Neurofibromin 1 Is a miRNA Target in Neurons

Abstract

Mutations of the neurofibromin 1 gene cause neurofibromatosis type 1, a disease in which learning and behavioral abnormalities are common. The disease is completely penetrant but shows variable phenotypic expression in patients. The repertoire of regulatory interactions utilized by neurons to control neurofibromin 1 expression is poorly understood. Here, we examined the contribution of microRNAs into this regulatory network. Using reporter assays, we provided evidence that miR-128 and to a lesser extent miR-137 and miR-103 reduced neurofibromin 1 reporter levels through specific binding to Nf1 3′-UTR. Mutations in all three predicted binding sites eliminated the reporter response. MiR-128 and miR-137, unlike miR-103 that showed a more ubiquitous expression, were predominantly expressed in brain with a distribution that resembled neurofibromin 1 expression in different tissues as well as during the course of neuronal development. In the nervous system, all three microRNAs showed highest expression in neurons and least in Schwann cells and astrocytes. Overexpression of miR-128 alone or with miR-103 and miR-137 significantly reduced endogenous neurofibromin 1 protein levels, while antisense inhibition of these microRNAs enhanced translation of endogenous neurofibromin 1 and reporter in primary cultures of hippocampal neurons. These findings revealed a significant additional mechanism by which neurofibromin 1 is regulated in neurons and implicated new candidates for the treatment of multifarious neurofibromatosis type 1 cognitive symptoms.

A RASopathy gene commonly mutated in cancer: the neurofibromatosis type 1 tumour suppressor

“…Downregulation of neurofibromin may also result from the methylation of NF1 in cancer cells 78,79 . NF1 is also a target of micro-RNAs (mi RNAs); expression of miR-128 in neurons and miR-193b in head and neck squamous cell carcinoma cells decreased the levels of NF1 mRNA and neurofibromin 80,81 .…”

MicroRNAs in adrenal tumors: relevance for pathogenesis, diagnosis, and therapy

“…In MAX-mutation-related PCC, however, these two microRNAs were underexpressed, thus MAX-mutations might result in a microRNA profile distinct from other PCC classes. miR-137 is underexpressed in several malignancies and its targets include mRNAs involved in gene expression regulation and signaling [82][83][84]. The oncogene c-MYC was found among the validated targets of miR-382 [85] that might be relevant as MAX (MYC-associated factor X) forms part of the c-MYC network [69].…”

U6 snRNA is a Suitable Endogenous Control for microRNA-124 and -134 in Cultured Rat Hippocampal Neurons

“…We found that the U6 snRNA was stable under BDNF treatment, so perhaps the issue is that U6 snRNA is affected by the retinoic acid treatment performed by Lim et al (2011) rather than their argument that it is inconsistently expressed. Furthermore, the miRNAs that they propose as endogenous controls are not suitable in a system looking at maturing neurons undergoing synaptogenesis as the expression of these miRNAs have been reported to change in developing neurons -for miR-103 (Paschou & Doxakis 2012) and in response to BDNF for miR-26b (Caputo et al 2011). Meanwhile contrary to Lim et al (2011), a study has reported that miR-106b expression changes during neuronal differentiation and it is involved in neurogenesis (Brett et al 2011), therefore this miRNA is also not a good candidate as an endogenous control.…”