Domingues Rafael R, Andrade Fabiana S, Paulo N Andrade Joao, Moghbeli Sadrollah M, Gomez-Leon Victor, Madureira Guilherme, Mello Marco R B, Kirkpatrick Brian W, Wiltbank Milo C
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, USA.
Endocrinology and Reproductive Physiology Program, University of Wisconsin-Madison, USA.
Reproduction. 2023 Jan 18;165(3):269-279. doi: 10.1530/REP-22-0232. Print 2023 Mar 1.
Follicle selection is a key event in monovular species. In this manuscript, we demonstrate the role of SMAD6 in promoting decreased granulosa cell proliferation and follicle growth rate in carriers vs noncarriers of the Trio allele and after vs before follicle deviation.
Cattle are generally considered a monovular species; however, recently, a bovine high fecundity allele, termed the Trio allele, was discovered. Carriers of Trio have an elevated ovulation rate (3-5), while half-sibling noncarriers are monovular. Carriers of the Trio allele have overexpression in granulosa cells of SMAD6, an inhibitor of oocyte-derived regulators of granulosa cell proliferation and differentiation. In experiment 1, follicle size was tracked for each follicle during a follicular wave. Follicle growth rate was greater before vs after follicle deviation in both carriers and noncarriers. Additionally, follicle growth rate was consistently less in carriers vs noncarriers. In experiment 2, we collected granulosa cells from follicles before and after deviation for evaluation of granulosa cell gene expression. Granulosa cell proliferation was less in carriers vs noncarriers and after vs before follicle deviation (decreased expression of cell cycle genes CCNB1 and CCNA2). The decreased granulosa cell proliferation in noncarriers after deviation was associated with increased SMAD6 expression. Similarly, in experiment 3, decreased expression of SMAD6 in granulosa cells of noncarriers cultured in vitro for 60 h was associated with increased expression of cell cycle genes. This suggests that SMAD6 may not just be inhibiting follicle growth rate in carriers of Trio but may also play a role in the decreased follicle growth after deviation in noncarriers. The hypotheses were supported that (1) follicle growth and granulosa cell proliferation decrease after deviation in both carriers and noncarriers and that (2) granulosa cell proliferation is reduced in carriers compared to noncarriers.
卵泡选择是单胎物种中的一个关键事件。在本论文中，我们证明了SMAD6在促进Trio等位基因携带者与非携带者以及卵泡偏离前后颗粒细胞增殖减少和卵泡生长速率降低方面的作用。
牛通常被认为是单胎物种；然而，最近发现了一种名为Trio等位基因的牛高繁殖力等位基因。Trio的携带者排卵率升高（3 - 5个），而半同胞非携带者是单胎的。Trio等位基因的携带者在颗粒细胞中过度表达SMAD6，SMAD6是卵母细胞衍生的颗粒细胞增殖和分化调节因子的抑制剂。在实验1中，在卵泡波期间跟踪每个卵泡的大小。在携带者和非携带者中，卵泡偏离前的卵泡生长速率均高于偏离后。此外，携带者的卵泡生长速率始终低于非携带者。在实验2中，我们收集了偏离前后卵泡的颗粒细胞，以评估颗粒细胞基因表达。携带者的颗粒细胞增殖低于非携带者，且卵泡偏离后低于偏离前（细胞周期基因CCNB1和CCNA2的表达降低）。非携带者偏离后颗粒细胞增殖减少与SMAD6表达增加有关。同样，在实验3中，体外培养60小时的非携带者颗粒细胞中SMAD6表达降低与细胞周期基因表达增加有关。这表明SMAD6可能不仅抑制Trio携带者的卵泡生长速率，还可能在非携带者偏离后卵泡生长减少中起作用。以下假设得到支持：（1）携带者和非携带者在卵泡偏离后卵泡生长和颗粒细胞增殖均减少；（2）与非携带者相比，携带者的颗粒细胞增殖减少。
