RNA activation of haploinsufficient Foxg1 gene in murine neocortex

Abstract

More than one hundred distinct gene hemizygosities are specifically linked to epilepsy, mental retardation, autism, schizophrenia and neuro-degeneration. Radical repair of these gene deficits via genome engineering is hardly feasible. The same applies to therapeutic stimulation of the spared allele by artificial transactivators. Small activating RNAs (saRNAs) offer an alternative, appealing approach. As a proof-of-principle, here we tested this approach on the Rett syndrome-linked, haploinsufficient, Foxg1 brain patterning gene. We selected a set of artificial small activating RNAs (saRNAs) upregulating it in neocortical precursors and their derivatives. Expression of these effectors achieved a robust biological outcome. saRNA-driven activation (RNAa) was limited to neural cells which normally express Foxg1 and did not hide endogenous gene tuning. saRNAs recognized target chromatin through a ncRNA stemming from it. Gene upregulation required Ago1 and was associated to RNApolII enrichment throughout the Foxg1 locus. Finally, saRNA delivery to murine neonatal brain replicated Foxg1-RNAa in vivo.

Differential microRNA expression in the prefrontal cortex of mouse offspring induced by glyphosate exposure during pregnancy and lactation

“…It is widely acknowledged that miRNAs can regulate target mRNAs and affect the activities of cells and tissues, implicating the importance of target gene prediction ( 46 ). For example, among miR-34b-5p target genes, Chl1 , Fgfr1 , Foxg1 and Nrn1 were reported to be involved in certain neurological disorders, including autism, schizophrenia and bipolar disorder ( 47 – 49 ).…”

Small Activating RNAs: Towards the Development of New Therapeutic Agents and Clinical Treatments

“…Their results showed that the transactivation of Emx2 can result in delayed differentiation, self-renewal, and decreased death of neuronally committed precursors [ 24 ]. Exogenous saRNA-mediated gene activation in the brain has been reported by Fimiani and his co-workers [ 22 ]. Synthesized saRNAs induce the Foxg1 transcription factor, a key regulator of cortico-cerebral development and function.…”

“…Based on many studies, two models of locus-specific gene activation have been reported, promoter-targeted duplex RNA activating and natural antisense disruption, leading to changes in chromatin structure [ 8 , 14 , 15 , 20 ]. Several studies show that endogenous saRNAs selectively activate gene expression in neurons through targeting promoter sequences [ 21 , 22 ]. Kuwabara et al have reported a neural-specific dsRNA of about 20 bp containing the NRSE (neuron restrictive silencer element) sequence.…”

“…Foxg1 allele duplication and deletion in humans results in West and Rett syndromes, respectively [ 25 ]. As a prospective RNAa therapy of Rett syndrome, Foxg1 gene expression in neural cells has been induced in vitro and in vivo by intraventricular injection of saRNA to mouse neonates [ 22 ]. NATs destruction is another alternative locus-specific gene activation mechanism, which holds great therapeutic promise.…”

RNA Activation: A Diamond in the Rough for Genome Engineers

“…Thus, saRNA-Ago2 forms the binary core of the RITA effector complex which associates with heterogeneous nuclear proteins (hnRNPs), transcription factors, and RNAP II in order to induce targeted gene expression [Schwartz et al, 2008, Hu et al, 2012, Portnoy et al, 2016. In addition, a recent work shows that other argonaute family member, the argonaute 1 (Ago1) protein, is also required to mediate RNAa-based activation of the Foxg1 gene, a key transcription factor during brain development [Fimiani et al, 2016].…”