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Maturation of the mammalian nervous system requires adequate provision of thyroid hormone and mechanisms that enhance tissue responses to the hormone. Here, we report that the development of cones, the photoreceptors for daylight and color vision, requires protection from thyroid hormone by type 3 deiodinase, a thyroid hormone-inactivating enzyme. Type 3 deiodinase, encoded by Dio3, is expressed in the immature mouse retina. In Dio3-/- mice, ~80% of cones are lost through neonatal cell death. Cones that express opsin photopigments for response to both short (S) and medium-long (M) wavelength light are lost. Rod photoreceptors, which mediate dim light vision, remain essentially intact. Excessive thyroid hormone in wild-type pups also eliminates cones. Cone loss is mediated by cone-specific thyroid hormone receptor β2 (TRβ2) as deletion of TRβ2 rescues cones in Dio3-/- mice. However, rescued cones respond to short but not longer wavelength light because TRβ2 under moderate hormonal stimulation normally induces M opsin and controls the patterning of M and S opsins over the retina. The results suggest that type 3 deiodinase limits hormonal exposure of the cone to levels that safeguard both cone survival and the patterning of opsins that is required for cone function. [ABSTRACT FROM AUTHOR]

Little is known of microRNA interactions with cellular pathways. Few reports have associated microRNAs with the Notch pathway, which plays key roles in nervous system development and in brain tumors. We previously implicated the Notch pathway in gliomas, the most commonand aggressive brain tumors. While investigating Notch mediators, we noted microRNA-326 was upregulated following Notch-1 knockdown. This neuronally expressed microRNA was not only suppressed by Notch but also inhibited Notch proteins and activity, indicating a feedback loop. MicroRNA-326 was downregulated in gliomas via decreased expression of its host gene. Transfection of microRNA-326 into both established and stem cell-like glioma lines was cytotoxic, and rescue was obtained with Notch restoration. Furthermore, miR-326 transfection reduced glioma cell tumorigenicity in vivo. Additionally, we found microRNA-326 partially mediated the toxic effects of Notch knockdown. This work demonstrates a microRNA-326/Notch axis, shedding light on the biology of Notch and suggesting microRNA-326 delivery as a therapy. [ABSTRACT FROM AUTHOR]

Great interest persists in useful prognostic and therapeutic targets in glioblastoma. In this study, we report the definition of miRNA (miR)-148a as a novel prognostic oncomiR in glioblastoma. miR-148a expression was elevated in human glioblastoma specimens, cell lines, and stem cells (GSC) compared with normal human brain and astrocytes. High levels were a risk indicator for glioblastoma patient survival. Functionally, miR-148a expression increased cell growth, survival, migration, and invasion in glioblastoma cells and GSCs and promoted GSC neurosphere formation. Two direct targets of miR-148a were identified, the EGF receptor (EGFR) regulator MIG6 and the apoptosis regulator BIM, which rescue experiments showed were essential to mediate the oncogenic activity of miR-148a. By inhibiting MIG6 expression, miR-148a reduced EGFR trafficking to Rab7-expressing compartments, which includes late endosomes and lysosomes. This process coincided with reduced degradation and elevated expression and activation of EGFR. Finally, inhibition of miR-148a strongly suppressed GSC and glioblastoma xenograft growth in vivo. Taken together, our findings provide a comprehensive analysis of the prognostic value and oncogenic function of miR-148a in glioblastoma, further defining it as a potential target for glioblastoma therapy. [ABSTRACT FROM AUTHOR]

Epidermal growth factor receptor (EGFR) is involved in development and progression of many human cancers. We have previously demonstrated that the ubiquitin-specific peptidase Usp18 (Ubp43) is a potent regulator of EGFR protein expression. Here we report that the 3'-untranslated region (3'-UTR) of the EGFR message modulates RNA translation following cell treatment with Usp18 siRNA, suggesting microRNA as a possible mediator. Given earlier evidence of EGFR regulation by the microRNA miR-7, we assessed whether miR-7 mediates Uspl8 siRNA effects. We found that Usp18 depletion elevates miR-7 levels in several cancer cell lines because of a transcriptional activation and/or mRNA stabilization of miR-7 host genes and that miR-7 acts downstream of Usp18 to regulate EGFR mRNA translation via the 3'-UTR. Also, depletion of Usp18 led to a decrease in protein levels of other known oncogenic targets of miR-7, reduced cell proliferation and soft agar colony formation, and increased apoptosis. Notably, all of these phenotypes were reversed by a specific inhibitor of miR-7. Thus, our findings support a model in which Usp18 inhibition promotes upregulation of miR-7, which in turn inhibits EGFR expression and the tumorigenic activity of cancer cells. [ABSTRACT FROM AUTHOR]

Background: Glioblastoma (GBM) is the most common primary malignant brain tumor. The aim of this study was to elucidate the role of microenvironment and intrinsic T-type calcium channels (Cav3) in regulating tumor growth and progression., Methods: We grafted syngeneic GBM cells into Cav3.2 knockout mice to assess the role of microenvironment T-Type calcium channels on GBM tumor growth. We performed single-cell RNA-seq (scRNA-seq) of tumors from WT and Cav3.2 KO mice to elucidate the regulation of tumors by the microenvironment. We used neurons from WT and Cav3.2 KO mice in co-culture with GBM stem cells (GSC) to assess the effects of Cav3.2 on neuron/GSC synaptic connections and tumor cell growth., Results: Cav3.2 KO in the microenvironment led to significant reduction of GBM growth and prolongation of animal survival. scRNA-seq showed that microenvironment Cav3.2 regulates neuronal and glial biological processes. Microenvironment Cav3.2 downregulated numerous genes associated with regulating the OPC cell state in GBM tumors such as SOX10 and Olig2. Neuronal Cav3.2 promoted neuron/GSC synaptic connections and GSC growth. Treatment of GSCs with the Cav3 blocker mibefradil downregulated genes associated with neuronal processes. The Cav3 blocker drug mibefradil synergized with temozolomide (TMZ) and radiation to reduce in vivo tumor growth and prolong animal survival., Conclusions: Together these data reveal a role for microenvironment Cav3 in promoting GBM tumor progression through regulating neuronal and glial processes particularly associated with the OPC-cell state. Targeting both intrinsic and microenvironment Cav3 with the inhibitor mibefradil significantly enhanced the anti-GBM effects of TMZ and radiation., Competing Interests: Conflict of Interest The authors have declared that no conflicts of interest exist