Mitochondrial signals mediate paternal effects on offspring metabolism (small RNA-Seq)

Spermatozoa deliver a complex and environment sensitive pool of small non-coding RNAs (sncRNA) to the oocyte at fertilisation, which influences offspring development and adult phenotypic trajectories. Whether mature spermatozoa in the epididymis can directly sense the environment is still not fully understood. Here, we used two distinct paradigms of preconception acute High Fat Diet challenge to dissect epididymal vs spermatogenic contributions to the sperm sncRNA pool and offspring health. We show that epididymal spermatozoa, but not developing germ cells, are sensitive to the environment and identify mitochondrial tRNA fragments as sperm-born sensors. In human spermatozoa, we found mt-tsRNAs in linear association with BMI and showed that paternal overweight at conception is sufficient to double offspring obesity risk and compromise metabolic health. Using mouse genetics and metabolic phenotypic data, we show that alterations of mt-tsRNAs are downstream of mitochondrial dysfunction in mice. Most importantly, single embryo transcriptomics of genetically hybrid two-cell embryos demonstrated sperm-to-oocyte transfer of mt-tsRNAs at fertilisation and implied them in the control of early embryo metabolism. Our study supports the importance of paternal health at conception for offspring metabolism, propose mt-tsRNAs as sperm-born environmental effectors of paternal inheritance and demonstrate, for the first time in a physiological and unperturbed setting, father-to-offspring transfer of sperm mt-tsRNAs at fertilisation. Small rna have been studied from cauda spermatozoa and spermatids from mice exposed to HFD and LFD.精子在受精过程中会向卵母细胞递送一组结构复杂且对环境高度敏感的小型非编码RNA（small non-coding RNAs, sncRNA）库，该RNA库可调控子代发育及成年个体的表型轨迹。目前学界尚未完全明确附睾中的成熟精子是否能够直接感知外界环境变化。本研究采用两种截然不同的孕前急性高脂饮食（High Fat Diet, HFD）干预范式，以解析附睾精子与生精细胞分别对精子sncRNA库及子代健康的贡献。我们证实，附睾精子而非发育中的生殖细胞对环境敏感，并鉴定出线粒体tRNA片段（mitochondrial tRNA fragments, mt-tsRNAs）作为精子源性的环境感应分子。在人类精子样本中，我们发现mt-tsRNAs的水平与体质量指数（Body Mass Index, BMI）呈线性相关，同时证实受孕时父亲超重即可使子代肥胖风险翻倍，并损害子代代谢健康。借助小鼠遗传学实验与代谢表型数据分析，我们证明mt-tsRNAs的表达改变源于小鼠体内的线粒体功能障碍。最为关键的是，对遗传杂交的两细胞胚胎开展单胚胎转录组分析，证实了受精过程中精子向卵母细胞转移mt-tsRNAs，并提示其参与调控早期胚胎的代谢过程。本研究证实了受孕时父亲的健康状况对子代代谢具有重要意义，提出mt-tsRNAs可作为父系遗传的精子源性环境效应因子，并首次在生理状态且未受扰动的实验模型中，证实了受精过程中精子线粒体tRNA片段向子代的父系传递。已有研究针对暴露于高脂饮食（HFD）与低脂饮食（Low Fat Diet, LFD）的小鼠附睾尾部精子及精子细胞的小型RNA进行了相关分析。