Expression of the endothelial lipase gene in murine embryos and reproductive organs

Endothelial lipase (EL) is a recently discovered member of the triglyceride-lipase family that is involved in plasma HDL metabolism. In this study, we investigated the putative role of EL in mouse reproduction by studying EL gene expression in mouse embryos and adult reproductive organs. PCR analysis revealed that EL mRNA is expressed in mouse embryos on embryonic day 8.5 (E8.5) to E11.5, but not later in development. In situ hybridization studies on E10.5 whole embryos and embryonic sections showed expression of EL mRNA in multiple tissues, although of varying intensity. High expression was found in the neuroepithelium of the brain and the neural tube, the mesenchymal cells between organs, the optic lens and cup, and the otocyst. In adult mice, EL mRNA expression was high in ovaries from pregnant mice but low in ovaries from nonpregnant mice. EL mRNA was also highly expressed in placenta and testes. In situ hybridization studies demonstrated intense EL mRNA staining of lutein cells in corpora lutei in ovaries, of spermatocytes in the late pachytene and diplotene stages in testes, and of principal cells in epididymis. These results suggest that EL, in addition to its effects on plasma lipoprotein metabolism, plays a role in murine reproduction.