在使用liger整合单细胞RNA-seq的文章中,我提到liger的数据结构和函数调用不及seurat那么方便和个性化,因此将两者的优势结合起来能够大大便利我们的单细胞数据分析。本文主要介绍以下两种方法:
- 使用SeuratWrappers在seurat中直接调用liger进行降维聚类
- 使用liger内置的函数在liger对象和seurat对象之间进行转换
SeuratWrappers
SeuratWrappers相当于seurat的社区工具,能够使得我们很方便地调用别的包的一些代码和方法来处理seurat对象。SeuratWrappers目前支持Monocle3、glmpca、LIGER、Harmony以及Velocity等13个常用的单细胞转录组相关的包,具体的细节可以参考GitHub。这里不再对代码做任何讲解,因为使用方法和参数与liger基本完全一致,如果有困惑可以参考使用liger整合单细胞RNA-seq。
############################################ ## Project: Liger-learning ## Script Purpose: Integrating Seurat objects using LIGER ## Data: 2020.11.01 ## Author: Yiming Sun ############################################ # general setting setwd(\'~/sunym/project/liger_learning/\') # library library(liger) library(Seurat) library(dplyr) library(tidyverse) library(viridis) library(SeuratData) library(SeuratWrappers) # 1.Systematic comparative analysis of human PBMC data(\"pbmcsca\") #pbmcsca is a seurat object pbmcsca <- NormalizeData(pbmcsca) pbmcsca <- FindVariableFeatures(pbmcsca,selection.method = \'vst\',nfeatures = 2000) #scale by dfferent methods --> intagrate different methods pbmcsca <- ScaleData(pbmcsca,split.by = \'Method\',do.center = FALSE) pbmcsca <- RunOptimizeALS(pbmcsca,k = 20,lambda = 5,split.by = \'Method\',max.iters = 30,thresh = 1e-06) pbmcsca <- RunQuantileNorm(pbmcsca,split.by = \'Method\',knn_k = 20,quantiles = 50,min_cells = 20,do.center = FALSE, max_sample = 1000,refine.knn = TRUE,eps = 0.9) #can further cluster the data and find neighbours pbmcsca <- FindNeighbors(pbmcsca,reduction = \'iNMF\',dims = 1:20) pbmcsca <- FindClusters(pbmcsca,resolution = 0.3) #dimension reduction and plotting pbmcsca <- RunUMAP(pbmcsca,dims = 1:20,reduction = \'iNMF\') pdf(file = \'./res/fig_201101/pbmc_split_by_methods.pdf\',width = 18,height = 5) DimPlot(pbmcsca,group.by = c(\'Method\',\'RNA_snn_res.0.3\',\'CellType\'),ncol = 3) dev.off()
Liger内置函数
Liger包中内置了两个函数ligerToSeurat和seuratToLiger,通常我们用的比较多的是将降维聚类过后的liger对象转换成seurat对象用于做后续的差异表达分析。我们可以简单的来看一下这两个函数的效果。首先先创建一个liger对象。
############################################ ## Project: Liger-learning ## Script Purpose: liger and seurat ## Data: 2020.11.14 ## Author: Yiming Sun ############################################ # general setting setwd(\'/data/User/sunym/project/liger_learning/\') #libarry library(liger) library(Seurat) library(dplyr) library(tidyverse) library(viridis) ####################################### #liger to seurat ####################################### #load data ctrl_dge <- readRDS(\"./data/PBMC_control.RDS\") stim_dge <- readRDS(\"./data/PBMC_interferon-stimulated.RDS\") #initialize a liger object ifnb_liger <- createLiger(list(ctrl = ctrl_dge, stim = stim_dge)) #explore liger object dim([email protected]$ctrl) head(colnames([email protected]$ctrl)) head(rownames([email protected]$ctrl)) dim([email protected]$stim) #normalize data ifnb_liger <- normalize(ifnb_liger) #select variable gene ifnb_liger <- selectGenes(ifnb_liger) #scale data but not center ifnb_liger <- scaleNotCenter(ifnb_liger) #integrate NMF ifnb_liger <- optimizeALS(ifnb_liger,k = 20,lambda = 5,max.iters = 30,thresh = 1e-06) #Quantile Normalization and Joint Clustering ifnb_liger <- quantile_norm(ifnb_liger,knn_k = 20,quantiles = 50,min_cells = 20,do.center = FALSE, max_sample = 1000,refine.knn = TRUE,eps = 0.9) # you can use louvain cluster to detect and assign cluster ifnb_liger <- louvainCluster(ifnb_liger, resolution = 0.25) #Visualization and Downstream Analysis ifnb_liger <- runUMAP(ifnb_liger, distance = \'cosine\', n_neighbors = 30, min_dist = 0.3) all.plots <- plotByDatasetAndCluster(ifnb_liger, axis.labels = c(\'UMAP 1\', \'UMAP 2\'), return.plots = T) pdf(file = \'./res/fig_201114/plot_by_dataset_and_cluster.pdf\',width = 8,height = 4) all.plots[[1]] all.plots[[2]] dev.off()
#liger to seurat #use nms ifnb_seurat <- ligerToSeurat(ifnb_liger,use.liger.genes = TRUE,by.dataset = FALSE,renormalize = TRUE) table([email protected]) head([email protected]) head(colnames(ifnb_seurat))
可以直接用ligerToSeurat函数进行转换,use.liger.genes参数表示是否保留variable gene的信息,by.dataset参数表示是否在cluster的名字之前加入dataset的名字以作区分,另外默认nms参数为names([email protected]),这个参数会在细胞的barcode之前加入dataset的名称并在orig.ident中标注出数据集的来源。可以看下输出简单理解下。
> #liger to seurat > #use nms > ifnb_seurat <- ligerToSeurat(ifnb_liger,use.liger.genes = TRUE,by.dataset = FALSE,renormalize = TRUE) Warning: No assay specified, setting assay as RNA by default. Warning: No columnames present in cell embeddings, setting to \'iNMF_1:20\' Warning: No assay specified, setting assay as RNA by default. Warning: No columnames present in cell embeddings, setting to \'tSNE_1:2\' Warning: Feature names cannot have underscores (\'_\'), replacing with dashes (\'-\') Performing log-normalization 0% 10 20 30 40 50 60 70 80 90 100% [----|----|----|----|----|----|----|----|----|----| **************************************************| > table([email protected]) 1 0 2 9 4 3 6 7 5 8 10 1500 2309 609 37 384 444 238 140 251 56 32 > head([email protected]) orig.ident nCount_RNA nFeature_RNA ctrl_ctrlTCAGCGCTGGTCAT-1 ctrl 2232 815 ctrl_ctrlTTATGGCTTCATTC-1 ctrl 2466 760 ctrl_ctrlACCCACTGCTTAGG-1 ctrl 1085 452 ctrl_ctrlATGGGTACCCCGTT-1 ctrl 3242 925 ctrl_ctrlTGACTGGACAGTCA-1 ctrl 635 333 ctrl_ctrlGTGTAGTGGTTGTG-1 ctrl 1462 549 > head(colnames(ifnb_seurat)) [1] \"ctrl_ctrlTCAGCGCTGGTCAT-1\" \"ctrl_ctrlTTATGGCTTCATTC-1\" [3] \"ctrl_ctrlACCCACTGCTTAGG-1\" \"ctrl_ctrlATGGGTACCCCGTT-1\" [5] \"ctrl_ctrlTGACTGGACAGTCA-1\" \"ctrl_ctrlGTGTAGTGGTTGTG-1\"
如果令nms = NULL。
> #not use nms > ifnb_seurat <- ligerToSeurat(ifnb_liger,nms = NULL,use.liger.genes = TRUE,by.dataset = FALSE,renormalize = TRUE) Warning: No assay specified, setting assay as RNA by default. Warning: No columnames present in cell embeddings, setting to \'iNMF_1:20\' Warning: No assay specified, setting assay as RNA by default. Warning: No columnames present in cell embeddings, setting to \'tSNE_1:2\' Warning: Feature names cannot have underscores (\'_\'), replacing with dashes (\'-\') Performing log-normalization 0% 10 20 30 40 50 60 70 80 90 100% [----|----|----|----|----|----|----|----|----|----| **************************************************| > table([email protected]) 1 0 2 9 4 3 6 7 5 8 10 1500 2309 609 37 384 444 238 140 251 56 32 > head([email protected]) orig.ident nCount_RNA nFeature_RNA ctrlTCAGCGCTGGTCAT-1 SeuratProject 2232 815 ctrlTTATGGCTTCATTC-1 SeuratProject 2466 760 ctrlACCCACTGCTTAGG-1 SeuratProject 1085 452 ctrlATGGGTACCCCGTT-1 SeuratProject 3242 925 ctrlTGACTGGACAGTCA-1 SeuratProject 635 333 ctrlGTGTAGTGGTTGTG-1 SeuratProject 1462 549 > head(colnames(ifnb_seurat)) [1] \"ctrlTCAGCGCTGGTCAT-1\" \"ctrlTTATGGCTTCATTC-1\" [3] \"ctrlACCCACTGCTTAGG-1\" \"ctrlATGGGTACCCCGTT-1\" [5] \"ctrlTGACTGGACAGTCA-1\" \"ctrlGTGTAGTGGTTGTG-1\"
使用seurat的函数做个性化的差异表达分析,参考文章Seurat进行单细胞RNA-seq聚类分析。
#use liger cluster as cell type and do the DE analysis new.cluster.ids <- c(\"a\", \"b\", \"c\", \"d\", \"e\", \"f\", \"g\", \"h\", \"i\", \"j\", \"k\") names(new.cluster.ids) <- levels([email protected]) ifnb_seurat <- RenameIdents(ifnb_seurat, new.cluster.ids) ifnb_seurat$cell_type <- [email protected] Idents(ifnb_seurat) <- \'cell_type\' all.marker <- FindAllMarkers(ifnb_seurat,only.pos = TRUE,min.pct = 0.25,logfc.threshold = 0.25) cluster_a_vs_b_marker <- FindMarkers(ifnb_seurat,group.by = \'cell_type\',ident.1 = \'a\',ident.2 = \'b\',only.pos = TRUE)
手动导出liger中的降维图并导入seurat。
#get the tsne manually tsne.obj <- CreateDimReducObject(embeddings = [email protected],key = \'testUMAP_\',global = TRUE) ifnb_seurat[[\'tsne\']] <- tsne.obj pdf(file = \'./res/fig_201114/dimplot_tsetUMAP.pdf\',width = 9,height = 5) DimPlot(ifnb_seurat,group.by = \'cell_type\') dev.off()
注意tsne.obj的barcode要与seurat中的barcode相对应,因此可以将nms设为NULL或者为tsne.obj手动加上dataset的标签。
可以看到key参数中的内容被成功导入进去了。最后我们也可以将seurat对象转换为liger对象。
> ################################################### > #seurat to liger > ################################################### > ifnb_liger <- seuratToLiger(ifnb_seurat,combined.seurat = TRUE,meta.var = \'orig.ident\',renormalize = TRUE) > head([email protected]) ctrlTCAGCGCTGGTCAT-1 ctrlTTATGGCTTCATTC-1 ctrlACCCACTGCTTAGG-1 a a b ctrlATGGGTACCCCGTT-1 ctrlTGACTGGACAGTCA-1 ctrlGTGTAGTGGTTGTG-1 a c b Levels: a b c d e f g h i j k > head([email protected]) tSNE_1 tSNE_2 ctrlTCAGCGCTGGTCAT-1 -9.5633178 -1.5025842 ctrlTTATGGCTTCATTC-1 -7.4026990 -0.5618219 ctrlACCCACTGCTTAGG-1 3.7179575 4.9839707 ctrlATGGGTACCCCGTT-1 -11.0730367 -4.6024990 ctrlTGACTGGACAGTCA-1 0.5273923 -8.4171533 ctrlGTGTAGTGGTTGTG-1 8.8018236 5.2826267
写在最后
这部分的内容比较枯燥,主要是我自己探索了一下seurat和liger的数据结构以及他们之间如何进行相互转换,想在这里记录一下以免自己忘了。
参考链接
Integrating Seurat objects using LIGER
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