Abstract 132: The First Mouse Mutants of a Novel Epigenetic Modifier, Rearranged L-Myc Fusion, Display Defects in Heart Development
Rearranged L-Myc Fusion, Rlf, was recently identified as a novel epigenetic modifier from a mouse N-ethyl-N-nitrosourea mutagenesis screen. The mice used in this study carry a multi-copy green fluorescent protein (GFP) transgene linked to an erythroid specific α-globin promoter that is sensitive to epigenetic silencing. Three independent mouse lines with mutations in Rlf were each found to have a decrease in GFP expression, suggesting Rlf acts an epigenetic modifier. Our study is the first to reveal a role for Rlf in epigenetics.
Preliminary phenotyping has found loss of Rlf results in perinatal lethality. Late gestation homozygous null Rlf mutants were found to weigh significantly less than their heterozygous or wild type littermates. Histological analysis of mid gestation embryos has identified a potential heart defect in homozygous mutants. Rlf mutants display a thin compact layer, an overabundance of trabeculae and a fenestrated interventricular septum. The Rlf mutant phenotype is reminiscent of ventricular noncompaction defects observed in humans, such as left ventricular noncompaction cardiomyopathy.
RNA-seq analysis of mid gestation Rlf wild type and null hearts, prior to the observation of a cardiac defect, was undertaken to determine which pathways may be regulated by Rlf in the heart. More genes were observed to be significantly down-regulated in Rlf mutant hearts compared to wild types. Pathway analysis of differentially expressed genes showed genes involved in cell-cell adhesion, cell signalling, glycosylation and the Notch pathway were dysregulated. These findings indicate that Rlf may play a critical role in cardiac development.
Whole genome bisulphite sequencing of different embryonic tissue/stages has shown loss of Rlf results in an increase in methylation at a large number of distinct loci across the genome. Many of which were found to overlap sites reported to be putative regulatory elements, and histone marks associated with active or poised regulatory elements in the heart.
Our data suggest Rlf plays a key role in regulating gene expression pathways during heart development. These are the first mouse mutants available to study how Rlf functions as an epigenetic modifier and the phenotypic consequences of Rlf inactivation.
Author Disclosures: L.M. Bourke: None. S. Harten: None. V. Bharti: None. H. Oey: None. N. Whitelaw: None. E. Whitelaw: None.
- © 2015 by American Heart Association, Inc.