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: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:To gain insight into transcriptional changes that occur in SmoM2 SHH-MB tumor cells that lack Pten and could account for the cell autonomous changes we observed in tumors of a mouse model, we performed single cell RNA-sequencing (scRNA-seq) of whole tumors dissected from P22 SmoM2 (Atoh1-FlpoER/+; R26MASTR/LSL-SmoM2) and P16 SmoM2-Ptenfl/fl (Atoh1-FlpoER/+; R26MASTR/LSL-SmoM2; Ptenfl/fl) mice (n = 2 per genotype).
Project description:RNAi-mediated knockdown of DICER1 and DROSHA, enzymes critically involved in miRNA biogenesis, has been postulated to affect the homeostasis and the angiogenic capacity of human endothelial cells. To re-evaluate this issue, we reduced the expression of DICER1 or DROSHA by RNAi-mediated knockdown and subsequently investigated the effect of these interventions on the angiogenic capacity of human umbilical vein endothelial cells (HUVEC) in vitro (proliferation, migration, tube formation, endothelial cell spheroid sprouting) and in a HUVEC xenograft assay in immune incompetent NSGTM mice in vivo. In contrast to previous reports, neither knockdown of DICER1 nor knockdown of DROSHA profoundly affected migration or tube formation of HUVEC or the angiogenic capacity of HUVEC in vivo. Furthermore, knockdown of DICER1 and the combined knockdown of DICER1 and DROSHA tended to increase VEGF-induced BrdU incorporation and induced angiogenic sprouting from HUVEC spheroids. Consistent with these observations, global proteomic analyses showed that knockdown of DICER1 or DROSHA only moderately altered HUVEC protein expression profiles but additively reduced, for example, expression of the angiogenesis inhibitor thrombospondin-1. In conclusion, global reduction of miRNA biogenesis by knockdown of DICER1 or DROSHA does not inhibit the angiogenic capacity of HUVEC. Further studies are therefore needed to elucidate the influence of these enzymes in the context of human endothelial cell-related angiogenesis.
Project description:DNA methylation data of a novel group of mesenchymal tumors with DICER1 alteration which includes two novel classes designated “low-grade mesenchymal tumor with DICER1 alteration” (LGMT DICER1) and “high-grade sarcoma with DICER1 alteration” (HGS DICER1), as well as the recently described class of primary intracranial sarcoma, DICER1-mutant (PIS DICER1)
Project description:DICER1 syndrome (OMIM 606241, 601200) is a rare autosomal dominant familial tumor predisposition disorder with a heterozygous DICER1 germline mutation. The most common tumor seen clinically is the pleuropulmonary blastoma (PPB), a lung neoplasm of early childhood which is classified on its morphologic features into four types (IR, I, II and III) with tumor progression over time within the first 4-5 years of life from the prognostically favorable cystic type I to the unfavorable solid type III. Following the initial report of PPB, its association with other cystic neoplasms was demonstrated in family studies. The detection of the germline mutation in DICER1 provided the opportunity to identify and continue to recognize a number seemingly unrelated extrapulmonary neoplasms: Sertoli-Leydig cell tumor, gynandroblastoma, embryonal rhabdomyosarcomas of the cervix and other sites, multinodular goiter, differentiated and poorly differentiated thyroid carcinoma, cervical-thyroid teratoma, cystic nephroma-anaplastic sarcoma of kidney, nasal chondromesenchymal hamartoma, intestinal juvenile-like hamartomatous polyp, ciliary body medulloepithelioma, pituitary blastoma, pineoblastoma, primary central nervous system sarcoma, embryonal tumor with multilayered rosettes-like cerebellar tumor, PPB-like peritoneal sarcoma, DICER1-associated presacral malignant teratoid neoplasm and other non-neoplastic associations. Each of these neoplasms is characterized by a second somatic mutation in DICER1. In this review, we have summarized the salient clinicopathologic aspects of these tumors whose histopathologic features have several overlapping morphologic attributes particularly the primitive mesenchyme often with rhabdomyoblastic and chondroid differentiation and an uncommitted spindle cell pattern. Several of these tumors have an initial cystic stage from which there is progression to a high grade, complex patterned neoplasm. These pathologic findings in the appropriate clinical setting should serve to alert the pathologist to the possibility of a DICER1-associated neoplasm and initiate appropriate testing on the neoplasm and to alert the clinician about the concern for a DICER1 mutation.