Temporal and spatial localization patterns of Gata4 during porcine gonadogenesis

The zinc ringer transcription factor Gata4, is associated with gonadal deve lopment in many species. The present study characterizes temporal and spati al localization of Gata4 throughout gonadogenesis in porcine embryos. Immun ohistochemical studies illustrated that Gata4 protein is present in the coe lomic epithelium prior to histological differentiation of the nascent bipot ential gonad, marking the future site of both XX and XY porcine gonads. Man y somatic cells of both XX and XY bipotential gonads continue to retain Gat a4 immunoreactivity throughout sexual differentiation and subsequent gonada l development. Testicular cords were evident by 26 days postcoitum. Gata4 w as present in Sertoli cells, identified by virtue of coexpression with Mull erian inhibiting substance and also interstitial cells including Leydig cel ls throughout fetal and postnatal life. Many somatic cells of the different iating ovary including follicular cells also contained Gata4 protein throug hout fetal and postnatal life. Gata4 was not present in germ cells, endothe lial cells, or other undifferentiated mesenchymal cells of both XX and XY g onads. A population of Gata4-positive cells in the dorsal mesentery was con tinuous with the coelomic epithelium of the gonad. This localization patter n led to the hypothesis that a subpopulation of somatic cells in the dorsal mesentery moves toward the gonad. An in vitro cell migration assay demonst rated that Gata4-positive cells preferentially migrate toward explanted gon adal tissue, and morphological features of the developing gonad supported t his hypothesis. This study illustrates that Gata4 is a very early marker fo r gonad formation, highlights species differences in temporal and spatial l ocalization patterns, and suggests a potential role for Gata4 in the develo pment of both XX and XY porcine gonads. Further, we suggest that mesenchyma l cells of the dorsal mesentery may provide a source of somatic cells that migrate and incorporate into the gonad and contribute to various somatic ce ll lineages. Overall, the spatial and temporal localization patterns of Gat a4 during porcine gonadogenesis implies a much earlier and wider role for G ata4 than previously reported in other species.