Last updated: 2025-10-18

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Knit directory: Canon-analysis/

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1.Introduction

In this tutorial, we illustrate the use of Canon through one subset sc-CRISPR dataset which can be downloaded here: KRAS cancer data

2.Load data

In this step, we load the data into the environment

load("~/Projects/MR_perturbation/tutorial_example_data.rds")
gene_expression <- data_example$gene_expression
gRNA_mat <- data_example$gRNA

Let’s take a brief look at the gene expression data and gRNA data respectively.

print(gene_expression[1:5, 1:5])
       ATCACGATCGATAGAA-1-31 ACTTGTTAGTTGTAGA-1-27 TTGGAACTCGGAAACG-1-14
SAMD11            -0.3943890             2.6997235            -0.4345025
HES4              -0.9122419            -0.8447953            -0.7541952
ISG15             -0.4786171            -0.3884422            -0.3706382
ERRFI1            -0.5157255             0.6373354            -0.8968230
ENO1               1.0510503            -1.5117935            -0.3409592
       ACATCAGTCCCTAATT-1-31 CTAAGACGTGTGCCTG-1-19
SAMD11            -0.4461569            -0.4918990
HES4              -0.5702732            -0.6156242
ISG15              2.9862552            -0.3358234
ERRFI1            -0.7713618             0.7877674
ENO1               0.6426609             0.7882333
print(gRNA_mat[1:5, 1:5])
                      T20R T158T M111L V112I T50I
ATCACGATCGATAGAA-1-31    0     0     0     0    0
ACTTGTTAGTTGTAGA-1-27    0     0     0     0    0
TTGGAACTCGGAAACG-1-14    0     0     0     0    0
ACATCAGTCCCTAATT-1-31    0     0     1     0    0
CTAAGACGTGTGCCTG-1-19    0     0     0     0    0

3.Run Canon

The core function of Canon is run_Canon. For a detailed description of all the input parameters and output values, please refer to its documentation by typing ?run_Canon in R. Canon is able to model an initial set of candidate gRNAs and perform automated instrument selection to identify suitable gRNAs to serve as instrumental variables. Additionally, Canon relies on a scalable sampling-based inference algorithm to identify genes that are potentially causally influenced by perturbed target genes across diverse sc-CRISPR platforms.

We use gene PLAU as an example to illustrate the usage of Canon

library(Canon)
xin <- scale(as.matrix(gene_expression["KRAS", ]))
yin <- scale(as.matrix(gene_expression["PLAU", ]))
zin <- scale(gRNA_mat)

## The prior information can be adjusted based on the experience
cond <- try(result <- run_Canon(x_expression = xin, y_expression = yin, gRNA = zin, 
                                      Gibbsnumber = 1000, pi_beta_shape = 0.7, pi_beta_scale = 0.7,
                                      a_beta = 21, b_beta = 0.01, pi_eta_shape = 1, pi_eta_scale = 1,
                                      off_target = T))

4.Results

## Causal effect estimate
print(result$causal_effect)
[1] 0.5347347
## Causal effect pvalue
print(result$causal_pvalue)
[1] 0.01260536

sessionInfo()
R version 4.5.1 (2025-06-13)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 22.04.5 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 
LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.20.so;  LAPACK version 3.10.0

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

time zone: America/New_York
tzcode source: system (glibc)

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] Canon_1.0       workflowr_1.7.2

loaded via a namespace (and not attached):
 [1] jsonlite_1.8.8    compiler_4.5.1    promises_1.3.0    Rcpp_1.0.12      
 [5] stringr_1.5.1     git2r_0.36.2      callr_3.7.6       later_1.4.4      
 [9] jquerylib_0.1.4   yaml_2.3.8        fastmap_1.2.0     R6_2.6.1         
[13] knitr_1.46        tibble_3.2.1      rprojroot_2.1.1   bslib_0.7.0      
[17] pillar_1.9.0      rlang_1.1.3       utf8_1.2.4        cachem_1.1.0     
[21] stringi_1.8.4     httpuv_1.6.15     xfun_0.44         getPass_0.2-4    
[25] fs_1.6.4          sass_0.4.9        cli_3.6.2         magrittr_2.0.3   
[29] ps_1.7.6          digest_0.6.35     processx_3.8.4    rstudioapi_0.16.0
[33] lifecycle_1.0.4   vctrs_0.6.5       evaluate_0.23     glue_1.8.0       
[37] whisker_0.4.1     fansi_1.0.6       rmarkdown_2.27    httr_1.4.7       
[41] tools_4.5.1       pkgconfig_2.0.3   htmltools_0.5.8.1