Role of miR-146a in neural stem cell differentiation and neural lineage determination: relevance for neurodevelopmental disorders

Abstract

BackgroundMicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression at the post-transcriptional level. miRNAs have emerged as important modulators of brain development and neuronal function and are implicated in several neurological diseases. Previous studies found miR-146a upregulation is the most common miRNA deregulation event in neurodevelopmental disorders such as autism spectrum disorder (ASD), epilepsy, and intellectual disability (ID). Yet, how miR-146a upregulation affects the developing fetal brain remains unclear.MethodsWe analyzed the expression of miR-146a in the temporal lobe of ASD children using Taqman assay. To assess the role of miR-146a in early brain development, we generated and characterized stably induced H9 human neural stem cell (H9 hNSC) overexpressing miR-146a using various cell and molecular biology techniques.ResultsWe first showed that miR-146a upregulation occurs early during childhood in the ASD brain. In H9 hNSC, miR-146a overexpression enhances neurite outgrowth and branching and favors differentiation into neuronal like cells. Expression analyses revealed that 10% of the transcriptome was deregulated and organized into two modules critical for cell cycle control and neuronal differentiation. Twenty known or predicted targets of miR-146a were significantly deregulated in the modules, acting as potential drivers. The two modules also display distinct transcription profiles during human brain development, affecting regions relevant for ASD including the neocortex, amygdala, and hippocampus. Cell type analyses indicate markers for pyramidal, and interneurons are highly enriched in the deregulated gene list. Up to 40% of known markers of newly defined neuronal lineages were deregulated, suggesting that miR-146a could participate also in the acquisition of neuronal identities.ConclusionOur results demonstrate the dynamic roles of miR-146a in early neuronal development and provide new insight into the molecular events that link miR-146a overexpression to impaired neurodevelopment. This, in turn, may yield new therapeutic targets and strategies.Electronic supplementary materialThe online version of this article (10.1186/s13229-018-0219-3) contains supplementary material, which is available to authorized users.

Loss of the neurodevelopmental disease-associated gene miR-146a impairs neural progenitor differentiation and causes learning and memory deficits

“…6). These results are in line with the previously published in vitro studies demonstrating that increased miR-146a level enhanced neuronal differentiation in mouse NSC [36] and in H9 human neural stem cells [12]. Yet, while miR-146a overexpression in cultured NSC halts cell cycle progression and promotes neuronal differentiation through NOTCH pathway, how loss of miR-146a causes defective neuronal differentiation and which miR-146a target(s) may mediate these effects in the mutant brains is still an open question.…”

“…Altered balance between aRG and IP populations in the Mir146a −/− neocortex miR-146a has been shown to regulate the balance of cell cycle progression and differentiation of cultured progenitor cells in vitro [12]. Yet, we observed that the number of cortical neurons is unaltered in the adult Mir146a −/− brain ( Figure S1, Additional file 1), suggesting that, in vivo, there is no major defect in proliferation of neural progenitors.…”

“…miR-146a is known for regulating NFκB [17], NOTCH [18], and WNT/β-catenin [19,20] pathways in a tissue and developmental stage-dependent manner. Our group has also demonstrated the pro-neuronal effects of miR-146a overexpression in a H9 model of human neural stem cells [12]. Moreover, a body of in vitro works also suggests a role of miR-146a in neuron survival and apoptosis [21,22], axonal growth [23], and AMPA receptor endocytosis [24].…”

“…Among the differentially expressed miRNAs identified by transcriptomic analysis in DBD patients, miR-146a-5p (referred to as miR-146a from now on) is one of the most commonly observed [7]. In ASD cases, it has been reported in five different cohorts and tissue types including post-mortem brain [11,12] olfactory mucosal stem cells, fibroblasts [9], and lymphoblastoid cell line [13]. Its abnormal expression has also been reported in ID [9] and epilepsy [14].…”

CircNAPEPLD is expressed in human and murine spermatozoa and physically interacts with oocyte miRNAs

“…In line with these results, we investigated the possibility that circNAPEPLDiso1 may act as sponge by retrieving miRNAs physically interacting with it through a miR-CATCH approach (see Materials and Methods). Interestingly, we identified five miRNAs physically interacting with circNAPEPLDiso1, many of which are known to be expressed in HS oocytes, blastocysts and blastocoel fluid (see Table 3) [34][35][36][37][38][39][40][41][42][43] and whose targets are involved in pathways related to cancer and cell cycle (see Tables 4 and 5). Therefore, it is conceivable that SPZ-derived circNAPEPLD may function as a decoy to inhibit the anti-proliferative activity of some oocyte-derived miRNAs, thus allowing cell proliferation, a massive event during the first stages of embryo development.…”