The effects of methyl-donor deficiency on mutation induction and transgenerational instability in mice
thesisposted on 07.06.2013, 14:54 by Mariel Voutounou
Data from various recent human and animal studies link epigenetic changes caused by dietary deficiency of methyl donors like folate with many common human diseases, including cancer (Esteller, 2007; Feinberg, 2007). However, the mechanisms underlying the observed links between epigenetic alterations and disease remain elusive (Ames & Wakimoto, 2002; Davis & Uthus, 2004). Since the development of cancer is a multistep process in which somatic cells acquire mutations in a specific clonal lineage (Loeb et al., 2003), it appears plausible that hypomethylation following dietary restriction may destabilise the genome of treated animals. To determine whether a methyl-donor deficient diet can cause longterm changes in the mutation rates of treated animals, BALB/c male mice were kept on a synthetic diet lacking in choline and folic acid for a duration of 8 weeks, directly after weaning. Sperm tissue was collected and analysed either at the end of treatment or 6 and 10 weeks after the end of dietary restriction. Single-molecule PCR technique was used to establish the frequency of mutation at the mouse expanded simple tandem repeat (ESTR) locus Ms6-hm in the treated males as well as their age-matched control groups. The results of this study showed that 8-weeks of dietary restriction did not affect ESTR mutation rate in the germline of treated male mice. Given that the epigenetic landscape of mammalian cell is not fixed and undergoes massive reprogramming during development (Reik, 2007), it can potentially be affected by a variety of environmental factors (Cropley et al., 2006; Waterland et al., 2006). To investigate any transgenerational effects of methyl-donor deficiency on genome stability, sperm and brain tissues from the first-generation offspring of treated animals were also analysed. The frequency of ESTR mutation in the offspring of treated males did not significantly differ from that in controls, therefore implying the lack of measurable transgenerational effects of paternal dietary restriction. Taken together, the results of this study suggest that the effects of methyl-donor deficient diet on mutation induction and transgenerational instability in mice are likely to be negligible (Voutounou et al., 2012).