Transcription profiling by high throughput sequencing of oocytes from four inbred mouse strains (129/Sv, C57Bl/6J, C3H/HeN, and DBA/2J)

Current understanding of oocyte quality and developmental potential maintains that stochastic or epigenetic processes modulate the action of determinants that are laid in the oocyte during oogenesis. These determinants are considered to be rather conserved across mice, leading different strains of mice to be used interchangeably. We challenged this assumption and studied the relationship between oocyte composition and developmental quality in four inbred strains of mice, namely 129Sv, C57Bl/6, C3H/HeN and DBA/2J. These oocytes showed large variability developmental competence and embryo quality irrespective of the developmental stimulus (fertilization, somatic cell nuclear transfer, parthenogenesis). To unravel the molecular basis of the observed phenotypes we applied state-of-the-art proteomics (SILAC LC-MS/MS) combined with transcriptomics (RNA deep sequencing). We quantified 1839 proteins and 20413 transcripts simultaneously in oocytes of all four strains. The proteome and the transcriptome had little correlation with each other, highlighting the importance of proteomic quantifications in embryology. We found that proteins that were most variably expressed between oocytes from different strains mainly relate to oocyte biology, ribosome and RNA biogenesis as well as embryo differentiation and chromatin remodelling. Thus, different strains of mice should not be used interchangeably in biology when tackling questions about oogenesis and early development.当前学界对于卵母细胞（oocyte）质量与发育潜能的认知认为，随机过程或表观遗传过程会调控卵发生（oogenesis）阶段沉积于卵母细胞内的决定因子的功能。这类决定因子在小鼠中被认为具有高度保守性，因此不同小鼠品系常被互换使用。本研究对这一假设提出质疑，针对四种小鼠近交品系——129Sv、C57Bl/6、C3H/HeN与DBA/2J，探究了卵母细胞组成与发育质量之间的关联。无论采用何种发育刺激手段（受精、体细胞核移植、孤雌生殖），这些卵母细胞均表现出显著的发育能力与胚胎质量差异。为阐明观测到的表型背后的分子机制，本研究采用前沿蛋白质组学（SILAC LC-MS/MS）结合转录组学（RNA deep sequencing）技术，同时对四种小鼠品系的卵母细胞中的1839种蛋白质与20413条转录本进行了定量分析。结果显示，蛋白质组与转录组之间相关性极低，这凸显了蛋白质组定量分析在胚胎学研究中的重要性。研究发现，不同品系卵母细胞间表达差异最显著的蛋白质主要与卵母细胞生物学、核糖体与RNA生物发生、胚胎分化及染色质重塑相关。因此，在探究卵发生与早期发育相关生物学问题时，不应互换使用不同小鼠品系。