Development and application of a system for seminolipid metabolism using mouse seminiferous tubules

Properties, metabolism and roles of sulfogalactosylglycerolipid in male reproduction

Sulfogalactosylglycerolipid (SGG, aka seminolipid) is selectively synthesized in high amounts in mammalian testicular germ cells (TGCs). SGG is an ordered lipid and directly involved in cell adhesion. SGG is indispensable for spermatogenesis, a process that greatly depends on interaction between Sertoli cells and TGCs. Spermatogenesis is disrupted in mice null for Cgt and Cst, encoding two enzymes essential for SGG biosynthesis. Sperm surface SGG also plays roles in fertilization. All of these results indicate the significance of SGG in male reproduction. SGG homeostasis is also important in male fertility. Approximately 50% of TGCs become apoptotic and phagocytosed by Sertoli cells. SGG in apoptotic remnants needs to be degraded by Sertoli lysosomal enzymes to the lipid backbone. Failure in this event leads to a lysosomal storage disorder and sub-functionality of Sertoli cells, including their support for TGC development, and consequently subfertility. Significantly, both biosynthesis and degradation pathways of the galactosylsulfate head group of SGG are the same as those of sulfogalactosylceramide (SGC), a structurally related sulfoglycolipid important for brain functions. If subfertility in males with gene mutations in SGG/SGC metabolism pathways manifests prior to neurological disorder, sperm SGG levels might be used as a reporting/predicting index of the neurological status.

Effective Selection of a Well-Differentiated Type of Human Uterine Endometrial Carcinoma Cells by Transfection of the Sulfotransferase Gene and Possible Association of Sulfoglycolipids With Well-Differentiated Phenotypes

OBJECTIVES

Sulfatide has been shown to be characteristically increased on the apical surface of the normal endometrium at the secretory phase, and to be related with the formation of the glandular structure and the secretion of mucin from glands for the implantation of a fertilized egg. Additionally, sulfatides are expressed in the well-differentiated type, but not in the poorly differentiated type, of endometrial carcinomas. This suggests that sulfatides are a molecular marker of differentiated phenotypes. To further elucidate the biological significance of sulfoglycolipids, we transfected the sulfotransferase gene into endometrial carcinoma-derived cells without sulfoglycolipids and compared their glycolipid compositions and phenotypes with those of the original cells.

MATERIALS AND METHODS

The glycolipid sulfotransferase gene was transfected into endometrial carcinoma-derived SNG-II cells, the resultant transfected cells being found to frequently form a domelike structure, and some of them were selected as SNG-II-GST cells. We compared the glycolipid compositions and phenotypes of SNG-II and SNG-II-GST cells.

RESULTS

Although the original SNG-II cells grew in a paving stone pattern, SNG-II-GST cells formed a domelike structure. SNG-II-GST cells exhibited high GST activity and contained sulfoglycolipids, IISO3-LacCer and IISO3-Gg3Cer, which were not found in SNG-II cells. The amounts of sulfoglycolipids in SNG-II-GST cells were 1.5 times higher than those of gangliosides, and the proportions of LacCer and GM3 in SNG-II-GST cells were greatly different from those in SNG-II cells. SNG-II and SNG-II GST cells exhibited poorly differentiated and well-differentiated phenotypes on histochemical examination of cancerous nodules in nude mice. However, by means of an oxygen electrode, SNG-II-GST cells were found to be more resistant to anticancer drugs than SNG-II cells.

CONCLUSION

Enhanced expression of sulfoglycolipids in poorly differentiated cells is a feasible means of selecting well-differentiated ones, and sulfoglycolipids are involved in the well-differentiated phenotype like those in the normal endometrium at the secretory phase.