Genetic variation in the NEIL2 DNA glycosylase gene is associated with oxidative DNA damage in BRCA2 mutation carriers

Abstract

In this report, we have tried to gain molecular insight into a single nucleotide polymorphism (SNP) in the NEIL2 gene previously identified as "cancer risk modifier" for BRCA2 mutation carriers. To that end, we studied the role of this SNP (rs804271) on NEIL2 transcriptional regulation, oxidative DNA damage and genome instability in two independent set of samples: The first one was a series of eighty-six BRCA1 and BRCA2 mutation carriers and eighty non-carrier controls in which we evaluated the effect of the SNP on NEIL2 gene expression and oxidative DNA damage accumulation. The second was a set of twenty lymphoblastoid cell lines (LCLs), thirteen BRCA1 mutation carriers and seven non-carriers control, that were used to analyze the correlation between NEIL2 mRNA and/or protein levels, the oxidative and the double stranded break (DSB) DNA damage levels. Our results suggest that an excessive production of NEIL2 enzyme, associated with the SNP, may have a deleterious effect modifying cancer risk susceptibility in BRCA2 mutation carriers. We hypothesize that due to the SNP impact on NEIL2 transcriptional upregulation, a cascade of events may converge in the accumulation of oxidative DNA damage and its posterior conversion into DSBs for this specific group of patients.

Keywords: BRCA1 and BRCA2; NEIL2 polymorphism cancer risk modifier; mRNA levels; oxidative DNA damage.

Figure 1

(A) Comparative analysis of NEIL2 mRNA expression according BRCA mutational status in FBOC series (BRCA1 and BRCA2 mutation carriers are compared with Controls). (B) Comparative analysis of NEIL2 mRNA expression according the SNP status ((Carriers (GT/TT) Vs Non-carriers (GG)) among the different FBOC groups (BRCA1, BRCA2 mutation carriers and BRCA1/BRCA2 non-carrier Controls). Bars represent the mean and the standard deviation for each group. Unpaired student t test was used to test for potential significant differences between means. (*p < 0.05).

Figure 2

(A) Correlation analysis between NEIL2 mRNA and protein levels. (B) Correlation analysis between NEIL2 mRNA levels and the relative amount of “NEIL2-lesions”. (C) Correlation analysis between the NEIL2 protein levels and the relative amount of “NEIL2-lesions”. Spearman test, was used to test whether correlation is significant. significant p-value when (p < 0.05).

Figure 3

(A) Comparative analysis of the relative number of NEIL2-lesions found at telomeres according BRCA mutational status in FBOC series (BRCA1 and BRCA2 mutation carriers are compared with Controls). (B) Comparative analysis of the relative amount of “NEIL2-lesions” found at telomeres according the SNP status ((Carriers (GT/TT) Vs Non-carriers (GG)) among the different BRCA mutational groups in FBOC series (BRCA1, BRCA2 mutation carriers and BRCA1/BRCA2 non-carrier Controls). Unpaired student t test was used to test for potential significant differences. (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001).

Figure 4. Correlation analysis between relative amount of “NEIL2-lesions” and the γH2AX nuclear intensity signal (DSBs)

Spearman test, was used to test whether correlation is significant. significant p-value when (p < 0.05).