Haverfield Jenna, Dean Nicola L, Nöel Diana, Rémillard-Labrosse Gaudeline, Paradis Veronique, Kadoch Isaac-Jacques, FitzHarris Greg
Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), University of Montréal, 900 Rue St Denis, Montréal, Québec, Canada H2X 0A9.
Department of Obstetrics and Gynaecology, University of Montréal, Montréal, Québec, Canada H3T 1J4.
Hum Reprod. 2017 Jun 1;32(6):1293-1303. doi: 10.1093/humrep/dex083.
What are the chromosome segregation errors in human oocyte meiosis-I that may underlie oocyte aneuploidy?
Multiple modes of chromosome segregation error were observed, including tri-directional anaphases, which we attribute to loss of bipolar spindle structure at anaphase-I.
Oocyte aneuploidy is common and associated with infertility, but mechanistic information on the chromosome segregation errors underlying these defects is scarce. Lagging chromosomes were recently reported as a possible mechanism by which segregation errors occur.
STUDY DESIGN, SIZE, DURATION: Long-term confocal imaging of chromosome dynamics in 50 human oocytes collected between January 2015 and May 2016.
PARTICIPANTS/MATERIALS, SETTING, METHODS: Germinal vesicle (GV) stage oocytes were collected from women undergoing intracytoplasmic sperm injection cycles and also CD1 mice. Oocytes were microinjected with complementary RNAs to label chromosomes, and in a subset of oocytes, the meiotic spindle. Oocytes were imaged live through meiosis-I using confocal microscopy. 3D image reconstruction was used to classify chromosome segregation phenotypes at anaphase-I. Segregation phenotypes were related to spindle dynamics and cell cycle timings.
Most (87%) mouse oocytes segregated chromosomes with no obvious defects. We found that 20% of human oocytes segregated chromosomes bi-directionally with no lagging chromosomes. The rest were categorised as bi-directional anaphase with lagging chromosomes (20%), bi-directional anaphase with chromatin mass separation (34%) or tri-directional anaphase (26%). Segregation errors correlated with chromosome misalignment prior to anaphase. Spindles were tripolar when tri-directional anaphases occurred. Anaphase phenotypes did not correlate with meiosis-I duration (P = 0.73).
Not applicable.
LIMITATIONS, REASONS FOR CAUTION: Oocytes were recovered at GV stage after gonadotrophin-stimulation, and the usual oocyte quality caveats apply. Whilst the possibility that imaging may affect oocyte physiology cannot be formally excluded, detailed controls and justifications are presented.
This is one of the first reports of live imaging of chromosome dynamics in human oocytes, introducing tri-directional anaphases as a novel potential mechanism for oocyte aneuploidy.
STUDY FUNDING/COMPETING INTEREST(S): This study was funded by grants from Fondation Jean-Louis Lévesque (Canada), CIHR (MOP142334) and CFI (32711) to GF. JH is supported by Postdoctoral Fellowships from The Lalor Foundation and CIHR (146703). The authors have no conflict of interest.
人类卵母细胞减数分裂I中可能导致卵母细胞非整倍性的染色体分离错误有哪些？
观察到多种染色体分离错误模式，包括三向后期，我们将其归因于减数分裂I后期双极纺锤体结构的丧失。
卵母细胞非整倍性很常见且与不孕有关，但关于这些缺陷背后染色体分离错误的机制信息很少。最近有报道称滞后染色体是发生分离错误的一种可能机制。
研究设计、规模、持续时间：对2015年1月至2016年5月收集的50个人类卵母细胞中的染色体动态进行长期共聚焦成像。
参与者/材料、设置、方法：从接受胞浆内单精子注射周期的女性以及CD1小鼠中收集生发泡（GV）期卵母细胞。用互补RNA对卵母细胞进行显微注射以标记染色体，在一部分卵母细胞中还标记减数分裂纺锤体。使用共聚焦显微镜对卵母细胞进行减数分裂I全过程实时成像。采用三维图像重建对减数分裂I后期的染色体分离表型进行分类。分离表型与纺锤体动态和细胞周期时间相关。
大多数（87%）小鼠卵母细胞染色体分离无明显缺陷。我们发现20%的人类卵母细胞以双向方式分离染色体且无滞后染色体。其余的被分类为有滞后染色体的双向后期（20%）、有染色质团分离的双向后期（34%）或三向后期（26%）。分离错误与后期前染色体排列错误相关。出现三向后期时纺锤体为三极。后期表型与减数分裂I持续时间无关（P = 0.73）。
不适用。
局限性、谨慎理由：卵母细胞是在促性腺激素刺激后的GV期回收的，适用通常的卵母细胞质量注意事项。虽然不能正式排除成像可能影响卵母细胞生理学的可能性，但已给出详细的对照和理由。
这是关于人类卵母细胞染色体动态实时成像的首批报告之一，引入三向后期作为卵母细胞非整倍性的一种新的潜在机制。
研究资金/竞争利益：本研究由让 - 路易·勒维克基金会（加拿大）、加拿大卫生研究院（MOP1 | 42334）和加拿大创新基金会（32711）授予GF的资助。JH得到了拉勒基金会和加拿大卫生研究院（146703）的博士后奖学金支持。作者没有利益冲突。
