It is found that the ablation of Mettl14 in postmitotic neurons leads to impaired axonal projection during corticogenesis, and the authors show that m6A RNA marks recruit YTHDF2-associated transport machinery that favors transport over degradation, localizing selected mRNAs to neurites to promote cortical axon projection.
Abstract
Proper nervous system development is critical for brain function, and deficits in neural development are implicated in many brain disorders. Neurons are distinctly polarized cells where mRNA can be transported to distal structures like axons and dendrites. Recent discoveries of widespread mRNA chemical modifications raise the question of their post-transcriptional regulatory role in brain development and function. N6-methyladenosine (m6A), installed by the METTL3/METTL14 methyltransferase complex, is the most prevalent internal mRNA modification, influencing stability, translation, splicing, and localization. However, the impact of m6A modification on RNA transport in developing neurons is not well understood. In this study, we find that the ablation of Mettl14 in postmitotic neurons leads to impaired axonal projection during corticogenesis. RNA-seq and single-molecule in situ hybridization reveal mislocalization of mRNAs in neurites of neurons with m6A loss-of-function. Furthermore, m6A-SAC-seq to identify a single nucleotide resolution m6A maps in the perinatal brain uncovers m6A-tagged transcripts associated with synapse organization, mRNA processing, and axonogenesis. We also identify YTHDF2 as the reader protein responsible for mRNA transport in callosal projection axons. YTHDF2 interacts with motor proteins, translational regulators, and microtubules to facilitate distal transport of m6A-tagged mRNA. Our data suggest that FMRP may serve as a context-guiding interactor that reshapes the YTHDF2 complex by recruiting specific cofactors and motor proteins, thereby promoting transport rather than degradation of m⁶A-tagged transcripts. Together, these findings provide insight into the epitranscriptomic mechanisms governing axon projection and guidance during mammalian cortical neurogenesis. Precise mRNA transport into neurites is essential for neural circuit formation. Here, the authors show that m6A RNA marks recruit YTHDF2-associated transport machinery that favors transport over degradation, localizing selected mRNAs to neurites to promote cortical axon projection.
The potential role of ribonucleoprotein-based transport as a primary mechanism driving circRNA localization is explored and how such spatial distribution influences synaptic plasticity and post-transcriptional gene regulation is examined.
Nicolò Salvi, M. Morlando· Non-Coding RNA· 0 citations
This study indicates that KIF2C may regulate microtubule dynamics to control deep-layer cortical neuron number and organization and modulate neuronal projections and signaling pathways and provides a foundation for understanding the role of KIF2C in neural development.
Hundreds of neuronal cell types and subtypes have been identified through transcriptome profiling of the mammalian brain and are thought to arise from lineage-restricted neural progenitors during early development. However, how neurons might further diversify their transcriptional identities during postmitotic development and through adulthood remains poorly understood. Here, we combine genetic and biochemical approaches to uncover granule neuron subpopulations in the anterior cerebellum, which we term C1 and C2. We find that a large proportion of granule neurons predominantly express the C2 gene program during early postmitotic differentiation, but that C2 genes are downregulated in a subset of neurons during late postnatal development, leading to comparable proportions of C1 and C2 neurons in adulthood. Using an in vivo genetic mini-screen, we identify calcium signaling pathways, together with the transcription factor ETV1, that establish the transcriptional program of C2 neurons. Finally, C1 and C2 granule neurons are differentially engaged during behavior and this reflects their roles in cerebellar-dependent associative learning. Together, these findings reveal postmitotic mechanisms that continue to shape neuronal identity in the brain.
PURPOSE
A comprehensive understanding of the mechanisms regulating the development of retinal ganglion cells (RGCs) and their neurites carries both theoretical significance and translational implications. The YTHDF family members, comprising Ythdf1, Ythdf2, and Ythdf3, are key readers for N6-methyladenosine (m6A), the most abundant internal modification of mRNA. Mounting evidence has demonstrated essential roles of Ythdf family m6A readers in various biological processes. This study aimed to investigate the roles of Ythdf family m6A readers in RGC development and their neurite outgrowth.
METHOD
An in vitro induced RGC (iRGC) system was employed to generate RGC-like neurons. Short hairpin RNAs (shRNAs) were used for gene knockdown expression, coding sequence (CDS)-containing constructs for gene overexpression, immunofluorescence staining for protein expression detection, patch-clamp recording for assessing neuronal electrophysiological properties, and RNA-seq for transcriptome profiling.
RESULTS
Knockdown of Ythdf1 and Ythdf3 significantly reduced iRGC reprogramming efficiency and axon length, whereas overexpression of these two m6A readers exerted the opposite effects. Ythdf2 knockdown had no impact on iRGC reprogramming or axonogenesis, while Ythdf2 overexpression promoted axon growth.
CONCLUSION
Ythdf1 and Ythdf3 are essential for iRGC fate reprogramming and axon development, whereas Ythdf2 is dispensable for these processes but can promote axon growth when overexpressed. These findings reveal important roles of m6A readers in RGC and their neurite development, which may facilitate future fundamental research and translational applications.
Ting Zhang, Kezhong Zhang, Qinghai He et al.· Experimental Eye Research· 0 citations
How dysfunction in NMD pathway components—specifically core degradation factors, the exon junction complex, and neuron-specific splicing regulators—underpins an extensive array of neurodevelopmental disorders (NDDs) is examined.
Polina E. Anisimova, A. Filat'eva, Victor S. Tarabykin et al.· Frontiers in Molecular Biosc...· 0 citations
Transcription factors are central to neuronal development, yet their functions beyond the cells in which they are expressed remain poorly understood. Here, we uncover unexpected non-cell-autonomous roles for UNC-3, a terminal selector of cholinergic motor neuron identity in C. elegans, whose human ortholog (EBF3) is linked to a neurodevelopmental syndrome. Single-cell RNA-sequencing reveals unc-3 loss in cholinergic motor neurons elicits pronounced transcriptional changes in GABAergic motor neurons that do not express unc-3, which can be rescued by cholinergic-specific UNC-3 restoration. Mechanistically, gene network analysis identifies the pro-regenerative bZIP factor CEBP-1/CEBPB as a key driver of these transcriptional changes. At the circuit level, unc-3 loss causes synaptic and axon pathfinding defects in GABA motor neurons alongside misregulation of neurite development genes. Finally, UNC-3 not only acts as a direct transcriptional activator but also suppresses inappropriate gene expression through indirect mechanisms. Together, these findings broaden terminal selectors as both intrinsic and extrinsic regulators of neuronal identity and circuit assembly, providing a mechanistic framework for understanding EBF3-associated neurodevelopmental disease. The non-cell-autonomous functions of transcription factors in neuronal development remain poorly understood. Here, the authors show that UNC-3, the C. elegans homolog of the neurodevelopmental disorder gene EBF3, regulates not only the development of UNC-3–expressing neurons but also that of neighboring neurons, revealing previously unrecognized mechanisms of neural circuit assembly.
Jayson J. Smith, Seth R. Taylor, Honorine Destain et al.· Nature Communications· 0 citations
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