymorphism, recently reported to be associated with male infertility in some populations.
  
  
  METHODS
  The polymorphic CAG repeat (usually 10 codons long) in the POLG gene was studied in 1298 male subjects: 429 patients with infertility/subfertility, and 869 controls (495 men from the general population with unknown fertility and 374 recent fathers). In all subjects, the POLG polymorphism was assessed in relation to their semen quality, and--in the fertile controls--with biological fecundity measured as waiting time-to-pregnancy (TTP) for the couples. In the patients lacking the common POLG allele, the outcome of the assisted reproductive techniques (ART) for the couples was evaluated.
  
  
  RESULTS
  The absence of one (10/ not equal to 10) or both common POLG alleles (not equal to 10/not equal to 10) was more frequent among the subfertile patients than among fertile controls (P=0.021 and P=0.04 respectively). The estimated predictive value for infertility in a man homozygous for the POLG polymorphism was 15.5% (95% CI: 4.8-51%). There was a positive association with sperm concentration: 14.3% of the normospermic subfertile patients were homozygous for the absence of the common POLG allele (not equal to 10/not equal to 10), in comparison with 2.3% of unselected controls (P=0.001) and 0.9% of the fertile men (P=0.0001). No association with sperm motility, morphology and TTP was found. Spermatozoa of the three not equal to 10/not equal to 10 patients treated with IVF retained the ability to penetrate the egg, but the fertilization rate was low. Nine homozygous not equal to 10/ not equal to 10 patients were treated with ICSI, resulting in pregnancy in seven couples.
  
  
  CONCLUSIONS
  The POLG gene polymorphism should be considered as a possible contributing factor in patients with unexplained subfertility and normal spermiograms. The oocyte penetration ability of sperm may be partially impaired in the not equal to 10/not equal to 10 patients but most of them can be successfully treated with ICSI.
authors.affiliation: Department of Growth and Reproduction, Copenhagen University Hospital (Rigshospitalet), DK-2100 Copenhagen, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Jensen
authors.forename: Henrik
authors.initials: H
authors.lastname: Leffers
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Petersen
authors.forename: Anders
authors.initials: A
authors.lastname: Nyboe Andersen
authors.forename: Niels
authors.initials: N
authors.lastname: Jørgensen
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Carlsen
authors.forename: Tina Kold
authors.initials: TK
authors.lastname: Jensen
authors.forename: Niels E
authors.initials: NE
authors.lastname: Skakkebaek
authors.forename: Ewa
authors.initials: E
authors.lastname: Rajpert-De Meyts
mesh_terms: D000328:Adult; D000483:Alleles; D016022:Case-Control Studies; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase / Q000235:genetics*; D005260:Female; D005298:Fertility / Q000235:genetics; D005307:Fertilization in Vitro; D005787:Gene Frequency; D006720:Homozygote; D006801:Humans; D007248:Infertility, Male / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D011110:Polymorphism, Genetic; D011247:Pregnancy; D018873:Pregnancy Rate; D012661:Semen; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa
chemical_list: D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; C413027:POLG protein, human