xPierGenes | R Documentation

## Function to prioritise genes from an input network and the weight info imposed on its nodes

### Description

`xPierGenes` is supposed to prioritise genes given an input graph and a list of seed nodes. It implements Random Walk with Restart (RWR) and calculates the affinity score of all nodes in the graph to the seeds. The priority score is the affinity score. Parallel computing is also supported for Linux-like or Windows operating systems. It returns an object of class "pNode".

### Usage

    xPierGenes(data, network = c("STRING_highest", "STRING_high",
    "STRING_medium", "STRING_low", "PCommonsUN_high", "PCommonsUN_medium",
    "PCommonsDN_high", "PCommonsDN_medium", "PCommonsDN_Reactome",
    "PCommonsDN_KEGG", "PCommonsDN_HumanCyc", "PCommonsDN_PID",
    "PCommonsDN_PANTHER", "PCommonsDN_ReconX", "PCommonsDN_TRANSFAC",
    "PCommonsDN_PhosphoSite", "PCommonsDN_CTD", "KEGG", "KEGG_metabolism",
    "KEGG_genetic", "KEGG_environmental", "KEGG_cellular",
    "KEGG_organismal",
    "KEGG_disease", "REACTOME"), STRING.only = c(NA, "neighborhood_score",
    "fusion_score", "cooccurence_score", "coexpression_score",
    "experimental_score", "database_score", "textmining_score")[1],
    weighted = FALSE, network.customised = NULL,
    seeds.inclusive = TRUE, normalise = c("laplacian", "row", "column",
    "none"), restart = 0.7, normalise.affinity.matrix = c("none",
    "quantile"), parallel = TRUE, multicores = NULL, verbose = TRUE,
    RData.location = "http://galahad.well.ox.ac.uk/bigdata")

### Arguments

`data` | a named input vector containing a list of seed nodes (ie gene symbols). For this named vector, the element names are seed/node names (e.g. gene symbols), the element (non-zero) values used to weight the relative importance of seeds. Alternatively, it can be a matrix or data frame with two columns: 1st column for seed/node names, 2nd column for the weight values

`network`

the built-in network. Currently two sources of network information are supported: the STRING database (version 10) and the Pathway Commons database (version 7). STRING is a meta-integration of undirect interactions from the functional aspect, while Pathways Commons mainly contains both undirect and direct interactions from the physical/pathway aspect. Both have scores to control the confidence of interactions. Therefore, the user can choose the different quality of the interactions. In STRING, "STRING_highest" indicates interactions with highest confidence (confidence scores>=900), "STRING_high" for interactions with high confidence (confidence scores>=700), "STRING_medium" for interactions with medium confidence (confidence scores>=400), and "STRING_low" for interactions with low confidence (confidence scores>=150). For undirect/physical interactions from Pathways Commons, "PCommonsUN_high" indicates undirect interactions with high confidence (supported with the PubMed references plus at least 2 different sources), "PCommonsUN_medium" for undirect interactions with medium confidence (supported with the PubMed references). For direct (pathway-merged) interactions from Pathways Commons, "PCommonsDN_high" indicates direct interactions with high confidence (supported with the PubMed references plus at least 2 different sources), and "PCommonsUN_medium" for direct interactions with medium confidence (supported with the PubMed references). In addition to pooled version of pathways from all data sources, the user can also choose the pathway-merged network from individual sources, that is, "PCommonsDN_Reactome" for those from Reactome, "PCommonsDN_KEGG" for those from KEGG, "PCommonsDN_HumanCyc" for those from HumanCyc, "PCommonsDN_PID" for those froom PID, "PCommonsDN_PANTHER" for those from PANTHER, "PCommonsDN_ReconX" for those from ReconX, "PCommonsDN_TRANSFAC" for those from TRANSFAC, "PCommonsDN_PhosphoSite" for those from PhosphoSite, and "PCommonsDN_CTD" for those from CTD. For direct (pathway-merged) interactions sourced from KEGG, it can be 'KEGG' for all, 'KEGG_metabolism' for pathways grouped into 'Metabolism', 'KEGG_genetic' for 'Genetic Information Processing' pathways, 'KEGG_environmental' for 'Environmental Information Processing' pathways, 'KEGG_cellular' for 'Cellular Processes' pathways, 'KEGG_organismal' for 'Organismal Systems' pathways, and 'KEGG_disease' for 'Human Diseases' pathways. 'REACTOME' for protein-protein interactions derived from Reactome pathways

`STRING.only`

the further restriction of STRING by interaction type. If NA, no such restriction. Otherwide, it can be one or more of "neighborhood_score","fusion_score","cooccurence_score","coexpression_score","experimental_score","database_score","textmining_score". Useful options are c("experimental_score","database_score"): only experimental data (extracted from BIND, DIP, GRID, HPRD, IntAct, MINT, and PID) and curated data (extracted from Biocarta, BioCyc, GO, KEGG, and Reactome) are used

`weighted` | logical to indicate whether edge weights should be considered. By default, it sets to false. If true, it only works for the network from the STRING database

`network.customised`

an object of class "igraph". By default, it is NULL. It is designed to allow the user analysing their customised network data that are not listed in the above argument 'network'. This customisation (if provided) has the high priority over built-in network. If the user provides the "igraph" object with the "weight" edge attribute, RWR will assume to walk on the weighted network

`seeds.inclusive` | logical to indicate whether non-network seed genes are included for prioritisation. If TRUE (by default), these genes will be added to the netowrk
`normalise` | the way to normalise the adjacency matrix of the input graph. It can be 'laplacian' for laplacian normalisation, 'row' for row-wise normalisation, 'column' for column-wise normalisation, or 'none'

`restart`

the restart probability used for Random Walk with Restart (RWR). The restart probability takes the value from 0 to 1, controlling the range from the starting nodes/seeds that the walker will explore. The higher the value, the more likely the walker is to visit the nodes centered on the starting nodes. At the extreme when the restart probability is zero, the walker moves freely to the neighbors at each step without restarting from seeds, i.e., following a random walk (RW)

`normalise.affinity.matrix` | the way to normalise the output affinity matrix. It can be 'none' for no normalisation, 'quantile' for quantile normalisation to ensure that columns (if multiple) of the output affinity matrix have the same quantiles
`parallel` | logical to indicate whether parallel computation with multicores is used. By default, it sets to true, but not necessarily does so. Partly because parallel backends available will be system-specific (now only Linux or Mac OS). Also, it will depend on whether these two packages "foreach" and "doMC" have been installed
`multicores` | an integer to specify how many cores will be registered as the multicore parallel backend to the 'foreach' package. If NULL, it will use a half of cores available in a user's computer. This option only works when parallel computation is enabled
`verbose` | logical to indicate whether the messages will be displayed in the screen. By default, it sets to true for display
`RData.location` | the characters to tell the location of built-in RData files. See `xRDataLoader` for details

### Value

an object of class "pNode", a list with following components:

- `priority`: a matrix of nNode X 6 containing node priority information, where nNode is the number of nodes in the input graph, and the 5 columns are "name" (node names), "node" (1 for network genes, 0 for non-network seed genes), "seed" (1 for seeds, 0 for non-seeds), "weight" (weight values), "priority" (the priority scores that are rescaled to the range [0,1]), "rank" (ranks of the priority scores), "description" (node description)

- `g`: an input "igraph" object

### Note

The input graph will treat as an unweighted graph if there is no 'weight' edge attribute associated with

### See Also

`xRDataLoader`, `xPierSNPs`, `xPier`, `xPierPathways`

### Examples

    ## Not run:
    # Load the library
    library(Pi)

    ## End(Not run)

    RData.location <- "http://galahad.well.ox.ac.uk/bigdata"
    ## Not run:
    # a) provide the seed nodes/genes with the weight info
    ## load ImmunoBase
    ImmunoBase <- xRDataLoader(RData.customised='ImmunoBase',
    RData.location=RData.location)
    ## get genes within 500kb away from AS GWAS lead SNPs
    seeds.genes <- ImmunoBase$AS$genes_variants
    ## seeds weighted according to distance away from lead SNPs
    data <- 1- seeds.genes/500000

    # b) perform priority analysis
    pNode <- xPierGenes(data=data, network="PCommonsDN_medium",restart=0.7,
    RData.location=RData.location)

    # c) save to the file called 'Genes_priority.txt'
    write.table(pNode$priority, file="Genes_priority.txt", sep="\t",
    row.names=FALSE)

    ## End(Not run)