# Multiplexed single-cell RNA-seq through transient barcoding for simultaneous expression profiling of varied drug perturbations – Science Advances

0
4

## INTRODUCTION

In contrast to standard bulk measurements, single-cell RNA sequencing (scRNA-seq) permits evaluation of the transcriptomes of particular person cells (1–Three), and this has make clear the variations in cell populations, resembling tumor heterogeneity. Platforms resembling Drop-Seq (four), inDrop (5), and 10X Genomics Chromium (6) present high-throughput single-cell info over hundreds of cells. Whereas the variety of cells in a position to be profiled has elevated and per-cell value has dropped, challenges in scRNA-seq nonetheless embrace excessive pattern preparation value, ambiguous identification of true single cells, and sample-dependent batch results (7), limiting the widespread adoption and scope of scRNA-seq. For experiments requiring the evaluation of a number of single-cell samples (i.e., quite a few samples of varied situations or samples from many sufferers), a separate scRNA-seq run should be carried out for every pattern. With out the usage of multiplexing, performing scRNA-seq for a number of samples is labor intensive and is proscribed by the excessive pattern preparation value slightly than the per-cell value in sequencing. Subsequently, the demand for multiplexing samples in scRNA-seq is constantly growing, requiring strategies through which samples are pooled and subjected to a single scRNA-seq run.

To take care of the challenges said above, a way has lately been developed for multiplexing samples from numerous sufferers by their endogenous genetic barcodes (Eight). On this strategy, single-nucleotide polymorphisms in every affected person function a pattern barcode for figuring out the pattern identification of every cell, enabling a number of samples to be pooled and sequenced concurrently. Whereas this strategy can partially take care of multiplexing issues, relevant samples are restricted to those who are genetically distinct. Nonetheless, multiplexing between samples genetically similar however in numerous situations stays a problem, necessitating a common strategy for barcoding and multiplexing samples whatever the pattern identities.

Throughout drug discovery, gene expression profiling may be utilized to annotate the perform of small molecules (9) and to elucidate the mechanisms underlying a organic pathway (10, 11). Whereas systematic approaches to profile gene expression for numerous small molecules utilizing microarray expertise have been carried out (12, 13), they’re restricted to bulk measurements. To seize numerous responses of extremely heterogeneous samples resembling tumor cells, single-cell gene expression profiling is indispensable, though present applied sciences will not be appropriate for a number of screening. We envisioned that improvement of multiplexed scRNA-seq can present simultaneous expression profiling of varied drug perturbations in a really environment friendly method.

Right here, we designed a multiplexed scRNA-seq methodology that concerned transient transfection of brief barcoding oligos (SBOs) to label samples from numerous experimental situations. We demonstrated that this methodology counting on easy transfection can be utilized for simultaneous single-cell transcriptome profiling for a number of medicine.

## RESULTS

### Design for transient barcoding methodology

SBO, a single-stranded oligodeoxynucleotides, consists of a pattern barcode and a poly-A sequence (fig. S1A). Transient transfection of SBO permits a pattern to be labeled with a novel barcode. The barcoded samples of varied situations are pooled and concurrently processed for scRNA-seq (Fig. 1A). The poly-A sequence within the SBOs ensures that the mRNAs and SBOs are captured and reverse-transcribed collectively through the scRNA-seq course of (fig. S1B). Computational evaluation of digital depend matrices of SBOs permits us to demultiplex and decide pattern origins. This common barcoding methodology, based mostly on easy transfection, enabled pattern multiplexing, recognized multiplets and negatives, and diminished the preparation value per pattern.

Fig. 1 Scheme and validation of transient barcoding methodology.

(A) Scheme of multiplexed scRNA-seq by transient barcoding methodology utilizing SBOs. (1) Samples with numerous situations are ready. (2) Every pattern is transfected with SBO containing a novel pattern barcode. (Three) Barcoded cells are pooled collectively and processed for scRNA-seq (e.g., Drop-Seq). (four) Cells are lysed inside droplets, and the launched mRNAs and SBOs are captured, reverse-transcribed, and sequenced. (5) Cells are demultiplexed and assigned to their origins and processed for additional evaluation. (B) Heatmap of normalized SBO counts for 6-plex human/mouse species-mixing experiment. Rows symbolize cells, and columns symbolize SBOs. Cells are assessed whether or not they’re constructive for a specific SBO based mostly on the SBO depend matrix (see Supplies and Strategies). Cells have been labeled as singlets (constructive for a novel SBO), multiplets (constructive for a couple of SBO), or negatives (not constructive for any SBO) and ordered by their classifications. (C) Scatter plot exhibiting uncooked counts between two SBOs. SBOs 1 and 6 have been used to barcode totally different samples (Human 1, Mouse 2) (left). SBOs Three and four have been used to barcode the identical pattern (Human Three) (proper). (D) Species-mixing plot of samples related to SBOs 1 and 5. Cells have been labeled in response to their SBO classifications. Black dots point out Human 1 pattern barcoded with SBO 1, pink dots point out Mouse 1 pattern barcoded with SBO 5, and grey dots point out doublets which might be constructive for each SBOs. (E) Distribution of RNA transcript counts in cells between singlets (inexperienced), multiplets (blue), and negatives (pink). Negatives, which suggest beads uncovered to ambient RNA, had the bottom variety of transcripts. Multiplets had barely extra transcripts than singlets, indicating extra RNA content material inside a droplet.

### Validation of potential and accuracy for transient barcoding methodology

To display our methodology’s potential and accuracy of multiplexing samples, we carried out a 6-plex human/mouse species-mixing experiment. Two samples every of HEK293T and NIH3T3 cells carried a single distinctive SBO, and one pattern of every cell line carried a mixture of the 2 SBOs (fig. S1C). We pooled all of the samples collectively in equal proportions and carried out a single run of Drop-Seq. Cells have been intentionally overloaded throughout Drop-Seq to extend the possibility of multiplets. We obtained 2759 cell barcodes, through which no less than 500 transcripts have been detected, and the cells have been efficiently assigned to their pattern origins. Multiplets and detrimental cells have been detected on the premise of the SBO depend matrix (see Supplies and Strategies). Cells that have been labeled as singlets virtually completely specific their pattern barcodes, whereas multiplets and negatives specific a number of or no pattern barcode, respectively (Fig. 1B). Scatter plots of SBO counts that originated from two totally different samples confirmed an unique relationship, whereas SBO counts from the identical pattern confirmed a powerful correlation of their expressions (Fig. 1C and fig. S2A). Species classification utilizing SBOs was in step with the transcriptome-based species-mixing plot outcomes (Fig. 1D and fig. S2, B and C). We additionally noticed a transparent distinction within the distribution of RNA transcripts between singlets, multiplets, and negatives as anticipated, indicating the unambiguous detection of multiplets and negatives (Fig. 1E). These outcomes urged that our methodology enabled pattern multiplexing in single-cell experiments with excessive accuracy and specificity, and elimination of multiplets and negatives. We additionally verified that the SBO barcoding strategy could possibly be utilized to mannequin heterogeneous samples with out cell kind–particular bias (fig. S3, A to E). Our knowledge additionally display that transient transfection didn’t have an effect on the gene expression profiles (fig. S3, F and G).

### Time-resolved expression profiles in drug perturbations

We envisioned that our methodology could possibly be used when eager about screening a number of gene expression profiles in single cells subjected to drug perturbations. We carried out a 5-plex time-course scRNA-seq within the Okay562 cell line, which is derived from persistent myeloid leukemia and expresses the Bcr-Abl fusion gene (14). Making use of our multiplexing technique, we investigated the single-cell transcriptional response of Okay562 cells to imatinib, a BCR–ABL–focusing on drug (15), over remedy time (see Supplies and Strategies). In contrast to standard scRNA-seq, by regressing out technical batch results, multiplexed scRNA-seq utilized right here allows the detection of refined transcriptional modifications within the built-in evaluation of a number of samples, facilitating extra exact evaluation. Following the drug therapies, samples have been pooled, sequenced, and demultiplexed. After eradicating doublets and negatives, single cells have been subjected to downstream evaluation.

Pseudotime evaluation of single cells in multiplexed samples collected from 5 time factors confirmed a branched gene expression trajectory and a sequential development in trajectory over drug remedy time (Fig. 2A). The branched trajectory confirmed that two transition states existed because of imatinib remedy. Samples exhibited asynchronous patterns in pseudotime, though the common elevated with drug remedy time (Fig. 2B). We famous that even within the zero-time pattern, cells have been extremely heterogeneous by way of pseudotime. As well as, we noticed an accumulation on the higher transition state because the drug remedy time elevated. Differential expression evaluation over pseudotime recognized a number of gene cohorts that change through the transition (Fig. 2, C and D). Notably, the expression ranges of erythroid-related genes resembling HBZ and ALAS2 had elevated over pseudotime (Fig. 2C). This was in step with earlier research which have proven elevated expression of HBZ in imatinib-treated cells (16, 17). Differentially expressed genes (DEGs) between the 2 transition states have been additionally recognized, and totally different expression patterns between them have been noticed (Fig. 2E).

Fig. 2 Pseudotime evaluation in 5-plex time-course experiment.

(A) Monocle pseudotime trajectory of Okay562 cells handled with imatinib at totally different time factors. Cells are labeled by pseudotime (prime) and drug remedy time (backside). The Zero-, 6-, 12-, 24-, and 48-hour samples encompass 133, 109, 79, 49, 58, 52, and 90 cells, respectively. (B) Boxplot exhibiting the distribution of pseudotime inside every pattern. (C) Distinguished gene expression alterations in 5-plex time-course experiments of imatinib remedy. Observe that the cells are labeled by drug remedy time and will not be synchronously distributed over pseudotime. (D) Expression heatmap exhibiting 50 genes with the bottom q values. (E) Expression heatmap exhibiting DEGs between two transition states with q < 1 ×10−four. Prebranch refers back to the cells earlier than department 1, Cell destiny 1 refers back to the cells of higher transition state, and Cell destiny 2 refers back to the cells within the decrease transition state.

### Simultaneous expression profiling of Okay562 subjected to varied drug perturbations

Subsequent, we assessed whether or not our strategy could possibly be used for simultaneous single-cell transcriptome profiling for a number of medicine in Okay562 cells. We chosen 45 medicine, of which most have been kinase inhibitors, together with a number of BCR-ABL–focusing on medicine. Three dimethyl sulfoxide (DMSO) samples have been used as controls (desk S1). A 48-plex single-cell experiment was carried out by barcoding and pooling all samples after drug therapies. A complete of 3091 cells have been obtained and demultiplexed after eliminating multiplets and negatives. The averaged expression profiles of every drug have been visualized as a heatmap (Fig. 3A). Every drug exhibited its personal expression sample of responsive genes. Unsupervised hierarchical clustering of the averaged expression knowledge for every drug revealed that the response-inducing medicine clustered collectively by their protein targets, whereas medicine that induced no response confirmed related expression patterns with DMSO controls, indicating our methodology’s potential to establish drug targets by expression profiles (Fig. 3A and fig. S4). As well as, we may consider cell toxicity by analyzing the cell counts of every drug. Medication that focused BCR-ABL or ABL confirmed the strongest response and toxicity, and medicines that focused MAPK kinase (MEK) or mammalian goal of rapamycin (mTOR) confirmed comparatively delicate response. Differential expression evaluation based mostly on the single-cell gene expression knowledge recognized DEGs for every drug (Fig. 3B and fig. S5). We word that extremely expressed erythroid-related genes resembling HBZ, HBA, and HBG have been up-regulated, and genes resembling DDX21, NCL, ENO1, and NPM1 have been down-regulated within the pattern handled with imatinib (Fig. 3B). Related DEGs have been recognized for different medicine focusing on BCR-ABL. Medication resembling vinorelbine and neratinib confirmed distinctive gene expression signatures and DEGs. We subsequent grouped the medicine by their protein targets and carried out differential expression evaluation. The evaluation confirmed totally different relationships between DEGs of every protein goal (Fig. 3C). As well as, comparative evaluation between mTOR inhibitors and BCR-ABL inhibitors revealed that ribosomal protein-coding genes together with RPL4, RPS2, and RPS3 and regulatory genes resembling MYC and GSTP1 are up-regulated within the mTOR inhibitor group (Fig. 3D).

Fig. Three Gene expression evaluation in 48-plex drug remedy experiments.

(A) Hierarchical clustered heatmap of averaged gene expression profiles for 48-plex drug remedy experiments in Okay562 cells. Every column represents averaged knowledge in a drug, and every row represents a gene. DEGs have been used on this heatmap. The dimensions bar of relative expression is on the appropriate aspect. The flexibility of the medicine to inhibit kinase proteins is proven as binary colours (darkish grey indicating constructive) on the prime. The bar plot on the prime reveals the cell depend for every. (B) Volcano plot displaying DEGs of imatinib mesylate in contrast with DMSO controls. Genes which have a P worth smaller than Zero.05 and an absolute worth of log (fold change) bigger than Zero.25 are thought of vital. Up-regulated genes are coloured in inexperienced, down-regulated genes are coloured in pink, and insignificant genes are coloured in grey. Ten genes with the bottom P worth are labeled. (C) Venn diagram exhibiting the connection between DEGs of three drug teams. Fourteen medicine are labeled into three teams in response to their protein targets (see Fig. 2C, prime), and differential expression evaluation is carried out by evaluating every group with DMSO controls. Relations of each positively (left) and negatively (proper) regulated genes in every group are proven. (D) Plot exhibiting a correlation between fold modifications of expression in cells handled with mTOR inhibitors and BCR-ABL inhibitors in contrast with DMSO controls.

To comprehensively analyze the drug screening knowledge at a single-cell decision, we carried out unsupervised clustering evaluation on all of the single-cell datasets. We noticed six clusters (Fig. 4A), which weren’t clearly separated probably as a result of a extremely advanced transcriptional area. Nonetheless, for every drug, the relative abundance of cells assigned to every cluster was numerous (Fig. 4B and fig. S6). Many of the cells affected by BCR-ABL and MEK inhibitors have been concentrated in cluster four, whereas cells affected by mTOR inhibitors have been primarily concentrated in cluster Three. Particularly, a lot of the cells in cluster 5 belong to the neratinib-treated pattern. A number of markers related to every cluster have been verified by differential expression evaluation (Fig. four, C and D). Evaluation of cell cycle states revealed no affiliation between cell cycle states and particular clusters (Fig. 4A). The fraction of extremely proliferative state (G2 part) was decreased in samples handled with BCR-ABL–focusing on medicine probably as a result of drug-induced cell cycle arrest (Fig. 4B) (18).

Fig. four Single-cell evaluation in 48-plex drug remedy experiments.

(A) The t-distributed stochastic neighbor embedding (t-SNE) plot of single cells within the 48-plex Okay562 samples. Plot reveals six clusters (prime), and extra t-SNE plot is labeled by cell cycle states (backside). (B) Bar plots for 48-plex drug remedy experiments in Okay562 cells. The flexibility of the medicine to inhibit kinase proteins is proven as binary colours on the prime (from Fig. 3A). The bar plot within the center represents a relative fraction of cells in every t-SNE cluster [shown in (A)], and the underside bar plot shows fractions of cell cycle states for each pattern. Medication are sorted by hierarchical clustering. (C) Expression heatmap exhibiting the markers of the clusters. The numbers on the backside symbolize cluster numbers. (D) Scaled expression of consultant genes throughout the t-SNE plot. Depth of the purple shade determines expression ranges, with increased depth correlating with increased gene expression.

To validate the common applicability of our strategies, we carried out a 48-plex drug screening experiment on the A375 cell line [BRAF V600E positive (19)] with an similar drug set. Much like Okay562 cells, response-inducing medicine have been clustered collectively in a target-specific method in A375 cells (fig. S7). Our outcomes confirmed that multiplexed scRNA-seq could possibly be used to display single-cell transcriptional responses to medicine in a high-throughput method and drug targets could possibly be estimated by their transcriptional patterns.

## DISCUSSION

We’ve got developed a novel methodology for multiplexing samples in scRNA-seq, through which samples have been transiently transfected via SBOs containing their very own barcodes, pooled, and concurrently sequenced. This methodology presents a number of benefits over at the moment out there scRNA-seq. Our barcoding strategy has a number of benefits by way of time and price in comparison with operating a number of particular person scRNA-seq experiments. Apart from the next-generation sequencing (NGS) value, we consider that value constraints happen within the scRNA-seq procedures and NGS preparation steps for every pattern. For every pattern, the price of one Drop-Seq run and the corresponding NGS preparation course of is roughly $160. As compared, our SBO transfection methodology prices roughly$5 (e.g., oligos, transfection reagents, and SBO NGS preparation prices) for every further pattern. If a number of scRNA-seqs are individually processed, then every further pattern may devour a further value greater than 30 instances the barcoding strategy of scRNA-seq with a number of samples. This value saving in library preparation turns into substantial as the scale of samples will increase. As well as, “batch impact” is without doubt one of the main challenges in scRNA-seq (7). These technical noises may be important and obscure true indicators in built-in evaluation for a number of samples from totally different preparations. By pooling and operating all samples collectively, batch results may be considerably diminished, enabling extra exact evaluation between single-cell samples.

We demonstrated that our methodology may additionally remove multiplets and negatives based mostly on SBO depend matrix, enabling filtering of true single cells. Figuring out expression profiles of true single cells improves knowledge high quality and is advantageous for downstream single-cell evaluation. As well as, the flexibility to remove multiplets and negatives has potential to extend throughput of scRNA-seq through the use of a excessive focus of cells as an enter and filtering single cells subjected to downstream evaluation. Throughput of scRNA-seq may be elevated past the experimental restrict by the multiplexed RNA-seq.

Not too long ago, a way for multiplexing samples utilizing genetically pure barcodes has been developed (Eight). Genetically numerous samples are required in multiplexing by the demuxlet algorithm. Our methodology presents a number of benefits over the earlier printed strategies for scRNA-seq (fig. S8). Notably, our methodology is able to multiplexing samples genetically similar however in several experimental situations, whereas the strategy utilizing the demuxlet algorithm is just not able to doing. Extra lately, a way for pattern multiplexing utilizing an antibody tagging has been reported (20). Nevertheless, the strategy requires costly reagents and floor markers, limiting the variety of samples that may be virtually utilized.

Our methodology introduced right here may be very easy and readily relevant to particular person laboratories due to the simply accessible reagents and easy experimental course of. As well as, as a result of our methodology relies on liposomal transfection, it has a possible to be utilized to nucleus samples. As well as, through the use of totally different combos of SBOs, our methodology presents a excessive capability for multiplexing. We count on that our multiplexing technique will broadly contribute to the adoption of scRNA-seq.

## MATERIALS AND METHODS

### Cell traces and cell tradition

All cell traces have been obtained from the Korean Cell Line Financial institution (KCLB) and maintained at 37°C with 5% CO2. The human embryonic kidney HEK293T, the mouse embryo fibroblast NIH3T3, and the human malignant melanoma A375 cell traces have been cultured in Dulbecco’s modified Eagle’s medium (DMEM; Gibco, USA) supplemented with 10% fetal bovine serum (FBS; Gibco, USA) and 1% penicillin-streptomycin (Thermo Fisher Scientific, USA). The human persistent myelogenous leukemia Okay562 cell line and the human colorectal adenocarcinoma SW480 cell line have been cultured in RPMI 1640 (Gibco, USA) supplemented with 10% FBS and 1% penicillin-streptomycin.

### Barcode design and transfection

The SBO accommodates a novel Eight–base pair (bp) pattern barcode, an amplification deal with, and a poly-A tail. 5′-TCCAAGGTACAGACCTCTGACGNNNNNNNN(A)30-Three′ is the complete SBO sequence. “TCCAAGGTACAGACCTATATCTGACG” is the amplification deal with sequence, “NNNNNNNN” is the pattern barcode sequence, and (A)30 is the poly-A tail sequence. All SBOs have been ready by IDT (Built-in DNA Applied sciences, USA) with none modifications. 4 hours earlier than Drop-Seq, SBO (28 pmol/ml) was transfected per properly utilizing Lipofectamine 3000 (Life Applied sciences, USA) in response to the producer’s protocol.

### Drop-Seq: NGS preparation of mRNA and SBOs

For every experiment, samples of varied situations have been pooled collectively. The pooled cells have been handed via a 40-μm filter and diluted at a remaining mixed focus of 100 to 400 cells/μl in response to Drop-Seq protocol directions (four). Droplets have been generated and processed as beforehand described. Droplets have been collected, and the recovered beads have been processed for fast reverse transcription, adopted by exonuclease I remedy. The ensuing complementary DNA (cDNA) was divided into acceptable variety of tubes, amplified utilizing the KAPA HiFi HotStart PCR Equipment (Kapa Biosystems Inc., Switzerland). cDNA amplification was carried out in 50 μl of polymerase chain response (PCR), which included four μl of 10 μM SMART PCR primer, 25 μl of KAPA HiFi DNA polymerase, and as much as 21 μl of nuclease-free water. Then, PCR was carried out utilizing the next protocol: Three min at 95°C; 4 cycles of 20 s at 98°C, 45 s at 65°C, Three min at 72°C; 9 cycles of 20 s at 98°C, 20 s at 67°C, Three min s at 72°C; 5 min at 72°C. The PCR merchandise have been purified twice utilizing Zero.6× AMPure (Beckman Coulter, USA) beads in response to the producer’s directions. To acquire reverse-transcribed SBOs which might be a lot shorter than cDNA, the primary supernatant from AMPure purification step was additional purified including 1.four× do-it-yourself AMPure beads [using Sera-Mag SpeedBeads (Thermo Scientific, USA), hereafter Serapure beads (21)]. The cDNA merchandise have been fragmented and additional amplified utilizing the Nextera XT DNA Library Preparation Equipment (Illumina, USA).

The SBO library preparation was carried out utilizing a two-step PCR protocol. One nanogram of the SBO cDNA product was loaded into 20 μl of the primary adaptor PCR, which included 1 μl of 10 μM ahead and reverse primers, 10 μl of KAPA HiFi DNA polymerase, and as much as Eight μl of nuclease-free water. PCR was carried out utilizing the next protocol: Three min at 95°C; eight cycles of 20 s at 95°C, 20 s at 64°C, 20 s at 72°C; 5 min at 72°C utilizing the next primers: SMART+AC; P7-SBO hybrid. After 1.Eight× Serapure bead purification, Eight μl of the primary PCR product was loaded into 20 μl of the second index PCR, which included 1 μl of 10 μM ahead and reverse primers, and 10 μl of KAPA HiFi DNA polymerase. PCR was carried out utilizing the next protocol: Three min at 95°C; six cycles of 20 s at 95°C, 20 s at 60°C, 20 s at 72°C; 5 min at 72°C utilizing the next primers: New-P5-SMART PCR hybrid; Nextera index oligo. The second PCR product was purified utilizing 1.2× Serapure beads. All primers have been ready by IDT. Sequencing was carried out on an Illumina NextSeq 500 system utilizing a NextSeq 500/550 Excessive Output v2 package (75 cycles) (Illumina, USA). The sequences of primers have been offered in desk S1. The sequencing depth and variety of cells of every experiment are offered in fig. S9.

### 6-Plex human/mouse species-mixing experiment

HEK293T and NIH3T3 cells have been ready 1 day earlier than Drop-Seq and plated on six-well plates (Techno Plastic Merchandise, Switzerland) at roughly 70% confluency. Transfection of SBO (28 pmol/ml) was carried out four hours earlier than Drop-Seq, as described above. All cell samples have been trypsinized utilizing trypsin-EDTA (Zero.25%) and phenol pink (Gibco, USA), pooled collectively, and washed 4 instances with phosphate-buffered saline (PBS; Gibco, USA). The cells have been then resuspended in Zero.01% bovine serum albumin (BSA) + PBS, handed via a 40-μm filter, counted utilizing the LUNA Automated Cell Counter (Logos Biosystems, Korea), and diluted at a remaining mixed focus of 400 cells/μl. The diluted pattern library was run as soon as in Drop-Seq, and pattern preparation and sequencing have been carried out as above. From one Drop-Seq run, about 77,000 beads have been obtained and divided into 24 PCRs for cDNA amplification. Pattern preparation was accomplished utilizing two reactions of the Nextera XT DNA Library Preparation Equipment (Illumina, USA).

### SBO transfection effectivity and its impact on blended cultures

To imitate heterogeneous samples, cell traces with totally different transfection efficiencies have been blended after which SBOs have been transfected into the blended cell line cultures to look at the transfection effectivity and impact on the gene expression profile. HEK293T, NIH3T3, A375, and SW480 cell traces have been cultured in DMEM supplemented with 10% FBS and 1% penicillin-streptomycin. All cell traces have been ready 1 day earlier than SBO transfection and plated into six-well plates at roughly 70% confluency with the identical variety of cells for every cell line. All subsequent steps have been the identical as described above within the 6-plex human/mouse species-mixing experiment. After the Drop-Seq run, the pooled beads have been divided into 24 PCRs for cDNA amplification. Pattern preparation was accomplished utilizing three reactions of the Nextera XT DNA Library Preparation Equipment.

We carried out the identical experiment to look at the impact of SBO transfection on the gene expression profile of Okay562 cells on the bulk stage. These cells have been cultured in six-well plates at roughly 30% confluency. After four hours of SBO transfection, whole RNA of management and transfected Okay562 cells was extracted utilizing an RNA extraction package (RNeasy Mini Equipment, Qiagen, USA). Whole RNA (2 μg) of management and transfected Okay562 cells was used for cDNA synthesis. Then, pattern preparation was accomplished utilizing the Nextera XT DNA Library Preparation Equipment.

### 5-Plex time-course experiment of drug remedy

Okay562 cells have been plated on six-well plates at roughly 30% confluency. Imatinib (1 μM) was handled to Okay562 for 5 time factors (Zero, 6, 12, 24, and 48 hours after remedy). Transfection of SBO (28 pmol/ml) was carried out four hours earlier than Drop-Seq, as described above, and the cells of every situation have been pooled, washed 4 instances with PBS, and resuspended with Zero.01% BSA + PBS. After filtering and counting, the pooled cells have been diluted at a remaining mixed focus of 100 cells/μl. The diluted pattern library was run as soon as in Drop-Seq. Pattern preparation and sequencing have been carried out as above. From one Drop-Seq run, the pooled beads have been divided into 24 PCRs for cDNA amplification. Pattern preparation was accomplished utilizing two reactions of the Nextera XT DNA Library Preparation Equipment.

### 48-Plex drug screening experiment in Okay562 cells

Okay562 cells have been plated on 24-well plates at roughly 30% confluency and handled with 1 μM of every drug. After 44 hours, transfection of SBO (28 pmol/ml) was carried out. 4 hours after the transfection, the cell samples from every drug remedy have been pooled. The diluted pattern library was run thrice in Drop-Seq. All subsequent steps have been the identical as described above within the 5-plex time-course experiment. After three Drop-Seq runs, the pooled beads have been divided into 48 PCRs for cDNA amplification. Pattern preparation was accomplished utilizing three reactions of the Nextera XT DNA Library Preparation Equipment.

### 48-Plex drug screening experiment in A375 cells

A375 cells have been ready 1 day earlier than drug screening and plated on 24-well plates at roughly 30% confluency. All subsequent steps have been the identical as described above within the 48-plex drug remedy experiment. After three Drop-Seq runs, the pooled beads have been divided into 48 PCRs for cDNA amplification. Pattern preparation was accomplished utilizing three reactions of the Nextera XT DNA Library Preparation Equipment.

### Single-cell transcriptome knowledge processing

For every NextSeq sequencing run, uncooked sequencing knowledge have been transformed to FASTQ recordsdata utilizing bcl2fastq2 software program (Illumina). Every sequencing pattern was demultiplexed utilizing Nextera N7xx indices. Tagging, trimming, alignment, and including annotation tags have been carried out in response to the usual Drop-Seq pipeline (http://mccarrolllab.org/dropseq/). Briefly, reads have been first tagged in response to the 12-bp cell barcode sequence and the Eight-bp distinctive molecular identifier (UMI) in “learn 1.” Then, reads in “learn 2” have been aligned with the hg19 or hg19-mm10 concatenated reference relying on the experiments and collapsed onto 12-bp cell barcodes that corresponded to particular person beads. A Hamming distance of 1 was used to break down UMI inside every transcript. Digital expression matrix was obtained by collapsing filtered and mapped reads for every gene by UMI sequence inside every cell barcode.

### Pattern barcode (SBOs) processing

FASTQ recordsdata of SBOs have been generated as described above. Uncooked sequencing reads have been trimmed to take away PCR handles. Cell barcodes and UMIs have been extracted from learn 1, and pattern barcodes have been extracted from learn 2. Reads have been assigned to Eight-mer of pattern barcode reference (desk S1) with a single-base error tolerance (Hamming distance = 1), and cell barcodes × pattern barcodes depend matrix (hereinafter known as SBO matrix) was generated with consideration to UMI de-duplication. All of the processes have been made by our do-it-yourself python scripts.

### Merging pattern barcode and transcriptome knowledge

Independently obtained cell barcodes from the 2 matrices (SBO matrix and transcriptome matrix) have been in contrast and merged on the premise of the cell barcodes from the transcriptome matrix. When merging, a Hamming distance of 1 was allowed. Final, the columns of the SBO and the transcriptome matrix consisted of the identical cell barcodes.

### Demultiplexing and classification of samples utilizing SBO matrix

SBO matrix was normalized utilizing a modified model of centered log ratio (CLR) transformation (22)xi’=ln(xi+1)−1D∑j=1Dln(xi+1)xi′ denotes the normalized depend for a selected SBO in cell i, xi denotes the uncooked depend, and D is the entire cell quantity. In CLR transformation, the uncooked counts of SBO are divided by the geometric imply of particular person SBO throughout cells and are log-transformed. We added the uncooked counts of SBO to 1 to keep away from infinite values. We hypothesized that we are able to discriminate constructive indicators from detrimental (background) indicators by becoming the distribution of detrimental indicators of every SBO and thresholding the normalized counts to a selected worth of every SBO. Following the normalization, for every SBO, we excluded the cells with the very best expression of the SBO amongst all SBOs. We fitted a detrimental binomial distribution to the remaining cells to acquire a distribution of detrimental indicators. Subsequent, we calculated a quantile with Zero.99 likelihood to get the brink worth of every SBO. Cells which have increased SBO counts than the brink worth have been thought of as positives for that SBO. Cells have been demultiplexed and labeled into singlets, multiplets, and negatives based mostly on the above outcomes.

### 6-Plex human-mouse species-mixing experiment evaluation

Transcriptome and SBO knowledge processing have been carried out as described above. We obtained 2759 of cell barcodes after filtering out cells with lower than 500 transcripts. After the SBO matrix normalization and classification, we labeled singlets as constructive for one in every of SBOs, multiplets as constructive for a couple of SBO, and negatives as constructive for none of SBOs. For species-mixing plots in Fig. 1D and fig. S4, solely singlets and doublets of the 2 specified SBOs have been used.

### Pseudotime evaluation

For pseudotime evaluation of 5-plex time-course experiment, we utilized the R package deal “Monocle 2” (23). After eradicating multiplets and negatives, samples have been demultiplexed, quality-controlled, and analyzed. A single-cell trajectory was constructed by Discriminative Dimensionality Discount with Bushes (DDRTree) (24) algorithm utilizing genes differentially expressed at totally different time factors. Cells have been ordered throughout the trajectory by setting the state containing Zero-hour pattern as a time zero, and pseudotime was calculated. To establish DEGs over pseudotime, a probability ratio take a look at within the detrimental binomial mannequin was carried out and genes with a q worth lower than Zero.01 have been chosen as DEGs. When drawing the heatmap, genes have been clustered by their pseudotime expression patterns. Differential expression evaluation between two transition states in department 1 was carried out utilizing BEAM perform in Monocle package deal.

### 48-Plex drug screening knowledge evaluation

Following the alignment of sequencing reads, downstream evaluation of the 48-plex drug screening experiment was carried out utilizing the R package deal “Seurat” (25). After demultiplexing and eradicating multiplets and negatives, cells have been quality-controlled on the premise of the mitochondrial reads fraction, variety of UMI, and variety of genes. We recognized 3091 cells through which no less than 500 transcripts and 300 genes have been detected. RNA expression matrix was log-normalized and processed for the additional evaluation. To cluster the one cells, we ran principal elements evaluation (PCA) utilizing the expression matrix of variable genes after which carried out t-distributed stochastic neighbor embedding (t-SNE) utilizing the primary six PCA elements. We recognized six clusters utilizing FindClusters perform in Seurat with decision = Zero.6. We assigned cell cycle part scores utilizing cell cycle markers (26) and labeled every cell to G2-M, S, or G1 part. To attract a hierarchical clustered heatmap, we first recognized DEGs for every drug with adjusted P < Zero.05 by Wilcoxon rank-sum take a look at and obtained 469 responsive genes by merging the DEGs altogether. Expression ranges of every drug for the responsive genes have been normalized, averaged, and scaled and have been used for drawing the heatmap. To assemble the dendrogram on the heatmap, hierarchical clustering was carried out on the premise of correlations among the many expression ranges throughout medicine. Normalized and scaled gene expression knowledge have been used within the heatmap. To establish DEGs in Fig. 2D and fig. S7, we carried out probability ratio take a look at between single cells in every drug and single cells in DMSO controls. To investigate samples by their protein targets, 14 medicine have been labeled into three teams (BCR-ABL inhibitors, MEK inhibitors, and mTOR inhibitors). Differential expression evaluation between cells in every group and cells in DMSO controls was carried out as described above. The evaluation of drug screening experiment of A375 was carried out in the identical method as Okay562.

Acknowledgments: We thank W. Namkung (Division of Pharmacy, Yonsei College) for contributing the kinase inhibitor library (catalog no. L1200, Selleck Chemical substances). Funding: This work was supported by the next sources: (i) the Mid-career Researcher Program (NRF-2018R1A2A1A05079172) via the Nationwide Analysis Basis of Korea (NRF), funded by the Ministry of Science, ICT and Future Planning; (ii) the Bio & Medical Expertise Improvement Program of the Nationwide Analysis Basis (NRF) funded by the Korean authorities (MSIT; NRF-2016M3A9B6948494); (iii) the Bio & Medical Expertise Improvement Program of the Nationwide Analysis Basis (NRF) funded by the Korean authorities (MSIT; NRF-2018M3A9H3024850); and (iv) by the Ministry of Science, ICT and Future Planning (grant no. NRF-2018R1A2B2001322). Creator contributions: D.S., W.L., J.H.L., and D.B. developed the ideas and designed the research. D.S. and W.L. carried out the experiments. D.S. carried out bioinformatic evaluation and analyzed the info. D.S. and W.L. wrote the manuscript with suggestions from all authors. J.H.L. and D.B. supervised the venture. Competing pursuits: D.B., W.L., and D.S. are inventors on a provisional patent software with Yonsei College Trade-Educational Cooperation Basis (no. 10-2018-0075669, filed on 29 June 2018). The authors declare no different competing pursuits. Knowledge and supplies availability: Full sequencing knowledge have been deposited within the Sequence Reads Archive (PRJNA493658). All knowledge generated or analyzed throughout this research are included on this printed article. Extra knowledge associated to this paper can be offered by the corresponding authors upon request.