Epithelial-to-mesenchymal transition–based morphogenesis of dorsal mesentery and gonad

•Progenitors of the dorsal mesentery and gonad arise from ventro-medial lateral plate mesoderm (LPM).•Ventromedial LPM repetitively undergoes epithelial to mesenchymal transitioning (EMT) during embryogenesis.•Transition of BMP4 expression medio-lateral axis to dorso-medial axis plays key roles in the gonad and mesentery formation.•Sonic hedgehog, secreted from endoderm, maintains BMP4 expression to establish dorso-ventral patterning in medial LPM.•Ovarian surface epithelium, a progeny of coelomic epithelium, causes EMT in a strictly regulated manner. Dorsal mesentery and gonad (ovary and testis) are formed in distinct regions of the body and have different characteristics. Recent studies using chicken embryos showed that progenitors of these two organs are derived from the coelomic lining region, a ventral part of the medial lateral plate mesoderm (M-LPM). Furthermore, both types of progenitors develop in a similar manner, concomitant with morphological changes termed the epithelial-to-mesenchymal transition (EMT). EMT processes in both dorsal mesentery and gonad formation are regulated by BMP signaling. Interestingly, EMT-based morphogenetic events occur repetitively at M-LPM specification before dorsal mesenteric and gonadal formation, at ovary formation later in embryogenesis, and even during adult ovary repair. We review recent findings related to EMT-based morphogenesis and the governing molecular mechanisms, mainly in early dorsal mesenteric and gonadal formation, as well as in their anlages and derivatives.