The size of the CAG repeat in exon 1 of the androgen receptor gene shows no significant relationship to impaired spermatogenesis in an infertile Caucasoid sample of German origin

The androgen receptor (AR) gene, located on the X-chromosome at Xq11-12, contains in exon 1 a polymorphic CAG repeat which codes for a polyglutamine tract. Contractions of the CAG repeat are said to be related to prostate cancer. In contrast, sizeable expansion of the CAG repeat can cause spinal and bulbar muscular atrophy (SBMA). In infertile patients of Chinese origin and in a Melbourne multinational population impaired sperm production has been postulated to be related to moderate expansions of the polyglutamine tract. In a study of a Swedish population of infertile patients these findings could not be corroborated. The aim of our investigation was to examine the correlation between the length of the CAG repeat and impaired sperm production in an infertile Caucasoid patient sample of German ethnic origin. We found no statistically significant relationship between the size of the CAG repeat or polyglutamine tract and idiopathic impaired sperm production in the population studied. The variability of the results by various investigators may be attributed to different ethnic origins and hence different genetic modifiers of the populations studied and/or to the high probability that these infertile males may represent a heterogeneous group with respect to the causes of defective spermatogenesis.