Question: Is the Targeted Gene Expression assay compatible with nuclei?
Answer: The Targeted Gene Expression assay is compatible with Whole Transcriptome Analysis (WTA) libraries prepared from single cells or from single nuclei.
When comparing targeted libraries prepared from single-cell and single nuclei WTA libraries, both perform well with respect to the recovered complexity of the targeted libraries, and with respect to the correlation of UMI counts between targeted libraries and their parent WTA libraries.
However, the fraction of reads mapped to the targeted transcriptome is typically lower for targeted libraries prepared from single nuclei WTA libraries as compared to their whole-cell counterparts. This is mainly because single nuclei WTA libraries typically have higher levels of reads mapping antisense to genes than single-cell WTA libraries.
Due to the double-stranded nature of libraries, antisense reads are enriched as efficiently as sense reads in the targeted assay. Therefore, both sense and antisense reads corresponding to targeted genes can be observed in the targeted library. The vast majority of antisense reads in targeted libraries map to targeted genes.
In Cell Ranger, antisense reads are filtered out and do not contribute to the final UMI count for reads mapping to the targeted transcriptome. Therefore, a higher level of antisense reads leads to a lower fraction of reads mapping to the targeted transcriptome.
Note regarding intronic reads:
- In the Targeted Gene Expression assay, baits are designed to capture exons, not introns. Therefore, the fraction of intronic reads tend to be lower in targeted libraries, even if high levels of intronic reads were present in the parent WTA library.
- Although we recommend including introns for WTA data analysis, the recommended (and default) mode for Targeted Gene Expression analysis is exon-only. This is because 10x Genomics supported baits are designed to capture exons only.
- In addition, if you plan to use
cellranger targeted-compareto compare a targeted and its parent WTA library, we recommend setting the--include-introns=falsefor both WTA and targeted library, .- This is because baits are designed to capture exons, most of intronic reads will not be recovered in the targeted library. If introns are included in the comparisons, metrics related to UMI recovery will be apparently lower.
Note: The Targeted Gene Expression assay has been discontinued. For alternative options, please see: What options are there for performing a targeted enrichment for my gene expression libraries?
Products: Targeted Gene Expression, Single Cell Gene Expression, Single Cell Immune Profiling