Background The development of novel fertilization treatments, including in vitro fertilization and intracytoplasmic injection, has made pregnancy possible regardless of the level of activity of the spermatozoa; however, the etiology of male-factor infertility is poorly understood. Multiple studies, primarily through the use of transgenic animals, have contributed to a list of candidate genes that may affect male infertility in humans. We examined single nucleotide polymorphisms (SNPs) as a cause of male infertility in an analysis of spermatogenesis-specific genes. Methods and Finding We carried out the prevalence of SNPs in the coding region of phosphoglycerate mutase 4 (PGAM4) on the X chromosome by the direct sequencing of PCR-amplified DNA from male patients. Using RT-PCR and western blot analyses, we identified that PGAM4 is a functional retrogene that is expressed predominantly in the testes and is associated with male infertility. PGAM4 is expressed in post-meiotic stages, including spermatids and spermatozoa in the testes, and the principal piece of the flagellum and acrosome in ejaculated spermatozoa. A case-control study revealed that 4.5% of infertile patients carry the G75C polymorphism, which causes an amino acid substitution in the encoded protein. Furthermore, an assay for enzymatic activity demonstrated that this polymorphism decreases the enzyme’s activity both in vitro and in vivo. Conclusion These results suggest that PGAM4, an X-linked retrogene, is a fundamental gene in human male reproduction and may escape meiotic sex chromosome inactivation. These findings provide fresh insight into elucidating the mechanisms of male infertility.
Vemuganti SA, Bell TA, Scarlett CO, Parker CE, de Villena FP, et al. (2007) Three male germline-specific aldolase A isozymes are generated by alternative splicing and retrotransposition. Dev Biol 309: 18–31.
Hendriksen PJ, Hoogerbrugge JW, Baarends WM, de Boer P, Vreeburg JT, et al. (1997) Testis-specific expression of a functional retroposon encoding glucose-6-phosphate dehydrogenase in the mouse. Genomics 41: 350–359.
Khil PP, Smirnova NA, Romanienko PJ, Camerini-Otero RD (2004) The mouse X chromosome is enriched for sex-biased genes not subject to selection by meiotic sex chromosome inactivation. Nat Genet 36: 642–646.
Nakamura N, Mori C, Eddy EM (2010) Molecular complex of three testis-specific isozymes associated with the mouse sperm fibrous sheath: hexokinase 1, phosphofructokinase M, and glutathione S-transferase mu class 5. Biol Reprod 82: 504–515.
Travis AJ, Foster JA, Rosenbaum NA, Visconti PE, Gerton GL, et al. (1998) Targeting of a germ cell-specific type 1 hexokinase lacking a porin-binding domain to the mitochondria as well as to the head and fibrous sheath of murine spermatozoa. Mol Biol Cell 9: 263–276.
Miki K, Qu W, Goulding EH, Willis WD, Bunch DO, et al. (2004) Glyceraldehyde 3-phosphate dehydrogenase-S, a sperm-specific glycolytic enzyme, is required for sperm motility and male fertility. Proc Natl Acad Sci U S A 101: 16501–16506.
Koga M, Tanaka H, Yomogida K, Nozaki M, Tsuchida J, et al. (2000) Isolation and characterization of a haploid germ cell-specific novel complementary deoxyribonucleic acid; testis-specific homologue of succinyl CoA:3-Oxo acid CoA transferase. Biol Reprod 63: 1601–1609.
Tanaka H, Kohroki J, Iguchi N, Onishi M, Nishimune Y (2002) Cloning and characterization of a human orthologue of testis-specific succinyl CoA: 3-oxo acid CoA transferase (Scot-t) cDNA. Mol Hum Reprod 8: 16–23.