Single-cell sequencing of primate preimplantation embryos reveals chromosome elimination via cellular fragmentation and blastomere exclusion
Single-cell sequencing of primate preimplantation embryos reveals chromosome elimination via cellular fragmentation and blastomere exclusion
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DOI：
10.1101/gr.239830.118
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发表时间：
2019-03-01
期刊：
影响因子：
7
通讯作者：
Chavez, Shawn L.
中科院分区：
文献类型：
--
作者：
Daughtry, Brittany L.;Rosenkrantz, Jimi L.;Chavez, Shawn L.
在减数分裂和/或有丝分裂期间出现的非整倍性是早期胚胎损失的主要原因。我们先前表明，人类植入前胚胎在经历细胞碎片化时将错误分离的染色体封装到微核中，并且碎片可以包含染色体物质，但这种DNA的来源未知。在这里，我们利用非人灵长类动物模型和单细胞DNA测序（scDNA-seq）来检查471个个体样本的染色体内容，这些样本包括来自大量（N = 50）拆解的恒河猴卵裂期胚胎的254个卵裂球、42个极体和175个细胞片段。我们的分析表明，非整倍体和微核率是保守的人类和猕猴之间，和片段封装整个和/或部分染色体从卵裂球丢失。单细胞/片段基因分型表明，这些含染色体的细胞片段（CCF）可以是母系或父系衍生的，并显示双链DNA断裂。DNA断裂进一步表明，相互亚染色体损失/获得之间的卵裂球和大的节段性错误，主要是在染色体的末端检测。通过将延时成像与scDNA-seq相结合，我们确定了受精卵或两细胞阶段的多极分裂与CCF相关，并产生了具有单亲或双亲起源的染色体正常和异常卵裂球的随机混合物。尽管在卵裂阶段经常发生染色体错误分离，但我们表明，显示出广泛DNA损伤的CCF和非分裂非整倍体胚泡被阻止掺入囊胚。这些发现表明，胚胎通过包裹到微核中，通过细胞碎片消除染色体错误，并对高度非整倍体卵裂球进行选择，以克服植入前发育过程中的染色体不稳定性。
Aneuploidy that arises during meiosis and/or mitosis is a major contributor to early embryo loss. We previously showed that human preimplantation embryos encapsulate missegregated chromosomes into micronuclei while undergoing cellular fragmentation and that fragments can contain chromosomal material, but the source of this DNA was unknown. Here, we leveraged the use of a nonhuman primate model and single-cell DNA-sequencing (scDNA-seq) to examine the chromosomal content of 471 individual samples comprising 254 blastomeres, 42 polar bodies, and 175 cellular fragments from a large number (N = 50) of disassembled rhesus cleavage-stage embryos. Our analysis revealed that the aneuploidy and micronucleation frequency is conserved between humans and macaques, and that fragments encapsulate whole and/or partial chromosomes lost from blastomeres. Single-cell/fragment genotyping showed that these chromosome-containing cellular fragments (CCFs) can be maternally or paternally derived and display double-stranded DNA breaks. DNA breakage was further indicated by reciprocal subchromosomal losses/gains between blastomeres and large segmental errors primarily detected at the terminal ends of chromosomes. By combining time-lapse imaging with scDNA-seq, we determined that multipolar divisions at the zygote or two-cell stage were associated with CCFs and generated a random mixture of chromosomally normal and abnormal blastomeres with uniparental or biparental origins. Despite frequent chromosome missegregation at the cleavage-stage, we show that CCFs and nondividing aneuploid blastomeres showing extensive DNA damage are prevented from incorporation into blastocysts. These findings suggest that embryos respond to chromosomal errors by encapsulation into micronuclei, elimination via cellular fragmentation, and selection against highly aneuploid blastomeres to overcome chromosome instability during preimplantation development.