Final Report: Cryptorchidism, or retained testicles, is one of the common congenital problems in dogs. The testes of cryptorchids are more prone to testicular cancer and infertility. Hence cryptorchids and animals carrying genes for cryptorchidism should be eliminated from the breeding population. Some evidence exists to suggest that it appears to be caused by many genes.
Therefore, the present study was performed to find the genetic differences on all chromosomes (genome wide) between 24 unrelated cryptorchid male dogs (cases) and 24 normal dogs (controls). A total of 173,662 genetic differences called single nucleotide polymorphisms (SNPs) through out the genome were tested between 24 cases and 24 controls using the CanineHD Genotyping BeadChip at GeneSeek, Lincoln, NE. Several advanced statistical methods including case-control association analyses and haplotype analyses using the PLINK software and Bayesian methods using GenSel software were implemented to find the associated chromosomal regions and the genes within the regions for canine cryptorchidism.
Our statistical association analyses indicated a better association of a region on chromosome 27 containing a gene called collagen type II alpha 1 (COL2A1) with this defect. These results are in agreement with our earlier study, which also found the association of COL2A1 utilizing a different approach called candidate gene approach. Hence the present results are very interesting but still inconclusive. However, since this study used only 24 cases and 24 controls, the results need to be further validated with a larger number of cryptorchid cases and controls.
A similar project funded by CHF with a larger number of cases and controls is now ongoing in our laboratory. It is likely that a recommendation will be provided for future genetic tests for canine cryptorchidism after the completion of this ongoing CHF funded project (Grant number 1248) with more number of cases and controls.