An N-ethyl-N-Nitrosourea Mutagenesis Screen in Mice Reveals a Mutation in Nuclear Respiratory Factor 1 (Nrf1) Altering the DNA Methylation State and Correct Embryonic Development

Abstract

We have established a genome-wide N-ethyl-N-nitrosourea (ENU) mutagenesis screen to identify novel genes playing a role in epigenetic regulation in mammals. We hypothesize that the ENU mutagenesis screen will lead to the discovery of unknown genes responsible of the maintenance of the epigenetic state as the genes found are modifiers of variegation of the transgene green fluorescent protein (GFP) expression in erythrocytes, which are named MommeD. Here we report the generation of a novel mutant mouse line, MommeD46, that carries a new missense mutation producing an amino acid transversion (L71P) in the dimerization domain of Nuclear Respiratory Factor 1 (Nrf1). The molecular characterization of the mutation reveals a decrease in the Nrf1 mRNA levels and a novel role of Nrf1 in the maintenance of the DNA hypomethylation in vivo. The heritability of the mutation is consistent with paternal imprinting and haploinsufficiency. Homozygous mutants display embryonic lethality at 14.5 days post-coitum and developmental delay. This work adds a new epi-regulatory role to Nrf1 and uncovers unknown phenotypical defects of the Nrf1 hypomorph. The generated mouse line represents a valuable resource for studying NRF1-related diseases.

This research was funded by the National Health and Medical Research Council of Australia under Grant APP0552445, along with the 2020 Marie Skłodowska-Curie Individual Fellowship from the European Commission under Grant 893384, 2020 Miguel Servet fellowship from the Instituto de Salud Carlos III (Spanish National Institute of Health) under Grant CP20/00039 and European Social Fund (ESF) “Investing in your future”, and the Raine Medical Research Foundation under Grant RPG-004-19 given to A.S., and the Emergent Research Group Recognition Award from the University and Research Grants Management Agency of Catalonia (Spain) under Grant 2017SRG1620 given to M.A.S. The research was supported by CERCA Programme of Generalitat de Catalunya and the IRBLleida—Fundació Dr. Pifarré.