A common polymorphism in the human relaxin-like factor (RLF) gene: No relationship with cryptorchidism

The incidence of impaired testicular descent (cryptorchidism) is high; 1-2% of boys at the age of 3 mo an diagnosed for this condition in western coun tries, Recent data on mice with targeted disruption of the Insl3/relaxin-li ke factor (RLF) gene proposed that this factor plays a role in testicular d escent in fetal life. Male RLF-/- mice exhibit bilateral cryptorchidism due to developmental abnormalities of the gubernaculum, associated with abnorm al spermatogenesis and infertility. In the present study, we have sequenced the promoter region and both exons of the RLF gene in a cohort of 30 boys, seven of whom presented with a possible familial form of cryptorchidism an d 23 with sporadic cryptorchidism. One of the nucleotide substitutions dete cted, G to A at position 178, predicted amino acid change. The mutation was localized to the C-peptide region, resulting in an alanine to threonine ch ange and therefore classified as a conservative mutation. Four of the 30 ca ses analyzed were homozygous (13%), and 15 were heterozygous for the mutati on (50%). However, the same mutation was also found in a control group of 8 9 men; 10% of them were homozygous, and 39% were heterozygous. Our results indicate that mutations in the RLF gene are not a common reason for cryptor chidism and that the common G178A polymorphism has no apparent relationship with this condition.