Together with SMCHD1, involved in chromosome X inactivation in females by promoting the compaction of heterochromatin (PubMed:23542155). Also able to repress the ligand-induced transcriptional activity of retinoic acid receptor alpha (RARA), possibly through direct recruitment of histone deacetylases (PubMed:17455211). Also required for silencing of the DUX4 locus in somatic cells (PubMed:32467133). Interacts with RARA (PubMed:17455211). Interacts with SMCHD1; leading to recruitment to inactivated chromosome X in females (PubMed:23542155). Interacts (via PxVxL motif) with HP1 (CBX1/HP1-beta, CBX3/HP1-gamma and CBX5/HP1-alpha) (PubMed:23542155). Localizes to Barr body; recruited by SMCHD1. Widely expressed, with the highest expression levels in heart, liver and placenta. The Pro-Xaa-Val-Xaa-Leu (PxVxL) motif mediates interaction with HP1 (CBX1/HP1-beta, CBX3/HP1-gamma and CBX5/HP1-alpha). The disease is caused by variants affecting distinct genetic loci, including the gene represented in this entry. The disease is caused by a LRIF1 homozygous variant resulting in loss of isoform 1, in the presence of an haplotype on chromosome 4 permissive for chromatin relaxation of the D4Z4 macrosatellite and inappropriate DUX4 expression. Deregulated expression of DUX4 in skeletal muscle can lead to cell death. Belongs to the LRIF1 family. Truncated N-terminus.