UCLA UCLA Previously Published Works Title Genetic programs in human and mouse early embryos revealed by single-cell RNA sequencing. Permalink https://escholarship.org/uc/item/4n1561d1 Journal Nature, 500(7464) ISSN 0028-0836 Authors Xue, Zhigang Huang, Kevin Cai, Chaochao et al. Publication Date 2013-08-01 DOI 10.1038/nature12364 Peer reviewed eScholarship.org Powered by the California Digital Library University of California LETTER doi:10.1038/nature12364 Genetic programs in human and mouse early embryos revealed by single-cell RNA sequencing Zhigang Xue1*, Kevin Huang2*, Chaochao Cai2, Lingbo Cai3, Chun-yan Jiang3, Yun Feng1, Zhenshan Liu1, Qiao Zeng1, Liming Cheng1, Yi E. Sun1, Jia-yin Liu3, Steve Horvath2 & Guoping Fan2 Mammalian pre-implantation development is a complex process Intriguingly, cluster analyses showed that both pronuclear and involving dramatic changes in the transcriptional architecture1–4. zygote (1-cell stage) embryos clustered closely together but away from We report here a comprehensive analysis of transcriptome dynamics oocytes and cleavage embryos, indicating that the 1-cell stage exhibits a from oocyte to morula in both human and mouse embryos, using distinct transcriptome pattern. Comparisons between mature oocytes single-cell RNA sequencing. Based on single-nucleotide variants in and 1-cell embryos identified 149 differentially expressed genes (false human blastomere messenger RNAs and paternal-specific single- discovery rate (FDR) , 5%, .2-fold change), 79 and 70 of which were nucleotide polymorphisms, we identify novel stage-specific mono- up- and downregulated in 1-cell embryos, respectively (Fig. 1c). Inter- allelic expression patterns for a significant portion of polymorphic estingly, approximately half of the upregulated genes remain highly gene transcripts (25 to 53%). By weighted gene co-expression network expressed in 2- and 4-cell stages but are downregulated at the 8-cell analysis5,6, we find that each developmental stage can be delineated stage, whereas the other half is further upregulated at the 8-cell stage concisely by a small number of functional modules of co-expressed (Fig. 1d). By performing similar single-cell RNA-seq in mouse pre- genes. This result indicates a sequential order of transcriptional changes implantation embryos (Supplementary Table 1), we observed 520 trans- in pathways of cell cycle, gene regulation, translation and metabo- cripts that were upregulated in pronuclei compared to mature oocytes lism, acting in a step-wise fashion from cleavage to morula. Cross- (Supplementary Fig. 1), confirming that both human and mouse species species comparisons with mouse pre-implantation embryos reveal exhibit a conserved minor wave of ZGA before the major wave of ZGA that the majority of human stage-specific modules (7 out of 9) are (or EGA). These results indicated that our approach has overall greater notably preserved, but developmental specificity and timing differ abMorula between human and mouse. Furthermore, we identify conserved key 1 members (or hub genes) of the human and mouse networks. These 8-cell 1-cell genes represent novel candidates that are likely to be key in driving 0 mammalian pre-implantation development. Together, the results Zygote Pronucleus –1 Oocyte (3) provide a valuable resource to dissect gene regulatory mechanisms Pronucleus (3) Zygote PCA 2 Zygote (2) underlying progressive development of early mammalian embryos. Oocyte 2-cell (3) Mammalian pre-implantation development involves sequential decay –2 4-cell (4) 2-cell 8-cell (11) of maternally stored RNAs in parallel with massive induction of new 4-cell Morula (3) –3 transcripts from the embryonic genome in a process called zygotic (or 0.4 0.3 0.2 0.1 0 –2 –1 0 1 2 embryonic) genome activation (ZGA or EGA)7–9. However, previous Dissimilarity PCA 1 gene expression profiling of human pre-implantation has been limited 10–13 cd5 by blastomere sample size and quantitation platforms . Recent NS (14616) 14–17 3 advances in single-cell RNA sequencing (RNA-seq) technology ) Up (79) 10 4 Down (70) have provided the unprecedented opportunity to study gene regulation 2 1 in early human embryos under high resolution. We mapped approxi- 3 mately 700 million sequencing reads derived from 33 single cells of 0 multiple stages, ranging from mature oocytes to 8-cell blastomeres. 2 –1 To control the quality of single-cell RNA-seq from technical errors, we 1 –2 1-cell expression (log 1-cell expression focused on libraries (26 out of a total 33, or 79%) that share at least 80% –3 similarity with other libraries derived from identical pre-implantation 0 O P Z 2 4 8 M stages (Supplementary Table 1). In addition, we performed RNA-seq 12 34 5 Oocyte expression (log ) forthreesamplesofindividualmorula embryos. The typical number of 10 detectable genes (reads per kilobase per million (RPKM ) . 0.1) ranged Figure 1 | High-resolution single-cell transcriptome analysis of human pre- approximately from 8,500 to 12,000 genes in individual cells, demon- implantation embryos. a, Unsupervised hierarchical clustering. b, Principal strating that our technique has greater sensitivity and coverage com- component analysis of single blastomere expression patterns for seven stages of pared with previous microarray methods10–13. Unsupervised hierarchal oocytes and pre-implantation embryos. Sister cells from the same 8-cell embryo are highlighted together. The number of samples for each stage are indicated in clustering analysis and principal component analysis revealed that cells the PCA legend in parenthesis as well as in Supplementary Table 1. of different pre-implantation stages form distinct clusters (Fig. 1a, b). c, Scatterplot showing the number of activated (red) and reduced (blue) genes Furthermore, single-cell resolution revealed that blastomeres from the in 1-cell embryos (n 5 5) compared to oocytes (n 5 3). d, Heatmap showing same 8-cell embryo are more similar to each other than blastomeres relative expression patterns of 1-cell activated genes (n 5 79) across all from a separate 8-cell embryo (Fig. 1a, b). pre-implantation stages. NS, not significant. 1Translational Center for Stem Cell Research, Tongji Hospital, Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai 200065, China. 2Department of Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA. 3State Key Laboratory of Reproductive Medicine, Center of Clinical Reproductive Medicine, First Affiliated Hospital, Nanjing Medical University, Nanjing 210029, China. *These authors contributed equally to this work. 29 AUGUST 2013 | VOL 500 | NATURE | 593 ©2013 Macmillan Publishers Limited. All rights reserved RESEARCH LETTER quantitation for identifying gene expression changes between different Notably, the rs3829009 SNP in CDCA2 is a missense variant that stages of pre-implantation development. results in a benign Arg to Ser amino acid change23 (Fig. 2d). As RNA- Single-cell RNA-seq enabled base-resolution scrutiny without con- seq produces base-resolution information for codons, we further founding effects from cell population heterogeneity. In this unique examined the global prevalence of potentially deleterious transcript study, all embryos were derived from intra-cytoplasmic sperm injec- expression. Using multiple single-cells from the same 8-cell embryo, tion of different egg donors with the same sperm donor. Based on the we consistently identified 1,225 homozygous SNP variants, 3.5% of paternal genotype as assayed by exome sequencing of the sperm which are predicted as damaging non-synonymous variants (Sup- donor’s blood sample, we were able to follow the paternal genome in plementary Fig. 5). This result suggests that single-cell RNA-seq would embryos through single-nucleotide polymorphism (SNP) analysis18–20. be a powerful approach for genome-scale screening of potentially We identified paternally or maternally expressed genes either by infer- deleterious variants in embryos. ring phased paternal haplotype information21,22 or by leveraging sites Thus far the analyses focused on individual gene-transcript changes which are paternally homozygous in exome sequencing, but heterozyg- during each transitional stage, but did not reveal the crucial shift of ous in embryo transcripts (Fig. 2a and Supplementary Table 2). In total, gene networks in pre-implantation development. To understand the we determined the parent-of-origin expression for approximately co-expression relationships between genes at a systems level, we per- 850 to 1,400 gene transcripts (or 15–20% of all detected gene transcripts formed weighted gene co-expression network analysis (WGCNA)5,6. per stage). For further validation of allele-specific expression in early This unsupervised and unbiased analysis identified distinct co-expression embryos, we analysed the status of imprinting genes that exhibit known modules corresponding to clusters of correlated transcripts (Fig. 3a). parent-of-origin expression patterns (see Supplementary Text and Notably, 9 out of 25 co-expression modules showed stage-specific Supplementary Figs 2 and 3). Unexpectedly, we found that 53% of 8-cell expression values, that is, these modules are comprised of genes that embryo transcripts and 23% of morula transcripts exhibit monoallelic tend to be overexpressed in a single developmental stage (r . 0.7, maternal expression patterns (Fig. 2b), even though major EGA in P , 1023, Supplementary Fig. 6). human early embryos already occurred during the transition of 4- to