Lrif1 modulates Trim28-mediated repression of the Dux locus in mouse embryonic stem cells

Germline mutations in SMCHD1, DNMT3B and LRIF1 can cause facioscapulohumeral muscular dystrophy type 2 (FSHD2). FSHD is an epigenetic skeletal muscle disorder in which partial failure in heterochromatinization of the D4Z4 macrosatellite repeat causes spurious expression of the repeat-embedded DUX4 gene in skeletal muscle, ultimately leading to muscle weakness and wasting. All three proteins play a role in chromatin organization and gene silencing; however, their functional relationship has not been fully elucidated. Here, we show that knockdown of Lrif1 , but not of the other two FSHD2 genes, in mouse embryonic stem cells leads to modest upregulation of the 2-cell cleavage stage transcriptional program driven by the transcription factor Dux, which is the mouse functional homologue of human DUX4. Furthermore, we show that Lrif1 interacts with Trim28, a known Dux repressor and that this interaction is independent of Cbx proteins and Smchd1. We uncover that modest Dux upregulation in Lrif1 knockdown mESCs coincides with decreased Trim28 occupancy at the Dux locus. Together, our results provide evidence for a conserved function of Lrif1 in repressing an early zygotic genome activator in mice and humans.