An ENU mutagenesis screen identifies novel and known genes involved in epigenetic processes in the mouse

Abstract

BackgroundWe have used a sensitized ENU mutagenesis screen to produce mouse lines that carry mutations in genes required for epigenetic regulation. We call these lines Modifiers of murine metastable epialleles (Mommes).ResultsWe report a basic molecular and phenotypic characterization for twenty of the Momme mouse lines, and in each case we also identify the causative mutation. Three of the lines carry a mutation in a novel epigenetic modifier, Rearranged L-myc fusion (Rlf), and one gene, Rap-interacting factor 1 (Rif1), has not previously been reported to be involved in transcriptional regulation in mammals. Many of the other lines are novel alleles of known epigenetic regulators. For two genes, Rlf and Widely-interspaced zinc finger (Wiz), we describe the first mouse mutants. All of the Momme mutants show some degree of homozygous embryonic lethality, emphasizing the importance of epigenetic processes. The penetrance of lethality is incomplete in a number of cases. Similarly, abnormalities in phenotype seen in the heterozygous individuals of some lines occur with incomplete penetrance.ConclusionsRecent advances in sequencing enhance the power of sensitized mutagenesis screens to identify the function of previously uncharacterized factors and to discover additional functions for previously characterized proteins. The observation of incomplete penetrance of phenotypes in these inbred mutant mice, at various stages of development, is of interest. Overall, the Momme collection of mouse mutants provides a valuable resource for researchers across many disciplines.

Facioscapulohumeral Muscular Dystrophy As a Model for Epigenetic Regulation and Disease

“…ICF patients have extreme hypomethylation of all D4Z4 repeats, including the 4q35 macrosatellite, but show no indications of muscle weakness; however, the majority of ICF patients die before the typical age of onset in FSHD. Interestingly, as with Smchd1, mutations in Dnmt3b were identified in the same screen for modifiers of metastable epialleles (36). In future studies, we may find that mutations in DNMT3B, similar to SMCHD1, result in FSHD2 or modify the severity of FSHD1.…”

“…The identities of many of the underlying mutations have been recently reported and, not surprisingly, many occur in genes with known functions in DNA methylation and chromatin modification (4,13,14,36,37). The screen revealed both enhancers and suppressors of epigenetic variegation, including DNMTs (Dnmt1 and Dnmt3b), HMTs (Setdb1, Suv39h1), a histone deacetylase (Hdac1), components of chromatin remodeling machines (Smarca4/BRG1, Smarca5, Smarcc1/BAF155, Pbrm1/BAF180, and Hdac1), epigenetic regulators (Smchd1, Uhrf1, Trim28/KAP1/TIF1b, and WIZ), telomeric proteins (Rif1, Smchd1), chromatin-dependent transcriptional regulators (Brd1, Rlf, and Baz1b), and the translation initiation factor eIF3h.…”

Loss of Rearranged L-Myc Fusion (RLF) results in defects in heart development in the mouse

“…Among the mutant lines produced in this screen, three independent lines carried mutations in Rlf -MommeD8, MommeD28, and MommeD34 (Daxinger et al, 2013;Blewitt et al, 2005). Identification of Rlf as the gene carrying the causative mutations in these lines has been described previously (Daxinger et al, 2013).…”

“…Mutations in genes involved in the establishment and/or maintenance of epigenetic regulation in Although only a handful of epigenetic regulators have been implicated in human cases of CHD, mouse studies from our laboratory and others point to a broader role of epigenetic pathways in this set of diseases. Developmental heart defects are observed in mice null for a wide range of epigenetic modifiers, including the DNA methyltransferase Dnmt3b (Ueda et al, 2006), the chromatin remodeller Pbrm1 (Daxinger et al, 2013;Wang et al, 2004) and the histone modifying gene Dot1l (Nguyen et al, 2011).…”

Lung: Translocations in Small Cell Carcinoma

“…Depletion of Rlf leads to DNA hypermethylation in the mouse. RLF is likely to be involved in epigenetic processes (Daxinger et al, 2013), RLF is translocated with 10 different partners (herein below) in SCLCs; -BCL2L1 (20q11) an inhibitor of cell death, involved in various cancers, translocated with 7 different partners (herein below) in SCLCs; -PVT1 (8q24), a non-protein coding and oncofetal gene, translocated with various partners in: breast cancer, Ewing/PNET spectrum, and hematological malignancies, and with 7 different partners (herein below) in SCLCs; PVT1 is a hotspot for chromosomal breaks during MYC amplification (L'Abbate et al, 2014). -Other genes recurrently found are HM13 (20q11), translocated with 3 different partners, and MYCL, BMP8B (1p34), CAP1 (1p34), CREBBP (16p13), and DNM2 (19p13), implicated twice each.…”