The dog as a model to study human epididymal function at a molecular level.

Approaches to study human epididymal functions are limited. Therefore, suitable animal models are highly desirable, yet difficult to find among the few species studied on a molecular level to date. This review summarizes our progress in the development of the canine epididymis as an alternative model. Dogs are biomedically a key species because they are subject to many of the same diseases as humans and already serve as a model for a number of human pathologies, including genetic diseases. It is thus consistent that an appraisal of epididymal specific gene expression has been started in the dog, including the molecular cloning and characterization of canine epididymal proteins. These proteins, in addition to a high overall sequence similarity to the human, show a similar tissue distribution, relative abundance and spatial pattern within the epididymis. Moreover, the dog epididymis offers an excellent source for cell culture studies, and immortalization of the canine epididymal duct epithelium has been achieved, encouraging regulatory studies of epididymal gene expression in vitro. Thus, the dog already fulfils many of the criteria of a good model of the human epididymis on a molecular level. Further progress may be expected with the advance of the canine genome project. If there is a genetic basis for male infertility, then the dog provides the advantage of the exploitation of a species that combines a maximum of genetic variation within a species with the capacity to minimize that variation within a defined pedigree.