Aflatoxin B₁-Induced Hepatic Mutagenesis in Mice Expressing Gene-Edited Neil1

Hepatocellular carcinoma (HCC) remains one of the leading causes of cancer-associated mortality, correlating with obesity, alcohol consumption, hepatitis B and C infections, and dietary exposure to aflatoxin B₁ (AFB₁). The etiology of AFB₁-induced HCC involves the formation of highly mutagenic guanine lesions that can be repaired by a branch of the base excision repair pathway initiated by the DNA glycosylase, NEIL1. In a murine model, NEIL1 deficiency results in increased AFB₁-induced mutagenesis and carcinogenesis. Previous analyses identified several defective NEIL1 variants in human populations, including the temperature-sensitive A51V and glycosylase-deficient G83D variants. Herein, we report AFB₁-induced mutagenesis in mice expressing the A51V and G83D NEIL1 variants. Cohorts of 6-day-old Neil1^A51V and Neil1^G83D homozygous mice were injected with a single dose of AFB₁, and frequencies and spectra of mutations were assessed in liver genomes 2.5 months post-exposure using duplex sequencing. Comparisons of these data with previously generated data on AFB₁-induced mutagenesis in wild-type (WT) and Neil1^-/- mice revealed that although mutation frequencies in Neil1^A51V and Neil1^G83D animals were comparable to those measured in WT, elevated proportions of base substitutions at A/T sites were consistent with NEIL1 deficiency in both of these models. These findings suggest that individuals carrying these NEIL1 variants could be at an elevated risk for the development of AFB₁-induced HCC.