Cited by 515Single-cell and spatial transcriptomicsGenomics and Phylogenetic StudiesGene expression and cancer classification

The DOI matches its Crossref record; 25 of the 25 references it cites were found in a registry or an index; 4 of the 5 sources its claims cite were checked for support.

Souporcell: robust clustering of single-cell RNA-seq data by genotype without reference genotypes

Open access

Abstract

Methods to deconvolve single-cell RNA-sequencing (scRNA-seq) data are necessary for samples containing a mixture of genotypes, whether they are natural or experimentally combined. Multiplexing across donors is a popular experimental design that can avoid batch effects, reduce costs and improve doublet detection. By using variants detected in scRNA-seq reads, it is possible to assign cells to their donor of origin and identify cross-genotype doublets that may have highly similar transcriptional profiles, precluding detection by transcriptional profile. More subtle cross-genotype variant contamination can be used to estimate the amount of ambient RNA. Ambient RNA is caused by cell lysis before droplet partitioning and is an important confounder of scRNA-seq analysis. Here we develop souporcell, a method to cluster cells using the genetic variants detected within the scRNA-seq reads. We show that it achieves high accuracy on genotype clustering, doublet detection and ambient RNA estimation, as demonstrated across a range of challenging scenarios.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

souporcell clusters single-cell RNA-seq cells by genotype without reference genotypes, using variants detected directly in the reads. It jointly calls genotype clusters, cross-genotype doublets, and ambient RNA, and the paper reports that it outperforms demuxlet, vireo, and scSplit across synthetic, maternal/fetal, and *Plasmodium falciparum* benchmarks.

Key findings

  • On a synthetic mixture of five human iPSC lines, souporcell assigned 6612/6622 singletons and 415/451 doublets correctly; four singletons were falsely labeled as doublets, 35 doublets were misidentified as singletons, and one doublet and four singletons were unassigned.
  • For doublet detection on a synthetic mixture with 6% doublets and 10% ambient RNA, ROC AUC was 0.98 for souporcell and 0.91 for vireo; demuxlet’s posterior doublet probability was reported as poorly calibrated, with nearly 40% false positive doublets at its default threshold.
  • Cell assignment versus demuxlet on three experimental iPSC mixture replicates gave Adjusted Rand Index 1.0 for souporcell and vireo and an average of 0.97 for scSplit.
  • Across ambient RNA from 2.5%–50%, souporcell and vireo retained high accuracy, with souporcell more robust at calling doublets in high-ambient-RNA cases; all tools performed well down to a minority cluster of 1.2% (50 cells), but only souporcell and vireo correctly identified all minority sample singletons down to 0.6% of all cells.
  • In maternal/fetal samples, souporcell clusters agreed with demuxlet and segregated with expected cell types, while vireo and scSplit had major discordances; in *P. falciparum* datasets, souporcell had superior ARI across the board, with vireo performing poorly on one dataset (ARI versus demuxlet 0.24).

Methods

  • Reads are remapped with minimap2 rather than using STAR-aligned BAMs directly, putative SNPs are called with freebayes, and per-cell allele counts are obtained with vartrix.
  • Clustering uses a sparse mixture model fit by a deterministic annealing variant of expectation maximization, with cluster centers represented as alternate allele fractions; doublets are detected with a beta-binomial model, and genotype plus ambient RNA are co-inferred in STAN by maximum likelihood/gradient descent.
  • Validation used five HipSci human iPSC lines sequenced individually and in mixtures with 10x Chromium, synthetic mixtures with simulated doublets and ambient RNA, maternal/fetal samples from Vento et al., and three *P. falciparum* datasets containing six genetically distinct strains with 1893–2608 cells and median UMIs of ~1000.

Limitations

  • The paper states that limitations include low signal-to-noise due to decreased UMI per cell and high numbers of donors causing increased local maxima.
  • The text also makes evident that genotype accuracy from scRNA-seq is significantly lower than from whole-genome sequencing because most variants have very low coverage per cluster.
  • The paper notes that no good generative models were available for batch effects, allele-specific expression, ambient RNA, and doublets in scRNA-seq, so realistic benchmarking required experimentally generated mixtures rather than fully in silico data.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41592-020-0820-1

Cites

25 of 25 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

20 Own result · 14 Own interpretation · 7 No basis given · 2 Supported · 2 Partly supported · 1 No full text of the sources · accuracy not yet measured

Show all 22 claims

  • It may state two separate claims as one. 21
  • Probably not a substantial claim. 3
24 of 24
  • The authors state this as an assumption.

    Allele counts for locus i of each cluster j are drawn from a binomial distribution with an alternative allele fraction of (1-ρ)fij+ρ*ai, where fij is 0, 0.5, or 1 (with a haploid mode limited to 0 and 1), ρ is the amount of ambient RNA, and ai is the average allele fraction in the experiment.

    “we assume that the allele counts for locus i of each cluster j are drawn from a binomial distribution with an alternative allele fraction of (1-ρ)fij+ρ*ai, where fij is 0, 0.5, or 1 (with a haploid mode limited to 0 and 1), ρ is a parameter representing the amount of ambient RNA and ai is the average allele fraction in the experiment.”
  • The paper relies on this without support.

    There are no good generative models available for batch effects, allele-specific expression, ambient RNA, and doublets in scRNAseq that can be used to generate in silico data for testing methods that cluster by genotype.

    “Currently, there are no good generative models available for batch effects, allele-specific expression, ambient RNA, and doublets in scRNAseq that can be used to generate in silico data for testing methods that cluster by genotype.”
  • The paper relies on this without support.

    Malaria infections often contain parasites from multiple different genetic backgrounds, and it is not possible to separate the strains prior to sequencing.

    “Malaria infections often contain parasites from multiple different genetic backgrounds, and it is not possible to separate the strains prior to sequencing.”
  • The paper relies on this without support.

    The decidua is primarily composed of maternal cells with some invading fetal trophoblasts, while the placenta is largely composed of cells of fetal origin with the exception of maternal macrophages.

    “The decidua is primarily composed of maternal cells with some invading fetal trophoblasts, while the placenta is largely composed of cells of fetal origin with the exception of maternal macrophages.”
  • The paper relies on this without support.

    In scRNAseq data most variants have very low coverage per cluster compared to what would be generated from WGS data, so genotype accuracy is significantly lower than one would attain with genome sequencing.

    “In scRNAseq data most variants have very low coverage per cluster compared to what would be generated from WGS data, thus the genotype accuracy is significantly lower than one would attain with genome sequencing.”
  • The authors state this as an assumption.

    The majority of barcodes contain a single cell.

    “It is important for some assumptions in this model that the majority of barcodes contain a single cell.”
  • The authors state this as an assumption.

    Only biallelic variants are considered.

    “We will assume only biallelic variants.”
  • The authors state this as an assumption.

    Ploidy is limited to 1 or 2.

    “We assume ploidy is limited to 1 or 2.”
  • The authors state this as an assumption.

    Each cluster is independent and each locus is independent.

    “We treat each cluster as independent and each locus as independent, before marginalizing across the possible genotypes.”
  • The authors state this as an assumption.

    The observed allele fractions are drawn from a binomial distribution with a probability skewed away from p = g/P by the level of ambient RNA ρ.

    “The observed allele fractions are assumed to have been drawn from a binomial distribution with a probability that was skewed away from p = g/P by the level of ambient RNA ρ.”
  • The authors state this as an assumption.

    Allele counts of each cell at each locus are drawn from a beta-binomial distribution from either a single cluster or a pair of clusters.

    “We treat the allele counts of each cell at each locus as random variables drawn from a beta-binomial distribution from either a single cluster or a pair of clusters.”
  • The authors state this as an assumption.

    The expected allele fractions of a doublet coming from cluster i and cluster j is the average of the allele fractions of the two clusters.

    “The expected allele fractions of a doublet coming from cluster i, and cluster j is the average of the allele fractions of the two clusters.”
  • The authors state this as an assumption.

    The beta-binomial is used to model uncertainty in the binomial parameter p.

    “The beta-binomial is used to model our uncertainty in the binomial parameter p.”
  • The authors state this as an assumption.

    Each locus in each cluster comes from one of three genotypes for diploid (0/0, 0/1, 1/1) and two genotypes for haploid (0, 1).

    “The model treats each locus in each cluster as coming from one of three genotypes for diploid (0/0, 0/1, 1/1, here denoted by g = 0, 1, or 2) and two genotypes from haploid (0, 1).”
14 of 14

Claims other papers make about this one

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Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

2 of 2

Citations

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Metadata

Authors
Heaton, H., Talman, A. M., Knights, A., Imaz, M., Gaffney, D. J., Durbin, R., Hemberg, M., & Lawniczak, M. K. N.
Affiliations
  • Wellcome Sanger Institute (GB)
  • Centre National de la Recherche Scientifique (FR)
  • University of Cambridge (GB)
Corresponding author
  • Heaton, Haynes
  • Hemberg, Martin
  • Lawniczak, Mara K. N.
Venue
Nature Methods
Published
2020-05-04
Volume
17
Issue
6
Pages
615-620
ISSN
  • 1548-7091 (ISSN-L)
  • 1548-7105
OpenAlex
W3023290106
Cited by
506
References
25
Citations by year
2026: 95 · 2025: 88 · 2024: 126 · 2023: 77 · 2022: 69 · 2021: 38 · 2020: 11
FWCI
13.53
Type
journal article
Language
en
Open access
Locations
  • Nature Methods (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion)
  • HAL (Le Centre pour la Communication Scientifique Directe) (submittedVersion)
  • Apollo (University of Cambridge) (submittedVersion)
  • Apollo
Funders
  • Wellcome Trust (206194/Z/17/Z)
  • British Heart Foundation (RG/13/13/30194; RG/18/13/33946)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Single-cell and spatial transcriptomics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Gene expression and cancer classification
Keywords
single-cell RNA sequencing, genotype clustering, cell lysis, batch effects
MeSH terms
RNA-Seq, Algorithms, Base Sequence, Cell Line, Genotype, Humans, RNA, Sensitivity and Specificity, Software, Cluster Analysis, Polymorphism, Single Nucleotide, Single-Cell Analysis

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