Cloning of Smad 1, Smad5 and Smad8 from the Chicken Ovary and Characterization of Their Expression during Chicken Ovarian Development

Abstract

We have previously demonstrated that the oocyte-secreted bone morphogenetic protein 15 (BMP15) and its cognate receptors are abundantly expressed in the ovaries from both sexual immature and mature chickens, strongly suggesting that it plays an important role in controlling ovarian development. To test this hypothesis, in the present study, we have further examined the expression of the downstream signaling molecules (Smad1, Smad5 and Smad8) responsible for BMP15 signaling in the chicken ovary. We first cloned the full-length cDNAs encoding Smad1, Smad5 and Smad8 from the chicken ovary. The cloned Smad1 (465 a. a. ), Smad5 (465 a. a. ) and Smad8 (476 a. a. ) share high homologies with their mammalian counterparts (Smad1: ~96%, Smad5: ~95%, Smad8: ~80%). Using semi-quantitative RT-PCR, we demonstrated that Smad1, Smad5 and Smad8 were expressed not only in all of the developing follicles from adult chickens, but also in the developing ovaries of all stages examined (3-week, 6-week, 10-week, 13-week and 16-week). Moreover, the expression of Smad1, Smad5 and Smad8 could also be detected in the cultured ovarian granulosa cells from F4+5 and F1 follicles, suggesting that the ovarian granulosa cell is one of the action sites of oocyte-derived BMP15. Taken together, the co-expression of BMP15, BMP15 receptor and its downstream signaling molecules (Smad1, 5 and Smad8) in the chicken ovary provides convincing evidence that BMP15 is actively involved in controlling ovarian development in chicken.