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Paternal imprinted genes (H19 and Gtl2) are pivotal for prenatal embryonic development in mice. Nongrowing oocytes and sperm- or oocyte-originated haploid embryonic stem cells (haESCs) carrying both H19-DMR (differentially DNA-methylated region) and IG (intergenic)-DMR deletions that partially mimic paternal imprinting of H19-Igf2 and Dlk1-Dio3 can be employed as sperm replacement to efficiently support full-term embryonic development. However, how H19-DMR and IG-DMR act together to regulate embryonic development is still largely unknown. Here, using androgenetic haESC (AG-haESC)-mediated semi-cloned (SC) technology, we showed that paternal H19-DMR and IG-DMR are not essential for pre-implantation development of SC embryos generated through injection of AG-haESCs into oocytes. H19-DMR plays critical roles before 12.5 days of gestation while IG-DMR is essential for late-gestation of SC embryos. Interestingly, we found that combined deletions of H19 and H19-DMR can further improve the efficiency of normal development of SC embryos at mid-gestation compared to DKO SC embryos. Transcriptome and histology analyses revealed that H19 and H19-DMR combined deletions rescue the placental defects. Furthermore, we showed that H19, H19-DMR and IG-DMR deletions (TKO) give rise to better prenatal and postnatal embryonic development of SC embryos compared to DKO. Together, our results indicate the temporal regulation of paternal imprinted loci during embryonic development.

The field of long noncoding RNA (lncRNA) research has been rapidly advancing in recent years. Technological advancements and deep-sequencing of the transcriptome have facilitated the identification of numerous new lncRNAs, many with unusual properties, however, the function of most of these molecules is still largely unknown. Some evidence suggests that several of these lncRNAs may regulate their own transcription in cis, and that of nearby genes, by recruiting remodeling factors to local chromatin. Notably, lncRNAs are known to exist at many imprinted gene clusters. Genomic imprinting is a complex and highly regulated process resulting in the monoallelic silencing of certain genes, based on the parent-of-origin of the allele. It is thought that lncRNAs may regulate many imprinted loci, however, the mechanism by which they exert such influence is poorly understood. This review will discuss what is known about the lncRNAs of major imprinted loci, and the roles they play in the regulation of imprinting.