<!-- README.md is generated from README.Rmd. Please edit that file -->
# CellaRepertorium
This package contains methods for clustering, pairing and testing single
cell RepSeq data, especially as generated by [10X genomics VDJ
solution](https://support.10xgenomics.com/single-cell-vdj).
## Installation
devtools::install_github('amcdavid/CellaRepertorium')
Requires R \>= 3.5.
## Data requirements and package structure
The fundamental unit this package operates on is the **contig**, which
is a section of contiguously stitched reads from a **single cell**. Each
contig belongs to one (and only one) cell, however, cells generate
multiple contigs.
<img src = man/figures/contig_schematic.png />
Contigs can also belong to a **cluster**. Because of these two
many-to-one mappings, these data can be thought as a series of ragged
arrays. The links between them mean they are relational data. A
`ContigCellDB()` object wraps each of these objects as a sequence of
three `data.frames` (`dplyr::tibble()`, actually). `ContigCellDB()` also
tracks columns (the primary keys) that uniquely identify each row in
each of these tables. The `contig_tbl` is the `tibble` containing
**contigs**, the `cell_tbl` contains the **cells**, and the
`cluster_tbl` contains the **clusters**.
The `contig_pk`, `cell_pk` and `cluster_pk` specify the columns that
identify a contig, cell and cluster, respectively. These will serve as
foreign keys that link the three tables together. The tables are kept in
sync so that subsetting the contigs will subset the cells, and clusters,
and vice-versa.
<img src = man/figures/table_schematic.png />
Of course, each of these tables can contain many other columns that will
serve as covariates for various analyses, such as the **CDR3** sequence,
or the identity of the **V**, **D** and **J** regions. Various derived
quantities that describe cells and clusters can also be calculated, and
added to these tables, such as the **medoid** of a cluster – a contig
that minimizes the average distance to all other clusters.
## Some functions of interest
Mainly, this package seeks to enforce proper schema of single cell
repertoire data and stay out the user’s way for various summaries they
might conduct.
However, there are a variety of specialized functions, as well:
- `cdhit_ccdb()`: An R interface to CDhit, which was originally ported
by Thomas Lin Pedersen.
- `fine_clustering()`: clustering CDR3 by edit distances (possibly
using empirical amino acid substitution matrices)
- `canonicalize_cell()`: Return a single contig for each cell, e.g.,
for combining VDJ information with 5’-based single cell expression
- `cluster_permute_test()`: permutation tests of cluster statistics
- `pairing_tables()`: Generate pairings of contigs within each cell in
a way that they can be plotted
## Interfacing related packages for clonal analyses
- To combine repertoire information with expression of endogenous
mRNAs, this package has been used with
`SingleCellExperiment::SingleCellExperiment()` and
[Seurat](https://satijalab.org/seurat/) after generating cell
canonicalizations.
- Functionality is under development facilitate submitting actual
contig `fasta` to tools such as the IGMT’s
[HighV-QUEST](http://imgt.org/HighV-QUEST/home.action)
- Many tools from the
[Immcantation](https://alakazam.readthedocs.io/en/version-0.2.11/)
suite can work directly on `ContigCellDB()` objects.
## Roadmap
The data structure and accessor APIs are relatively stable. In the short
term, models that test for segment pairing and CDR3 over-representation
are a priority, as are procedures for QC of contigs and cells.