Abstract
Long non-coding RNAs (lncRNA) comprise a diverse group of non-protein-coding RNAs >200 bp in length that are involved in various normal cellular processes and disease states, and can affect coding gene expression through mechanisms in cis or in trans. Since the discovery of the first functional lncRNAs transcribed by RNA Polymerase II, H19 and Xist, many others have been identified and noted for their unusual transcriptional pattern, whereby expression from one chromosome homolog is strongly favored over the other, also known as mono-allelic or differential allelic expression. lncRNAs with differential allelic expression have been observed to play critical roles in developmental gene regulation, chromosome structure, and disease. Here, we will focus on known examples of differential allelic expression of lncRNAs and highlight recent research describing functional lncRNAs expressed from both imprinted and random mono-allelic expression domains.
Highlights
Sequencing of the human genome and other eukaryotic species from both close and distant lineages has revealed that the number and composition of protein-coding genes are unmistakably similar, fueling the idea that development of complex organisms may be in large part due to non-coding elements
While RNA Pol I and RNA Pol III are responsible for transcription of the majority of the ncRNA mass in higher eukaryotes, this review is focused on the Long non-coding RNAs (lncRNA) that are transcribed by RNA Pol II
We focus on the subset of lncRNAs that are expressed preferentially from one chromosome homolog, a phenomenon known as mono-allelic, or differential allelic expression (DAE)
Summary
Sequencing of the human genome and other eukaryotic species from both close and distant lineages has revealed that the number and composition of protein-coding genes are unmistakably similar, fueling the idea that development of complex organisms may be in large part due to non-coding elements. Within the context of dosage compensation on the X chromosome in females, epigenetic differences in DAE results in a mosaic pattern of expression with half of cells expressing the maternal allele and the other half expressing the paternal allele, a pattern of expression referred to as random mono-allelic expression (RME; Figure 1C). Given that inherent genomic heterozygosity results in slight differences between each allele of every gene, RME of even a small number of autosomal genes can generate an extremely high number of unique allelic combinations (Figure 1D) One such system involves the clustered protocadherins (Pcdhs), cell adhesion proteins expressed in the mammalian brain that display RME and form heteromultimeric cis-tetramers, allowing for a combinatorial “explosion” of the number of possible unique neuronal identities [18]. The lncRNA gene LINC01081, a regulator of the FOXF1 coding gene that is expressed in a parent- and tissue-specific manner, contains a variant that has an opposite association with LDL-C depending on its parent of origin context [29]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
