Original Research
The Genetic Architecture of Carbon Tetrachloride-Induced Liver Fibrosis in Mice

https://doi.org/10.1016/j.jcmgh.2020.08.010Get rights and content
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Background & Aims

Liver fibrosis is a multifactorial trait that develops in response to chronic liver injury. Our aim was to characterize the genetic architecture of carbon tetrachloride (CCl4)-induced liver fibrosis using the Hybrid Mouse Diversity Panel, a panel of more than 100 genetically distinct mouse strains optimized for genome-wide association studies and systems genetics.

Methods

Chronic liver injury was induced by CCl4 injections twice weekly for 6 weeks. Four hundred thirty-seven mice received CCl4 and 256 received vehicle, after which animals were euthanized for liver histology and gene expression. Using automated digital image analysis, we quantified fibrosis as the collagen proportionate area of the whole section, excluding normal collagen.

Results

We discovered broad variation in fibrosis among the Hybrid Mouse Diversity Panel strains, demonstrating a significant genetic influence. Genome-wide association analyses revealed significant and suggestive loci underlying susceptibility to fibrosis, some of which overlapped with loci identified in mouse crosses and human population studies. Liver global gene expression was assessed by RNA sequencing across the strains, and candidate genes were identified using differential expression and expression quantitative trait locus analyses. Gene set enrichment analyses identified the underlying pathways, of which stellate cell involvement was prominent, and coexpression network modeling identified modules associated with fibrosis.

Conclusions

Our results provide a rich resource for the design of experiments to understand mechanisms underlying fibrosis and for rational strain selection when testing antifibrotic drugs.

Keywords

CCl4
Systems Genetics
Liver Toxicity and Injury
Genome-Wide Association Study

Abbreviations used in this paper

bp
base pair
CCl4
carbon tetrachloride
CPA%
collagen proportionate area
ECM
extracellular matrix
eQTL
expression quantitative trait locus
GWAS
genome-wide association study
HCV
hepatitis C virus
HMDP
Hybrid Mouse Diversity Panel
HSC
hepatic stellate cell
MUP
mouse urinary protein
NAFLD
nonalcoholic fatty liver disease
NASH
nonalcoholic steatohepatitis
SD
standard deviation
SNP
single nucleotide polymorphism
TPM
transcripts per million
WGCNA
weighted gene coexpression network analysis

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Conflicts of interest The authors disclose no conflicts.

Funding Supported by Sigrid Juselius Foundation (IT), Orion-Farmos Research Foundation (IT), K99 HL121172 (MC), HL28481, HL144651 and DK117850 (AJL), K08DK088998 (SWB), Ruth L. Kirschstein National Research Service Award T32HL069766 (BKF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

a

Authors share co-first authorship.