Analysis of RXFP2 (LGR8) as Candidate Gene for Canine Cryptorchidism

Over the last years several studies looked for association between human cryptorchidism and nucleotide variations in the INSL3 and LGR8 genes. Only rare mutations have been identified though. A recent paper shows that the mutation at the amino acid 222 of LGR8 (T222P) is exclusively associated to the testicular maldescent phenotype (Bogatcheva, 2007, Am J Physiol Endocrinol Metab 292:E138–144). Aim of the present work is the identification of polymorphisms within the canine RXFP2 (also referred to as LGR8) gene possibly associated with cryptorchidism. Starting from sequences available in public databases, specific primer pairs were designed to amplify the coding regions of the gene. Genomic DNA from 20 cryptorchid dogs, including 4 abdominal bilateral ones, and from 4 healthy dogs used as controls was amplified by PCR and directly sequenced. So far the sequence analysis have been carried out in the regions from nucleotide 42 to 374, and from 591 to 662 (GenBank Acc no AY749634). The latter correspond to the human LGR8 exon 8, where the polymorphism that originates the identified amino acid mutation T222P had been found. The coding portion analysed in this study shows complete homology between cryptorchid and healthy dogs, that is no nucleotide variations exist. Some SNPs have been identified, but only in the putative intronic regions. Based on the data produced so far, no nucleotide mutation leading to the corresponding human amino acid substitution at position 222 or any other nucleotide mutations have been identified.