Table 1.

Phenotypes of knockout male mouse models.

	ArKO	αERKO	βERKO	αβERKO	NOER	MOER
Fertility	Initially fertile although with advancing age they developed progressive infertility.	Infertile	Fertile/Infertile*	Infertile	Initially subfertile, becoming infertile with advancing age	Infertile
Gonadotropins
Serum LH	Elevated	Not significantly higher	NA	NA	Normal	NA
Serum FSH	Normal	Not significantly higher	NA	NA	Normal	NA
Serum Steroids
Androgens	Tendency toward elevated levels	Elevated	NA	NA	Elevated	NA
Estrogens		Normal	NA	NA	Normal	NA
Testicular function	At ~12–14 weeks of age the internal anatomy of the male ArKO mice showed increased weight because of the seminal vesicles (caused by increased volume of secretions) and combined urinary bladder/prostate but no difference in the testes weight. Leydig cell hyperplasia/hypertrophy	Testis weight significantly reduced. Disruption of seminiferous tubules.	Normal with some age-related abnormalities in the prostate and bladder	Showed similar phenotype as male αERKO mice.	At 4 months of age seminiferous tubular degeneration. At 8 months of age: significant histological alterations in testis, rete testis, and efferent ductus.	NA
Sperm	Disruptions in spermatogenesis with increased frequency of germ cell apoptosis and defects in spermiogenesis with the epididymis showing reduced or complete absence of sperm	In adulthood quantity and quality of sperm affected. Spermatogenic stem cells not affected	Normal	Similar to male αERKO mice	Decreased sperm production with impaired sperm motility and viability	NA

^*AnERβ mouse mutant generated by Cre/LoxP deletion of exon 3; reported impaired mating, suggesting male infertility (46).

NA, Not Available.