IntroductionHematopoiesis is a tightly regulated process of proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs) toward mature blood cells. Lineage commitment and differentiation of HSPCs are orchestrated by transcription factors that are expressed at specific developmental stages. For example, CCAAT/ Enhancer-Binding Protein-Alpha (C/EBPA) is a master regulatory transcription factor that is not expressed in hematopoietic stem cells (HSCs), but starts to be expressed in a small fraction of multipotent progenitor (MPP) cells and increases steeply during the transition from the common myeloid progenitor (CMP) toward the GMP. C/EBPA drives granulopoiesis by controlling the expression of myeloid-specific genes. 1-2 miRNAs belong to a class of small (approximately 22 nt) noncoding RNAs. The RNA-induced silencing complex-bound miRNAs bind to complementary sequences that are predominantly located in the 3Ј-untranslated regions of target mRNAs and regulate gene expression by transcript destabilization and inhibition of protein translation. 3 Recently, the function of miRNAs in myeloid cells has been investigated using mouse models. For example, miRs-17/20/93/106 promote progenitor cell expansion by targeting Sequestosome-1-regulated pathways. 4 In addition, miR-223 negatively regulates myeloid progenitor proliferation and fine-tunes granulocyte differentiation and activity. 5 In addition, miR-146a inhibits the activity of both myeloid and lymphoid cell lineages and plays key roles in the regulation of inflammation. 6 DICER1 is an evolutionarily conserved member of the RNase III family of endoribonucleases that is critical for processing of specific precursor hairpin sequences, the so-called pre-miRNAs, into miRNAs. 7 Genetic deletion of Dicer1 in mice results in early embryonic mortality due to depletion of the Oct-4-positive pluripotent embryonic stem cell pool at embryonic day 6-7 (E6-E7). 8 A floxed Dicer1 allele (Dicer1 fl ) has been generated that allows conditional deletion of Dicer1 in a cell type-and developmental stage-specific fashion. 9 Hematopoietic lineage-specific conditional deletion of Dicer1 has revealed the involvement of miRNAs in the survival, maturation, and homeostasis of peripheral T lymphocytes and in Ab diversity and survival of B lymphocytes. [10][11][12] In addition, conditional Dicer1 deletion in osteoprogenitors using mice that have Cre recombinase under the transcriptional control of the osterix promoter (Osx-GFP-Cre) results in myeloid dysplasia and acute myelogenous leukemia with acquired genetic abnormalities but intact Dicer1. 13 Mouse primary HSCs are impaired by Dicer1 loss and are unable to reconstitute hematopoiesis. 14 In addition, conditional deletion of Ars2, another gene required for miRNA biogenesis, in HSCs results in BM failure and increased apoptosis of hematopoietic cells in thymus and spleen. 15 Therefore, the overall contribution of miRNAs to myeloid-lineage specification remains elusive. To address this issue, we generated a myeloid-specif...

Background— Genome-wide association studies enabled us to discover a large number of variants and genomic loci contributing to cardiovascular and metabolic disorders. However, because the vast majority of the identified variants are thought to merely be proxies for other functional variants, the causal mechanisms remain to be elucidated. We hypothesized that the part of the functional variants involved in deregulating cardiometabolic genes is located in microRNA (miRNA)-binding sites. Methods and Results— Using the largest genome-wide association studies available on glycemic indices, lipid traits, anthropometric measures, blood pressure, coronary artery diseases, and type 2 diabetes mellitus, we identified 11 067 variants that are associated with cardiometabolic phenotypes. Of these, 230 variants are located within miRNA-binding sites in the 3′-untranslated region of 155 cardiometabolic genes. Thirty-seven of 230 variants were found to fulfill our predefined criteria for being functional in their genomic loci. Ten variants were subsequently selected for experimental validation based on genome-wide association studies results, expression quantitative trait loci (eQTL) analyses, and coexpression of their host genes and regulatory miRNAs in relevant tissues. Luciferase reporter assays revealed an allele-specific regulation of genes hosting the variants by miRNAs. These cotransfection experiments showed that rs174545 ( FADS1 :miR-181a-2), rs1059611 ( LPL :miR-136), rs13702 ( LPL :miR-410), rs1046875 ( FN3KRP :miR-34a), rs7956 ( MKRN2 :miR-154), rs3217992 ( CDKN2B :miR-138-2-3p), and rs11735092 ( HSD17B13 :miR-375) decrease or abrogate miRNA-dependent regulation of the genes. Conversely, 2 variants, rs6857 ( PVRL2 :miR-320e) and rs907091 ( IKZF3 :miR-326), were shown to enhance the activity of miRNAs on their host genes. Conclusions— We provide evidence for a model in which polymorphisms in miRNA-binding sites can both positively and negatively affect miRNA-mediated regulation of cardiometabolic genes.

MicroRNAs (miRNAs) serve as key post-transcriptional regulators of gene expression. Genetic variation in miRNAs and miRNA-binding sites may affect miRNA function and contribute to disease risk. Here, we investigated the extent to which variants within miRNA-related sequences could constitute a part of the functional variants involved in developing Alzheimer’s disease (AD), using the largest available genome-wide association study of AD. First, among 237 variants in miRNAs, we found rs2291418 in the miR-1229 precursor to be significantly associated with AD (p-value = 6.8 × 10−5, OR = 1.2). Our in-silico analysis and in-vitro miRNA expression experiments demonstrated that the variant’s mutant allele enhances the production of miR-1229-3p. Next, we found miR-1229-3p target genes that are associated with AD and might mediate the miRNA function. We demonstrated that miR-1229-3p directly controls the expression of its top AD-associated target gene (SORL1) using luciferase reporter assays. Additionally, we showed that miR-1229-3p and SORL1 are both expressed in the human brain. Second, among 42,855 variants in miRNA-binding sites, we identified 10 variants (in the 3′ UTR of 9 genes) that are significantly associated with AD, including rs6857 that increases the miR-320e-mediated regulation of PVRL2. Collectively, this study shows that miRNA-related variants are associated with AD and suggests miRNA-dependent regulation of several AD genes.

MicroRNAs (miRNAs) are small noncoding RNAs that serve as key regulators of gene expression. They have been shown to be involved in a wide range of biological processes including neurodegenerative diseases. Genetic variants in miRNAs or miRNA-binding sites on their target genes could affect miRNA function and contribute to disease risk. Here, we investigated the association of miRNA-related genetic variants with Parkinson disease (PD) using data from the largest GWAS on PD. Of 243 miRNA variants, we identified rs897984:T>C in miR-4519 (P value = 1.3×10(-5) and OR = 0.93) and rs11651671:A>G in miR-548at-5p (P value = 1.1×10(-6) and OR = 1.09) to be associated with PD. We showed that the variant's mutant alleles change the secondary structure and decrease expression level of their related miRNAs. Subsequently, we highlighted target genes that might mediate the effects of miR-4519 and miR-548at-5p on PD. Among them, we experimentally showed that NSF is a direct target of miR-4519. Furthermore, among 48,844 miRNA-binding site variants, we found 32 variants (within 13 genes) that are associated with PD. Four of the host genes, CTSB, STX1B, IGSF9B, and HSD3B7, had not previously been reported to be associated with PD. We provide evidence supporting the potential impact of the identified miRNA-binding site variants on miRNA-mediated regulation of their host genes.