diff --git a/topics/single-cell/tutorials/scrna-case-cell-annotation/slides.html b/topics/single-cell/tutorials/scrna-case-cell-annotation/slides.html index 241bb2e5a83775..eb81eb7045fb88 100644 --- a/topics/single-cell/tutorials/scrna-case-cell-annotation/slides.html +++ b/topics/single-cell/tutorials/scrna-case-cell-annotation/slides.html @@ -36,11 +36,11 @@ ### What is Cell Annotation? -- Categorising cells into cell type categories based on transcriptomic data +- Classify cells in your data into different cell types based on gene expression data - Can be done manually or automatically -- Is possible due to single-cell sequencing technology +- Single-cell sequencing technology provides higher resolution than bulk RNA-seq ![Basic pipeline for automated cell annotation](../../images/scrna-cell-annotation/cell-annotation.png) @@ -52,9 +52,35 @@ --- -### Why is it Important? +### Why is Cell Annotation Important? -- Able to process and analyse single cell data much faster than manual analysis + +- To understand the composition of cell types in samples (cellular heterogeneity) + +- To compare changes in cell populations or states across different condition and phenotypes + +- To perform differential expression within each cell type to avoid signal dilution from mixed cell type population + +- To identify novel cell states and study some cell population further + +??? + +The power of single-cell RNA-seq lies in its ability to capture the transcriptome at single-cell resolution. + +However, a significant challenge is accurately classifying cells into distinct types before beginning downstream analysis. + +Once cells are annotated, we can examine the composition of cell types within each sample and compare them across conditions. + +This precise classification enables differential expression analysis within specific cell types, a key objective of single-cell experiments. + + +--- + +### Why Automate Cell Annotation? + +- Each single-cell experiment can generate data for thousands of cells + +- Manual annotation is time consuming and requires domain expertise - Can produce results more consistently allowing for reproducibility of results @@ -84,7 +110,7 @@ - Cell annotation uses sc-RNA seq data -- Gene expressions are stored in a gene expression matrix (X) +- Gene expressions are stored in a gene expression matrix (X)

Common data types: @@ -106,14 +132,19 @@ --- -### Challenges +### Challenges in Automated Cell Type Annotation + +- Noise due to amplification techniques, varying sequencing depths, and sequencing errors -- Data is often noisy due to amplification techniques, varying sequencing depths, and errors in the reads +- Difference in QC steps for reference and query dataset may introduce a bias - Cell type definitions are inherently subjective and may be suboptimal +- Lack of a suitable reference panel for the query dataset can result in inaccurate classification, especially when dealing with unknown cell states + - Dealing with unknown cell types due to undiscovered classifications + ??? There are some challenges that need to be faced in order to perform automated cell annotation: @@ -128,9 +159,11 @@ ### Manual Cell Annotation -- Generate a cluster map and manually annotate each clusters +- Requires known marker genes for cell types of interest + +- Generate the UMAP/tSNE (see below) to visualize the expression values -- Requires the researchers to find known marker genes in the data +- If you have clustered the cells, you can use dotplots or violin plots to measure the average expression of these genes ![Various cell cluster diagrams showing the expression values of various marker genes](../../images/scrna-cell-annotation/manual-annotation.png) @@ -154,7 +187,7 @@ .pull-left[ -- The process of identifying unique gene expressions that can be used for identifying cell types +- The process of identifying genes that are uniquely expressed in certain cell types - Genes are selected based on how differently they are expressed across different cell types