Denomme Michelle M, White Carlee R, Gillio-Meina Carolina, Macdonald William A, Deroo Bonnie J, Kidder Gerald M, Mann Mellissa R W
Children's Health Research Institute, London, ON, Canada.
Front Genet. 2012 Jul 11;3:129. doi: 10.3389/fgene.2012.00129. eCollection 2012.
Growth and maturation of healthy oocytes within follicles requires bidirectional signaling and intercellular gap junctional communication. Aberrant endocrine signaling and loss of gap junctional communication between the oocyte and granulosa cells leads to compromised folliculogenesis, oocyte maturation, and oocyte competency, consequently impairing fertility. Given that oocyte-specific DNA methylation establishment at imprinted genes occurs during this growth phase, we determined whether compromised endocrine signaling and gap junctional communication would disrupt de novo methylation acquisition using ERβ and connexin37 genetic models. To compare mutant oocytes to control oocytes, DNA methylation acquisition was first examined in individual, 20-80 μm control oocytes at three imprinted genes, Snrpn, Peg3, and Peg1. We observed that each gene has its own size-dependent acquisition kinetics, similar to previous studies. To determine whether compromised endocrine signaling and gap junctional communication disrupted de novo methylation acquisition,individual oocytes from Esr2- and Gja4-deficient mice were also assessed for DNA methylation establishment. We observed no aberrant or delayed acquisition of DNA methylation at Snrpn, Peg3, or Peg1 in oocytes from Esr2-deficient females, and no perturbation in Snrpn or Peg3de novo methylation in oocytes from Gja4-null females. However, Gja4 deficiency resulted in a loss or delay in methylation acquisition at Peg1. One explanation for this difference between the three loci analyzed is the late establishment of DNA methylation at the Peg1 gene. These results indicate that compromised fertility though impaired intercellular communication can lead to imprinting acquisition errors. Further studies are required to determine the effects of subfertility/infertility originating from impaired signaling and intercellular communication during oogenesis on imprint maintenance during preimplantation development.
卵泡内健康卵母细胞的生长和成熟需要双向信号传导和细胞间缝隙连接通讯。卵母细胞与颗粒细胞之间异常的内分泌信号传导以及缝隙连接通讯的丧失会导致卵泡发生、卵母细胞成熟和卵母细胞能力受损，从而损害生育能力。鉴于在这个生长阶段会发生印记基因上卵母细胞特异性DNA甲基化的建立，我们使用雌激素受体β（ERβ）和连接蛋白37（connexin37）基因模型来确定受损的内分泌信号传导和缝隙连接通讯是否会破坏从头甲基化的获得。为了将突变卵母细胞与对照卵母细胞进行比较，首先在单个20 - 80μm的对照卵母细胞中检测了三个印记基因Snrpn、Peg3和Peg1的DNA甲基化获得情况。我们观察到每个基因都有其自身大小依赖性的获得动力学，这与先前的研究相似。为了确定受损的内分泌信号传导和缝隙连接通讯是否会破坏从头甲基化的获得，我们还评估了Esr2和Gja4缺陷小鼠的单个卵母细胞的DNA甲基化建立情况。我们观察到，Esr2缺陷雌性小鼠的卵母细胞在Snrpn、Peg3或Peg1处没有异常或延迟的DNA甲基化获得，Gja4基因敲除雌性小鼠的卵母细胞在Snrpn或Peg3的从头甲基化方面也没有受到干扰。然而，Gja4缺陷导致Peg1处甲基化获得的缺失或延迟。分析的三个基因座之间这种差异的一种解释是Peg1基因的DNA甲基化建立较晚。这些结果表明，尽管细胞间通讯受损导致生育能力受损，但这可能会导致印记获得错误。需要进一步研究来确定卵子发生过程中信号传导和细胞间通讯受损引起的亚生育力/不育对植入前发育期间印记维持的影响。
