Project description:Recurrent somatic hotspot mutations of DICER1 appear to be clustered around each of four critical metal binding residues in the RNase IIIB domain of DICER1. This domain is responsible for cleavage of the 3’ end of the 5p-miRNA strand of a pre-mRNA hairpin. To investigate the effects of these cancer-associated “hotspot” mutations we engineered mouse Dicer1-deficient ES cells to express wild-type and an allelic series of the mutant human DICER1 variants. Global miRNA and mRNA profiles from cells carrying the metal binding site mutations were compared to each other and wild-type human DICER1. The miRNA and mRNA profiles generated through the expression of the hotspot mutations were virtually identical, and the DICER1 hotspot mutation carrying cells were distinct from both wild-type and Dicer1-deficient cells. Further, miRNA profiles showed mutant DICER1 results in a dramatic loss in processing of mature 5p-miRNA strands but were still able to create 3p-strand miRNAs. Messenger-RNA profile changes were consistent with the loss of 5p-strand miRNAs and showed enriched expression for predicted targets of the lost 5p derived miRNAs. We therefore conclude that cancer-associated somatic hotspot mutations of DICER1, affecting any one of four metal binding residues in the RNase IIIB domain, are functionally equivalent with respect to miRNA-processing and are hypomorphic alleles, yielding a global loss in processing of mature 5p-strand miRNA. We further propose that this resulting 3p-strand bias in mature miRNA expression likely underpins the oncogenic potential of these hotspot mutations. A total of 28 Affymetrix Mouse Gene ST arrays were done for mRNA expression profiling of various DICER1 mutants (n=14), wildtype controls (n=6), vector only (n=3) and parental cell lines (n=5).
Project description:Recurrent somatic hotspot mutations of DICER1 appear to be clustered around each of four critical metal binding residues in the RNase IIIB domain of DICER1. This domain is responsible for cleavage of the 3’ end of the 5p-miRNA strand of a pre-mRNA hairpin. To investigate the effects of these cancer-associated “hotspot” mutations we engineered mouse Dicer1-deficient ES cells to express wild-type and an allelic series of the mutant human DICER1 variants. Global miRNA and mRNA profiles from cells carrying the metal binding site mutations were compared to each other and wild-type human DICER1. The miRNA and mRNA profiles generated through the expression of the hotspot mutations were virtually identical, and the DICER1 hotspot mutation carrying cells were distinct from both wild-type and Dicer1-deficient cells. Further, miRNA profiles showed mutant DICER1 results in a dramatic loss in processing of mature 5p-miRNA strands but were still able to create 3p-strand miRNAs. Messenger-RNA profile changes were consistent with the loss of 5p-strand miRNAs and showed enriched expression for predicted targets of the lost 5p derived miRNAs. We therefore conclude that cancer-associated somatic hotspot mutations of DICER1, affecting any one of four metal binding residues in the RNase IIIB domain, are functionally equivalent with respect to miRNA-processing and are hypomorphic alleles, yielding a global loss in processing of mature 5p-strand miRNA. We further propose that this resulting 3p-strand bias in mature miRNA expression likely underpins the oncogenic potential of these hotspot mutations.
Project description:DICER1 plays a critical role in microRNA (miRNA) biogenesis. Recurrent somatic “hotspot” mutations at four mental binding sites within the RNase IIIb domain of DICER1, were identified in ovarian sex cord-stromal tumors and have since been described in other pediatric tumors. In this study, we identified and characterized DICER1 hotspot mutations in endometrial cancers derived from The Cancer Genome Atlas (TCGA) and our local tumor bank. DICER1 hotspot mutations are found in ~2% of endometrial tumors. Using Illumina and Sanger targeted resequencing we observed biallelic DICER1 mutations in more than 50% of cases with hotspot mutations and identified an additional recurrent mutation G1809R in 2 cases. Through small RNA deep sequencing and real-time PCR, we demonstrated mutations that add a positively charged side chain to residue 1809 have similar detrimental effects on 5p miRNA production as mutations at metal binding sites. In one case G1809R was compound heterozygous with a germline S839F mutation, which contributes to loss of DICER1 expression by promoting protein degradation. As expected, 5p miRNAs are globally reduced in tumors and cell lines with hotspot mutations. Pathway analysis of gene expression profiles indicated that genes derepressed due to loss of 5p miRNAs are strongly associated with cell cycle related pathways. Using a Dicer null cell line model, we demonstrated that DICER1 hotspot mutants abolished the inhibitory effects of wildtype DICER1 on cell proliferation upon re-expression. Furthermore, targets of let-7 family miRNAs are enriched among the upregulated genes, suggesting loss of let-7 may be impacting downstream pathways.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:The aim of the study was to investigate whether the trefoil peptide genes, in concerted action with a miRNA regulatory network, were contributing to nutritional maintrenance. Using a Tff2 knock-out mouse model, 48 specific miRNAs were noted to be significantly deregulated when compared to the wild type strain.
Project description:The aim of the study was to investigate whether the trefoil peptide genes, in concerted action with a miRNA regulatory network, were contributing to nutritional maintrenance. Using a Tff3 knock-out mouse model, 21 specific miRNAs were noted to be significantly deregulated when compared to the wild type strain.
Project description:Co-chaperone Aha1 activates HSP90 ATPase to promote the folding of client proteins. However, the client proteins of Aha1 are largely unknown. By employing ascorbate peroxidase (APEX) based proximity labeling, we identified 32 proximity proteins of HSP90 that are modulated by genetic depletion of Aha1. Among them, Dicer1 is one of the top-ranked proteins, which were further confirmed by streptavidin pull-down followed by Western blot analysis, demonstrating the reliability of the approach. Flag pull-down result showed interactions between endogenous HSP90 and Dicer1 and Aha1. The Dicer1 level is regulated synergistically by Aha1 and HSP90. Maturation-dependent interaction results showed a preferential binding of Aha1 and HSP90 to nascently translated Dicer1. Reconstitution of Aha1-depleted cells with WT Aha1 restored Dicer1 level, while the HSP90-binding-defective E67K mutant exhibited partial restoration. Moreover, knockdown of Aha1 and inhibition of HSP90 can diminish the levels of mature miRNA, let-7b and mir-30a. Overall, our study uncovers, for the first time, Dicer1 and transporter proteins as clients of Aha1 and HSP90.
Project description:DICER1 syndrome is a tumor predisposition syndrome caused by familial genetic mutations in DICER1. Pathogenic variants of DICER1 have been discovered in many rare cancers, including cystic liver tumors. However, the molecular mechanisms underlying liver lesions induced by these variants remain unclear. In the present study, we sought to gain a better understanding of the pathogenesis of these variants by generating a mouse model of liver-specific DICER1 syndrome. The mouse model developed bile duct hyperplasia with fibrosis, similar to congenital hepatic fibrosis, as well as cystic liver tumors resembling those in Caroli's syndrome, intrahepatic cholangiocarcinoma, and hepatocellular carcinoma. Interestingly, the mouse model of DICER1 syndrome showed abnormal formation of primary cilia in the bile duct epithelium, which is a known cause of bile duct hyperplasia and cyst formation. These results indicated that DICER1 mutations contribute to cystic liver tumors by inducing defective primary cilia. The mouse model generated in this study will be useful for elucidating the potential mechanisms of tumorigenesis induced by DICER1 variants and for obtaining a comprehensive understanding of DICER1 syndrome.
Project description:To confirm the lack of expression of most miRNAs in DICER1 knock-out cell lines, we performed miRNA microarray analysis. The purpose of this study is to classify DICER1-dependent Small RNA and independent Small RNA using DICER1 cells using deficient cell lines, and to identify novel small RNA and small RNA processing mechanisms.