Developmental Contribution of Wnt-signal-responsive Cells to Mouse Reproductive Tract Formation.

In mammals, the müllerian duct (MD) is an embryonic tubular structure that gives rise to the female reproductive tract (FRT). The MD originates from the coelomic epithelium (CoE) and takes on a rostral to caudal shape to establish the primary structure of the FRT under the regulation of morphogenetic signals. During these developmental processes, the MD and its derivatives require proper regulation of the Wnt-signaling-pathway. Here, to investigate the developmental contribution of FRT primordia under the influence of the Wnt-signaling, genetic lineage tracing was carried out using TopCreER/Rosa-LacZ mice to follow the fate of Wnt-signal-responsive cells during reproductive tract formation. TopCreER-marked-LacZ+ cells, arising from the Wnt-signal-responsive progenitors in CoE, give rise to spatially restricted MD and the uterine luminal epithelium. Similarly, the progeny from LacZ+ mesenchymal cells surrounding the MD contribute to both the uterine smooth muscle and stroma. Furthermore, in males, the Wnt-signal-responsive MD mesenchyme develops into the epididymis. These results show, for the first time, evidence of the sequential involvement of reproductive tract progenitors under the influence of Wnt-signal throughout the developmental term. This study provides a precise outline for assessing the lineage relation between the reproductive tract and the cell fate of its primordia in a temporally regulated manner.