Studies in large-scale genome sequencing have shown that only 2% of the mammalian genome encodes mRNAs, but the most part is transcribed as long and short non-coding RNAs (ncRNAs). The ncRNAs with gene regulatory functions are starting to be seen as a common feature of mammalian gene regulation. Genomic imprinting is a form of epigenetic regulation and imprinted genes are silenced in a parental-specific manner. Imprinted genes tend to occur in clusters and ncRNAs have been found at all well-characterized imprinted clusters. Although the exact mechanism how imprinted ncRNA regulates gene expression remains largely unknown, it is general accepted that imprinted ncRNAs binds to chromatin modifying complexes, such as PRC2, TRX, and G9a, and generates specific silencing of genomic loci both in cis and trans. Imprinting is associated with many human diseases or syndromes (e.g. Prader-Willi, Angelman, Beckwith-Wiedemann, Retts, and Silver-Russell syndromes) and various cancers (e.g. breast, prostate, and colorectal cancers), but its role in leukemogenesis remain elusive. In this present study, a panel of 24 human imprinted ncRNAs genes, including ampd3, cpa4, snuf, rasgrf1, slc22a3, lgf2, treb3c, gabrb3, c15orf2, sfmbt2, rtl1, copg2, h19, l3mbtl, ppp1r9a, tspan32, lnpp5f, impact, nr3251, nr3252, znf215, prim2, peg3as and znf264, has been mined using Bioinformatics approach. We investigated the expression of these imprinted ncRNA genes using real-time quantitative RT-PCR in 67 newly-diagnosed acute myeloid leukemia patients with normal karyotypes (AML-NK), 22 AML patients with abnormal karyotypes (AML-AK), and 39 healthy individuals. In AML-NK patients, the expression of lgf2, h19, slc22a3, copg2, and impact were significantly upregulated than in healthy individuals (p < 0.0001). In AML-AK patients, besides lgf2, h19 and impact genes, ampd3 and gabrb3 were also significantly upregulated than in healthy individuals (p < 0.0001). Expression of igf2 was almost undetectable in healthy individuals but drastically increased in all AML patients. Both lgf2 and h19 were significantly increased in both AML-NK and AML-AK patients. From our preliminary results, it is reasonable to hypothesize that loss imprinting of lgf2/h19 is critical for the leukemogenesis of AML and under NK or AK conditions different additional ncRNAs are activated and affect different imprinted gene expression and thus leading to different clinical outcomes. Based on our findings, we will further perform methylation analysis of promoter CpG sites in AML patients to investigate if hypomethylation is responsible for the upregulation of these imprinted ncRNAs. We will also carry out in vitro functional analysis to elucidate the functions and mechanisms of these imprinted ncRNAs in AML tumorigenesis. Updated results of these analysis will be presented at the meeting.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.