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

Share:

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 or Mac operating systems. It returns an object of class "pNode".

Usage

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
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"), weighted = FALSE, network.customised = NULL,
normalise = c("laplacian", "row", "column", "none"), restart = 0.75,
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 Pathways 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 addtion 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

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

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. It can be installed via: source("http://bioconductor.org/biocLite.R"); biocLite(c("foreach","doMC")). If not yet installed, this option will be disabled

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 5 containing node priority information, where nNode is the number of nodes in the input graph, and the 5 columns are "name" (node names), "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

  • call: the call that produced this result

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

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
## Not run: 
# Load the library
library(Pi)

## End(Not run)

RData.location <- "http://galahad.well.ox.ac.uk/bigdata_dev"
# 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

## Not run: 
# 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)

Want to suggest features or report bugs for rdrr.io? Use the GitHub issue tracker.