Sinonasal Hamartomas.

A variety of hamartomatous lesions have been described in the sinonasal tract. These include respiratory epithelial adenomatoid hamartoma (REAH), seromucinous hamartoma (SH), and nasal chondromesenchymal hamartoma (NCMH). REAH and SH, demonstrate significant morphologic overlap with each other and with reactive conditions, while also being described to develop in association with other distinct tumors entities. NCMH affects a specific patient population with a specific molecular driver. The hamartomatous/neoplastic nature of REAH and SH are a topic of debate. There are emerging sinonasal hamartomatous entities that appear related to REAH and SH.

Shedding light on the DICER1 mutational spectrum of uncertain significance in malignant neoplasms.

The Dicer protein is an indispensable player in such fundamental cell pathways as miRNA biogenesis and regulation of protein expression in a cell. Most recently, both germline and somatic mutations in DICER1 have been identified in diverse types of cancers, which suggests Dicer mutations can lead to cancer progression. In addition to well-known hotspot mutations in RNAase III domains, DICER1 is characterized by a wide spectrum of variants in all the functional domains; most are of uncertain significance and unstated clinical effects. Moreover, various new somatic DICER1 mutations continuously appear in cancer genome sequencing. The latest contemporary methods of variant effect prediction utilize machine learning algorithms on bulk data, yielding suboptimal correlation with biological data. Consequently, such analysis should be conducted based on the functional and structural characteristics of each protein, using a well-grounded targeted dataset rather than relying on large amounts of unsupervised data. Domains are the functional and evolutionary units of a protein; the analysis of the whole protein should be based on separate and independent examinations of each domain by their evolutionary reconstruction. Dicer represents a hallmark example of a multidomain protein, and we confirmed the phylogenetic multidomain approach being beneficial for the clinical effect prediction of Dicer variants. Because Dicer was suggested to have a putative role in hematological malignancies, we examined variants of DICER1 occurring outside the well-known hotspots of the RNase III domain in this type of cancer using phylogenetic reconstruction of individual domain history. Examined substitutions might disrupt the Dicer function, which was demonstrated by molecular dynamic simulation, where distinct structural alterations were observed for each mutation. Our approach can be utilized to study other multidomain proteins and to improve clinical effect evaluation.

Somatic DICER1-Mutant Benign Thyroid Nodules in Adults: A Group of Follicular Nodular Disease With Continuous Growth.

BACKGROUND: Germline DICER1 mutations cause familial multinodular goiter (MNG). However, the prevalence of somatic DICER1 mutations in non-MNG benign thyroid nodules and their characteristics remain unknown. METHODS: Adult-onset thyroid nodules with a pathological diagnosis were genotyped via targeted sequencing. DICER1-mutant nodules were assessed clinically and pathologically. Organoids were established to investigate follicular formation and growth. Transcriptomic analysis was conducted to evaluate transcriptional features, which were validated by immunofluorescence. RESULTS: Among 931 adult-onset thyroid nodules, we identified 13 benign thyroid nodules with DICER1 hotspot mutations. The majority harbored a somatic DICER1 hotspot mutation with a somatic DICER1 truncating variant. Clinically, 38.5% of the DICER1-mutant nodules exhibited substantial growth. DICER1-mutant nodules with durations longer than 2 years were substantially enlarged (P=.0448). Pathologically, all DICER1-mutant nodules were defined as thyroid follicular nodular disease (TFND). The TFND nodules with DICER1 mutations grew faster than those with wild-type DICER1. Organoid culture of a DICER1-mutant nodule revealed increased active follicular formation. Compared with the normal thyroid tissues, the DICER1-mutant nodules had comparable thyroid differentiation scores, significantly higher ERK scores (P=.0141) and lower epithelial‒mesenchymal transition scores (P=.0001). Moreover, the expression of genes related to follicular polarity, such as CDH16, SLC5A5, TSHR and TPO, was downregulated in the DICER1-mutant nodules. CONCLUSIONS: Somatic DICER1 two-hit mutations represent a notable percentage in adult TFND patients, and DICER1-mutant benign thyroid nodules were characterized by continuous growth.

MicroRNA and Rare Human Diseases.

BACKGROUND: The role of microRNAs (miRNAs) in the pathogenesis of rare genetic disorders has been gradually discovered. MiRNAs, a class of small non-coding RNAs, regulate gene expression by silencing target messenger RNAs (mRNAs). Their biogenesis involves transcription into primary miRNA (pri-miRNA), processing by the DROSHA-DGCR8 (DiGeorge syndrome critical region 8) complex, exportation to the cytoplasm, and further processing by DICER to generate mature miRNAs. These mature miRNAs are incorporated into the RNA-induced silencing complex (RISC), where they modulate gene expression. METHODS/RESULTS: The dysregulation of miRNAs is implicated in various Mendelian disorders and familial diseases, including DICER1 syndrome, neurodevelopmental disorders (NDDs), and conditions linked to mutations in miRNA-binding sites. We summarized a few mechanisms how miRNA processing and regulation abnormalities lead to rare genetic disorders. Examples of such genetic diseases include hearing loss associated with MIR96 mutations, eye disorders linked to MIR184 mutations, and skeletal dysplasia involving MIR140 mutations. CONCLUSIONS: Understanding these molecular mechanisms is crucial, as miRNA dysregulation is a key factor in the pathogenesis of these conditions, offering significant potential for the diagnosis and potential therapeutic intervention.

Understanding the Dosage-Dependent Role of Dicer1 in Thyroid Tumorigenesis.

Tumors originating from thyroid follicular cells are the most common endocrine tumors, with rising incidence. Despite a generally good prognosis, up to 20% of patients experience recurrence and persistence, highlighting the need to identify the underlying molecular mechanisms. Dicer1 has been found to be altered in papillary thyroid cancer (PTC). Studies suggest that Dicer1 functions as a haploinsufficient tumor suppressor gene: partial loss promotes tumorigenesis, while complete loss prevents it. To investigate the effects of partial or total Dicer1 loss in PTC in vitro, we generated stable Dicer1 (+/-) cell lines from TPC1 using CRISPR-Cas9, though no Dicer1 (-/-) lines could be produced. Therefore, siRNA against Dicer1 was transfected into Dicer1 (+/-) cell lines to further decrease its expression. Transcriptomic analysis revealed changes in proliferation and cell locomotion. BrdU staining indicated a slow-down of the cell cycle, with fewer cells in S phase and more in G0-G1-phase. Additionally, transwell assays showed decreased invasion and migration after Dicer1 knockdown by siRNA. Moreover, Dicer1 overexpression led to decreased proliferation, invasion, and increased apoptosis. Our findings deepen the understanding of Dicer1's role in thyroid cancer, demonstrating that both complete elimination and overexpression of Dicer1 inhibit thyroid oncogenesis, highlighting Dicer1 as a promising target for novel therapeutic strategies.

Establishment and Characterization of a Novel Pleuropulmonary Blastoma Cell Line.

PURPOSE: Pleuropulmonary blastoma (PPB) is an infrequently encountered childhood malignant intrathoracic neoplasm associated with unfavorable clinical behavior. Since a well-characterized preclinical model is essential for developing competent agents for PPB, we aim to establish and characterize the world's first cell line of PPB, and attempt to perform the cytotoxicity assay on the PPB cell line. EXPERIMENTAL DESIGN: The index case is a 2-year-old female who developed a right thoracic tumor that was surgically removed and treated with multi-agent chemotherapy. The patient is free from recurrence, although it was 9 years after the diagnosis when she developed a thyroid tumor. We performed in vitro cultivation of the isolated neoplastic cells from the tumor, cytogenetic findings and molecular analysis, and tetrazolium colorimetric assay. RESULT: The histology was consistent with PPB. Serial passage of cultivation produced a continuously growing cell line, KCMC-PPB-1. Conventional cytogenetic analysis of the established cell line revealed complex numerical and structural chromosomal abnormalities, including add(17)(p11). Mutation analysis on the cultured cells revealed amino-acid substitution mutation on exon 4 of TP53 (NM_001276760.3:c.212_213delTG; NP_001263689.1:p.Leu72ArgfsTer37) and compound heterozygous mutations of DICER1 (NM_177438.3:c. 4910C>A; NP_803187.1:Ser1637* and NM_177438.3:c. 5114A>T; NP_803187.1:Glu1705Val). The cultivated cells demonstrated vulnerability to bortezomib on cytotoxicity assay. CONCLUSION: Our KCMC-PPB-1 is the first genuine, molecularly characterized PPB cell line. The cell line is transplantable to nu/nu mice; therefore, it is suitable for a preclinical model for new drug development. The cytotoxicity assay demonstrated that bortezomib is active in the current PPB model.

Simultaneous occurrence of thyroblastoma and papillary carcinoma.

Not required for Clinical Vignette.

Sphingosine kinase 2 controls the aggressive phenotype of oral squamous cell carcinoma by regulating miR-205 and miR-296 through p53.

Alterations in microRNAs, p53, and sphingolipid metabolism have been associated with head and neck squamous cell carcinoma (HNSCC). However, sphingosine kinase 2, a critical enzyme in sphingolipid metabolism, is poorly understood in HNSCC. Our aim was to investigate how SK2 and p53 interact to regulate miR-205 and miR-296. Analysis of small-RNA-seq data from non-tumor oral keratinocytes with SK2 overexpression (NOK-SK2) compared to NOK-control (NOK- Ø) revealed differential expression of more than 100 miRNAs being half regulated by p53. The expression of miR-205 was downregulated, and miR-296 was upregulated in NOK-SK2 cells; however, cells with SK2 knockdown and p53 overexpression showed an opposite profile. Proteins involved in miRNA biogenesis were increased in NOK-SK2 cells while their levels were decreased in NOK-SK2 cells with p53 overexpression. miR-205 mimic and miR-296 inhibitor decreased the aggressiveness and cancer stem-like cells in oral keratinocytes and oral carcinoma cells with SK2 deregulation. Overexpression of miR-205 in HN12-SK2 cells decreased tumor formation capacity and NOK-SK2 cells abrogated the tumor growth in mice. Our results indicate crosstalk between SK2 and p53 in regulating miR-205 and miR-296, which could be potential targets for HNSCC therapy.

UVB radiation suppresses Dicer expression through ß-catenin.

Ultraviolet (UV) rays prompt a natural response in epidermal cells, particularly within melanocytes. The changes in gene expression and related signaling pathways in melanocytes following exposure to UVR are still not entirely understood. Our findings reveal that UVB irradiation suppresses the expression of Dicer. This repression is intricately linked to the activation of the PI3K, RSK, and WNT/ß-catenin signaling pathways and is directly associated with transcriptional repression by ß-catenin. Notably, we have identified specific binding sites for the LEF/ß-catenin complex in the Dicer promoter. Collectively, these results emphasize the significance of the UV-induced pathway involving LEF/ß-catenin, which impacts Dicer expression. UV radiation also reduced the levels of specific miRNAs known to be important in the biology of melanocytes. This pathway holds potential importance in governing melanocyte physiology.

Schwann cell-derived exosomes ameliorate peripheral neuropathy induced by ablation of dicer in Schwann cells.

Background: MicroRNAs (miRNAs) in Schwann cells (SCs) mediate peripheral nerve function. Ablating Dicer, a key gene in miRNA biogenesis, in SCs causes peripheral neuropathy. Exosomes from healthy SCs (SC-Exo) ameliorate diabetic peripheral neuropathy in part via miRNAs. Thus, using transgenic mice with conditional and inducible ablation of Dicer in proteolipid protein (PLP) expressing SCs (PLP-cKO), we examined whether SC-Exo could reduce peripheral neuropathy in PLP-cKO mice. Methods: PLP-cKO mice at the age of 16 weeks (8 week post-Tamoxifen) were randomly treated with SC-Exo or saline weekly for 8 weeks. Age-and sex-matched wild-type (WT) littermates were used as controls. Peripheral neurological functions, sciatic nerve integrity, and myelination were analyzed. Quantitative RT-PCR and Western blot analyses were performed to examine miRNA and protein expression in sciatic nerve tissues, respectively. Results: Compared to the WT mice, PLP-cKO mice exhibited a significant decrease in motor and sensory conduction velocities, thermal sensitivity, and motor coordination. PLP-cKO mice exhibited substantial demyelination and axonal damage of the sciatic nerve. Treatment of PLP-cKO mice with SC-Exo significantly ameliorated the peripheral neuropathy and sciatic nerve damage. PLP-cKO mice showed a substantial reduction in a set of Dicer-related miRNAs known to regulate myelination, axonal integrity, and inflammation such as miR-138, -146a and - 338 in the sciatic nerve. In addition, PLP-cKO mice exhibited significant reduction of myelin forming proteins, early growth response 2 (EGR2) and sex determining region Y-box10 (Sox10), but significantly increased myelination inhibitors, Notch1, c-Jun, and Sox2 and the axonal growth inhibitor phosphatase and tens in homolog (PTEN). However, SC-Exo treatment reversed the PLP-cKO altered miRNAs and proteins. Conclusion: This study demonstrates that exogenous SC-Exo ameliorate peripheral neuropathy induced by Dicer ablation in PLP expressing SCs. The therapeutic benefit may be mediated by the SC-Exo altered miRNAs and their targeted genes.

Next-Cell Hypothesis: Mechanism of Obesity-Associated Carcinogenesis.

Higher body fat content is related to a higher risk of mortality, and obesity-related cancer represents approximately 40% of all cancer patients diagnosed each year. Furthermore, epigenetic mechanisms are involved in cellular metabolic memory and can determine one's predisposition to being overweight. Low-grade chronic inflammation, a well-established characteristic of obesity, is a central component of tumor development and progression. Cancer-associated adipocytes (CAA), which enhance inflammation- and metastasis-related gene sets within the cancer microenvironment, have pro-tumoral effects. Adipose tissue is a major source of the exosomal micro ribonucleic acids (miRNAs), which modulate pathways involved in the development of obesity and obesity-related comorbidities. Owing to their composition of cargo, exosomes can activate receptors at the target cell or transfer molecules to the target cells and thereby change the phenotype of these cells. Exosomes that are released into the extracellular environment are internalized with their cargo by neighboring cells. The tumor-secreted exosomes promote organ-specific metastasis of tumor cells that normally lack the capacity to metastasize to a specific organ. Therefore, the communication between neighboring cells via exosomes is defined as the "next-cell hypothesis." The reciprocal interaction between the adipocyte and tumor cell is realized through the adipocyte-derived exosomal miRNAs and tumor cell-derived oncogenic miRNAs. The cargo molecules of adipocyte-derived exosomes are important messengers for intercellular communication involved in metabolic responses and have very specific signatures that direct the metabolic activity of target cells. RNA-induced silencing regulates gene expression through various mechanisms. Destabilization of DICER enzyme, which catalyzes the conversion of primary miRNA (pri-miRNA) to precursor miRNA (pre-miRNA), is an important checkpoint in cancer development and progression. Interestingly, adipose tissue in obesity and tumors share similar pathogenic features, and the local hypoxia progress in both. While hypoxia in obesity leads to the adipocyte dysfunction and metabolic abnormalities, in obesity-related cancer cases, it is associated with worsened prognosis, increased metastatic potential, and resistance to chemotherapy. Notch-interleukin-1 (IL-1)-Leptin crosstalk outcome is referred to as "NILCO effect." In this chapter, obesity-related cancer development is discussed in the context of "next-cell hypothesis," miRNA biogenesis, and "NILCO effect."

Impacts of DROSHA (rs10719) and DICER (rs3742330) Variants on Breast Cancer Risk and Their Distribution in Blood and Tissue Samples of Egyptian Patients.

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression and play critical roles in tumorigenesis. Genetic variants in miRNA processing genes, DROSHA and DICER, have been implicated in cancer susceptibility and progression in various populations. However, their role in Egyptian patients with breast cancer (BC) remains unexplored. This study aims to investigate the association of DROSHA rs10719 and DICER rs3742330 polymorphisms with BC risk and clinical outcomes. This case-control study included 209 BC patients and 106 healthy controls. Genotyping was performed using TaqMan assays in blood, tumor tissue, and adjacent non-cancerous tissue samples. Associations were analyzed using logistic regression and Fisher's exact test. The DROSHA rs10719 AA genotype was associated with a 3.2-fold increased risk (95%CI = 1.23-9.36, p < 0.001), and the DICER rs3742330 GG genotype was associated with a 3.51-fold increased risk (95%CI = 1.5-8.25, p = 0.001) of BC. Minor allele frequencies were 0.42 for rs10719 A and 0.37 for rs3742330 G alleles. The risk alleles were significantly more prevalent in tumor tissue than adjacent normal tissue (rs10719 A: 40.8% vs. 0%; rs3742330 G: 42.7% vs. 0%; p < 0.001). However, no significant associations were observed with clinicopathological features or survival outcomes over a median follow-up of 17 months. In conclusion, DROSHA rs10719 and DICER rs3742330 polymorphisms are associated with increased BC risk and more prevalent in tumor tissue among our cohort, suggesting a potential role in miRNA dysregulation during breast tumorigenesis. These findings highlight the importance of miRNA processing gene variants in BC susceptibility and warrant further validation in larger cohorts and different ethnic populations.

The coexistence of a BRCA2 germline and a DICER1 somatic variant in two first-degree cousins suggests their potential synergic effect.

Cancer predisposition syndromes are recognized in about 10% of pediatric malignancies with several genes specifically involved in a subset of pediatric tumors such as DICER1, in pleuropulmonary blastoma, cystic nephroma, and brain sarcomas. By contrast, the role of BRCA1/2 in pediatric cancer predisposition is still under investigation. We present two cases of young first-degree cousins, both carrying a germline BRCA2 variant and developing tumors characterized by somatic DICER1 mutations. Patient 1 presented with a cystic nephroma harboring a somatic DICER1 variant (p.Asp1810Tyr), while patient 2 had a primary intracranial DICER1-mutated sarcoma showing a distinct somatic DICER1 variant (p.Asp1709Glu) as well as biallelic inactivation of TP53 (p.Val173Leu, VAF 91%) and APC (p.Ile1307Lys, VAF 95%) and a pathogenic variant in KRAS (p.Gln61His). Both patients carried the same germline BRCA2 variant (p.Arg2842Cys) of unknown significance. The same variant was found in the mother of patient 2 and in the father of patient 1, who are siblings. A homologous recombination deficiency signature was not identified in any of the two tumors, possibly suggesting a reduction of BRCA2 activity. The association of BRCA2 and DICER1 variants in our cases hints at a potential cooperative role in cancer pathogenesis. Further studies are warranted to elucidate the interplay between BRCA1/2 and DICER1 variants and their implications for cancer predisposition and treatment in pediatric patients.

DICER1 Variants in Pediatric and Young Adult Thyroid Nodules.

Background: Recent studies have suggested that pathogenic variants of the DICER1 gene could be a driver of alterations in some pediatric thyroid nodules, but data are still limited. The aim of this study was to detect variants in the DICER1 gene in a large cohort of pediatric thyroid nodules and then correlate them with clinicopathological data, with a focus on the disease prognosis in patients with thyroid carcinoma. Methods: This retrospective cohort study consisted of 350 pediatric and young adult patients (aged 2-21 years) with thyroid nodules, from whom 275 fresh-frozen thyroid nodule samples and 92 fine-needle aspiration biopsy (FNAB) samples were collected. After an analysis of variants in major genetic alterations of thyroid tumors, variants in the DICER1 gene were identified using next-generation sequencing and multiplex ligation-dependent probe amplification methods. Peripheral blood was analyzed from patients with DICER1-positive tumors. The results of genetic analysis were then correlated with clinicopathological data. Results: Variants in the DICER1 gene were detected in a total of 24/350 (6.9%; 95%CI [4.4;10.0]) pediatric and young adult patients, respectively, in 10/119 (8.4%; [4.1;14.9]) patients with benign fresh-frozen tissue, in 8/141 (5.7%; [1.9;9.5]) with papillary thyroid carcinoma (PTC) and in 6/86 (7.0%; [4.1;14.6]) patients with FNAB. No other gene alteration was found in DICER1-positive samples. Germline DICER1 variants were identified in 11/24 (45.8%; [25.6;67.2]) patients. Two somatic (biallelic) variants in the DICER1 gene were found in 9/24 (37.5%; [18.8;59.4]) thyroid nodules. Somatic deletions of at least 3 Mbp long were revealed in 2/24 (8.3%; [1.0;27.0]) cases. DICER1-positive PTCs were significantly associated with the follicular subtype of PTC (p = 0.001), encapsulation (p = 0.006) and were larger in size (p = 0.035), but with no extrathyroidal extension (p = 0.039), and less frequent lymph node metastases (p = 0.003) compared with DICER1-negative PTCs. Patients with DICER1-positive PTC had an excellent response to treatment in 75% of cases. Conclusions: Variants of the DICER1 gene are frequently found in the thyroid nodules of pediatric and young adult patients. In our patients, DICER1-positive PTCs showed low invasiveness. Our findings support considering more conservative management for DICER1-positive low-risk PTCs.

Beyond RNAi: How the Dicer protein modulates the antiviral innate immune response in mammalian cells: Mammalian Dicer could regulate the innate immune response in an RNAi-independent manner as a result of losing long dsRNA processive activity.

While Dicer plays an important antiviral role through the RNAi pathway in plants and invertebrates, its contribution to antiviral immunity in vertebrates and more specifically mammals is more controversial. The apparent limited RNAi activity in mammalian cells has been attributed to the reduced long dsRNA processive activity of mammalian Dicer, as well as a functional incompatibility between the RNAi and IFN pathways. Why Dicer has lost this antiviral activity in the profit of the IFN pathway is still unclear. We propose that the primary direct antiviral activity of Dicer has been functionally replaced by other sensors in the IFN pathway, leading to its specialization toward microRNA maturation. As a result, Dicer can regulate the innate immune response and prevent basal activation of the IFN pathway in mammals. Here, we discuss this hypothesis, highlighting how the adaptation of the helicase domain of mammalian Dicer may be key to this process.

DICER1-sarcomas of GYN tract: Expanding on an emerging entity.

Tumors with pathogenic DICER1 mutation are rare and encompass sporadic or hereditary benign, intermediate and malignant tumors. DICER1-associated sarcomas are heterogeneous; however, the prototypical ones in the GYN-tract include embryonal rhabdomyosarcoma, adenosarcoma and moderately to poorly differentiated Sertoli-Leydig tumor. In this report, we present three unique uterine sarcomas with DICER1 mutation and remarkable diffuse round/spindle cell morphology. The tumors occurred in cervix (n = 1), and uterine corpus (n = 2). The patient ages were 30, 37 and 59 years with tumor size of 8.8, 10 and 8.6 cm, respectively. Morphologically all three tumors were characterized by distinct spindle/round cell morphology and various amounts of neuroectodermal differentiation (yolk sac-like tubules, blastomatous areas and rosette formation). Other morphologic features of DICER1-sarcoma reported in the literature including cambium layer, focal or diffuse anaplasia, solid and cystic architecture, and chondroid/osteoid areas were absent. All three sarcomas were positive for SALL4 and had variable neuroendocrine marker expression. Whole genome methylation analysis was performed on one of the uterine sarcomas, which clustered the tumor with embryonal tumor with multilayered rosettes. Follow up information was available on all three cases. Two patients were alive with no evidence of disease 13 and 14 months post operation, while one patient had imaging evidence of local recurrence 4 months post operation. In summary, we describe three unique DICER1-sarcomas and expand the phenotypic spectrum of this emerging entity, particularly with GYN-tract origin.

Exomic and epigenomic analysis of pulmonary blastoma.

OBJECTIVE: Pulmonary blastoma is a rare, biphasic, adult-onset lung tumor. In this study, we investigate whether DICER1 pathogenic variants are a feature of pulmonary blastomas through in-depth analysis of the molecular events defining them. METHODS: We performed exome-wide sequencing and DNA methylation profiling of 8 pulmonary blastomas from 6 affected persons. RESULTS: We identified biallelic somatic DICER1 pathogenic variants in 7 of 8 cases. The remaining case had a solitary missense pathogenic variant in the RNase IIIb domain of DICER1. Six of 8 cases carried a CTNNB1 hotspot variant and 4 of 8 had a somatic pathogenic variant in TP53. Methylation analysis showed that the pulmonary blastomas clustered with other DICER1-mutated tumors and not with other more common types of lung cancer. CONCLUSION: We conclude somatic DICER1 pathogenic variants are the major driver of pulmonary blastoma and are likely to act in conjunction with CTNNB1 hotspot variants that are often present.

Structural determinants in the miRNA/miRNA* duplex and the DCL1 PAZ domain for precise and efficient plant miRNA processing.

The accessory proteins Hyponastic-like 1 (HYL1) and Serrated (SE) enhance the precise and efficient processing of miRNAs by Dicer-like 1 (DCL1), which is important for proper miRNA function. However, other factors determining the precision and efficiency of miRNA biogenesis are not well-known. Here, we found that an asymmetric bulge (AB) at the 3' end of miR-5p (produced from the 5' arm of the pre-miRNA) reduced the precision of the second cleavage, whereas an AB at other sites of miR-5p mainly affected the accumulation level of miR-5p in transient expression in Nicotiana benthamiana. In contrast, many ABs in miR-3p (produced from the 3' arm of the pre-miRNA) impose strong negative impact on the processing precision and the accumulation level of miR-5p in N. benthamiana. Arabidopsis DCL1/SE/HYL1 complex-mediated miRNA processing was reconstituted in Saccharomyces cerevisiae to further investigate AB-mediated interference with DCL1 processing. With this system, the positional effect of AB on miRNA processing was tested. The results showed that ABs on the middle of miR-5p have less of an impact on DCL1 cleavage efficiency and precision, whereas those on miR-3p or near the ends of miR-5p strongly reduce DCL1 cleavage activity, precision or both. Studies using the yeast miRNA processing system and transgenic Arabidopsis also revealed the importance of the interaction between the 2-nt 3' overhang of pre-miRNA and the 3' overhang binding pocket (3'BP) on the precision of the second cleavage reaction for many endogenous miRNAs. These findings provide new insights into the mechanism of miRNA biogenesis.

Primary intracranial sarcoma, DICER-1 mutant, with hemorrhagic presentation: A case report.

Background: Primary intracranial sarcomas (PIS) are rare tumors with mesenchymal origins. These tumors have a heterogeneous clinical presentation and are associated with a poor prognosis. Case Description: This report highlights the complexities associated with PIS by focusing on a 26-year-old male with recurrent tumor growth facing unique challenges regarding diagnosis and treatment options . A high-grade spindle-celled neoplasm with sarcomatous features characterized the patient's tumor. There were additional morphologic changes, including multinucleated giant cells and rare foci with eosinophilic spheroids. Genomic analysis revealed a DICER1-associated PIS. Treatment involved endovascular embolization, multiple surgical interventions, intrathecal etoposide injections, and oral pazopanib with adjuvant radiation therapy. Conclusion: This case additionally highlights an unusual association between PIS and anomalous hypervascularity, refractory hemorrhage, and subdural effusions, a presentation that is increasingly being reported in this type of tumor.

Increased viral tolerance mediates by antiviral RNA interference in bat cells.

Bats harbor highly virulent viruses that can infect other mammals, including humans, posing questions about their immune tolerance mechanisms. Bat cells employ multiple strategies to limit virus replication and virus-induced immunopathology, but the coexistence of bats and fatal viruses remains poorly understood. Here, we investigate the antiviral RNA interference pathway in bat cells and discover that they have an enhanced antiviral RNAi response, producing canonical viral small interfering RNAs upon Sindbis virus infection that are missing in human cells. Disruption of Dicer function results in increased viral load for three different RNA viruses in bat cells, indicating an interferon-independent antiviral pathway. Furthermore, our findings reveal the simultaneous engagement of Dicer and pattern-recognition receptors, such as retinoic acid-inducible gene I, with double-stranded RNA, suggesting that Dicer attenuates the interferon response initiation in bat cells. These insights advance our comprehension of the distinctive strategies bats employ to coexist with viruses.