Prerequisites.RmdReputils can compute family-wise multiple sequence alignments of all repeat sequences in the genome to improve read mapping onto a consensus model. To do so, we require the genome assembly of our organism of choice stored as a BSgenome object. You can retrieve the full list of supported genomes by typing BSgenome::available.genomes() or create a custom BSgenome object following the instructions.
Since we are working with expression data from human cancer cell lines, we will first install the UCSC hg38 assemblies.
Important note: Do not use repeat-masked BSgenome objects (contain ‘masked’ suffix, e.g. BSgenome.Hsapiens.UCSC.hg38.masked)!
A convient solution is to download transposon coordinates from the Repeatmasker homepage or the DFAM database for your genome and assembly of choice. You can import the Repeatmasker fa.out.gz or DFAM dfam.hits.gz files using the Reputils importRMSK and importDFAM functions, respectively. Another option is to provide custom annotation as long as it provides the basic information about chromosome, start, end, strand, repname (family identifier), and id_unique (unique locus identifier). In this tutorial, we will show you how to import such information using the provided example datasets.
Reputils requires read alignment coordinates stored in BAM format as input, which are routinely generated during most common scRNA-seq workflows, including 10x’ Cellranger pipeline. BAM inputs should be duplicate removed, position sorted, and indexed. Chunking BAM inputs (e.g. by chromosome) can accelerate the import into your R environment using the importBAM function. Important: Reputils assumes the cell barcode is either stored as CB tag or BAM input files are seperated per cell. Other formats are currently not supported (e.g. cell barcode in read name).