Abstract
Genetic disruption of glycosyltransferases has provided clear information on the roles of their reaction products in the body. Our group has studied the function of glycosphingolipids by genetic engineering of glycosyltransferases in cell culture and in mice, which has demonstrated both expected and unexpected results. Among these findings, aspermatogenesis in ganglioside GM2/GD2 synthase knockout mice was one of the most surprising and intriguing results. There were no sperms in testis, and multinuclear giant cells were detected instead of spermatids. Although serum levels of testosterone in the male mice were extremely low, testosterone accumulated in the interstitial tissues, including Leydig cells, and seemed not to be transferred into the seminiferous tubules or vascular cavity from Leydig cells. This was considered to be the cause of aspermatogenesis and low serum levels of testosterone. Patients with a mutant GM2/GD2 synthase gene (SPG26) showed similar clinical signs, not only in terms of the neurological aspects, but also in the male reproductive system. The mechanisms for testosterone transport by gangliosides are discussed here based on our own results and reports from other laboratories.