1.数据的准备
1.1选择想要进行时间轨迹分析的seurat亚群,，并将亚群提取出来
代码语言：txt复制#走一遍seurat标准流程后，得到数据，提取亚群
table( Idents(sce ))
table(sce@meta.data$seurat_clusters)
table(sce@meta.data$orig.ident)
# 取子集
levels(Idents(sce))
sce = sce[, Idents(sce) %in% c( "FCGR3A Mono", "CD14 Mono" )]
#sce[基因,细胞]
levels(Idents(sce))
markers_df <- FindMarkers(object = sce, ident.1 = 'FCGR3A Mono',ident.2 = 'CD14 Mono', #logfc.threshold = 0,min.pct = 0.25)
head(markers_df)
挑选差异基因
cg_markers_df=markers_df[abs(markers_df$avg_log2FC) >1,]1.2 创建CellDataSet对象及monocle标准流程
详见此链接：https://www.jianshu.com/p/34c23dbd9dc1
创建CellDataSet对象
代码语言：txt复制library(monocle)
sample_ann <- sce@meta.data
sample_ann$celltype=Idents(sce)
#准备newCellDataSet函数的输入文件
gene_ann <- data.frame(gene_short_name = rownames(sce@assays$RNA, row.names = rownames(sce@assays$RNA))
pd <- new("AnnotatedDataFrame",
data=sample_ann)
fd <- new("AnnotatedDataFrame",
data=gene_ann)
ct=as.data.frame(sce@assays$RNA@counts)
sc_cds <- newCellDataSet(as.matrix(ct), phenoData = pd,featureData =fd,expressionFamily = negbinomial.size(),lowerDetectionLimit=1)monocle标准流程
代码语言：txt复制sc_cds <- detectGenes(sc_cds, min_expr = 1)
sc_cds <- sc_cds[fData(sc_cds$num_cells_expressed > 10, ]
cds <- estimateSizeFactors(cds)
cds <- estimateDispersions(cds)
disp_table <- dispersionTable(cds)
unsup_clustering_genes <- subset(disp_table,mean_expression >= 0.1)
cds <- setOrderingFilter(cds,unsup_clustering_genes$gene_id)
cds <- reduceDimension(cds, max_components = 2, num_dim = 6,reduction_method = 'tSNE', verbose = T)
cds <- clusterCells(cds, num_clusters = 6) 2.查找差异基因及时间轨迹分析
2.1 查找差异基因
根据自己生物学意图，选择查看哪个性状的轨迹
代码语言：txt复制将monocle的分群改为seurat分群
pData(cds)$Cluster=pData(cds)$celltype
table(pData(cds1)$Cluster)
#测试每个基因作为伪时间函数或根据指定的其他协变量的差异表达。fullModelFormulaStr 选择按照什么找差异
diff_test_res <- differentialGeneTest(cds,fullModelFormulaStr = "~Cluster")
# 选择 FDR < 10% 的基因作为差异基因
sig_genes <- subset(diff_test_res, qval < 0.1)
sig_genes<-sig_genes[order(sig_genes$pval),]
head(sig_genes[,c("gene_short_name", "pval", "qval")] )
cg=as.character(head(sig_genes$gene_short_name))
# 挑选差异最显著的基因可视化，将一个或多个基因的表达绘制点图
plot_genes_jitter(cds[cg,], grouping = "Cluster", color_by = "Cluster",nrow= 3,ncol = NULL )
cg2=as.character(tail(sig_genes$gene_short_name))
plot_genes_jitter(cds[cg2,],grouping = "Cluster",color_by = "Cluster",nrow= 3,ncol = NULL )
2.2 时间轨迹分析
第一步: 挑选合适的基因. 有多个方法，例如提供已知的基因集，这里选取统计学显著的差异基因列表。
代码语言：txt复制ordering_genes <- row.names (subse(diff_test_res, qval < 0.01))
ordering_genes
#准备聚类基因名单
cds <- setOrderingFilter(cds, ordering_genes)
plot_ordering_genes
第二步: 降维。降维的目的是为了更好的展示数据。函数里提供了很多种方法,不同方法的最后展示的图都不太一样, 其中“DDRTree”是Monocle2使用的默认方法。
代码语言：txt复制cds <- reduceDimension(cds, max_components = 2, method = 'DDRTree')第三步: 对细胞进行排序 学习描述细胞正在经历的生物过程的“轨迹”，并计算每个细胞在该轨迹内的位置。
代码语言：txt复制cds <- orderCells(cds)最后: 可视化
注意，伪时序的解读需要结合生物学意义
代码语言：txt复制plot_cell_trajectory(cds, color_by = "Cluster")
#绘制一个或多个基因的表达作为伪时序。
plot_genes_in_pseudotime(cds[cg,],color_by = "Cluster") 
前面根据差异基因，推断好了拟时序，也就是说把差异基因动态化了，后面就可以具体推断哪些基因随着拟时序如何的变化
代码语言：txt复制my_cds_subset=cds
# 拟时序数据和细胞位置在pData 中
head(pData(my_cds_subset))
# 这个differentialGeneTest会比较耗费时间，测试每个基因的拟时序表达
my_pseudotime_de <- differentialGeneTest(my_cds_subset,fullModelFormulaStr = "~sm.ns(Pseudotime)",cores = 4 )#cores调用的核心数
head(my_pseudotime_de)3.分析结果的精致可视化
代码语言：txt复制library(Seurat)
library(gplots)
library(ggplot2)
library(monocle)
library(dplyr)
cds=my_cds_subset
phe=pData(cds)
colnames(phe)
library(ggsci)
#绘制最小生成树
p1=plot_cell_trajectory(cds, color_by = "Cluster") scale_color_nejm()
p1
ggsave('trajectory_by_cluster.pdf')
plot_cell_trajectory(cds, color_by = "celltype")
p2=plot_cell_trajectory(cds, color_by = "Pseudotime")
p2
ggsave('trajectory_by_Pseudotime.pdf')
p3=plot_cell_trajectory(cds, color_by = "State") scale_color_npg()
p3
ggsave('trajectory_by_State.pdf')
library(patchwork)#拼图
p1 p2/p3
以qval前六的基因做图
代码语言：txt复制phe=pData(cds)
head(phe)
table(phe$State,phe$Cluster)
library(dplyr)
#%>% 管道函数 把左边的值发送给右边的表达式，并作为右件表达式函数的第一个参数
my_pseudotime_de %>% arrange(qval) %>% head()
# 保存前六的基因
my_pseudotime_de %>% arrange(qval) %>% head() %>% select(gene_short_name) -> my_pseudotime_gene
my_pseudotime_gene=my_pseudotime_gene[,1]
my_pseudotime_gene
#绘制一个或多个基因的拟时序
plot_genes_in_pseudotime(my_cds_subset[my_pseudotime_gene,]) scale_color_npg()
ggsave('monocle_top6_pseudotime_by_state.pdf')
将一个或多个基因的表达绘制点图
代码语言：txt复制plot_genes_jitter(my_cds_subset[my_pseudotime_gene,],grouping = "Cluster",color_by = "Cluster", nrow= 3,ncol = NULL ) scale_color_nejm()
ggsave('monocle_top6_pseudotime_by_cluster.pdf')
将前50个随拟时序变化的基因做聚类热图
代码语言：txt复制# cluster the top 50 genes that vary as a function of pseudotime
my_pseudotime_de %>% arrange(qval) %>% head(50) %>% select(gene_short_name) -> gene_to_cluster
gene_to_cluster <- gene_to_cluster[,1]
gene_to_cluster
colnames(pData(my_cds_subset))
table(pData(my_cds_subset)$Cluster,pData(my_cds_subset)$State)
ac=pData(my_cds_subset)[c('celltype','State','Pseudotime')]
head(ac)
# 这个热图绘制的并不是纯粹的细胞基因表达量矩阵，而是被 Pseudotime 好了的100列，50行的矩阵
my_pseudotime_cluster <- plot_pseudotime_heatmap(my_cds_subset[gene_to_cluster,],# num_clusters = 2, # add_annotation_col = ac,show_rownames = TRUE,
return_heatmap = TRUE)
my_pseudotime_cluster
pdf('monocle_top50_heatmap.pdf')
print(my_pseudotime_cluster)
dev.off()
分支表达分析建模 识别具有分支依赖性表达的基因。
代码语言：txt复制#计算建模分支节点
BEAM_branch1 <- BEAM(my_cds_subset, branch_point = 1, cores = 4)
head(BEAM_branch1)
colnames(BEAM_branch1)
BEAM_branch1 <- BEAM_branch1[order(BEAM_branch1$qval),]
BEAM_branch1 <- BEAM_branch1[,c("gene_short_name", "pval", "qval")]
head(BEAM_branch1)
BEAM_branch2 <- BEAM(my_cds_subset, branch_point = 2, cores = 20)
BEAM_branch2 <- BEAM_branch2[order(BEAM_branch2$qval),]
BEAM_branch2 <- BEAM_branch2[,c("gene_short_name", "pval", "qval")]
head(BEAM_branch2)使用全部的基因进行绘图 创建一个热图来展示基因表达沿两个分支的分叉
代码语言：txt复制BEAM_res = BEAM_branch1
my_branched_heatmap <- plot_genes_branched_heatmap( my_cds_subset[row.names(subset(BEAM_res, qval < 1e-4)),], branch_point = 1,num_clusters = 4, e_short_name = TRUE,show_rownames = F,return_heatmap = TRUE)
pdf('monocle_BEAM_branch1_heatmap.pdf')
print(my_branched_heatmap$ph)
dev.off()
BEAM_res = BEAM_branch2
my_branched_heatmap <- plot_genes_branched_heatmap(my_cds_subset[row.names(subset(BEAM_res, qval < 1e-4)),],branch_point = 1,num_clusters = 4, use_gene_short_name = TRUE,show_rownames = F,return_heatmap = TRUE)
pdf('monocle_BEAM_branch2_heatmap.pdf')
print(my_branched_heatmap$ph)
dev.off()
#将所做热图的基因和cluster提取出来
head(my_branched_heatmap$annotation_row)
table(my_branched_heatmap$annotation_row$Cluster)
my_row <- my_branched_heatmap$annotation_row
my_row <- data.frame(cluster = my_row$Cluster,
gene = row.names(my_row),
stringsAsFactors = FALSE)
head(my_row[my_row$cluster == 3,'gene'])
my_gene <- row.names(subset(fData(my_cds_subset),
gene_short_name %in% head(my_row[my_row$cluster == 2,'gene'])))
my_gene
# 绘制分支处的基因拟时序轨迹
#分支1
plot_genes_branched_pseudotime(my_cds_subset[my_gene,],
branch_point = 1,
ncol = 1)
#分支2
plot_genes_branched_pseudotime(my_cds_subset[my_gene,],
branch_point = 2,
ncol = 1)
分支1
分支2做热图查看拟时序基因在两个亚群的表达
代码语言：txt复制cds=my_cds_subset
phe=pData(cds)
colnames(phe)
plot_cell_trajectory(cds)
counts = Biobase::exprs(cds)
dim(counts)
library(dplyr)
my_pseudotime_de %>% arrange(qval) %>% head(100) %>% select(gene_short_name) -> my_pseudotime_gene
my_pseudotime_gene=my_pseudotime_gene[,1]
my_pseudotime_gene
library(pheatmap)
#数据中心化和归一化
n=t(scale(t( counts[my_pseudotime_gene,] ))) # 'scale'可以对log-ratio数值进行归一化
n[n>2]=2
n[n< -2]= -2
n[1:4,1:4]
pheatmap(n,show_colnames =F,show_rownames = F)
ac=phe[,c(10,16,17)]
head(ac)
rownames(ac)=colnames(n)
dim(n)
n[1:4,1:4]
pheatmap(n,show_colnames =F,
show_rownames = F,
annotation_col=ac)
od=order(ac$Pseudotime)
pheatmap(n[,od],show_colnames =F,
show_rownames = F,cluster_cols = F,
annotation_col=ac[od,])
参考来源
#section 3已更新#「生信技能树」单细胞公开课2021_哔哩哔哩_bilibili
致谢
I thank Dr.Jianming Zeng(University of Macau), and all the members of his bioinformatics team, biotrainee, for generously sharing their experience and codes.
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