The molecule events expression of TGF-β/Smad signaling pathway in morphological and structural developmental characteristics of gonads in goose embryos

China is the largest producer and consumer of geese with significant social and economic value in agriculture. The Jilin White Goose, known for its excellent egg-laying and reproductive characteristics, is a prominent breeding breed in the northeast of China widely used for cross-breeding.Gonad development is a complex process, which will differentiate into testes or ovaries, thus affecting sex determination. Since the level of gonadal development in geese of different sexes is also related to their productivity, the study of gonadal function in geese is of great theoretical and practical importance. In this study, we used the embryonic gonads of Jilin white geese as the research object to reveal the morphologic and histologic developmental characteristics and process of the gonads of goose embryos from the 9th day to the 28th day and to investigate the mechanisms regulating the differentiation of the gonads. The results of ALP-PAS staining by histomorphological observations showed that the primordial germ cells in the female gonads were fully differentiated at embryonic day 19 (E19) and in the male gonads at embryonic day 18 (E18).Previous studies indicate that the TGF-β /Smad signaling pathway is crucial for sex differentiation and gamete formation in animals. In our study, we quantitatively analyzed key genes and proteins in this pathway within goose embryos. We found that TGF-βRI/II receptors and Smad2/3 are involved in gonadal development early in differentiation. Smad2 protein levels peaked at E18 in male gonads and E19 in female gonads, while Smad3 peaked at E10 for both. It has been suggested that there is a novel interaction between TGF-β and Wnt/β-catenin signaling pathway. In this study, the expression of LEF1, a protein downstream of the Wnt/β-catenin signaling pathway, peaked at E19 in the female gonads and at E18 in the male gonads, and the protein expression level of β-catenin was significantly increased in the female gonads at E19 and E28 and peaked at E28 in the male gonads. β-catenin expression levels were significantly higher in the male gonads than in the other periods and reached a minimum at E28. We injected the TMAO drug, which activates the TGF-β /Smad pathway, into goose embryos using the embryo injection technique to study how it affects gene and protein expression in this signaling pathway. We found that in female gonads, the levels of Smad2/3 proteins were lower than in the control group at E18, but higher than the control group at E19. In male gonads, the results for Smad3 proteins matched those of the females, while the results for Smad2 proteins were the opposite. This shows that TMAO activation of the TGF-β /Smad signaling pathway may impact gonadal development in goose embryos. In conclusion, this study suggest that the TGF-β /Smad and Wnt signaling pathways may enhance gonadal tissue development in goose embryos. The study identified key time points in gonadogenesis, providing a new theoretical basis for further research on the molecular mechanisms of gonadal development.