Establishment of fetal gonad/mesonephros coculture system using EGFP transgenic mice

In developing mouse embryos, the Sertoli cells, Leydig cells, and seminifer ous cords are differentiated in the XY gonads. The migration of mesonephric cells into the gonads is required during the developmental stage for semin iferous cord formation in the male gonads. In previous experiments, an orga n coculture system has been used to examine morphologically developing gona ds. However, by the process used in this system for fixing and staining the gonad/ mesonephros complexes for examination, the kinetics of cell migrati on and the character of migrating cells cannot be observed. In the present study, we established an improved organ coculture system, using transgenic mice ubiquitously expressing Enhanced Green Fluorescent; Protein (EGFP). In this system, time-dependent morphological changes in male-specific migrati on were observable in the gonad/mesonephros complex. The cell migration occ urred at around 20 hr of coculture and began to spread at 25 hr with increa ses in the number of migrating cells occurring at 45 hr of coculture. No de generative changes were detected at the end of coculture. Our results indic ate that the present coculture system is very useful for investigating the mechanism of cell migration, as well as the characteristics of the migratin g cells, in developing gonads. (C) 2000Wiley-Liss,Inc.