Short Communication: The imprinted and paternally expressed <i>MIMT1</i> lncRNA ortholog in pigs

A subset of mammalian genes undergoes genomic imprinting, and parent-of-origin-dependent expression of imprinted genes is required for normal development. Although around 40 imprinted genes have been documented in pigs, more detailed investigations into imprinted domains are needed to uncover the imprinting of uncharacterized porcine long non-coding RNAs (lncRNAs). Our study objectives were to investigate the imprinting status of orthologous MIMT1 lncRNA transcripts in pigs, which remains unidentified, and to explore their allelic expression in multiple tissues and conditions within the PEG3 imprinted domain. To this end, we compared the single-base resolution DNA methylome between parthenogenetic and control porcine embryos and identified a differentially methylated region (DMR) that is maternally methylated in the promoter region shared by PEG3 and MIMT1 genes. This was followed by a significantly higher expression of the MIMT1 lncRNA transcript in control embryos (p < 0.05), suggesting its imprinted paternal expression. Based on single nucleotide variants, further analyses revealed that, in addition to confirming the paternal monoallelic expression of PEG3, MIMT1 lncRNA transcripts were enriched in the porcine brain and monoallelically expressed in the brain and its subregions, with the expressed alleles being paternally derived. Our results provide a foundation for investigating the role of the imprinted MIMT1 lncRNA in the growth and development of pigs.