Objective  Expression of bone morphogenetic proteins (BMPs) gene in chicken embryos at different developmental stages was studied for further investigation on the functions of the gene.

  Method  One hundred fertilized AA broiler eggs were used for the study. Six eggs were randomly selected each time on the 1^st, 2^nd, 3^rd, 4^th, 5^th, 6^th, 9^th, 12^th, 15^th, and 18^th day (designated as E1 to E18) after hatching. Whole embryos from the eggs of E1 to E6 and the brain, heart, and liver tissues as well as the leg muscles from the embryos of E12 to E18 were collected to determine the expressions of BMP2, BMP4 and BMP7 in the samples by qPCR.

  Result  The BMP2 expressions of E1–E6 increased at first and then decreased. Those of E4, E5, and E6 significantly higher than that of E1 (P＜0.05). BMP2 in the brain of E12 was significantly higher than that of E1 (P＜0.05), but that of E18 became significantly lower than that of E1 (P＜0.01). For E9, the expression of BMP2 in the heart was significantly higher than that for E1 at P＜0.05 and for the leg muscles at P＜0.01. In the later stages of embryonic development, such as E15 and E18, the expressions in the heart and liver were significantly or extremely significantly lower than those of E1 at P＜0.05 or P＜0.01. The expression of BMP4 of E1–E6 also increased initially and followed by a decline. Compared to E1, E3–E6 in embryo and E9 in brain, heart, liver and leg showed significantly higher on BMP4 expressions at P＜0.05 or at P＜0.01. BMP7 of E4 expressed significantly higher than E1 at P＜0.01, and of E5 and E6 at P＜0.05, but lower of E2 or E3 with a statistic significance at P＜0.01 on E2. From E4 through E18, the BMP7 expressions in the embryo and brain declined gradually, and that in the brain reached a significant level at P＜0.01 on E18. In the heart, the lowest expression was observed on E12 (P＜0.01), and in the liver on E12 and E15 (P＜0.01).

  Conclusion  As hatching progressed, the expressions of BMP2, BMP4 and BMP7 in the embryo firstly increased then decreased to arrive at a peak on E4, while BMP2 in the heart, liver and leg decreased on E9, E12, E15 and E18. It indicated that the BMP genes played a crucial role in the early stages of organ formation in fertilized chicken eggs. The effect diminished gradually as the embryonic development came close to completion.